Quickly getting to YYYY-mm-dd HH MM SS in Perl

Question

When writing Perl scripts I frequently find the need to obtain the current time represented as a string formatted as YYYY-mm-dd HH MM SS  say 2009-11-29 14 28 29    In doing this I find myself taking this quite cumbersome path    man perlfunc  localtime to search for localtime - repeat five times       n  to reach the relevant section of the manpage Copy the string   sec  min  hour  mday  mon  year  wday  yday  isdst    localtime time   from the manpage to my script  Try with my  now   sprintf   04d- 02d- 02d  02d  02d  02d    year   mon   mday   hour   min   sec   Remember gotcha  1  Must add 1900 to  year to get current year  Try with my  now   sprintf   04d- 02d- 02d  02d  02d  02d    year 1900   mon   mday   hour   min   sec   Remember gotcha  2  Must add 1 to  mon to get current month  Try with my  now   sprintf   04d- 02d- 02d  02d  02d  02d    year 1900   mon 1   mday   hour   min   sec   Seems ok  Done    While the process outlined above works it is far from optimal  I m sure there is a smarter way  so my question is simply   What is the easiest way to obtain a YYYY-mm-dd HH MM SS of the current date time in Perl   Where  easy  encompasses both  easy-to-write  and  easy-to-remember

User · Answer

Why not use the DateTime module to do the dirty work for you  It s easy to write and remember  use strict  use warnings  use DateTime   my  dt     DateTime- gt now      Stores current date and time as datetime object my  date    dt- gt ymd      Retrieves date as a string in  yyyy-mm-dd  format my  time    dt- gt hms      Retrieves time as a string in  hh mm ss  format  my  wanted    quot  date  time quot       creates  yyyy-mm-dd hh mm ss  string print  wanted   Once you know what s going on  you can get rid of the temps and save a few lines of code  use strict  use warnings  use DateTime   my  dt   DateTime- gt now  print join       dt- gt ymd   dt- gt hms

User · Answer

Time  Piece  datetime   can eliminate T   use Time  Piece  print localtime- gt datetime T   gt  q

User · Answer

if you just want a human readable time string and not that exact format    t   localtime  print   t n     prints   Mon Apr 27 10 16 19 2015   or whatever is configured for your locale

User · Answer

Use strftime in the standard POSIX module  The arguments to strftime in Perl   s binding were designed to align with the return values from localtime and gmtime  Compare  strftime fmt  sec  min  hour  mday  mon  year  wday   -1  yday   -1  isdst   -1    with  my            sec  min  hour  mday  mon  year  wday       yday       isdst    gmtime time     Example command-line use is    perl -MPOSIX -le  print strftime   F  T   localtime   T    or from a source file as in  use POSIX   print strftime   F  T   localtime time    Some systems do not support the  F and  T shorthands  so you will have to be explicit with  print strftime   Y- m- d  H  M  S   localtime time    or  print strftime   Y- m- d  H  M  S   gmtime time    Note that time returns the current time when called whereas   T is fixed to the time when your program started  With gmtime  the return value is the current time in GMT  Retrieve time in your local timezone with localtime

User · Answer

I made a little test  Perl v5 20 1 under FreeBSD in VM  calling the following blocks 1 000 000 times each   A  my   sec  min  hour  mday  mon  year  wday  yday  isdst    localtime time   my  now   sprintf   04d- 02d- 02d  02d  02d  02d    year 1900   mon 1   mday   hour   min   sec     B  my  now   strftime   Y m d H M S  localtime     C  my  now   Time  Piece  localtime- gt strftime   Y m d H M S      with the following results   A  2 seconds  B  11 seconds  C  19 seconds  This is of course not a thorough test or benchmark  but at least it is reproducable for me  so even though it is more complicated  I d prefer the first method if generating a datetimestamp is required very often   Calling  eg  under FreeBSD 10 1   my  now    date    Y m d H M S    tr -d   n      might not be such a good idea because it is not OS-independent and takes quite some time   Best regards  Holger

User · Answer

Time  Piece  in core since Perl 5 10  also has a strftime function and by default overloads localtime and gmtime to return Time  Piece objects   use Time  Piece  print localtime- gt strftime   Y- m- d      or without the overridden localtime   use Time  Piece      print Time  Piece  localtime- gt strftime   F  T

User · Answer

Try this   use POSIX qw strftime   print strftime   Y- m- d  localtime     the strftime method does the job effectively for me  Very simple and efficient

User · Answer

In many cases  the needed  current time  is rather   T  which is the time at which the script started running  in whole seconds  assuming only 60 second minutes  since the UNIX epoch   This to prevent that an early part of a script uses a different date  or daylight-saving status  than a later part of a script  for example in query-conditions and other derived values   For that variant of  current time   one can use a constant  also to document that it was frozen at compile time   use constant YMD HMS AT START   gt  POSIX  strftime    F  T   localtime   T      Alternative higher resolution startup time   0    Time  HiRes  stat   proc       - gt  10

User · Answer

Short and sweet  no additional modules needed   my  toDate    date   m  d  Y    l  M  S    p     Output for example would be  04 25 2017  9 30 33 AM

[perl] Quickly getting to YYYY-mm-dd HH:MM:SS in Perl

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