Programs & Examples On #Gdb

Use this tag for problems related to or involving GDB, the standard debugger for the GNU software system.

How do I print the elements of a C++ vector in GDB?

With GCC 4.1.2, to print the whole of a std::vector<int> called myVector, do the following:

print *(myVector._M_impl._M_start)@myVector.size()

To print only the first N elements, do:

print *(myVector._M_impl._M_start)@N


This is probably heavily dependent on your compiler version, but for GCC 4.1.2, the pointer to the internal array is:


And the GDB command to print N elements of an array starting at pointer P is:

print P@N

Or, in a short form (for a standard .gdbinit):

p P@N

How do I analyze a program's core dump file with GDB when it has command-line parameters?

You can use the core with GDB in many ways, but passing parameters which is to be passed to the executable to GDB is not the way to use the core file. This could also be the reason you got that error. You can use the core file in the following ways:

gdb <executable> <core-file> or gdb <executable> -c <core-file> or

gdb <executable>
(gdb) core <core-file>

When using the core file you don't have to pass arguments. The crash scenario is shown in GDB (checked with GDB version 7.1 on Ubuntu).

For example:

$ ./crash -p param1 -o param2
Segmentation fault (core dumped)
$ gdb ./crash core
GNU gdb (GDB) 7.1-ubuntu
Core was generated by `./crash -p param1 -o param2'. <<<<< See this line shows crash scenario
Program terminated with signal 11, Segmentation fault.
#0  __strlen_ia32 () at ../sysdeps/i386/i686/multiarch/../../i586/strlen.S:99
99    ../sysdeps/i386/i686/multiarch/../../i586/strlen.S: No such file or directory.
    in ../sysdeps/i386/i686/multiarch/../../i586/strlen.S

If you want to pass parameters to the executable to be debugged in GDB, use --args.

For example:

$ gdb --args ./crash -p param1 -o param2
GNU gdb (GDB) 7.1-ubuntu
(gdb) r
Starting program: /home/@@@@/crash -p param1 -o param2

Program received signal SIGSEGV, Segmentation fault.
__strlen_ia32 () at ../sysdeps/i386/i686/multiarch/../../i586/strlen.S:99
99    ../sysdeps/i386/i686/multiarch/../../i586/strlen.S: No such file or directory.
    in ../sysdeps/i386/i686/multiarch/../../i586/strlen.S

Man pages will be helpful to see other GDB options.

Counter exit code 139 when running, but gdb make it through

exit code 139 (people say this means memory fragmentation)

No, it means that your program died with signal 11 (SIGSEGV on Linux and most other UNIXes), also known as segmentation fault.

Could anybody tell me why the run fails but debug doesn't?

Your program exhibits undefined behavior, and can do anything (that includes appearing to work correctly sometimes).

Your first step should be running this program under Valgrind, and fixing all errors it reports.

If after doing the above, the program still crashes, then you should let it dump core (ulimit -c unlimited; ./a.out) and then analyze that core dump with GDB: gdb ./a.out core; then use where command.

How to disassemble a memory range with GDB?

You can force gcc to output directly to assembly code by adding the -S switch

gcc -S hello.c

Step out of current function with GDB

You can use the finish command.

finish: Continue running until just after function in the selected stack frame returns. Print the returned value (if any). This command can be abbreviated as fin.

(See 5.2 Continuing and Stepping.)

gdb: "No symbol table is loaded"

I met this issue this morning because I used the same executable in DIFFERENT OSes: after compiling my program with gcc -ggdb -Wall test.c -o test in my Mac(10.15.2), I ran gdb with the executable in Ubuntu(16.04) in my VirtualBox.

Fix: recompile with the same command under Ubuntu, then you should be good.

GDB: break if variable equal value

in addition to a watchpoint nested inside a breakpoint you can also set a single breakpoint on the 'filename:line_number' and use a condition. I find it sometimes easier.

(gdb) break iter.c:6 if i == 5
Breakpoint 2 at 0x4004dc: file iter.c, line 6.
(gdb) c

Breakpoint 2, main () at iter.c:6
6           printf("%d\n", i);

If like me you get tired of line numbers changing, you can add a label then set the breakpoint on the label like so:

#include <stdio.h>
     int i = 0;
     for(i=0;i<7;++i) {
        printf("%d\n", i);
     return 0;

(gdb) break main:looping if i == 5

Can I use GDB to debug a running process?

ps -elf doesn't seem to show the PID. I recommend using instead:

ps -ld | grep foo
gdb -p PID

How to print register values in GDB?

If you're trying to print a specific register in GDB, you have to omit the % sign. For example,

info registers eip

If your executable is 64 bit, the registers start with r. Starting them with e is not valid.

info registers rip

Those can be abbreviated to:

i r rip

Show current assembly instruction in GDB

From within gdb press Ctrl x 2 and the screen will split into 3 parts.

First part will show you the normal code in high level language.

Second will show you the assembly equivalent and corresponding instruction Pointer.

Third will present you the normal gdb prompt to enter commands.

See the screen shot

gdb fails with "Unable to find Mach task port for process-id" error

In Snow Leopard and later Mac OS versions, it isn't enough to codesign the gdb executable.

You have to follow this guide to make it work:

The guide explains how to do it for lldb, but the process is exactly the same for gdb.

Is there a C++ gdb GUI for Linux?

I loathe the idea of Windows development, but the VC++ debugger is among the best I've seen. I haven't found a GUI front end that comes close to the VC one.

GDB is awesome once you really get used to it. Use it in anger enough and you'll become very proficient. I can whiz around a program doing all the things you listed without much effort anymore. It did take a month or so of suffering over a SSH link to a remote server before I was proficient. I'd never go back though.

DDD is really powerful but it was quite buggy. I found it froze up quite often when it got messages from GDB that it didn't grok. It's good because it has a gdb interface window so you can see what's going on and also interact with gdb directly. DDD can't be used on a remote X session in my environment (a real problem, since I'm sitting at a thin client when I do Unix dev) for some reason so it's out for me.

KDevelop followed typical KDE style and exposed EVERYTHING to the user. I also never had any luck debugging non KDevelop programs in KDevelop.

The Gnat Programming Studio (GPS) is actually quite a good front-end to GDB. It doesn't just manage Ada projects, so it's worth trying out if you are in need of a debugger.

You could use Eclipse, but it's pretty heavy weight and a lot of seasoned Unix people I've worked with (me included) don't care much for its interface, which won't just STFU and get out of your way. Eclipse also seems to take up a lot of space and run like a dog.

How do I set a conditional breakpoint in gdb, when char* x points to a string whose value equals "hello"?

You can use strcmp:

break x:20 if strcmp(y, "hello") == 0

20 is line number, x can be any filename and y can be any variable.

Using gdb to single-step assembly code outside specified executable causes error "cannot find bounds of current function"

The most useful thing you can do here is display/i $pc, before using stepi as already suggested in R Samuel Klatchko's answer. This tells gdb to disassemble the current instruction just before printing the prompt each time; then you can just keep hitting Enter to repeat the stepi command.

(See my answer to another question for more detail - the context of that question was different, but the principle is the same.)

How do I get the backtrace for all the threads in GDB?

Is there a command that does?

thread apply all where

Can I set a breakpoint on 'memory access' in GDB?

Use watch to see when a variable is written to, rwatch when it is read and awatch when it is read/written from/to, as noted above. However, please note that to use this command, you must break the program, and the variable must be in scope when you've broken the program:

Use the watch command. The argument to the watch command is an expression that is evaluated. This implies that the variabel you want to set a watchpoint on must be in the current scope. So, to set a watchpoint on a non-global variable, you must have set a breakpoint that will stop your program when the variable is in scope. You set the watchpoint after the program breaks.

How do I run a program with commandline arguments using GDB within a Bash script?

gdb has --init-command <somefile> where somefile has a list of gdb commands to run, I use this to have //GDB comments in my code, then `

echo "file ./a.out" > run
grep -nrIH "//GDB"|
    sed "s/\(^[^:]\+:[^:]\+\):.*$/\1/g" |
    awk '{print "b" " " $1}'|
    grep -v $(echo $0|sed "s/.*\///g") >> run
gdb --init-command ./run -ex=r

as a script, which puts the command to load the debug symbols, and then generates a list of break commands to put a break point for each //GDB comment, and starts it running

How to attach a process in gdb

Try one of these:

gdb -p 12271
gdb /path/to/exe 12271

gdb /path/to/exe
(gdb) attach 12271

How to pass arguments and redirect stdin from a file to program run in gdb?

You can do this:

gdb --args path/to/executable -every -arg you can=think < of

The magic bit being --args.

Just type run in the gdb command console to start debugging.

How to modify memory contents using GDB?

Expanding on the answers provided here.

You can just do set idx = 1 to set a variable, but that syntax is not recommended because the variable name may clash with a set sub-command. As an example set w=1 would not be valid.

This means that you should prefer the syntax: set variable idx = 1 or set var idx = 1.

Last but not least, you can just use your trusty old print command, since it evaluates an expression. The only difference being that he also prints the result of the expression.

(gdb) p idx = 1
$1 = 1

You can read more about gdb here.

no debugging symbols found when using gdb

Hope the sytem you compiled on and the system you are debugging on have the same architecture. I ran into an issue where debugging symbols of 32 bit binary refused to load up on my 64 bit machine. Switching to a 32 bit system worked for me.

Core dump file is not generated

Also, check to make sure you have enough disk space on /var/core or wherever your core dumps get written. If the partition is almos full or at 100% disk usage then that would be the problem. My core dumps average a few gigs so you should be sure to have at least 5-10 gig available on the partition.

GDB: Listing all mapped memory regions for a crashed process

In GDB 7.2:

(gdb) help info proc
Show /proc process information about any running process.
Specify any process id, or use the program being debugged by default.
Specify any of the following keywords for detailed info:
  mappings -- list of mapped memory regions.
  stat     -- list a bunch of random process info.
  status   -- list a different bunch of random process info.
  all      -- list all available /proc info.

You want info proc mappings, except it doesn't work when there is no /proc (such as during pos-mortem debugging).

Try maintenance info sections instead.

What does <value optimized out> mean in gdb?

You need to turn off the compiler optimisation.

If you are interested in a particular variable in gdb, you can delare the variable as "volatile" and recompile the code. This will make the compiler turn off compiler optimization for that variable.

volatile int quantity = 0;

gdb: how to print the current line or find the current line number?

Keep in mind that gdb is a powerful command -capable of low level instructions- so is tied to assembly concepts.

What you are looking for is called de instruction pointer, i.e:

The instruction pointer register points to the memory address which the processor will next attempt to execute. The instruction pointer is called ip in 16-bit mode, eip in 32-bit mode,and rip in 64-bit mode.

more detail here

all registers available on gdb execution can be shown with:

(gdb) info registers

with it you can find which mode your program is running (looking which of these registers exist)

then (here using most common register rip nowadays, replace with eip or very rarely ip if needed):

(gdb)info line *$rip

will show you line number and file source

(gdb) list *$rip

will show you that line with a few before and after

but probably

(gdb) frame

should be enough in many cases.

Why GDB jumps unpredictably between lines and prints variables as "<value optimized out>"?

When debugging optimized programs (which may be necessary if the bug doesn't show up in debug builds), you often have to understand assembly compiler generated.

In your particular case, return value of cpnd_find_exact_ckptinfo will be stored in the register which is used on your platform for return values. On ix86, that would be %eax. On x86_64: %rax, etc. You may need to google for '[your processor] procedure calling convention' if it's none of the above.

You can examine that register in GDB and you can set it. E.g. on ix86:

(gdb) p $eax
(gdb) set $eax = 0 

How do I pass a command line argument while starting up GDB in Linux?

Once gdb starts, you can run the program using "r args".

So if you are running your code by:

$ executablefile arg1 arg2 arg3 

Debug it on gdb by:

$ gdb executablefile  
(gdb) r arg1 arg2 arg3

How do I print the full value of a long string in gdb?

The printf command will print the complete strings:

(gdb) printf "%s\n", string

How do I remove a single breakpoint with GDB?

You can list breakpoints with:

info break

This will list all breakpoints. Then a breakpoint can be deleted by its corresponding number:

del 3

For example:

 (gdb) info b
 Num     Type           Disp Enb Address    What
  3      breakpoint     keep y   0x004018c3 in timeCorrect at my3.c:215
  4      breakpoint     keep y   0x004295b0 in avi_write_packet atlibavformat/avienc.c:513
 (gdb) del 3
 (gdb) info b
 Num     Type           Disp Enb Address    What
  4      breakpoint     keep y   0x004295b0 in avi_write_packet atlibavformat/avienc.c:513

Core dump file analysis

Steps to debug coredump using GDB:

Some generic help:

gdb start GDB, with no debugging les

gdb program begin debugging program

gdb program core debug coredump core produced by program

gdb --help describe command line options

  1. First of all, find the directory where the corefile is generated.

  2. Then use ls -ltr command in the directory to find the latest generated corefile.

  3. To load the corefile use

    gdb binary path of corefile

    This will load the corefile.

  4. Then you can get the information using the bt command.

    For a detailed backtrace use bt full.

  5. To print the variables, use print variable-name or p variable-name

  6. To get any help on GDB, use the help option or use apropos search-topic

  7. Use frame frame-number to go to the desired frame number.

  8. Use up n and down n commands to select frame n frames up and select frame n frames down respectively.

  9. To stop GDB, use quit or q.

Printing all global variables/local variables?

In addition, since info locals does not display the arguments to the function you're in, use

(gdb) info args

For example:

int main(int argc, char *argv[]) {
    argc = 6*7;    //Break here.
    return 0;

argc and argv won't be shown by info locals. The message will be "No locals."

Reference: info locals command.

How to install gdb (debugger) in Mac OSX El Capitan?

Just spent a good few days trying to get this to work on High Sierra 10.13.1. The gdb 8.1 version from homebrew would not work no matter what I tried. Ended up installing gdb 8.0.1 via macports and this miraculously worked (after jumping through all of the other necessary hoops related to codesigning etc).

One additional issue is that in Eclipse you will get extraneous single quotes around all of your program arguments which can be worked around by providing the arguments inside .gdbinit instead.

How can one see content of stack with GDB?

You need to use gdb's memory-display commands. The basic one is x, for examine. There's an example on the linked-to page that uses

gdb> x/4xw $sp

to print "four words (w ) of memory above the stack pointer (here, $sp) in hexadecimal (x)". The quotation is slightly paraphrased.

Can't connect to MySQL server on 'localhost' (10061) after Installation

In Windows 7

  1. press Windows+R it opens Run
  2. Enter services.msc
  3. Find out mysql right click and start
  4. if mysql was not found
    1. Run cmd as administrator
    2. goto C:\Program Files (x86)\MySQL\MySQL Server 5.6\bin directory(to go back use cd..) and type mysqld.exe --install
  5. follow step 3

That's all

Fastest JSON reader/writer for C++

Don't really know how they compare for speed, but the first one looks like the right idea for scaling to really big JSON data, since it parses only a small chunk at a time so they don't need to hold all the data in memory at once (This can be faster or slower depending on the library/use case)

How does the Python's range function work?

A "for loop" in most, if not all, programming languages is a mechanism to run a piece of code more than once.

This code:

for i in range(5):
    print i

can be thought of working like this:

i = 0
print i
i = 1
print i
i = 2
print i
i = 3
print i
i = 4
print i

So you see, what happens is not that i gets the value 0, 1, 2, 3, 4 at the same time, but rather sequentially.

I assume that when you say "call a, it gives only 5", you mean like this:

for i in range(5):
print a

this will print the last value that a was given. Every time the loop iterates, the statement a=i+1 will overwrite the last value a had with the new value.

Code basically runs sequentially, from top to bottom, and a for loop is a way to make the code go back and something again, with a different value for one of the variables.

I hope this answered your question.

