convert perl timestamp to human readable - perl

Question

I am reading a log file which contains time stamps which I want to convert to human readable.
In this command, $1 contains a time stamp (like this 1403457192.663): $temp = localtime->mon($1) but instead of storing the month, $temp contains the same timestamp that was input. What am I doing wrong?

Answer 1

You're close. The time should be passed to the localtime function, not the mon method.:
$temp = localtime($1)->mon; # 6
You can use strftime with this to turn it into any arbitrary format
localtime($1)->strftime("%b %d %a"); # Jun 22 Sun
Or if you're not picky about the format you can just stringify it:
$temp = localtime($1);
print "$temp\n"; # Sun Jun 22 13:13:12 2014
This assumes that Time::Piece is loaded.

Answer 2

I'd simply go with
$ perl -E'
use POSIX qw( strftime );
say strftime("%Y/%m/%d %H:%M:%S", localtime(1403457192.663));
'
2014/06/22 13:13:12
But you're using Time::localtime. That module overrides the localtime builtin, so you need a slight modification if you use that.
Either avoid using Time::localtime's localtime
$ perl -E'
use POSIX qw( strftime );
use Time::localtime qw( localtime );
say strftime("%Y/%m/%d %H:%M:%S", CORE::localtime(1403457192.663));
'
2014/06/22 13:13:12
or flatten an existing Time::localtime object.
$ perl -E'
use POSIX qw( strftime );
use Time::localtime qw( localtime );
my $tm = localtime(1403457192.663);
say strftime("%Y/%m/%d %H:%M:%S", #$tm);
'
2014/06/22 13:13:12
All of these solutions lose the millisecond precision. If it's relevant, you'll have to extract it from the original input and reinsert it in the output.

Answer 3

For formatting dates most system strftime manual pages will list a few "shortcuts" to get you certain "standard" formats.
e.g. %F is equivalent to “%Y-%m-%d”.
~/% perl -MPOSIX -E'say strftime"%D",localtime'
06/25/14
~/% perl -MPOSIX -E'say strftime"%F",localtime'
2014-06-25
These can make using "ye olde" strftime easier ;-)

Answer 4

Perl since 5.10 now contains Time::Piece. This makes it the official way to handle time in Perl. Or, about as official as something gets in Perl. Since it's always available, you might as well learn to use that:
use strict;
use warnings;
use Time::Piece;
use Time::Seconds; # More time fun!
my $time = Time::Piece->new; # Gets the current timestamp
my $month = $time->mon(); # Month from 1 to 12
my $month = $time->month(); # Abbreviation of the name of month
my $month = $time->fullmonth(); # Full name of the month
my $time = $time + (ONE_DAY * 30) # Add thirty days to the time
my $date = $time->mdy # The date 30 days from now.