Shell Programming and Scripting

21 Jan 2012 05:46:59,146 
21 Jan 2012 02:12:30,113 
17 Jan 2012 09:08:10,417

$
$ cat f33
21 Jan 2012 05:46:59,146
21 Jan 2012 02:12:30,113
17 Jan 2012 09:08:10,417
$
$ perl -lne 'BEGIN {use Time::Local qw(timelocal_nocheck);
                    @mth = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)}
             ($x, $d, $mo, $y, $h, $mi, $s) = m/^((\d+) (\w+) (\d+) (\d+):(\d+):(\d+)).*$/;
             @m = grep {$mth[$_] eq $mo} (0..$#mth);
             $y -= 1900;
             $curr = timelocal_nocheck ($s, $mi, $h, $d, $m[0], $y);
             $max = $x if $curr > $prev;
             $prev = $curr;
             END {print "Greatest date value = ", $max}
            ' f33
Greatest date value = 21 Jan 2012 05:46:59
$
$

#!/bin/bash

d1="21 Jan 2012 05:46:59,146"
d2="21 Jan 2012 02:12:30,113"
d3="17 Jan 2012 09:08:10,417"
s1=$( date -d "${d1%%,*}" '+%s' )
s2=$( date -d "${d2%%,*}" '+%s' )
s3=$( date -d "${d3%%,*}" '+%s' )

echo -e "$s1\n$s2\n$s3" | sort -n | tail -1 | xargs -I {} date -d @{} '+%d %b %Y %T'

#!/bin/bash

val=0
while read line
do
        cur=$( date -d "${line%%,*}" '+%s' )
        test "$cur" -gt "$val" && val=$cur
done < infile

date -d @$val '+%d %b %Y %T'