Unexpected character encountered while parsing value

I faced similar error message in Xamarin forms when sending request to webApi to get a Token,

  • Make sure all keys (key : value) (ex.'username', 'password', 'grant_type') in the Json file are exactly what the webApi expecting, otherwise it fires this exception.

Unhandled Exception: Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0

What's the difference between Instant and LocalDateTime?

Table of all date-time types in Java, both modern and legacy


Instant and LocalDateTime are two entirely different animals: One represents a moment, the other does not.

  • Instant represents a moment, a specific point in the timeline.
  • LocalDateTime represents a date and a time-of-day. But lacking a time zone or offset-from-UTC, this class cannot represent a moment. It represents potential moments along a range of about 26 to 27 hours, the range of all time zones around the globe. A LocalDateTime value is inherently ambiguous.

Incorrect Presumption

LocalDateTime is rather date/clock representation including time-zones for humans.

Your statement is incorrect: A LocalDateTime has no time zone. Having no time zone is the entire point of that class.

To quote that class’ doc:

This class does not store or represent a time-zone. Instead, it is a description of the date, as used for birthdays, combined with the local time as seen on a wall clock. It cannot represent an instant on the time-line without additional information such as an offset or time-zone.

So Local… means “not zoned, no offset”.


enter image description here

An Instant is a moment on the timeline in UTC, a count of nanoseconds since the epoch of the first moment of 1970 UTC (basically, see class doc for nitty-gritty details). Since most of your business logic, data storage, and data exchange should be in UTC, this is a handy class to be used often.

Instant instant = ;  // Capture the current moment in UTC.


enter image description here

The class OffsetDateTime class represents a moment as a date and time with a context of some number of hours-minutes-seconds ahead of, or behind, UTC. The amount of offset, the number of hours-minutes-seconds, is represented by the ZoneOffset class.

If the number of hours-minutes-seconds is zero, an OffsetDateTime represents a moment in UTC the same as an Instant.


enter image description here

The ZoneOffset class represents an offset-from-UTC, a number of hours-minutes-seconds ahead of UTC or behind UTC.

A ZoneOffset is merely a number of hours-minutes-seconds, nothing more. A zone is much more, having a name and a history of changes to offset. So using a zone is always preferable to using a mere offset.


enter image description here

A time zone is represented by the ZoneId class.

A new day dawns earlier in Paris than in Montréal, for example. So we need to move the clock’s hands to better reflect noon (when the Sun is directly overhead) for a given region. The further away eastward/westward from the UTC line in west Europe/Africa the larger the offset.

A time zone is a set of rules for handling adjustments and anomalies as practiced by a local community or region. The most common anomaly is the all-too-popular lunacy known as Daylight Saving Time (DST).

A time zone has the history of past rules, present rules, and rules confirmed for the near future.

These rules change more often than you might expect. Be sure to keep your date-time library's rules, usually a copy of the 'tz' database, up to date. Keeping up-to-date is easier than ever now in Java 8 with Oracle releasing a Timezone Updater Tool.

Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

Time Zone = Offset + Rules of Adjustments

ZoneId z = ZoneId.of( “Africa/Tunis” ) ; 


enter image description here

Think of ZonedDateTime conceptually as an Instant with an assigned ZoneId.

ZonedDateTime = ( Instant + ZoneId )

To capture the current moment as seen in the wall-clock time used by the people of a particular region (a time zone):

ZonedDateTime zdt = z ) ;  // Pass a `ZoneId` object such as `ZoneId.of( "Europe/Paris" )`. 

Nearly all of your backend, database, business logic, data persistence, data exchange should all be in UTC. But for presentation to users you need to adjust into a time zone expected by the user. This is the purpose of the ZonedDateTime class and the formatter classes used to generate String representations of those date-time values.

ZonedDateTime zdt = instant.atZone( z ) ;
String output = zdt.toString() ;                 // Standard ISO 8601 format.

You can generate text in localized format using DateTimeFormatter.

DateTimeFormatter f = DateTimeFormatter.ofLocalizedDateTime( FormatStyle.FULL ).withLocale( Locale.CANADA_FRENCH ) ; 
String outputFormatted = zdt.format( f ) ;

mardi 30 avril 2019 à 23 h 22 min 55 s heure de l’Inde

LocalDate, LocalTime, LocalDateTime

Diagram showing only a calendar for a LocalDate.

Diagram showing only a clock for a LocalTime.

Diagram showing a calendar plus clock for a LocalDateTime.

The "local" date time classes, LocalDateTime, LocalDate, LocalTime, are a different kind of critter. The are not tied to any one locality or time zone. They are not tied to the timeline. They have no real meaning until you apply them to a locality to find a point on the timeline.

The word “Local” in these class names may be counter-intuitive to the uninitiated. The word means any locality, or every locality, but not a particular locality.

So for business apps, the "Local" types are not often used as they represent just the general idea of a possible date or time not a specific moment on the timeline. Business apps tend to care about the exact moment an invoice arrived, a product shipped for transport, an employee was hired, or the taxi left the garage. So business app developers use Instant and ZonedDateTime classes most commonly.

So when would we use LocalDateTime? In three situations:

  • We want to apply a certain date and time-of-day across multiple locations.
  • We are booking appointments.
  • We have an intended yet undetermined time zone.

Notice that none of these three cases involve a single certain specific point on the timeline, none of these are a moment.

One time-of-day, multiple moments

Sometimes we want to represent a certain time-of-day on a certain date, but want to apply that into multiple localities across time zones.

For example, "Christmas starts at midnight on the 25th of December 2015" is a LocalDateTime. Midnight strikes at different moments in Paris than in Montréal, and different again in Seattle and in Auckland.

LocalDate ld = LocalDate.of( 2018 , Month.DECEMBER , 25 ) ;
LocalTime lt = LocalTime.MIN ;   // 00:00:00
LocalDateTime ldt = LocalDateTime.of( ld , lt ) ;  // Christmas morning anywhere. 

Another example, "Acme Company has a policy that lunchtime starts at 12:30 PM at each of its factories worldwide" is a LocalTime. To have real meaning you need to apply it to the timeline to figure the moment of 12:30 at the Stuttgart factory or 12:30 at the Rabat factory or 12:30 at the Sydney factory.

Booking appointments

Another situation to use LocalDateTime is for booking future events (ex: Dentist appointments). These appointments may be far enough out in the future that you risk politicians redefining the time zone. Politicians often give little forewarning, or even no warning at all. If you mean "3 PM next January 23rd" regardless of how the politicians may play with the clock, then you cannot record a moment – that would see 3 PM turn into 2 PM or 4 PM if that region adopted or dropped Daylight Saving Time, for example.

For appointments, store a LocalDateTime and a ZoneId, kept separately. Later, when generating a schedule, on-the-fly determine a moment by calling LocalDateTime::atZone( ZoneId ) to generate a ZonedDateTime object.

ZonedDateTime zdt = ldt.atZone( z ) ;  // Given a date, a time-of-day, and a time zone, determine a moment, a point on the timeline.

If needed, you can adjust to UTC. Extract an Instant from the ZonedDateTime.

Instant instant = zdt.toInstant() ;  // Adjust from some zone to UTC. Same moment, same point on the timeline, different wall-clock time.

Unknown zone

Some people might use LocalDateTime in a situation where the time zone or offset is unknown.

I consider this case inappropriate and unwise. If a zone or offset is intended but undetermined, you have bad data. That would be like storing a price of a product without knowing the intended currency (dollars, pounds, euros, etc.). Not a good idea.

All date-time types

For completeness, here is a table of all the possible date-time types, both modern and legacy in Java, as well as those defined by the SQL standard. This might help to place the Instant & LocalDateTime classes in a larger context.

Table of all date-time types in Java (both modern & legacy) as well as SQL standard.

Notice the odd choices made by the Java team in designing JDBC 4.2. They chose to support all the java.time times… except for the two most commonly used classes: Instant & ZonedDateTime.

But not to worry. We can easily convert back and forth.

Converting Instant.

// Storing
OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC ) ;
myPreparedStatement.setObject( … , odt ) ;

// Retrieving
OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;
Instant instant = odt.toInstant() ;

Converting ZonedDateTime.

// Storing
OffsetDateTime odt = zdt.toOffsetDateTime() ;
myPreparedStatement.setObject( … , odt ) ;

// Retrieving
OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;
ZoneId z = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime zdt = odt.atZone( z ) ; 

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

Table of which java.time library to use with which version of Java or Android

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

How to efficiently count the number of keys/properties of an object in JavaScript?

For those that have Ext JS 4 in their project you can do:


The advantage of this is that it'll work on all Ext compatible browsers (IE6-IE8 included), however, I believe the running time is no better than O(n) though, as with other suggested solutions.

How do I clear my local working directory in Git?

You could create a commit which contains an empty working copy.

This is a generally safe, non-destructive approach because it does not involve the use of any brute-force reset mechanisms. First you hide all managed content with git checkout empty, then you are free to manually review and remove whatever unmanaged content remains.

## create a stand-alone, tagged, empty commit
true | git mktree | xargs git commit-tree | xargs git tag empty

## clear the working copy
git checkout empty

Your working copy should now be clear of any managed content. All that remains are unmanaged files and the .git folder itself.

To re-populate your working copy...

git checkout master ## or whatever branch you will be using

If you're a forward thinking individual, you might start your repository off on the right foot by basing everything on an initial empty commit...

git init
git commit --allow-empty --allow-empty-message -m ""
git tag empty

There are various uses for a tagged empty worktree. My favorite at the moment is to depopulate the root under a set of git worktree subfolders.

jquery onclick change css background image

I think this should be:

$('.home').click(function() {
     $(this).css('background', 'url(images/tabs3.png)');

and remove this:

<div class="home" onclick="function()">
     //-----------^^^^^^^^^^^^^^^^^^^^---------no need for this

You have to make sure you have a correct path to your image.

How do I create a timeline chart which shows multiple events? Eg. Metallica Band members timeline on wiki

As mentioned in the earlier comment, stacked bar chart does the trick, though the data needs to be setup differently.(See image below)

Duration column = End - Start

  1. Once done, plot your stacked bar chart using the entire data.
  2. Mark start and end range to no fill.
  3. Right click on the X Axis and change Axis options manually. (This did cause me some issues, till I realized I couldn't manipulate them to enter dates, :) yeah I am newbie, excel masters! :))

enter image description here

Set variable with multiple values and use IN

Use a Temp Table or a Table variable, e.g.

select 'A' as [value]
into #tmp
select 'B'
select 'C'

and then

FROM    foo 
WHERE   myField IN (select [value] from #tmp) 


FROM foo f INNER JOIN #tmp t ON f.myField = t.[value]

Insert null/empty value in sql datetime column by default

if there is no value inserted, the default value should be null,empty

In the table definition, make this datetime column allows null, be not defining NOT NULL:

DateTimeColumn DateTime,


Then , just insert NULL in this column:

INSERT INTO Table(name, datetimeColumn, ...)
VALUES('foo bar', NULL, ..);

Or, you can make use of the DEFAULT constaints:

DateTimeColumn DateTime DEFAULT NULL,

Then you can ignore it completely in the INSERT statement and it will be inserted withe the NULL value:

INSERT INTO Table(name, ...)
VALUES('foo bar', ..);

Iterating a JavaScript object's properties using jQuery

Late, but can be done by using Object.keys like,

var a={key1:'value1',key2:'value2',key3:'value3',key4:'value4'},_x000D_
var keys = Object.keys(a);_x000D_
   str+= '<li>'+keys[i]+' : '+a[keys[i]]+'</li>';_x000D_
<ul id="object-keys"></ul>

Find the min/max element of an array in JavaScript

if you have complex object, you could use sort....such as: if I want get item which contains MAX/MIN value of below objs.

var objs= [

I will do a sort:

objs.sort(function(a, b){return a.value-b.value});

Then: objs[0] is the MIN, objs[objs.length-1] is the MAX.

How to format a numeric column as phone number in SQL

Solutions that use SUBSTRING and concatenation + are nearly independent of RDBMS. Here is a short solution that is specific to SQL Server:

declare @x int = 123456789
select stuff(stuff(@x, 4, 0, '-'), 8, 0, '-')

What is the difference between DSA and RSA?

Btw, you cannot encrypt with DSA, only sign. Although they are mathematically equivalent (more or less) you cannot use DSA in practice as an encryption scheme, only as a digital signature scheme.

Unable to open debugger port in IntelliJ

You must set CHMOD +x (execute for *.sh or *.bat files). For example, I am using macOS

cd /Users/donhuvy/Documents/tools/apache-tomcat-9.0.12/bin
sudo chmod +x *.sh

Then IntelliJ IDEA, and Apache Tomcat running or debugging just good.

ARM compilation error, VFP registers used by executable, not object file

I encountered the issue using Atollic for ARM on STM32F4 (I guess it applies to all STM32 with FPU).

Using SW floating point didn't worked well for me (thus compiling correctly).

When STM32cubeMX generates code for TrueStudio (Atollic), it doesn't set an FPU unit in C/C++ build settings (not sure about generated code for other IDEs).

Set a FPU in "Target" for (under project Properties build settings):

  • Assembler
  • C Compiler
  • C Linker

Then you have the choice to Mix HW/SW fp or use HW.

Generated command lines are added with this for the intended target:

-mfloat-abi=hard -mfpu=fpv4-sp-d16

HashMap get/put complexity

It depends on many things. It's usually O(1), with a decent hash which itself is constant time... but you could have a hash which takes a long time to compute, and if there are multiple items in the hash map which return the same hash code, get will have to iterate over them calling equals on each of them to find a match.

In the worst case, a HashMap has an O(n) lookup due to walking through all entries in the same hash bucket (e.g. if they all have the same hash code). Fortunately, that worst case scenario doesn't come up very often in real life, in my experience. So no, O(1) certainly isn't guaranteed - but it's usually what you should assume when considering which algorithms and data structures to use.

In JDK 8, HashMap has been tweaked so that if keys can be compared for ordering, then any densely-populated bucket is implemented as a tree, so that even if there are lots of entries with the same hash code, the complexity is O(log n). That can cause issues if you have a key type where equality and ordering are different, of course.

And yes, if you don't have enough memory for the hash map, you'll be in trouble... but that's going to be true whatever data structure you use.

Synchronously waiting for an async operation, and why does Wait() freeze the program here

Here is what I did

private void myEvent_Handler(object sender, SomeEvent e)
  // I dont know how many times this event will fire
  Task t = new Task(() =>
    if (something == true) 

working great and not blocking UI thread

How do I display a wordpress page content?

@Marc B Thanks for the comment. Helped me discover this:

<?php if ( have_posts() ) : while ( have_posts() ) : the_post();
endwhile; else: ?>
<p>Sorry, no posts matched your criteria.</p>
<?php endif; ?>

Select from table by knowing only date without time (ORACLE)

Convert your date column to the correct format and compare:

SELECT * From my_table WHERE to_char(my_table.my_date_col,'MM/dd/yyyy') = '8/3/2010'

This part


Will result in string '8/3/2010'

Eclipse copy/paste entire line keyboard shortcut

The Ctrl+Alt+Down / Ctrl+Alt+Up flips my screen so I overrode that in the Eclipse shortcuts via Window => Preferences => General => Keys. Search for "dupl" to find the Duplicate Lines command. I overrode the default and chose Ctrl+Shift+D. For me, that's easy to remember just like Ctrl+D to delete lines

Is there anything like .NET's NotImplementedException in Java?

No there isn't and it's probably not there, because there are very few valid uses for it. I would think twice before using it. Also, it is indeed easy to create yourself.

Please refer to this discussion about why it's even in .NET.

I guess UnsupportedOperationException comes close, although it doesn't say the operation is just not implemented, but unsupported even. That could imply no valid implementation is possible. Why would the operation be unsupported? Should it even be there? Interface segregation or Liskov substitution issues maybe?

If it's work in progress I'd go for ToBeImplementedException, but I've never caught myself defining a concrete method and then leave it for so long it makes it into production and there would be a need for such an exception.

