How do I convert epoch time to normal time in Perl?

Question

I am attempting to write a Perl script that parses a log where on each line the second value is the date. The script takes in three arguments: the input log file, the start time, and the end time. The start and end time are used to parse out a certain value on each line that that falls between those two times. But to properly run this I am converting the start and end time to epoch time. The problem I am having is that to convert the loops 'i' value back to normal time to compare against the log file. After running localtime($i) I print the value and only see a reference printed not the actual value.

Here is the script I have so far (it is a work in progress):

#!/usr/bin/perl
use strict;
use warnings;
use Time::Local;
use Time::localtime;
use File::stat;

my $sec = 0;
my $min = 0;
my $hour = 0;
my $mday = 0;
my $mon = 0;
my $year = 0;
my $wday = 0;
my $yday = 0;
my $isdst = 0;

##########################
# Get the engine log date
##########################
my $date = `grep -m 1 'Metric' "$ARGV[0]" | awk '{print \$2}'`;
($year,$mon,$mday) = split('-', $date);
$mon--;

#########################################
# Calculate the start and end epoch time
#########################################
($hour,$min,$sec) = split(':', $ARGV[1]);
my $startTime = timelocal($sec,$min,$hour,$mday,$mon,$year);
($hour,$min,$sec) = split(':', $ARGV[2]);
my $endTime = timelocal($sec,$min,$hour,$mday,$mon,$year);


my $theTime = 0;
for (my $i = $startTime; $i <= $endTime + 29; $i++) {
        #print "$startTime   $i \n";

        $theTime = localtime($i);

        #my $DBInstance0 = `grep "$hour:$min:$sec" "$ARGV[0]"`;# | grep 'DBInstance-0' | awk '{print \$9}'`;
        #print "$DBInstance0\n";
        print "$theTime\n";
}
print "$startTime   $endTime \n";

The output looks like:

Time::tm=ARRAY(0x8cbbd40)
Time::tm=ARRAY(0x8cbc1a0)
Time::tm=ARRAY(0x8cbbe80)
Time::tm=ARRAY(0x8cbc190)
Time::tm=ARRAY(0x8bbb170)
Time::tm=ARRAY(0x8cbc180)
Time::tm=ARRAY(0x8cbbf30)
Time::tm=ARRAY(0x8cbc170)
Time::tm=ARRAY(0x8cbc210)
Time::tm=ARRAY(0x8cbc160)
1275760356   1275760773

I only have access to the core Perl modules and am unable to install any others.

Answer 1

You can use ctime, depending on your definition of "Normal time":

Example code:

use Time::Local; 
use Time::localtime; 
my $time=timelocal(1,2,3,24,6,2010);
print "$time\n"; 
$theTime = ctime($time); 
print "$theTime\n";

Result:

1279954921
Sat Jul 24 03:02:01 2010

Also, you don't need to use Time::Localtime (which is why you get Time::tm instead of a standard array/string from Perl's internal localtime):

use Time::Local; 
my $time=timelocal(1,2,3,24,6,2010); 
print "$time\n"; 
$theTime = localtime($time); 
print "$theTime\n";

1279954921
Sat Jul 24 03:02:01 2010

Answer 2

Don't forget to subtract 1900 from the year!

Remember that in scalar context, localtime and gmtime returns a ctime-formatted string, so you could use it as in the following. If that's unsuitable, you might want to use strftime from the POSIX module.

#! /usr/bin/perl

use warnings;
use strict;

use Time::Local;

my $start = "01:02:03";
my $end   = "01:02:05";
my $date  = "2010-02-10";

my($year,$mon,$mday) = split /-/, $date;
$mon--;
$year -= 1900;

my($startTime,$endTime) =
  map { my($hour,$min,$sec) = split /:/;
        timelocal $sec,$min,$hour,$mday,$mon,$year }
  $start, $end;

for (my $i = $startTime; $i <= $endTime + 29; $i++) {
  print scalar localtime($i), "\n";
}

print "$startTime   $endTime \n";

Tail of the output:

Wed Feb 10 01:02:26 2010
Wed Feb 10 01:02:27 2010
Wed Feb 10 01:02:28 2010
Wed Feb 10 01:02:29 2010
Wed Feb 10 01:02:30 2010
Wed Feb 10 01:02:31 2010
Wed Feb 10 01:02:32 2010
Wed Feb 10 01:02:33 2010
Wed Feb 10 01:02:34 2010
1265785323   1265785325