printf not printing on console

Question

I   m getting started in the C language  I am using eclipse  juno  as my IDE and installed CDT plugin  I have also unpacked mingw64  GCC Compiler   I wrote a very simple program to see if it works  This is my code    include  lt stdio h gt   int main         int age      printf  Hello  please enter your age  n        scanf   d    amp age       printf  Your age is  d   age       return 0      The problem is that the output buffer is filled with the string value of the first printf but does not output it to the console  I have to enter a number  and only then the buffer pours all the data to the console so I see the console something like this   1 Hello  please enter your age  Your age is 1   instead of what is expected that is   Hello  please enter your age  1 Your age is 1   Now  I found that I can use fflush stdout  after the first printf but I don t think that this solution is elegant and even necessary  Any ideas on how I can overcome this    EDIT - because I m learning this in my university  I can t use anything that wasn t learned in the course so I can only use printf and scanf  NEW EDIT - I think I have found an explanation for this  As I said  I am outputting to the console view inside Eclipse  The strange thing is that if I compile and run the program from the command line of Windows  I get the wanted result  Therefore  I think that eclipse is actually writing the output to a file and presenting it in the console window  How can I force eclipse to open a real command line window in my run configurations

User · Answer

You could try writing to stderr  rather than stdout   fprintf stderr   Hello  please enter your age n      You should also have a look at this relevant thread

User · Answer

As others have pointed out  output can be buffered within your program before a console or shell has a chance to see it   On unix-like systems  including macs  stdout has line-based buffering by default  This means that your program empties its stdout buffer as soon as it sees a newline   However  on windows  newlines are no longer special  and full buffering is used  Windows doesn t support line buffering at all  see the msdn page on setvbuf   So on windows  a good approach is to completely shut off stdout buffering like so   setvbuf  stdout  NULL   IONBF  0

User · Answer

Apparently this is a known bug of Eclipse  This bug is resolved with the resolution of WONT-FIX  I have no idea why though  here is the link  Eclipse C Console Bug

User · Answer

In your project folder  create a     gdbinit    text file  It will contain your gdb debugger configuration Edit     gdbinit     and add the line  without the quotes       set new-console on    After building the project right click on the project  Debug      Debug Configurations     as shown below  In the    debugger    tab  ensure the    GDB command file    now points to your     gdbinit    file  Else  input the path to your     gdbinit    configuration file    Click    Apply    and    Debug     A native DOS command line should be launched as shown below

User · Answer

Output is buffered  stdout is line-buffered by default  which means that   n  is supposed to flush the buffer  Why is it not happening in your case  I don t know  I need more info about your application environment  However  you can control buffering with setvbuf    setvbuf stdout  NULL   IOLBF  0    This will force stdout to be line-buffered  setvbuf stdout  NULL   IONBF  0    This will force stdout to be unbuffered  so you won t need to use fflush    Note that it will severely affect application performance if you have lots of prints

User · Answer

Try setting this before you print   setvbuf  stdout  NULL   IONBF  0

User · Answer

Add c  gygwin bin to PATH environment variable either as a system environment variable or in your eclipse project  properties-  run debug-  edit

[c] printf not printing on console

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