Convert Uri to String and String to Uri

You can use Drawable instead of Uri.

   ImageView iv=(ImageView)findViewById(;
   String pathName = "/external/images/media/470939"; 
   Drawable image = Drawable.createFromPath(pathName);

This would work.

How to remove the first Item from a list?

you would just do this

l = [0, 1, 2, 3, 4]

or l = l[1:]

Pros and Cons

Using pop you can retrieve the value

say x = l.pop(0) x would be 0

Bootstrap 4 multiselect dropdown

Because the bootstrap-select is a bootstrap component and therefore you need to include it in your code as you did for your V3

NOTE: this component only works in since version 1.13.0

<link rel="stylesheet" href="">_x000D_
<link rel="stylesheet" href="" />_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<select class="selectpicker" multiple data-live-search="true">_x000D_

SQL How to Select the most recent date item

Not sure of exact syntax (you use varchar2 type which means not SQL Server hence TOP) but you can use the LIMIT keyword for MySQL:

Select * FROM test_table WHERE user_id = value

Or rownum in Oracle

     (Select rownum as rnum, * FROM test_table WHERE user_id = value ORDER BY DATE_ADDED DESC)
 WHERE rnum = 1

If DB2, I'm not sure whether it's TOP, LIMIT or rownum...

Fastest way to count number of occurrences in a Python list

Combination of lambda and map function can also do the job:

list_ = ['a', 'b', 'b', 'c']
sum(map(lambda x: x=="b", list_))

How to get week numbers from dates?

Actually, I think you may have discovered a bug in the week(...) function, or at least an error in the documentation. Hopefully someone will jump in and explain why I am wrong.

Looking at the code:

> week
function (x) 
yday(x)%/%7 + 1
<environment: namespace:lubridate>

The documentation states:

Weeks is the number of complete seven day periods that have occured between the date and January 1st, plus one.

But since Jan 1 is the first day of the year (not the zeroth), the first "week" will be a six day period. The code should (??) be

(yday(x)-1)%/%7 + 1

NB: You are using week(...) in the data.table package, which is the same code as lubridate::week except it coerces everything to integer rather than numeric for efficiency. So this function has the same problem (??).

Detecting touch screen devices with Javascript

A helpful blog post on the subject, linked to from within the Modernizr source for detecting touch events. Conclusion: it's not possible to reliably detect touchscreen devices from Javascript.

Converting string format to datetime in mm/dd/yyyy

The following works for me.

string strToday = DateTime.Today.ToString("MM/dd/yyyy");

How do you make a HTTP request with C++?

Updated answer for April, 2020:

I've had a lot of success, recently, with cpp-httplib (both as a client and a server). It's mature and its approximate, single-threaded RPS is around 6k.

On more of the bleeding edge, there's a really promising framework, cpv-framework, that can get around 180k RPS on two cores (and will scale well with the number of cores because it's based on the seastar framework, which powers the fastest DBs on the planet, scylladb).

However, cpv-framework is still relatively immature; so, for most uses, I highly recommend cpp-httplib.

This recommendation replaces my previous answer (8 years ago).

How to commit changes to a new branch

git checkout -b your-new-branch

git add <files>

git commit -m <message>

First, checkout your new branch. Then add all the files you want to commit to staging. Lastly, commit all the files you just added. You might want to do a git push origin your-new-branch afterward so your changes show up on the remote.

Global Git ignore

If you use Unix system, you can solve your problem in two commands. Where the first initialize configs and the second alters file with a file to ignore.

$ git config --global core.excludesfile ~/.gitignore
$ echo '.idea' >> ~/.gitignore

Joining 2 SQL SELECT result sets into one

SELECT table1.col_a, table1.col_b, table2.col_c 
  FROM table1 
  INNER JOIN table2 ON table1.col_a = table2.col_a

The R %in% operator

You can use all

> all(1:6 %in% 0:36)
[1] TRUE
> all(1:60 %in% 0:36)

On a similar note, if you want to check whether any of the elements is TRUE you can use any

> any(1:6 %in% 0:36)
[1] TRUE
> any(1:60 %in% 0:36)
[1] TRUE
> any(50:60 %in% 0:36)

Notice: Undefined offset: 0 in

As explained it happens because there is no data in the $cur_votes[0] and hence it throws an error.

To ensure your code works fine, before performing "$votes_up = $cur_votes[0]+1;" echo the $cur_votes[0] value to see if there is any value stored or not.

Surely, there is no value stored.

How to construct a std::string from a std::vector<char>?

Just for completeness, another way is std::string(&v[0]) (although you need to ensure your string is null-terminated and std::string( is generally to be preferred.

The difference is that you can use the former technique to pass the vector to functions that want to modify the buffer, which you cannot do with .data().

Using Lato fonts in my css (@font-face)

Well, you're missing the letter 'd' in url("~/fonts/Lato-Bol.ttf"); - but assuming that's not it, I would open up your page with developer tools in Chrome and make sure there's no errors loading any of the files (you would probably see an issue in the JavaScript console, or you can check the Network tab and see if anything is red).

(I don't see anything obviously wrong with the code you have posted above)

Other things to check: 1) Are you including your CSS file in your html above the lines where you are trying to use the font-family style? 2) What do you see in the CSS panel in the developer tools for that div? Is font-family: lato crossed out?

What is the difference between Normalize.css and Reset CSS?

resetting seems a necessity to meet custom design specifications, especially on complex, non-boilerplate type design projects. It sounds as though normalizing is a good way to proceed with purely web programming in mind, but oftentimes websites are a marriage between web programming and UI/UX design rules.

Connecting to remote MySQL server using PHP

  • firewall of the server must be set-up to enable incomming connections on port 3306
  • you must have a user in MySQL who is allowed to connect from % (any host) (see manual for details)

The current problem is the first one, but right after you resolve it you will likely get the second one.

Basic text editor in command prompt?

MS-DOS Editor (or just edit) is a 16-bit text editor that is still included with 32-bit versions of Windows XP, Vista, 7, 8 and 8.1. It can edit files upto 65,279 lines long and has mouse support. Being an 16-bit DOS editor, it cannot run directly on 64-bit versions of Windows. It can be launched by typing edit at the command prompt.

Invariant Violation: Objects are not valid as a React child

I just got the same error but due to a different mistake: I used double braces like:


to insert the value of count instead of the correct:


which the compiler presumably turned into {{count: count}}, i.e. trying to insert an Object as a React child.

MySql Inner Join with WHERE clause

You are using two WHERE clauses but only one is allowed. Use it like this:

SELECT table1.f_id FROM table1
INNER JOIN table2 ON table2.f_id = table1.f_id
  table1.f_com_id = '430'
  AND table1.f_status = 'Submitted'
  AND table2.f_type = 'InProcess'

In SQL Server, how do I generate a CREATE TABLE statement for a given table?

If the application you are generating the scripts from is a .NET application, you may want to look into using SMO (Sql Management Objects). Reference this SQL Team link on how to use SMO to script objects.

How do I delete multiple rows with different IDs?

Delete from BA_CITY_MASTER where CITY_NAME in (select CITY_NAME from BA_CITY_MASTER group by CITY_NAME having count(CITY_NAME)>1);

How do I merge a specific commit from one branch into another in Git?


The other way to move introduced work from one branch to another is to cherry-pick it. A cherry-pick in Git is like a rebase for a single commit. It takes the patch that was introduced in a commit and tries to reapply it on the branch you’re currently on. This is useful if you have a number of commits on a topic branch and you want to integrate only one of them, or if you only have one commit on a topic branch and you’d prefer to cherry-pick it rather than run rebase. For example, suppose you have a project that looks like this:

enter image description here

If you want to pull commit e43a6 into your master branch, you can run

$ git cherry-pick e43a6
Finished one cherry-pick.
[master]: created a0a41a9: "More friendly message when locking the index fails."
 3 files changed, 17 insertions(+), 3 deletions(-)

This pulls the same change introduced in e43a6, but you get a new commit SHA-1 value, because the date applied is different. Now your history looks like this:

enter image description here

Now you can remove your topic branch and drop the commits you didn’t want to pull in.

How to replace all special character into a string using C#

Also, It can be done with LINQ

var str = "Hello@Hello&Hello(Hello)";
var characters = str.Select(c => char.IsLetter(c) ? c : ',')).ToArray();             
var output = new string(characters);

Is there any kind of hash code function in JavaScript?


you can use Es6 symbol to create unique key and access object. Every symbol value returned from Symbol() is unique. A symbol value may be used as an identifier for object properties; this is the data type's only purpose.

var obj = {};

obj[Symbol('a')] = 'a';
obj[Symbol.for('b')] = 'b';
obj['c'] = 'c';
obj.d = 'd';

How to read from a text file using VBScript?

Use first the method OpenTextFile, and then...

either read the file at once with the method ReadAll:

Set file = fso.OpenTextFile("C:\test.txt", 1)
content = file.ReadAll

or line by line with the method ReadLine:

Set dict = CreateObject("Scripting.Dictionary")
Set file = fso.OpenTextFile ("c:\test.txt", 1)
row = 0
Do Until file.AtEndOfStream
  line = file.Readline
  dict.Add row, line
  row = row + 1


'Loop over it
For Each line in dict.Items
  WScript.Echo line

The project cannot be built until the build path errors are resolved.

None of the other answers worked for me. Even after fixing my build path issues, doing a refresh, clean, rebuild, and restart (of both eclipse and the computer), I was still getting the little red exclamation point.

I fixed it by closing the project (right-click, close project) and reopening it (double-click the closed project), which seemed to force eclipse to "notice" that the build path problems had been corrected.

Is there an equivalent of 'which' on the Windows command line?

None of the Win32 ports of Unix which that I could find on the Internet are satistactory, because they all have one or more of these shortcomings:

  • No support for Windows PATHEXT variable. (Which defines the list of extensions implicitely added to each command before scanning the path, and in which order.) (I use a lot of tcl scripts, and no publicly available which tool could find them.)
  • No support for cmd.exe code pages, which makes them display paths with non-ascii characters incorrectly. (I'm very sensitive to that, with the ç in my first name :-))
  • No support for the distinct search rules in cmd.exe and the PowerShell command line. (No publicly available tool will find .ps1 scripts in a PowerShell window, but not in a cmd window!)

So I eventually wrote my own which, that suports all the above correctly.

Available there:

How to get character array from a string?

Array.prototype.slice will do the work as well.

const result ="Hello world!");_x000D_

Add items in array angular 4

Push object into your array. Try this:

export class FormComponent implements OnInit {
    name: string;
    empoloyeeID : number;
    empList: Array<{name: string, empoloyeeID: number}> = []; 
    constructor() {}
    ngOnInit() {}
        this.empList.push({ name:, empoloyeeID: this.empoloyeeID }); = "";
        this.empoloyeeID = 0;

Warning - Build path specifies execution environment J2SE-1.4

The actual cause of this warning is that you have configured your project to run with an earlier JRE version then you have installed. Generally this occurs whenever you use old projects with newer JREs.

This will likely cause no trouble at all. But if you want to be really on the save side, you should install the correct, old JDK. You can find them here:

If you then restart eclipse you can go into Window > Preferences > Java > Installed JREs > Execution Environments and set for in your case J2SE-1.4 the [perfect match] as eclipse calls it.

How to build an APK file in Eclipse?

Just right click on your project and then go to

*Export -> Android -> Export Android Application -> YOUR_PROJECT_NAME -> Create new key store path -> Fill the detail -> Set the .apk location -> Now you can get your .apk file*

Install it in your mobile.

PostgreSQL: Which version of PostgreSQL am I running?

The accepted answer is great, but if you need to interact programmatically with PostgreSQL version maybe it's better to do:

SELECT current_setting('server_version_num'); -- Returns 90603 (9.6.3)
-- Or using SHOW command:
SHOW server_version_num; -- Returns 90603 too

It will return server version as an integer. This is how server version is tested in PostgreSQL source, e.g.:

 * This is a C code from pg_dump source.
 * It will do something if PostgreSQL remote version (server) is lower than 9.1.0
if (fout->remoteVersion < 90100)
     * Do something...

More info here and here.

Maven Could not resolve dependencies, artifacts could not be resolved

Looks like you are missing some Maven repos. Ask for your friend's .m2/settings.xml, and you'll probably want to update the POM to include the repositories there.

--edit: after some quick googling, try adding this to your POM:

    <name>SpringSource Enterprise Bundle Repository - SpringSource Bundle Releases</name>
    <name>SpringSource Enterprise Bundle Repository - External Bundle Releases</name>

Change bar plot colour in geom_bar with ggplot2 in r

If you want all the bars to get the same color (fill), you can easily add it inside geom_bar.

ggplot(data=df, aes(x=c1+c2/2, y=c3)) + 
geom_bar(stat="identity", width=c2, fill = "#FF6666")

enter image description here

Add fill = the_name_of_your_var inside aes to change the colors depending of the variable :

c4 = c("A", "B", "C")
df = cbind(df, c4)
ggplot(data=df, aes(x=c1+c2/2, y=c3, fill = c4)) + 
geom_bar(stat="identity", width=c2)

enter image description here

Use scale_fill_manual() if you want to manually the change of colors.

ggplot(data=df, aes(x=c1+c2/2, y=c3, fill = c4)) + 
geom_bar(stat="identity", width=c2) + 
scale_fill_manual("legend", values = c("A" = "black", "B" = "orange", "C" = "blue"))

enter image description here

Open a local HTML file using in Chrome

window.location.href = 'file://///fileserver/upload/Old_Upload/05_06_2019/THRESHOLD/BBH/Look/chrs/Delia';

Nothing Worked for me.

Javascript form validation with password confirming

add this to your form:

<form  id="regform" action="insert.php" method="post">

add this to your function:

    function myFunction() {
        var pass1 = document.getElementById("pass1").value;
        var pass2 = document.getElementById("pass2").value;
        if (pass1 != pass2) {
            //alert("Passwords Do not match");
            document.getElementById("pass1").style.borderColor = "#E34234";
            document.getElementById("pass2").style.borderColor = "#E34234";
        else {
            alert("Passwords Match!!!");

"call to undefined function" error when calling class method


I stumbled upon this error today while testing a simple script. I am not using "class" function though so it take it with grain of salt. I was calling function before its definition & declaration ...something like this

       catch (exception $e)
            echo "$e->getMessage()";

       function foo(){
                       echo "blah blah blah";

so php was throwing me error "call to undefined function ".

This kinda seem classic programming error but may help someone in need of clue.

Fatal error: Call to undefined function socket_create()

I got this error when my .env file was not set up properly. Make sure you have a .env file with valid database login credentials.

How to check if element has any children in Javascript?

You could also do the following:

if (element.innerHTML.trim() !== '') {
    // It has at least one

This uses the trim() method to treat empty elements which have only whitespaces (in which case hasChildNodes returns true) as being empty.

