Convert formatted dates to seconds since the epoch

Here's an alternate approach (using mktime):

#!/bin/awk -f { split($6,A,":"); S1=sprintf("%d %d %d %d %d %d",$7,$4,$5,A[1],A[2],A[3]) T1=mktime(S1) if ($8=="-") { split($12,A,":"); S2=sprintf("%d %d %d %d %d %d",$13,$10,$11,A[1],A[2],A[3]) T2=mktime(S2) print $1,$2,T1,$8,T2,$14 } else { print $1,$2,T1,$8,$9,$10 } } 

You could do it like this with GNU sed:

convert_date.sed

: a s/(([A-Za-z]{3} ){2}[0-9]{1,2} ([0-9]{2}:){2}[0-9]{2} [0-9]{4})(.*)/\n\4\n\1/ h s/.*\n// s/^/date -d "/ s/$/" +%s/e G s/([^\n]+)\n([^\n]+)\n([^\n]+)\n.*/\2\1\3/ /([A-Za-z]{3} ){2}[0-9]{1,2} ([0-9]{2}:){2}[0-9]{2} [0-9]{4}/ta 

Run it like this:

sed -rf convert_date.sed infile 

Output:

pablo tty8 1351770681 still logged in (unknown tty8 1351770657 - 1351770681 (00:00) pablo tty2 1351770639 still logged in pablo tty7 1351770585 - 1351770656 (00:01) (unknown tty7 1351769672 - 1351770585 (00:15) 

Explanation

This may look a bit daunting at first, but the idea is not that complicated. This regular expression, ([A-Za-z]{3} ){2}[0-9]{1,2} ([0-9]{2}:){2}[0-9]{2} [0-9]{4}, which occurs in the first replace and the conditional at the end, matches the date type used in the input, it captures and isolates the date. The surrounding bits are stored in the hold space while date -d is run on the captured date. Finally, all the bits are collected in pattern space and reorganized into the correct order.

The conditional at the end repeats the process if any dates remain in pattern space.

With perl and its Date::Manip module:

perl -MDate::Manip -pe ' s/\w{3} \w{3} +\d+ \d\d:\d\d:\d\d \d+/ UnixDate ParseDate("$&"),"%s"/ge' 

The Perl solution provided by Stephane requires a non-core Perl module. One could use the core module (since 5.10), Time::Piece, similarly:

#!/usr/bin/env perl use strict; use warnings; use Time::Piece; my $t = Time::Piece->new; while (<>) { s{\w{3}\s(\w{3}\s\d{1,2}\s\d\d:\d\d:\d\d\s\d{4})} {$t=Time::Piece->strptime($1,"%b %d %H:%M:%S %Y"); sprintf "%s",$t->epoch}ge; print; }