NB: The above method doesn't filter out comments. (so a comment would classify a a child)

To filter out comments as well, we could make use of the read-only Node.nodeType property where Node.COMMENT_NODE (A Comment node, such as <!-- … -->) has the constant value - 8

if (element.firstChild?.nodeType !== 8 && element.innerHTML.trim() !== '' {
   // It has at least one

let divs = document.querySelectorAll('div');
for(element of divs) {
  if (element.firstChild?.nodeType !== 8 && element.innerHTML.trim() !== '') {
   console.log('has children')
  } else { console.log('no children') }
<div><span>An element</span>
<div>some text</div>
<div>     </div> <!-- whitespace -->
<div><!-- A comment --></div>

Uploading Files in without using the FileUpload server control

Yes you can achive this by ajax post method. on server side you can use httphandler. So we are not using any server controls as per your requirement.

with ajax you can show the upload progress also.

you will have to read the file as a inputstream.

using (FileStream fs = File.Create("D:\\_Workarea\\" + fileName))
        Byte[] buffer = new Byte[32 * 1024];
        int read = context.Request.GetBufferlessInputStream().Read(buffer, 0, buffer.Length);
        while (read > 0)
            fs.Write(buffer, 0, read);
            read = context.Request.GetBufferlessInputStream().Read(buffer, 0, buffer.Length);

Sample Code

function sendFile(file) {              
            url: 'handler/FileUploader.ashx?FileName=' +, //server script to process data
            type: 'POST',
            xhr: function () {
                myXhr = $.ajaxSettings.xhr();
                if (myXhr.upload) {
                    myXhr.upload.addEventListener('progress', progressHandlingFunction, false);
                return myXhr;
            success: function (result) {                    
                //On success if you want to perform some tasks.
            data: file,
            cache: false,
            contentType: false,
            processData: false
        function progressHandlingFunction(e) {
            if (e.lengthComputable) {
                var s = parseInt((e.loaded / * 100);
                $("#progress" + currFile).text(s + "%");
                $("#progbarWidth" + currFile).width(s + "%");
                if (s == 100) {

How to print a list in Python "nicely"

import json
some_list = ['one', 'two', 'three', 'four']
print(json.dumps(some_list, indent=4))



MySQL Orderby a number, Nulls last

Something like

SELECT * FROM tablename where visible=1 ORDER BY COALESCE(position, 999999999) ASC, id DESC

Replace 999999999 with what ever the max value for the field is

How to convert const char* to char* in C?

To be safe you don't break stuff (for example when these strings are changed in your code or further up), or crash you program (in case the returned string was literal for example like "hello I'm a literal string" and you start to edit it), make a copy of the returned string.

You could use strdup() for this, but read the small print. Or you can of course create your own version if it's not there on your platform. read stream to byte[]

Here's a clean solution:

private byte[] downloadUrl(URL toDownload) {
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

    try {
        byte[] chunk = new byte[4096];
        int bytesRead;
        InputStream stream = toDownload.openStream();

        while ((bytesRead = > 0) {
            outputStream.write(chunk, 0, bytesRead);

    } catch (IOException e) {
        return null;

    return outputStream.toByteArray();

Is there a way to collapse all code blocks in Eclipse?

The question is a bit old, but let me add a different approach. In addition to the above hot-key approaches, there are default preference settings that can be toggled.

As of Eclipse Galileo (and definitely in my Eclipse Version: Indigo Service Release 2 Build id: 20120216-1857) language specific preferences can open up new files to edit which are already collapsed or expanded.

Here is a link to Eclipse Galileo online docs showing the feature for C/C++: .

In my Eclipse Indigo I can open the Folding Preferences window via : menu/ Window/ Preferences/ Java/ Editor/ Folding and set all options on so I can open files by default that are completely collapsed.

Convert INT to FLOAT in SQL

In oracle db there is a trick for casting int to float (I suppose, it should also work in mysql):

select myintfield + 0.0 as myfloatfield from mytable

While @Heximal's answer works, I don't personally recommend it.

This is because it uses implicit casting. Although you didn't type CAST, either the SUM() or the 0.0 need to be cast to be the same data-types, before the + can happen. In this case the order of precedence is in your favour, and you get a float on both sides, and a float as a result of the +. But SUM(aFloatField) + 0 does not yield an INT, because the 0 is being implicitly cast to a FLOAT.

I find that in most programming cases, it is much preferable to be explicit. Don't leave things to chance, confusion, or interpretation.

If you want to be explicit, I would use the following.

CAST(SUM( AS FLOAT) * cp.price
-- using MySQL CAST FLOAT  requires 8.0

I won't discuss whether NUMERIC or FLOAT *(fixed point, instead of floating point)* is more appropriate, when it comes to rounding errors, etc. I'll just let you google that if you need to, but FLOAT is so massively misused that there is a lot to read about the subject already out there.

You can try the following to see what happens...

CAST(SUM( AS NUMERIC(10,4)) * CAST(cp.price AS NUMERIC(10,4))

If Radio Button is selected, perform validation on Checkboxes

function validateDays() {
    if (document.getElementById("option1").checked == true) {
        alert("You have selected Option 1");
    else if (document.getElementById("option2").checked == true) {
        alert("You have selected Option 2");
    else if (document.getElementById("option3").checked == true) {
        alert("You have selected Option 3");
    else {
        // DO NOTHING

Adding new line of data to TextBox

Following are the ways

  1. From the code (the way you have mentioned) ->

    displayBox.Text += sent + "\r\n";


    displayBox.Text += sent + Environment.NewLine;
  2. From the UI
    a) WPF

    Set TextWrapping="Wrap" and AcceptsReturn="True"   

    Press Enter key to the textbox and new line will be created

    b) Winform text box

    Set TextBox.MultiLine and TextBox.AcceptsReturn to true

Scanning Java annotations at runtime

With Spring you can also just write the following using AnnotationUtils class. i.e.:

Class<?> clazz = AnnotationUtils.findAnnotationDeclaringClass(Target.class, null);

For more details and all different methods check official docs:

parsing JSONP $http.jsonp() response in angular.js

This should work just fine for you, so long as the function jsonp_callback is visible in the global scope:

function jsonp_callback(data) {
    // returning from async callbacks is (generally) meaningless

var url = "";


Full demo: (disclaimer: I've never written any AngularJS code before)

How to create multiple class objects with a loop in python?

Creating a dictionary as it has mentioned, but in this case each key has the name of the object name that you want to create. Then the value is set as the class you want to instantiate, see for example:

class MyClass:
   def __init__(self, name): = name
       self.checkme = 'awesome {}'.format(

instanceNames = ['red', 'green', 'blue']

# Here you use the dictionary
holder = {name: MyClass(name=name) for name in instanceNames}

Then you just call the holder key and you will have all the properties and methods of your class available for you.



'awesome red'

How can I show/hide component with JSF?

You should use <h:panelGroup ...> tag with attribute rendered. If you set true to rendered, the content of <h:panelGroup ...> won't be shown. Your XHTML file should have something like this:

<h:panelGroup rendered="#{userBean.showPassword}">
    <h:outputText id="password" value="#{userBean.password}"/>

import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
public class UserBean implements Serializable{
    private boolean showPassword = false;
    private String password = "";

    public boolean isShowPassword(){
        return showPassword;
    public void setPassword(password){
        this.password = password;
    public String getPassword(){
        return this.password;

SQL RANK() over PARTITION on joined tables


How can I read comma separated values from a text file in Java?

Use BigDecimal, not double

The Answer by adatapost is right about using String::split but wrong about using double to represent your longitude-latitude values. The float/Float and double/Double types use floating-point technology which trades away accuracy for speed of execution.

Instead use BigDecimal to correctly represent your lat-long values.

Use Apache Commons CSV library

Also, best to let a library such as Apache Commons CSV perform the chore of reading and writing CSV or Tab-delimited files.

Example app

Here is a complete example app using that Commons CSV library. This app writes then reads a data file. It uses String::split for the writing. And the app uses BigDecimal objects to represent your lat-long values.

package work.basil.example;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVPrinter;
import org.apache.commons.csv.CSVRecord;

import java.math.BigDecimal;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

public class LatLong
    //----------|  Write  |-----------------------------
    public void write ( final Path path )
        List < String > inputs =
                        "28.515046280572285,77.38258838653564" ,
                        "28.51430151808072,77.38336086273193" ,
                        "28.513566177802456,77.38413333892822" ,
                        "28.512830832397192,77.38490581512451" ,
                        "28.51208605426073,77.3856782913208" ,
                        "28.511341270865113,77.38645076751709" );

        // Use try-with-resources syntax to auto-close the `CSVPrinter`.
        try ( final CSVPrinter printer = CSVFormat.RFC4180.withHeader( "latitude" , "longitude" ).print( path , StandardCharsets.UTF_8 ) ; )
            for ( String input : inputs )
                String[] fields = input.split( "," );
                printer.printRecord( fields[ 0 ] , fields[ 1 ] );
        } catch ( IOException e )

    //----------|  Read  |-----------------------------
    public void read ( Path path )
        // TODO: Add a check for valid file existing.

            // Read CSV file.
            BufferedReader reader = Files.newBufferedReader( path );
            Iterable < CSVRecord > records = CSVFormat.RFC4180.withFirstRecordAsHeader().parse( reader );
            for ( CSVRecord record : records )
                BigDecimal latitude = new BigDecimal( record.get( "latitude" ) );
                BigDecimal longitude = new BigDecimal( record.get( "longitude" ) );
                System.out.println( "lat: " + latitude + " | long: " + longitude );
        } catch ( IOException e )

    //----------|  Main  |-----------------------------
    public static void main ( String[] args )
        LatLong app = new LatLong();

        // Write
        Path pathOutput = Paths.get( "/Users/basilbourque/lat-long.csv" );
        app.write( pathOutput );
        System.out.println( "Writing file: " + pathOutput );

        // Read
        Path pathInput = Paths.get( "/Users/basilbourque/lat-long.csv" ); pathInput );

        System.out.println( "Done writing & reading lat-long data file. " + );


NodeJS/express: Cache and 304 status code

I had the same problem in Safari and Chrome (the only ones I've tested) but I just did something that seems to work, at least I haven't been able to reproduce the problem since I added the solution. What I did was add a metatag to the header with a generated timstamp. Doesn't seem right but it's simple :)

<meta name="304workaround" content="2013-10-24 21:17:23">

Update P.S As far as I can tell, the problem disappears when I remove my node proxy (by proxy i mean both express.vhost and http-proxy module), which is weird...

Does Java read integers in little endian or big endian?

I would read the bytes one by one, and combine them into a long value. That way you control the endianness, and the communication process is transparent.

How to remove jar file from local maven repository which was added with install:install-file?

I faced the same problem, went through all the suggestions above, but nothing worked. Finally I deleted both .m2 and .ivy folder and it worked for me.

Read line by line in bash script

If you want to use each of the lines of the file as command-line params for your application you can use the xargs command.

xargs -a <params_file> <command>

A params file with:


and the file

import sys
print sys.argv

The execution of

xargs -a params ./

gives the result:

['./', 'a', 'b', 'c', 'd']

JQuery get data from JSON array

try this

$.getJSON(url, function(data){
    $.each(, function (index, value) {

Getting DOM elements by classname

DOMDocument is slow to type and phpQuery has bad memory leak issues. I ended up using:

To select a class:

include 'includes/simple_html_dom.php';

$doc = str_get_html($html);
$href = $doc->find('.lastPage')[0]->href;

I hope this helps someone else as well

How do I add an element to a list in Groovy?

From the documentation:

We can add to a list in many ways:

assert [1,2] + 3 + [4,5] + 6 == [1, 2, 3, 4, 5, 6]
assert [1,2].plus(3).plus([4,5]).plus(6) == [1, 2, 3, 4, 5, 6]
    //equivalent method for +
def a= [1,2,3]; a += 4; a += [5,6]; assert a == [1,2,3,4,5,6]
assert [1, *[222, 333], 456] == [1, 222, 333, 456]
assert [ *[1,2,3] ] == [1,2,3]
assert [ 1, [2,3,[4,5],6], 7, [8,9] ].flatten() == [1, 2, 3, 4, 5, 6, 7, 8, 9]

def list= [1,2]
list.add(3) //alternative method name
list.addAll([5,4]) //alternative method name
assert list == [1,2,3,5,4]

list= [1,2]
list.add(1,3) //add 3 just before index 1
assert list == [1,3,2]
list.addAll(2,[5,4]) //add [5,4] just before index 2
assert list == [1,3,5,4,2]

list = ['a', 'b', 'z', 'e', 'u', 'v', 'g']
list[8] = 'x'
assert list == ['a', 'b', 'z', 'e', 'u', 'v', 'g', null, 'x']

You can also do:

def myNewList = myList << "fifth"

What do the result codes in SVN mean?

I usually use svn through a gui, either my IDE or a client. Because of that, I can never remember the codes when I do have to resort to the command line.

I find this cheat sheet a great help: Subversion Cheat Sheet

How to define a connection string to a SQL Server 2008 database?

Check out the connection strings web site which has tons of example for your connection strings.

Basically, you need three things:

  • name of the server you want to connect to (use "." or (local) or localhost for the local machine)
  • name of the database you want to connect to
  • some way of defining the security - either integrated Windows security, or define a user name / password combo

For example, if you want to connect to your local machine and the AdventureWorks database using integrated security, use:

server=(local);database=AdventureWorks;integrated security=SSPI;

Or if you have SQL Server Express on your machine in the default installation, and you want to connect to the AdventureWorksLT2008 database, use this:

server=.\SQLExpress;database=AdventureWorksLT2008;integrated Security=SSPI;

UnsupportedClassVersionError unsupported major.minor version 51.0 unable to load class

Well presumably it's not using the same version of Java when running it externally. Look through the startup scripts carefully to find where it picks up the version of Java to run. You should also check the startup logs to see whether they indicate which version is running.

Alternatively, unless you need the Java 7 features, you could always change your compiler preferences in Eclipse to target 1.6 instead.

error: member access into incomplete type : forward declaration of

Move doSomething definition outside of its class declaration and after B and also make add accessible to A by public-ing it or friend-ing it.

class B;

class A
    void doSomething(B * b);

class B
    void add() {}

void A::doSomething(B * b)

Embedding a media player in a website using HTML

I found the that either IE or Chrome choked on most of these, or they required external libraries. I just wanted to play an MP3, and I found the page very helpful.

<audio controls>
  <source src="horse.mp3" type="audio/mpeg">
  <embed height="50" width="100" src="horse.mp3">

Worked for me in the browsers I tried, but I didn't have some of the old ones around at this time.

How to copy to clipboard in Vim?

I've been struggling with this for months till now on MacOsX using keyboard shortcuts. I know question isn't about using keyboard shorts. But this might help someone with the same concern.

I found that if you uncheck:

View -> Allow Mouse Reporting

from Terminal menu, you'll be able to copy to clipboard using

command + c


Case insensitive comparison of strings in shell script

In Bash, you can use parameter expansion to modify a string to all lower-/upper-case:


echo ${var1,,} ${var2,,}
echo ${var1^^} ${var2^^}

How to add New Column with Value to the Existing DataTable?

Add the column and update all rows in the DataTable, for example:

DataTable tbl = new DataTable();
tbl.Columns.Add(new DataColumn("ID", typeof(Int32)));
tbl.Columns.Add(new DataColumn("Name", typeof(string)));
for (Int32 i = 1; i <= 10; i++) {
    DataRow row = tbl.NewRow();
    row["ID"] = i;
    row["Name"] = i + ". row";
DataColumn newCol = new DataColumn("NewColumn", typeof(string));
newCol.AllowDBNull = true;
foreach (DataRow row in tbl.Rows) {
    row["NewColumn"] = "You DropDownList value";
//if you don't want to allow null-values'
newCol.AllowDBNull = false;

What is 'PermSize' in Java?

lace to store your loaded class definition and metadata. If a large code-base project is loaded, the insufficient Perm Gen size will cause the popular Java.Lang.OutOfMemoryError: PermGen.

Is there a TRY CATCH command in Bash

I can recommend this in "bash -ue" mode:

set -ue
false && RET=$? || RET=$? 
echo "expecting 1, got ${RET}"
true && RET=$? || RET=$? 
echo "expecting 0, got ${RET}"

echo "test try...catch"
false && RET=$? || RET=$? 
if [ ${RET} -ne 0 ]; then
  echo "caught error ${RET}"

echo "beware, using '||' before '&&' fails"
echo "  -> memory aid: [A]nd before [O]r in the alphabet"
false || RET=$? && RET=$? 
echo "expecting 1, got ${RET}"
true || RET=$? && RET=$? 
echo "expecting 0, got ${RET}"

How do you check what version of SQL Server for a database using TSQL?

Try this:

    'the sqlserver is ' + substring(@@VERSION, 21, 5) AS [sql version]

When creating a service with sc.exe how to pass in context parameters?

This command works:

sc create startSvn binPath= "\"C:\Subversion\bin\svnserve.exe\" --service -r \"C:\SVN_Repository\"" displayname= "MyServer" depend= tcpip start= auto

White space showing up on right side of page when background image should extend full length of page

The problem is in the file :

style.css - line 721

#sub_footer {
    background: url("../images/exterior/sub_footer.png") repeat-x;
    background: -moz-linear-gradient(0% 100% 90deg,#102c40, #091925);
    background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#091925), to(#102c40));
    -moz-box-shadow: 3px 3px 4px #999999;
    -webkit-box-shadow: 3px 3px 4px #999999;
    box-shadow: 3px 3px 4px #999999;

remove the lines :

-moz-box-shadow: 3px 3px 4px #999999;
-webkit-box-shadow: 3px 3px 4px #999999;
box-shadow: 3px 3px 4px #999999; 

This basically gives a shadow gradient only to the footer. In Firefox, it is the first line that is causing the problem.

Non-resolvable parent POM for Could not find artifact and 'parent.relativePath' points at wrong local POM

In my case, the reason was a simple typo.


A missing character in the groupId org.s(p)ringframework lead to this error.

Add shadow to custom shape on Android

After Lots of search finally I got this

enter image description here

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="">

<!-- Bottom 2dp Shadow -->
    <shape  android:shape="rectangle">

        <solid android:color="#d8d8d8" />
        <corners android:radius="7dp" />


<!-- White Top color -->
<item android:bottom="3px">

    <shape  android:shape="rectangle">

    <solid android:color="#FFFFFF" />
    <corners android:radius="7dp" />




How can I require at least one checkbox be checked before a form can be submitted?

Here's an example using jquery and your html.

     <script src=""></script>

<script type="text/javascript">
$(document).ready(function () {
    $('#checkBtn').click(function() {
      checked = $("input[type=checkbox]:checked").length;

      if(!checked) {
        alert("You must check at least one checkbox.");
        return false;



<p>Box Set 1</p>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 1" required><label>Box 1</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 2" required><label>Box 2</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 3" required><label>Box 3</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 4" required><label>Box 4</label></li>
<p>Box Set 2</p>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 5" required><label>Box 5</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 6" required><label>Box 6</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 7" required><label>Box 7</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 8" required><label>Box 8</label></li>
<p>Box Set 3</p>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 9" required><label>Box 9</label></li>
<p>Box Set 4</p>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 10" required><label>Box 10</label></li>

<input type="button" value="Test Required" id="checkBtn">


ActiveRecord OR query

If you want to use arrays as arguments, the following code works in Rails 4:

query = Order.where(uuid: uuids, id: ids)
Order.where(" OR "))
#=> Order Load (0.7ms)  SELECT "orders".* FROM "orders" WHERE ("orders"."uuid" IN ('5459eed8350e1b472bfee48375034103', '21313213jkads', '43ujrefdk2384us') OR "orders"."id" IN (2, 3, 4))

More information: OR queries with arrays as arguments in Rails 4.

Checking whether a String contains a number value in Java

      return true;
}catch (Exception  e){
      return false;

or you can do it himself:

 for ( int i = 0; i < string.length; ++i ) {
      if ( !( string[i] >= '0' || string[i] <= '9' ) )
           return false;
 return true;

Of course is also function isDigit

How to set value to variable using 'execute' in t-sql?

A slight change in the execute query will solve the problem:

DECLARE @dbName nvarchar(128) = 'myDb'
DECLARE @siteId int 
exec ('SELECT TOP 1 **''@siteId''** = Id FROM ' + @dbName + '..myTbl')  
select @siteId

2 ways for "ClearContents" on VBA Excel, but 1 work fine. Why?

That is because you are not fully qualifying your cells object. Try this

With Worksheets("SheetName")
    .Range(.Cells(1, 1), .Cells(10, 2)).ClearContents
End With

Notice the DOT before Cells?

How to link 2 cell of excel sheet?

I Found Solution Of You Question But In Stack Not Allow to Upload Video See the link below it show better explain

How to link two (multiple) workbooks and cells in Excel...

How do I install a module globally using npm?

I had issues installing Express on Ubuntu:

If for some reason NPM command is missing, test npm command with npm help. If not there, follow these steps -

If just the Express command is not working, try:

sudo npm install -g express

This made everything work as I'm used to with Windows7 and OSX.

Hope this helps!

Creating a list of dictionaries results in a list of copies of the same dictionary

info is a pointer to a dictionary - you keep adding the same pointer to your list contact.

Insert info = {} into the loop and it should solve the problem:

content = []
for iframe in soup.find_all('iframe'):
    info = {}
    info['src'] = iframe.get('src')
    info['height'] = iframe.get('height')
    info['width'] = iframe.get('width')

Check if a string is a valid date using DateTime.TryParse

[TestCase("11/08/1995", Result= true)]
[TestCase("1-1", Result = false)]
[TestCase("1/1", Result = false)]
public bool IsValidDateTimeTest(string dateTime)
    string[] formats = { "MM/dd/yyyy" };
    DateTime parsedDateTime;
    return DateTime.TryParseExact(dateTime, formats, new CultureInfo("en-US"),
                                   DateTimeStyles.None, out parsedDateTime);

Simply specify the date time formats that you wish to accept in the array named formats.

How to concatenate two layers in keras?

You're getting the error because result defined as Sequential() is just a container for the model and you have not defined an input for it.

Given what you're trying to build set result to take the third input x3.

first = Sequential()
first.add(Dense(1, input_shape=(2,), activation='sigmoid'))

second = Sequential()
second.add(Dense(1, input_shape=(1,), activation='sigmoid'))

third = Sequential()
# of course you must provide the input to result which will be your x3
third.add(Dense(1, input_shape=(1,), activation='sigmoid'))

# lets say you add a few more layers to first and second.
# concatenate them
merged = Concatenate([first, second])

# then concatenate the two outputs

result = Concatenate([merged,  third])

ada_grad = Adagrad(lr=0.1, epsilon=1e-08, decay=0.0)

result.compile(optimizer=ada_grad, loss='binary_crossentropy',

However, my preferred way of building a model that has this type of input structure would be to use the functional api.

Here is an implementation of your requirements to get you started:

from keras.models import Model
from keras.layers import Concatenate, Dense, LSTM, Input, concatenate
from keras.optimizers import Adagrad

first_input = Input(shape=(2, ))
first_dense = Dense(1, )(first_input)

second_input = Input(shape=(2, ))
second_dense = Dense(1, )(second_input)

merge_one = concatenate([first_dense, second_dense])

third_input = Input(shape=(1, ))
merge_two = concatenate([merge_one, third_input])

model = Model(inputs=[first_input, second_input, third_input], outputs=merge_two)
ada_grad = Adagrad(lr=0.1, epsilon=1e-08, decay=0.0)
model.compile(optimizer=ada_grad, loss='binary_crossentropy',

To answer the question in the comments:

  1. How are result and merged connected? Assuming you mean how are they concatenated.

Concatenation works like this:

  a        b         c
a b c   g h i    a b c g h i
d e f   j k l    d e f j k l

i.e rows are just joined.

  1. Now, x1 is input to first, x2 is input into second and x3 input into third.

How to enable CORS in ASP.NET Core

Got this working with .Net Core 3.1 as follows

1.Make sure you place the UseCors code between app.UseRouting(); and app.UseAuthentication();




        app.UseEndpoints(endpoints => {

2.Then place this code in the ConfigureServices method

services.AddCors(options =>
                builder => builder.WithOrigins("http://localhost:4200", "")

3.And above the base controller I placed this

public class BaseController : ControllerBase

Now all my controllers will inherit from the BaseController and will have CORS enabled

How to compare files from two different branches?

In order to compare two files in the git bash you need to use the command:

git diff <Branch name>..master -- Filename.extension   

This command will show the difference between the two files in the bash itself.

How can I do string interpolation in JavaScript?

Supplant more for ES6 version of @Chris Nielsen's post.

String.prototype.supplant = function (o) {
  return this.replace(/\${([^\${}]*)}/g,
    (a, b) => {
      var r = o[b];
      return typeof r === 'string' || typeof r === 'number' ? r : a;

string = "How now ${color} cow? {${greeting}}, ${greeting}, moo says the ${color} cow.";

string.supplant({color: "brown", greeting: "moo"});
=> "How now brown cow? {moo}, moo, moo says the brown cow."

Scp command syntax for copying a folder from local machine to a remote server

In stall PuTTY in our system and set the environment variable PATH Pointing to putty path. open the command prompt and move to putty folder. Using PSCP command

Please check this

SQL Server String Concatenation with Null

This example will help you to handle various types while creating insert statements

'insert into doc(Id, CDate, Str, Code, Price, Tag )' + 
'values(' +
      '''' + convert(nvarchar(50), Id) + ''',' -- uniqueidentifier
    + '''' + LEFT(CONVERT(VARCHAR, CDate, 120), 10) + ''',' -- date
    + '''' + Str+ ''',' -- string
    + '''' + convert(nvarchar(50), Code)  + ''',' -- int
    + convert(nvarchar(50), Price) + ',' -- decimal
    + '''' + ISNULL(Tag, '''''') + '''' + ')'  -- nullable string

 from doc
 where CDate> '2019-01-01 00:00:00.000'

Visual Studio window which shows list of methods

With Visual Studio 2010

You choose Tools->Settings->Expert Settings

On the left-bottom corner, you will see the tab "Class View" right next tab "Solution Explorer"

In the top area of "Class View" layout, you will see the list of class name, enum, struct, ... In the bottom area of "Class View layout, you will see the list of member for these class, enum or struct

Combining node.js and Python

I'd recommend using some work queue using, for example, the excellent Gearman, which will provide you with a great way to dispatch background jobs, and asynchronously get their result once they're processed.

The advantage of this, used heavily at Digg (among many others) is that it provides a strong, scalable and robust way to make workers in any language to speak with clients in any language.

Why am I getting an error "Object literal may only specify known properties"?

As of TypeScript 1.6, properties in object literals that do not have a corresponding property in the type they're being assigned to are flagged as errors.

Usually this error means you have a bug (typically a typo) in your code, or in the definition file. The right fix in this case would be to fix the typo. In the question, the property callbackOnLoactionHash is incorrect and should have been callbackOnLocationHash (note the mis-spelling of "Location").

This change also required some updates in definition files, so you should get the latest version of the .d.ts for any libraries you're using.


interface TextOptions {
    alignment?: string;
    color?: string;
    padding?: number;
function drawText(opts: TextOptions) { ... }
drawText({ align: 'center' }); // Error, no property 'align' in 'TextOptions'

But I meant to do that

There are a few cases where you may have intended to have extra properties in your object. Depending on what you're doing, there are several appropriate fixes

Type-checking only some properties

Sometimes you want to make sure a few things are present and of the correct type, but intend to have extra properties for whatever reason. Type assertions (<T>v or v as T) do not check for extra properties, so you can use them in place of a type annotation:

interface Options {
    x?: string;
    y?: number;

// Error, no property 'z' in 'Options'
let q1: Options = { x: 'foo', y: 32, z: 100 };
// OK
let q2 = { x: 'foo', y: 32, z: 100 } as Options;
// Still an error (good):
let q3 = { x: 100, y: 32, z: 100 } as Options;

These properties and maybe more

Some APIs take an object and dynamically iterate over its keys, but have 'special' keys that need to be of a certain type. Adding a string indexer to the type will disable extra property checking


interface Model {
  name: string;
function createModel(x: Model) { ... }

// Error
createModel({name: 'hello', length: 100});


interface Model {
  name: string;
  [others: string]: any;
function createModel(x: Model) { ... }

// OK
createModel({name: 'hello', length: 100});

This is a dog or a cat or a horse, not sure yet

interface Animal { move; }
interface Dog extends Animal { woof; }
interface Cat extends Animal { meow; }
interface Horse extends Animal { neigh; }

let x: Animal;
if(...) {
  x = { move: 'doggy paddle', woof: 'bark' };
} else if(...) {
  x = { move: 'catwalk', meow: 'mrar' };
} else {
  x = { move: 'gallop', neigh: 'wilbur' };

Two good solutions come to mind here

Specify a closed set for x

// Removes all errors
let x: Dog|Cat|Horse;

or Type assert each thing

// For each initialization
  x = { move: 'doggy paddle', woof: 'bark' } as Dog;

This type is sometimes open and sometimes not

A clean solution to the "data model" problem using intersection types:

interface DataModelOptions {
  name?: string;
  id?: number;
interface UserProperties {
  [key: string]: any;
function createDataModel(model: DataModelOptions & UserProperties) {
 /* ... */
// findDataModel can only look up by name or id
function findDataModel(model: DataModelOptions) {
 /* ... */
// OK
createDataModel({name: 'my model', favoriteAnimal: 'cat' });
// Error, 'ID' is not correct (should be 'id')
findDataModel({ ID: 32 });

See also

MySQL SELECT only not null values

Yes use NOT NULL in your query like this below.

FROM table

MVC pattern on Android

You can implement MVC in Android, but it is not "natively supported" and takes some effort.

That said, I personally tend towards MVP as a much cleaner architectural pattern for Android development. And by saying MVP I mean this:

enter image description here

I have also posted a more detailed answer here.

After playing with the various approaches to MVC/MVP implementation in Android, I came up with a reasonable architectural pattern, which I described in a this post: MVP and MVC Architectural Patterns in Android.

Executable directory where application is running from?

You can write the following:

Path.Combine(Path.GetParentDirectory(GetType(MyClass).Assembly.Location), "Images\image.jpg")

CSS: Force float to do a whole new line

Use display:inline-block

You may also find vertical-align: top or vertical-align:middle useful.

Making WPF applications look Metro-styled, even in Windows 7? (Window Chrome / Theming / Theme)

i would recommend Modern UI for WPF .

It has a very active maintainer it is awesome and free!

Modern UI for WPF (Screenshot of the sample application

I'm currently porting some projects to MUI, first (and meanwhile second) impression is just wow!

To see MUI in action you could download XAML Spy which is based on MUI.

EDIT: Using Modern UI for WPF a few months and i'm loving it!

How to make the python interpreter correctly handle non-ASCII characters in string operations?

#!/usr/bin/env python
# -*- coding: utf-8 -*-

s = u"6Â 918Â 417Â 712"
s = s.replace(u"Â", "") 
print s

This will print out 6 918 417 712

Android intent for playing video?

from the debug info, it seems that the VideoIntent from the MainActivity cannot send the path of the video to VideoActivity. It gives a NullPointerException error from the uriString. I think some of that code from VideoActivity:

Intent myIntent = getIntent();
String uri = myIntent.getStringExtra("uri");
Bundle b = myIntent.getExtras();


Cannot receive the uri from here:

public void playsquirrelmp4(View v) {
    Intent VideoIntent = (new Intent(this, VideoActivity.class));
    VideoIntent.putExtra("android.resource://" + getPackageName()
        + "/"+   R.raw.squirrel, uri);

MySQL - SELECT all columns WHERE one column is DISTINCT

In MySQL you can simply use "group by". Below will select ALL, with a DISTINCT "col"

FROM tbl

How to change my Git username in terminal?

**Check by executing this** 
git config --list
**Change user email** 
git config --global "[email protected]"
**Change user name**
git config --global "user"
**Change user credential name** 
git config --global credential.username "new_username"
**After this a window popup asking password.
Enter password and proceed.**

What are the benefits of using C# vs F# or F# vs C#?

General benefits of functional programming over imperative languages:

You can formulate many problems much easier, closer to their definition and more concise in a functional programming language like F# and your code is less error-prone (immutability, more powerful type system, intuitive recurive algorithms). You can code what you mean instead of what the computer wants you to say ;-) You will find many discussions like this when you google it or even search for it at SO.

Special F#-advantages:

  • Asynchronous programming is extremely easy and intuitive with async {}-expressions - Even with ParallelFX, the corresponding C#-code is much bigger

  • Very easy integration of compiler compilers and domain-specific languages

  • Extending the language as you need it: LOP

  • Units of measure

  • More flexible syntax

  • Often shorter and more elegant solutions

Take a look at this document

The advantages of C# are that it's often more accurate to "imperative"-applications (User-interface, imperative algorithms) than a functional programming language, that the .NET-Framework it uses is designed imperatively and that it's more widespread.

Furthermore you can have F# and C# together in one solution, so you can combine the benefits of both languages and use them where they're needed.

How do I split a multi-line string into multiple lines?

Like the others said:

inputString.split('\n')  # --> ['Line 1', 'Line 2', 'Line 3']

This is identical to the above, but the string module's functions are deprecated and should be avoided:

import string
string.split(inputString, '\n')  # --> ['Line 1', 'Line 2', 'Line 3']

Alternatively, if you want each line to include the break sequence (CR,LF,CRLF), use the splitlines method with a True argument:

inputString.splitlines(True)  # --> ['Line 1\n', 'Line 2\n', 'Line 3']

Changing variable names with Python for loops

You probably want a dict instead of separate variables. For example

d = {}
for i in range(3):
    d["group" + str(i)] = self.getGroup(selected, header+i)

If you insist on actually modifying local variables, you could use the locals function:

for i in range(3):
    locals()["group"+str(i)] = self.getGroup(selected, header+i)

On the other hand, if what you actually want is to modify instance variables of the class you're in, then you can use the setattr function

for i in group(3):
    setattr(self, "group"+str(i), self.getGroup(selected, header+i)

And of course, I'm assuming with all of these examples that you don't just want a list:

groups = [self.getGroup(i,header+i) for i in range(3)]

How to convert a string to a date in sybase

Several ways to accomplish that but be aware that your DB date_format option & date_order option settings could affect the incoming format:

   cast('2008-09-16' as date)
from dummy;

How to make a div have a fixed size?

<div class="ai">a b c d e f</div> // something like ~100px
<div class="ai">a b c d e</div> // ~80
<div class="ai">a b c d</div> // ~60 


function _reWidthAll_div(classname) {

var _maxwidth = 0;


    var _width = $(this).width();

    _maxwidth = (_width >= _maxwidth) ? _width : _maxwidth; // define max width

$(classname).width(_maxwidth); // return all div same width




Insert the same fixed value into multiple rows

This is because in relational database terminology, what you want to do is not called "inserting", but "UPDATING" - you are updating an existing row's field from one value (NULL in your case) to "test"

UPDATE your_table SET table_column = "test" 
WHERE table_column = NULL 

You don't need the second line if you want to update 100% of rows.

What does "The APR based Apache Tomcat Native library was not found" mean?

Unless you're running a production server, don't worry about this message. This is a library which is used to improve performance (on production systems). From Apache Portable Runtime (APR) based Native library for Tomcat:

Tomcat can use the Apache Portable Runtime to provide superior scalability, performance, and better integration with native server technologies. The Apache Portable Runtime is a highly portable library that is at the heart of Apache HTTP Server 2.x. APR has many uses, including access to advanced IO functionality (such as sendfile, epoll and OpenSSL), OS level functionality (random number generation, system status, etc), and native process handling (shared memory, NT pipes and Unix sockets).

How do I cast a string to integer and have 0 in case of error in the cast with PostgreSQL?

You could also create your own conversion function, inside which you can use exception blocks:

CREATE OR REPLACE FUNCTION convert_to_integer(v_input text)
        v_int_value := v_input::INTEGER;
        RAISE NOTICE 'Invalid integer value: "%".  Returning NULL.', v_input;
        RETURN NULL;
RETURN v_int_value;
$$ LANGUAGE plpgsql;


=# select convert_to_integer('1234');
(1 row)

=# select convert_to_integer('');
NOTICE:  Invalid integer value: "".  Returning NULL.

(1 row)

=# select convert_to_integer('chicken');
NOTICE:  Invalid integer value: "chicken".  Returning NULL.

(1 row)

How to deal with bad_alloc in C++?

You can catch it like any other exception:

try {
catch (const std::bad_alloc&) {
  return -1;

Quite what you can usefully do from this point is up to you, but it's definitely feasible technically.

In general you cannot, and should not try, to respond to this error. bad_alloc indicates that a resource cannot be allocated because not enough memory is available. In most scenarios your program cannot hope to cope with that, and terminating soon is the only meaningful behaviour.

Worse, modern operating systems often over-allocate: on such systems, malloc and new can return a valid pointer even if there is not enough free memory left – std::bad_alloc will never be thrown, or is at least not a reliable sign of memory exhaustion. Instead, attempts to access the allocated memory will then result in a segmentation fault, which is not catchable (you can handle the segmentation fault signal, but you cannot resume the program afterwards).

The only thing you could do when catching std::bad_alloc is to perhaps log the error, and try to ensure a safe program termination by freeing outstanding resources (but this is done automatically in the normal course of stack unwinding after the error gets thrown if the program uses RAII appropriately).

In certain cases, the program may attempt to free some memory and try again, or use secondary memory (= disk) instead of RAM but these opportunities only exist in very specific scenarios with strict conditions:

  1. The application must ensure that it runs on a system that does not overcommit memory, i.e. it signals failure upon allocation rather than later.
  2. The application must be able to free memory immediately, without any further accidental allocations in the meantime.

It’s exceedingly rare that applications have control over point 1 — userspace applications never do, it’s a system-wide setting that requires root permissions to change.1

OK, so let’s assume you’ve fixed point 1. What you can now do is for instance use a LRU cache for some of your data (probably some particularly large business objects that can be regenerated or reloaded on demand). Next, you need to put the actual logic that may fail into a function that supports retry — in other words, if it gets aborted, you can just relaunch it:

lru_cache<widget> widget_cache;

double perform_operation(int widget_id) {
    std::optional<widget> maybe_widget = widget_cache.find_by_id(widget_id);
    if (not maybe_widget) {
        maybe_widget =, load_widget_from_disk(widget_id));
    return maybe_widget->frobnicate();


for (int num_attempts = 0; num_attempts < MAX_NUM_ATTEMPTS; ++num_attempts) {
    try {
        return perform_operation(widget_id);
    } catch (std::bad_alloc const&) {
        if (widget_cache.empty()) throw; // memory error elsewhere.

// Handle too many failed attempts here.

But even here, using std::set_new_handler instead of handling std::bad_alloc provides the same benefit and would be much simpler.

1 If you’re creating an application that does control point 1, and you’re reading this answer, please shoot me an email, I’m genuinely curious about your circumstances.

What is the C++ Standard specified behavior of new in c++?

The usual notion is that if new operator cannot allocate dynamic memory of the requested size, then it should throw an exception of type std::bad_alloc.
However, something more happens even before a bad_alloc exception is thrown:

C++03 Section says

An allocation function that fails to allocate storage can invoke the currently installed new_handler(, if any. [Note: A program-supplied allocation function can obtain the address of the currently installed new_handler using the set_new_handler function (] If an allocation function declared with an empty exception-specification (15.4), throw(), fails to allocate storage, it shall return a null pointer. Any other allocation function that fails to allocate storage shall only indicate failure by throw-ing an exception of class std::bad_alloc ( or a class derived from std::bad_alloc.

Consider the following code sample:

#include <iostream>
#include <cstdlib>

// function to call if operator new can't allocate enough memory or error arises
void outOfMemHandler()
    std::cerr << "Unable to satisfy request for memory\n";


int main()
    //set the new_handler

    //Request huge memory size, that will cause ::operator new to fail
    int *pBigDataArray = new int[100000000L];

    return 0;

In the above example, operator new (most likely) will be unable to allocate space for 100,000,000 integers, and the function outOfMemHandler() will be called, and the program will abort after issuing an error message.

As seen here the default behavior of new operator when unable to fulfill a memory request, is to call the new-handler function repeatedly until it can find enough memory or there is no more new handlers. In the above example, unless we call std::abort(), outOfMemHandler() would be called repeatedly. Therefore, the handler should either ensure that the next allocation succeeds, or register another handler, or register no handler, or not return (i.e. terminate the program). If there is no new handler and the allocation fails, the operator will throw an exception.

What is the new_handler and set_new_handler?

new_handler is a typedef for a pointer to a function that takes and returns nothing, and set_new_handler is a function that takes and returns a new_handler.

Something like:

typedef void (*new_handler)();
new_handler set_new_handler(new_handler p) throw();

set_new_handler's parameter is a pointer to the function operator new should call if it can't allocate the requested memory. Its return value is a pointer to the previously registered handler function, or null if there was no previous handler.

How to handle out of memory conditions in C++?

Given the behavior of newa well designed user program should handle out of memory conditions by providing a proper new_handlerwhich does one of the following:

Make more memory available: This may allow the next memory allocation attempt inside operator new's loop to succeed. One way to implement this is to allocate a large block of memory at program start-up, then release it for use in the program the first time the new-handler is invoked.

Install a different new-handler: If the current new-handler can't make any more memory available, and of there is another new-handler that can, then the current new-handler can install the other new-handler in its place (by calling set_new_handler). The next time operator new calls the new-handler function, it will get the one most recently installed.

(A variation on this theme is for a new-handler to modify its own behavior, so the next time it's invoked, it does something different. One way to achieve this is to have the new-handler modify static, namespace-specific, or global data that affects the new-handler's behavior.)

Uninstall the new-handler: This is done by passing a null pointer to set_new_handler. With no new-handler installed, operator new will throw an exception ((convertible to) std::bad_alloc) when memory allocation is unsuccessful.

Throw an exception convertible to std::bad_alloc. Such exceptions are not be caught by operator new, but will propagate to the site originating the request for memory.

Not return: By calling abort or exit.

How do I scroll the UIScrollView when the keyboard appears?

You actually don't need a UIScrollView to do this. I used this code and it works for me:

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField

   if (textField==_myTextField)
      [self keyBoardAppeared];
   return true;

-(void)textFieldDidEndEditing:(UITextField *)textField {
   if (textField==_myTextField)
      [self keyBoardDisappeared];

-(void) keyBoardAppeared
   CGRect frame = self.view.frame;

[UIView animateWithDuration:0.3
                    options: UIViewAnimationCurveEaseOut
                     self.view.frame = CGRectMake(frame.origin.x, frame.origin.y-215, frame.size.width, frame.size.height);
                 completion:^(BOOL finished){


-(void) keyBoardDisappeared
   CGRect frame = self.view.frame;

  [UIView animateWithDuration:0.3
                    options: UIViewAnimationCurveEaseOut
                     self.view.frame = CGRectMake(frame.origin.x, frame.origin.y+215, frame.size.width, frame.size.height);
                 completion:^(BOOL finished){


How do I get current URL in Selenium Webdriver 2 Python?

Selenium2Library has get_location():

import Selenium2Library
s = Selenium2Library.Selenium2Library()
url = s.get_location()

Declare variable in SQLite and use it

Herman's solution works, but it can be simplified because Sqlite allows to store any value type on any field.

Here is a simpler version that uses one Value field declared as TEXT to store any value:


INSERT OR REPLACE INTO Variables VALUES ('VarStr', 'Val1');
INSERT OR REPLACE INTO Variables VALUES ('VarInt', 123);
INSERT OR REPLACE INTO Variables VALUES ('VarBlob', x'12345678');

  FROM Variables
 WHERE Name = 'VarStr'
  FROM Variables
 WHERE Name = 'VarInt'
  FROM Variables
 WHERE Name = 'VarBlob';

How to detect a loop in a linked list?

This approach has space overhead, but a simpler implementation:

Loop can be identified by storing nodes in a Map. And before putting the node; check if node already exists. If node already exists in the map then it means that Linked List has loop.

public boolean loopDetector(Node<E> first) {  
       Node<E> t = first;  
       Map<Node<E>, Node<E>> map = new IdentityHashMap<Node<E>, Node<E>>();  
       while (t != null) {  
            if (map.containsKey(t)) {  
                 System.out.println(" duplicate Node is --" + t  
                           + " having value :" +;  

                 return true;  
            } else {  
                 map.put(t, t);  
            t =;  
       return false;  

How to get base url in CodeIgniter 2.*

Just load helper class


thats it.

Reading multiple Scanner inputs

If every input asks the same question, you should use a for loop and an array of inputs:

Scanner dd = new Scanner(;
int[] vars = new int[3];

for(int i = 0; i < vars.length; i++) {
  System.out.println("Enter next var: ");
  vars[i] = dd.nextInt();

Or as Chip suggested, you can parse the input from one line:

Scanner in = new Scanner(;
int[] vars = new int[3];

System.out.println("Enter "+vars.length+" vars: ");
for(int i = 0; i < vars.length; i++)
  vars[i] = in.nextInt();

You were on the right track, and what you did works. This is just a nicer and more flexible way of doing things.

CSS On hover show another element

You can use axe selectors for this.

There are two approaches:

1. Immediate Parent axe Selector (<)

#a:hover < #content + #b

This axe style rule will select #b, which is the immediate sibling of #content, which is the immediate parent of #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);

#a:hover < #content + #b {
display: inline-block;
<div id="content">
<div id="a">Hover me</div>

<div id="b">Show me</div>

<script src=""></script>

2. Remote Element axe Selector (\)

#a:hover \ #b

This axe style rule will select #b, which is present in the same document as #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);

#a:hover \ #b {
display: inline-block;
<div id="content">
<div id="a">Hover me</div>

<div id="b">Show me</div>

<script src=""></script>

How do I call a Django function on button click?

The following answer could be helpful for the first part of your question:

Django: How can I call a view function from template?

The simplest possible JavaScript countdown timer?

You can easily create a timer functionality by using setInterval.Below is the code which you can use it to create the timer.

window.onload = function() {_x000D_
  var minute = 5;_x000D_
  var sec = 60;_x000D_
  setInterval(function() {_x000D_
    document.getElementById("timer").innerHTML = minute + " : " + sec;_x000D_
    if (sec == 00) {_x000D_
      minute --;_x000D_
      sec = 60;_x000D_
      if (minute == 0) {_x000D_
        minute = 5;_x000D_
  }, 1000);_x000D_
Registration closes in <span id="timer">05:00<span> minutes!

Turn off display errors using file "php.ini"

Turn if off:

You can use error_reporting(); or put an @ in front of your fileopen().

PHP: merge two arrays while keeping keys instead of reindexing?

Considering that you have

$replaced = array('1' => 'value1', '4' => 'value4');
$replacement = array('4' => 'value2', '6' => 'value3');

Doing $merge = $replacement + $replaced; will output:

Array('4' => 'value2', '6' => 'value3', '1' => 'value1');

The first array from sum will have values in the final output.

Doing $merge = $replaced + $replacement; will output:

Array('1' => 'value1', '4' => 'value4', '6' => 'value3');

How can I replace a regex substring match in Javascript?

I would get the part before and after what you want to replace and put them either side.


var str   = 'asd-0.testing';
var regex = /(asd-)\d(\.\w+)/;

var matches = str.match(regex);

var result = matches[1] + "1" + matches[2];

// With ES6:
var result = `${matches[1]}1${matches[2]}`;

How to return more than one value from a function in Python?

Here is also the code to handle the result:

def foo (a):
    return (x,y)

(x,y) = foo(50)

How to split a string in Ruby and get all items except the first one?

You can also do this:

String is ex="test1, test2, test3, test4, test5"
array = ex.split(/,/)
array.size.times do |i|
  p array[i]

Android: remove notification from notification bar

NotificationManager.cancel(id) is the correct answer. Yet you can remove in Android Oreo and later notifications by deleting the whole notification channel. This should delete all messages in the deleted channel.

Here is the example from the Android documentation:

NotificationManager mNotificationManager =
        (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
// The id of the channel.
String id = "my_channel_01";

How to set editable true/false EditText in Android programmatically?

Try this it is working fine for me..

EditText.setFilters(new InputFilter[] {new InputFilter()
public CharSequence filter(CharSequence source, int start,
                            int end, Spanned dest, int dstart, int dend) 
return source.length() < 1 ? dest.subSequence(dstart, dend) : "";


Oracle - how to remove white spaces?

Say, we have a column with values consisting of alphanumeric characters and underscore only. We need to trim this column off all spaces, tabs or whatever white characters. The below example will solve the problem. The trimmed one and the original one both are being displayed for comparison. select '/'||REGEXP_REPLACE(my_column,'[^A-Z,^0-9,^_]','')||'/' my_column,'/'||my_column||'/' from my_table;

SQL Server: Error converting data type nvarchar to numeric

You might need to revise the data in the column, but anyway you can do one of the following:-

1- check if it is numeric then convert it else put another value like 0


2- select only numeric values from the column

where Isnumeric(COLUMNA) = 1

SQL update trigger only when column is modified

You have two way for your question :

1- Use Update Command in your Trigger.

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
    IF UPDATE (QtyToRepair) 
        SET modified = GETDATE()
           , ModifiedUser = SUSER_NAME()
           , ModifiedHost = HOST_NAME()
        ON S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
        WHERE S.QtyToRepair <> I.QtyToRepair

2- Use Join between Inserted table and deleted table

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]

    SET modified = GETDATE()
       , ModifiedUser = SUSER_NAME()
       , ModifiedHost = HOST_NAME()
    INNER JOIN Inserted I ON S.OrderNo = I.OrderNo and S.PartNumber = I.PartNumber
    INNER JOIN Deleted D ON S.OrderNo = D.OrderNo and S.PartNumber = D.PartNumber                  
    WHERE S.QtyToRepair <> I.QtyToRepair
    AND D.QtyToRepair <> I.QtyToRepair

When you use update command for table SCHEDULE and Set QtyToRepair Column to new value, if new value equal to old value in one or multi row, solution 1 update all updated row in Schedule table but solution 2 update only schedule rows that old value not equal to new value.

Check if a string within a list contains a specific string with Linq

I think you want Any:

if (myList.Any(str => str.Contains("Mdd LH")))

It's well worth becoming familiar with the LINQ standard query operators; I would usually use those rather than implementation-specific methods (such as List<T>.ConvertAll) unless I was really bothered by the performance of a specific operator. (The implementation-specific methods can sometimes be more efficient by knowing the size of the result etc.)

val() vs. text() for textarea

.val() always works with textarea elements.

.text() works sometimes and fails other times! It's not reliable (tested in Chrome 33)

What's best is that .val() works seamlessly with other form elements too (like input) whereas .text() fails.

Laravel assets url

Besides put all your assets in the public folder, you can use the HTML::image() Method, and only needs an argument which is the path to the image, relative on the public folder, as well:

{{ HTML::image('imgs/picture.jpg') }}

Which generates the follow HTML code:

<img src="http://localhost:8000/imgs/picture.jpg">

The link to other elements of HTML::image() Method:

What does <> mean in excel?

It means "not equal to" (as in, the values in cells E37-N37 are not equal to "", or in other words, they are not empty.)

Entity Framework: table without primary key

The error means exactly what it says.

Even if you could work around this, trust me, you don't want to. The number of confusing bugs that could be introduced is staggering and scary, not to mention the fact that your performance will likely go down the tubes.

Don't work around this. Fix your data model.

EDIT: I've seen that a number of people are downvoting this question. That's fine, I suppose, but keep in mind that the OP asked about mapping a table without a primary key, not a view. The answer is still the same. Working around the EF's need to have a PK on tables is a bad idea from the standpoint of manageability, data integrity, and performance.

Some have commented that they do not have the ability to fix the underlying data model because they're mapping to a third-party application. That is not a good idea, as the model can change out from under you. Arguably, in that case, you would want to map to a view, which, again, is not what the OP asked.

calculating the difference in months between two dates

Old question I know, but might help someone. I've used @Adam accepted answer above, but then checked if the difference is 1 or -1 then check to see if it is a full calendar month's difference. So 21/07/55 and 20/08/55 would not be a full month, but 21/07/55 and 21/07/55 would be.

/// <summary>
/// Amended date of birth cannot be greater than or equal to one month either side of original date of birth.
/// </summary>
/// <param name="dateOfBirth">Date of birth user could have amended.</param>
/// <param name="originalDateOfBirth">Original date of birth to compare against.</param>
/// <returns></returns>
public JsonResult ValidateDateOfBirth(string dateOfBirth, string originalDateOfBirth)
    DateTime dob, originalDob;
    bool isValid = false;

    if (DateTime.TryParse(dateOfBirth, out dob) && DateTime.TryParse(originalDateOfBirth, out originalDob))
        int diff = ((dob.Month - originalDob.Month) + 12 * (dob.Year - originalDob.Year));

        switch (diff)
            case 0:
                // We're on the same month, so ok.
                isValid = true;
            case -1:
                // The month is the previous month, so check if the date makes it a calendar month out.
                isValid = (dob.Day > originalDob.Day);
            case 1:
                // The month is the next month, so check if the date makes it a calendar month out.
                isValid = (dob.Day < originalDob.Day);
                // Either zero or greater than 1 month difference, so not ok.
                isValid = false;
        if (!isValid)
            return Json("Date of Birth cannot be greater than one month either side of the date we hold.", JsonRequestBehavior.AllowGet);
        return Json("Date of Birth is invalid.", JsonRequestBehavior.AllowGet);
    return Json(true, JsonRequestBehavior.AllowGet);

Can you break from a Groovy "each" closure?

Just using special Closure

// declare and implement:
def eachWithBreak = { list, Closure c ->
  boolean bBreak = false
  list.each() { it ->
     if (bBreak) return
     bBreak = c(it)

def list = [1,2,3,4,5,6]
eachWithBreak list, { it ->
  if (it > 3) return true // break 'eachWithBreak'
  println it
  return false // next it

Capturing URL parameters in request.GET

To clarify camflan's explanation, let's suppose you have

  • the rule url(regex=r'^user/(?P<username>\w{1,50})/$', view='views.profile_page')
  • a in incoming request for http://domain/user/thaiyoshi/?message=Hi

The URL dispatcher rule will catch parts of the URL path (here "user/thaiyoshi/") and pass them to the view function along with the request object.

The query string (here message=Hi) is parsed and parameters are stored as a QueryDict in request.GET. No further matching or processing for HTTP GET parameters is done.

This view function would use both parts extracted from the URL path and a query parameter:

def profile_page(request, username=None):
    user = User.objects.get(username=username)
    message = request.GET.get('message')

As a side note, you'll find the request method (in this case "GET", and for submitted forms usually "POST") in request.method. In some cases it's useful to check that it matches what you're expecting.

Update: When deciding whether to use the URL path or the query parameters for passing information, the following may help:

  • use the URL path for uniquely identifying resources, e.g. /blog/post/15/ (not /blog/posts/?id=15)
  • use query parameters for changing the way the resource is displayed, e.g. /blog/post/15/?show_comments=1 or /blog/posts/2008/?sort_by=date&direction=desc
  • to make human friendly URLs, avoid using ID numbers and use e.g. dates, categories and/or slugs: /blog/post/2008/09/30/django-urls/

Javascript Get Values from Multiple Select Option Box

Also, change this:

    SelBranchVal = SelBranchVal + "," + InvForm.SelBranch[x].value;


    SelBranchVal = SelBranchVal + InvForm.SelBranch[x].value+ "," ;

The reason is that for the first time the variable SelBranchVal will be empty

How do I check (at runtime) if one class is a subclass of another?

issubclass(class, classinfo)


Return true if class is a subclass (direct, indirect or virtual) of classinfo.

Calculating sum of repeated elements in AngularJS ng-repeat

This is my solution

sweet and simple custom filter:

(but only related to simple sum of values, not sum product, I've made up sumProduct filter and appended it as edit to this post).

angular.module('myApp', [])

    .filter('total', function () {
        return function (input, property) {
            var i = input instanceof Array ? input.length : 0;
// if property is not defined, returns length of array
// if array has zero length or if it is not an array, return zero
            if (typeof property === 'undefined' || i === 0) {
                return i;
// test if property is number so it can be counted
            } else if (isNaN(input[0][property])) {
                throw 'filter total can count only numeric values';
// finaly, do the counting and return total
            } else {
                var total = 0;
                while (i--)
                    total += input[i][property];
                return total;

JS Fiddle

EDIT: sumProduct

This is sumProduct filter, it accepts any number of arguments. As a argument it accepts name of the property from input data, and it can handle nested property (nesting marked by dot: property.nested);

  • Passing zero argument returns length of input data.
  • Passing just one argument returns simple sum of values of that properties.
  • Passing more arguments returns sum of products of values of passed properties (scalar sum of properties).

here's JS Fiddle and the code

angular.module('myApp', [])
    .filter('sumProduct', function() {
        return function (input) {
            var i = input instanceof Array ? input.length : 0;
            var a = arguments.length;
            if (a === 1 || i === 0)
                return i;

            var keys = [];
            while (a-- > 1) {
                var key = arguments[a].split('.');
                var property = getNestedPropertyByKey(input[0], key);
                if (isNaN(property))
                    throw 'filter sumProduct can count only numeric values';

            var total = 0;
            while (i--) {
                var product = 1;
                for (var k = 0; k < keys.length; k++)
                    product *= getNestedPropertyByKey(input[i], keys[k]);
                total += product;
            return total;

            function getNestedPropertyByKey(data, key) {
                for (var j = 0; j < key.length; j++)
                    data = data[key[j]];
                return data;

JS Fiddle

What causes a Python segmentation fault?

This happens when a python extension (written in C) tries to access a memory beyond reach.

You can trace it in following ways.

  • Add sys.settrace at the very first line of the code.
  • Use gdb as described by Mark in this answer.. At the command prompt

    gdb python
    (gdb) run /path/to/
    ## wait for segfault ##
    (gdb) backtrace
    ## stack trace of the c code

How to dismiss notification after action has been clicked

I found that when you use the action buttons in expanded notifications, you have to write extra code and you are more constrained.

You have to manually cancel your notification when the user clicks an action button. The notification is only cancelled automatically for the default action.

Also if you start a broadcast receiver from the button, the notification drawer doesn't close.

I ended up creating a new NotificationActivity to address these issues. This intermediary activity without any UI cancels the notification and then starts the activity I really wanted to start from the notification.

I've posted sample code in a related post Clicking Android Notification Actions does not close Notification drawer.

How to find out the MySQL root password

This worked for me:

On terminal type the following

$ sudo mysql -u root -p

Enter password://just press enter


Redirect echo output in shell script to logfile

echo "Hello World"
exec > script.log 2>&1
echo "Start logging out from here to a file"
bad command
echo "End logging out from here to a file"
exec > /dev/tty 2>&1 #redirects out to controlling terminal
echo "Logged in the terminal"


> ./                                                                
Hello World
Not logged in the file
> cat script.log
Start logging out from here to a file
./ line 6: bad: command not found
End logging out from here to a file

Read more here:

Fatal error: Maximum execution time of 30 seconds exceeded

Increase your script execution time by adding the following line at top of the PHP script.

ini_set('max_execution_time', 120); //120 seconds = 2 minutes

Reference has taken from Increase the PHP Script Execution Time

Simple way to read single record from MySQL

I agree that mysql_result is the easy way to retrieve contents of one cell from a MySQL result set. Tiny code:

$r = mysql_query('SELECT id FROM table') or die(mysql_error());
if (mysql_num_rows($r) > 0) {
    echo mysql_result($r); // will output first ID
    echo mysql_result($r, 1); // will ouput second ID

Magento How to debug blank white screen

In my case size of the index.php file was zero. I copied the original file back and it worked.

However, no idea about what erased the content of index.php.

Is it bad practice to use break to exit a loop in Java?

If you start to do something like this, then I would say it starts to get a bit strange and you're better off moving it to a seperate method that returns a result upon the matchedCondition.

boolean matched = false;
for(int i = 0; i < 10; i++) {
    for(int j = 0; j < 10; j++) {
        if(matchedCondition) {
            matched = true;
    if(matched) {

To elaborate on how to clean up the above code, you can refactor, moving the code to a function that returns instead of using breaks. This is in general, better dealing with complex/messy breaks.

public boolean  matches()
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            if(matchedCondition) {
                return true;
    return false;

However for something simple like my below example. By all means use break!

for(int i = 0; i < 10; i++) {
    if(wereDoneHere()) { // we're done, break.

And changing the conditions, in the above case i, and j's value, you would just make the code really hard to read. Also there could be a case where the upper limits (10 in the example) are variables so then it would be even harder to guess what value to set it to in order to exit the loop. You could of course just set i and j to Integer.MAX_VALUE, but I think you can see this starts to get messy very quickly. :)

Difference between Ctrl+Shift+F and Ctrl+I in Eclipse

If you press CTRL + I it will just format tabs/whitespaces in code and pressing CTRL + SHIFT + F format all code that is format tabs/whitespaces and also divide code lines in a way that it is visible without horizontal scroll.

How to position one element relative to another with jQuery?

Here is a jQuery function I wrote that helps me position elements.

Here is an example usage:

$(document).ready(function() {
  $('#el1').position('#el2', {
    anchor: ['br', 'tr'],
    offset: [-5, 5]

The code above aligns the bottom-right of #el1 with the top-right of #el2. ['cc', 'cc'] would center #el1 in #el2. Make sure that #el1 has the css of position: absolute and z-index: 10000 (or some really large number) to keep it on top.

The offset option allows you to nudge the coordinates by a specified number of pixels.

The source code is below:

jQuery.fn.getBox = function() {
  return {
    left: $(this).offset().left,
    top: $(this).offset().top,
    width: $(this).outerWidth(),
    height: $(this).outerHeight()

jQuery.fn.position = function(target, options) {
  var anchorOffsets = {t: 0, l: 0, c: 0.5, b: 1, r: 1};
  var defaults = {
    anchor: ['tl', 'tl'],
    animate: false,
    offset: [0, 0]
  options = $.extend(defaults, options);

  var targetBox = $(target).getBox();
  var sourceBox = $(this).getBox();

  //origin is at the top-left of the target element
  var left = targetBox.left;
  var top =;

  //alignment with respect to source
  top -= anchorOffsets[options.anchor[0].charAt(0)] * sourceBox.height;
  left -= anchorOffsets[options.anchor[0].charAt(1)] * sourceBox.width;

  //alignment with respect to target
  top += anchorOffsets[options.anchor[1].charAt(0)] * targetBox.height;
  left += anchorOffsets[options.anchor[1].charAt(1)] * targetBox.width;

  //add offset to final coordinates
  left += options.offset[0];
  top += options.offset[1];

    left: left + 'px',
    top: top + 'px'


PHP compare two arrays and get the matched values not the difference

OK.. We needed to compare a dynamic number of product names...

There's probably a better way... but this works for me...

... because....Strings are just Arrays of characters.... :>}

//  Compare Strings ...  Return Matching Text and Differences with Product IDs...

//  From MySql...
$productID1 = 'abc123';
$productName1 = "EcoPlus Premio Jet 600";   

$productID2 = 'xyz789';
$productName2 = "EcoPlus Premio Jet 800";   

$ProductNames = array(
    $productID1 => $productName1,
    $productID2 => $productName2

function compareNames($ProductNames){   

    //  Convert NameStrings to Arrays...    
    foreach($ProductNames as $id => $product_name){
        $Package1[$id] = explode(" ",$product_name);    

    // Get Matching Text...
    $Matching = call_user_func_array('array_intersect', $Package1 );
    $MatchingText = implode(" ",$Matching);

    //  Get Different Text...
    foreach($Package1 as $id => $product_name_chunks){
        $Package2 = array($product_name_chunks,$Matching);
        $diff = call_user_func_array('array_diff', $Package2 );
        $DifferentText[$id] = trim(implode(" ", $diff));

    $results[$MatchingText]  = $DifferentText;              
    return $results;    

$Results =  compareNames($ProductNames);


// Gives us this...
[EcoPlus Premio Jet] 
        [abc123] => 600
        [xyz789] => 800

Handling urllib2's timeout? - Python

In Python 2.7.3:

import urllib2
import socket

class MyException(Exception):

    urllib2.urlopen("", timeout = 1)
except urllib2.URLError as e:
    print type(e)    #not catch
except socket.timeout as e:
    print type(e)    #catched
    raise MyException("There was an error: %r" % e)

Execute ssh with password authentication via windows command prompt

Windows Solution

  1. Install PuTTY
  2. Press Windows-Key + R
  3. Enter putty.exe -ssh [username]@[hostname] -pw [password]

A python class that acts like dict

The problem with this chunk of code:

class myDict(dict):
    def __init__(self):
        self._dict = {}

    def add(id, val):
        self._dict[id] = val

md = myDict()
md.add('id', 123) that your 'add' method (...and any method you want to be a member of a class) needs to have an explicit 'self' declared as its first argument, like:

def add(self, 'id', 23):

To implement the operator overloading to access items by key, look in the docs for the magic methods __getitem__ and __setitem__.

Note that because Python uses Duck Typing, there may actually be no reason to derive your custom dict class from the language's dict class -- without knowing more about what you're trying to do (e.g, if you need to pass an instance of this class into some code someplace that will break unless isinstance(MyDict(), dict) == True), you may be better off just implementing the API that makes your class sufficiently dict-like and stopping there.

UIScrollView not scrolling

If your scrollView is a subview of a containerView of some type, then make sure that your scrollView is within the frame or bounds of the containerView. I had containerView.clipsToBounds = NO which still allowed me see the scrollView, but because scrollView wasn't within the bounds of containerView it wouldn't detect touch events.

For example:

containerView.frame = CGRectMake(0, 0, 200, 200);
scrollView.frame = CGRectMake(0, 200, 200, 200);
[containerView addSubview:scrollView];
scrollView.userInteractionEnabled = YES;

You will be able to see the scrollView but it won't receive user interactions.

What is Inversion of Control?

I found a very clear example here which explains how the 'control is inverted'.

Classic code (without Dependency injection)

Here is how a code not using DI will roughly work:

  • Application needs Foo (e.g. a controller), so:
  • Application creates Foo
  • Application calls Foo
    • Foo needs Bar (e.g. a service), so:
    • Foo creates Bar
    • Foo calls Bar
      • Bar needs Bim (a service, a repository, …), so:
      • Bar creates Bim
      • Bar does something

Using dependency injection

Here is how a code using DI will roughly work:

  • Application needs Foo, which needs Bar, which needs Bim, so:
  • Application creates Bim
  • Application creates Bar and gives it Bim
  • Application creates Foo and gives it Bar
  • Application calls Foo
    • Foo calls Bar
      • Bar does something

The control of the dependencies is inverted from one being called to the one calling.

What problems does it solve?

Dependency injection makes it easy to swap with the different implementation of the injected classes. While unit testing you can inject a dummy implementation, which makes the testing a lot easier.

Ex: Suppose your application stores the user uploaded file in the Google Drive, with DI your controller code may look like this:

class SomeController
    private $storage;

    function __construct(StorageServiceInterface $storage)
        $this->storage = $storage;

    public function myFunction () 
        return $this->storage->getFile($fileName);

class GoogleDriveService implements StorageServiceInterface
    public function authenticate($user) {}
    public function putFile($file) {}
    public function getFile($file) {}

When your requirements change say, instead of GoogleDrive you are asked to use the Dropbox. You only need to write a dropbox implementation for the StorageServiceInterface. You don't have make any changes in the controller as long as Dropbox implementation adheres to the StorageServiceInterface.

While testing you can create the mock for the StorageServiceInterface with the dummy implementation where all the methods return null(or any predefined value as per your testing requirement).

Instead if you had the controller class to construct the storage object with the new keyword like this:

class SomeController
    private $storage;

    function __construct()
        $this->storage = new GoogleDriveService();

    public function myFunction () 
        return $this->storage->getFile($fileName);

When you want to change with the Dropbox implementation you have to replace all the lines where new GoogleDriveService object is constructed and use the DropboxService. Besides when testing the SomeController class the constructor always expects the GoogleDriveService class and the actual methods of this class are triggered.

When is it appropriate and when not? In my opinion you use DI when you think there are (or there can be) alternative implementations of a class.

Normalizing images in OpenCV

If you want to change the range to [0, 1], make sure the output data type is float.

image = cv2.imread("lenacolor512.tiff", cv2.IMREAD_COLOR)  # uint8 image
norm_image = cv2.normalize(image, None, alpha=0, beta=1, norm_type=cv2.NORM_MINMAX, dtype=cv2.CV_32F)

Foreign key constraints: When to use ON UPDATE and ON DELETE

Do not hesitate to put constraints on the database. You'll be sure to have a consistent database, and that's one of the good reasons to use a database. Especially if you have several applications requesting it (or just one application but with a direct mode and a batch mode using different sources).

With MySQL you do not have advanced constraints like you would have in postgreSQL but at least the foreign key constraints are quite advanced.

We'll take an example, a company table with a user table containing people from theses company

     company_id INT NOT NULL,
     company_name VARCHAR(50),
     PRIMARY KEY (company_id)

     user_id INT, 
     user_name VARCHAR(50), 
     company_id INT,
     INDEX company_id_idx (company_id),
     FOREIGN KEY (company_id) REFERENCES COMPANY (company_id) ON...

Let's look at the ON UPDATE clause:

  • ON UPDATE RESTRICT : the default : if you try to update a company_id in table COMPANY the engine will reject the operation if one USER at least links on this company.
  • ON UPDATE CASCADE : the best one usually : if you update a company_id in a row of table COMPANY the engine will update it accordingly on all USER rows referencing this COMPANY (but no triggers activated on USER table, warning). The engine will track the changes for you, it's good.
  • ON UPDATE SET NULL : if you update a company_id in a row of table COMPANY the engine will set related USERs company_id to NULL (should be available in USER company_id field). I cannot see any interesting thing to do with that on an update, but I may be wrong.

And now on the ON DELETE side:

  • ON DELETE RESTRICT : the default : if you try to delete a company_id Id in table COMPANY the engine will reject the operation if one USER at least links on this company, can save your life.
  • ON DELETE CASCADE : dangerous : if you delete a company row in table COMPANY the engine will delete as well the related USERs. This is dangerous but can be used to make automatic cleanups on secondary tables (so it can be something you want, but quite certainly not for a COMPANY<->USER example)
  • ON DELETE SET NULL : handful : if you delete a COMPANY row the related USERs will automatically have the relationship to NULL. If Null is your value for users with no company this can be a good behavior, for example maybe you need to keep the users in your application, as authors of some content, but removing the company is not a problem for you.

usually my default is: ON DELETE RESTRICT ON UPDATE CASCADE. with some ON DELETE CASCADE for track tables (logs--not all logs--, things like that) and ON DELETE SET NULL when the master table is a 'simple attribute' for the table containing the foreign key, like a JOB table for the USER table.


It's been a long time since I wrote that. Now I think I should add one important warning. MySQL has one big documented limitation with cascades. Cascades are not firing triggers. So if you were over confident enough in that engine to use triggers you should avoid cascades constraints.

MySQL triggers activate only for changes made to tables by SQL statements. They do not activate for changes in views, nor by changes to tables made by APIs that do not transmit SQL statements to the MySQL Server

==> See below the last edit, things are moving on this domain

Triggers are not activated by foreign key actions.

And I do not think this will get fixed one day. Foreign key constraints are managed by the InnoDb storage and Triggers are managed by the MySQL SQL engine. Both are separated. Innodb is the only storage with constraint management, maybe they'll add triggers directly in the storage engine one day, maybe not.

But I have my own opinion on which element you should choose between the poor trigger implementation and the very useful foreign keys constraints support. And once you'll get used to database consistency you'll love PostgreSQL.

12/2017-Updating this Edit about MySQL:

as stated by @IstiaqueAhmed in the comments, the situation has changed on this subject. So follow the link and check the real up-to-date situation (which may change again in the future).

C# How to determine if a number is a multiple of another?


public bool IsDivisible(int x, int n)
   return (x % n) == 0;

The modulus operator % returns the remainder after dividing x by n which will always be 0 if x is divisible by n.

For more information, see the % operator on MSDN.

What does the [Flags] Enum Attribute mean in C#?

To add Mode.Write:

Mode = Mode | Mode.Write;

Laravel - Session store not set on request

I was getting this error with Laravel Sanctum. I fixed it by adding \Illuminate\Session\Middleware\StartSession::class, to the api middleware group in Kernel.php, but I later figured out this "worked" because my authentication routes were added in api.php instead of web.php, so Laravel was using the wrong auth guard.

I moved these routes here into web.php and then they started working properly with the AuthenticatesUsers.php trait:

Route::group(['middleware' => ['guest', 'throttle:10,5']], function () {
    Route::post('register', 'Auth\RegisterController@register')->name('register');
    Route::post('login', 'Auth\LoginController@login')->name('login');

    Route::post('password/email', 'Auth\ForgotPasswordController@sendResetLinkEmail');
    Route::post('password/reset', 'Auth\ResetPasswordController@reset');

    Route::post('email/verify/{user}', 'Auth\VerificationController@verify')->name('verification.verify');
    Route::post('email/resend', 'Auth\VerificationController@resend');

    Route::post('oauth/{driver}', 'Auth\OAuthController@redirectToProvider')->name('oauth.redirect');
    Route::get('oauth/{driver}/callback', 'Auth\OAuthController@handleProviderCallback')->name('oauth.callback');

Route::post('logout', 'Auth\LoginController@logout')->name('logout');

I figured out the problem after I got another weird error about RequestGuard::logout() does not exist.

It made me realize that my custom auth routes are calling methods from the AuthenticatesUsers trait, but I wasn't using Auth::routes() to accomplish it. Then I realized Laravel uses the web guard by default and that means routes should be in routes/web.php.

This is what my settings look like now with Sanctum and a decoupled Vue SPA app:


protected $middlewareGroups = [
    'web' => [
        // \Illuminate\Session\Middleware\AuthenticateSession::class,

    'api' => [

Note: With Laravel Sanctum and same-domain Vue SPA, you use httpOnly cookies for session cookie, and remember me cookie, and unsecure cookie for CSRF, so you use the web guard for auth, and every other protected, JSON-returning route should use auth:sanctum middleware.


'defaults' => [
    'guard' => 'web',
    'passwords' => 'users',


'guards' => [
    'web' => [
        'driver' => 'session',
        'provider' => 'users',

    'api' => [
        'driver' => 'token',
        'provider' => 'users',
        'hash' => false,

Then you can have unit tests such as this, where critically, Auth::check(), Auth::user(), and Auth::logout() work as expected with minimal config and maximal usage of AuthenticatesUsers and RegistersUsers traits.

Here are a couple of my login unit tests:


 * Creates and/or returns the designated regular user for unit testing
 * @return \App\User
public function user() : User
    $user = User::query()->firstWhere('email', '[email protected]');

    if ($user) {
        return $user;

    // User::generate() is just a wrapper around User::create()
    $user = User::generate('Test User', '[email protected]', self::AUTH_PASSWORD);

    return $user;

 * Resets AuthManager state by logging out the user from all auth guards.
 * This is used between unit tests to wipe cached auth state.
 * @param array $guards
 * @return void
protected function resetAuth(array $guards = null) : void
    $guards = $guards ?: array_keys(config('auth.guards'));

    foreach ($guards as $guard) {
        $guard = $this->app['auth']->guard($guard);

        if ($guard instanceof SessionGuard) {

    $protectedProperty = new \ReflectionProperty($this->app['auth'], 'guards');
    $protectedProperty->setValue($this->app['auth'], []);


protected $auth_guard = 'web';

/** @test */
public function it_can_login()
    $user = $this->user();

    $this->postJson(route('login'), ['email' => $user->email, 'password' => TestCase::AUTH_PASSWORD])
            'user' => [

    $this->assertEquals(Auth::check(), true);
    $this->assertEquals(Auth::user()->email, $user->email);
    $this->assertAuthenticatedAs($user, $this->auth_guard);


/** @test */
public function it_can_logout()



I overrided the registered and authenticated methods in the Laravel auth traits so that they return the user object instead of just the 204 OPTIONS:

public function authenticated(Request $request, User $user)
    return response()->json([
        'user' => $user,

protected function registered(Request $request, User $user)
    return response()->json([
        'user' => $user,

Look at the vendor code for the auth traits. You can use them untouched, plus those two above methods.

  • vendor/laravel/ui/auth-backend/RegistersUsers.php
  • vendor/laravel/ui/auth-backend/AuthenticatesUsers.php

Here is my Vue SPA's Vuex actions for login:

async login({ commit }, credentials) {
    try {
        const { data } = await'login'), {
            remember: credentials.remember || undefined,

        commit(FETCH_USER_SUCCESS, { user: data.user });

        return commit(CLEAR_INTENDED_URL);
    } catch (err) {
        throw new Error(`auth/login# Problem logging user in: ${err}.`);

async logout({ commit }) {
    try {

        return commit(LOGOUT);
    } catch (err) {

        throw new Error(`auth/logout# Problem logging user out: ${err}.`);

It took me over a week to get Laravel Sanctum + same-domain Vue SPA + auth unit tests all working up to my standard, so hopefully my answer here can help save others time in the future.

What should be the sizeof(int) on a 64-bit machine?

Doesn't have to be; "64-bit machine" can mean many things, but typically means that the CPU has registers that big. The sizeof a type is determined by the compiler, which doesn't have to have anything to do with the actual hardware (though it typically does); in fact, different compilers on the same machine can have different values for these.

How to delete directory content in Java?

Here is one possible solution to solve the problem without a library :

public static boolean delete(File file) {

    File[] flist = null;

    if(file == null){
        return false;

    if (file.isFile()) {
        return file.delete();

    if (!file.isDirectory()) {
        return false;

    flist = file.listFiles();
    if (flist != null && flist.length > 0) {
        for (File f : flist) {
            if (!delete(f)) {
                return false;

    return file.delete();

Cannot assign requested address - possible causes?

It turns out that the problem really was that the address was busy - the busyness was caused by some other problems in how we are handling network communications. Your inputs have helped me figure this out. Thank you.

EDIT: to be specific, the problems in handling our network communications were that these status updates would be constantly re-sent if the first failed. It was only a matter of time until we had every distributed slave trying to send its status update at the same time, which was over-saturating our network.

scatter plot in matplotlib

Maybe something like this:

import matplotlib.pyplot
import pylab

x = [1,2,3,4]
y = [3,4,8,6]



Let me see if I understand you correctly now:

You have:

       test1 | test2 | test3
test3 |   1   |   0  |  1

test4 |   0   |   1  |  0

test5 |   1   |   1  |  0

Now you want to represent the above values in in a scatter plot, such that value of 1 is represented by a dot.

Let's say you results are stored in a 2-D list:

results = [[1, 0, 1], [0, 1, 0], [1, 1, 0]]

We want to transform them into two variables so we are able to plot them.

And I believe this code will give you what you are looking for:

import matplotlib
import pylab

results = [[1, 0, 1], [0, 1, 0], [1, 1, 0]]

x = []
y = []

for ind_1, sublist in enumerate(results):
    for ind_2, ele in enumerate(sublist):
        if ele == 1:


Notice that I do need to import pylab, and you would have play around with the axis labels. Also this feels like a work around, and there might be (probably is) a direct method to do this.

Why is php not running?

When installing Apache and PHP under Ubuntu 14.04, I needed to specifically enable php configs by issuing a2enmod php5-cgi

How could I convert data from string to long in c#

long l1 = Convert.ToInt64(strValue);

That should do it.

Transfer data between databases with PostgreSQL

There are three options for copying it if this is a one off:

  1. Use a db_link (I think it is still in contrib)
  2. Have the application do the work.
  3. Export/import

If this is an ongoing need, the answers are:

  1. Change to schemas in the same DB
  2. db_link