Bash-script. Shift seconds

Question

In bash I don't know how to do that. I need to do a bash-script. At stdin I have .srt file of subtitles in this format:

num HH:MM:SS,SSS --> HH:MM:SS,SSS text line 1 text line 2 ... 

HH:MM:SS,SSS start and finish of title for text.

Script must shift seconds. (it can be + or -)

Example:

$cat bmt.srt 5 00:01:02,323 --> 00:01:05,572 Hello, my frieds! 6 .... $./shifter.sh +3<mbt.srt 5 00:01:05,323 --> 00:01:08,572 Hello, my frieds! 6 

I need to grab all HH:MM:SS and convert them to seconds firstly. Is somebody able do this without sed?

Answer 1

Unless the subtitle file spans more than 24 hours, you can use date for this:

#!/usr/bin/env bash set -o errexit -o noclobber -o nounset -o pipefail date_offset="$1" shift_date() { date --date="$1 $date_offset" +%T,%N | cut -c 1-12 } while read -r line do if [[ $line =~ ^[0-9][0-9]:[0-9][0-9]:[0-9][0-9],[0-9][0-9][0-9]\ --\>\ [0-9][0-9]:[0-9][0-9]:[0-9][0-9],[0-9][0-9][0-9]$ ]] then read -r start_date separator end_date <<<"$line" new_start_date="$(shift_date "$start_date")" new_end_date="$(shift_date "$end_date")" printf "%s %s %s\n" "$new_start_date" "$separator" "$new_end_date" echo "New date" else printf "%s\n" "$line" fi done 

For some reason you need to use decimal numbers with this, but it works:

$ ./shifter.sh "+3.0 seconds" < bmt.srt 5 00:01:05,323 --> 00:01:08,572 New date Hello, my frieds! 6 

Answer 2

Perl solution. I did not use any classical time handling module, as miliseconds handling is generally poorly supported.

#!/usr/bin/perl use warnings; use strict; use constant FACTORS => (60 * 60 * 1000, 60 * 1000, 1000, 1); sub time2ms { my $time = shift; my ($ms, $i) = (0, 0); $ms += (FACTORS)[$i++] * $_ for split /[^0-9]/, $time; return $ms; } sub ms2time { my $ms = shift; my $str = q(); for my $i (0 .. 3) { $str .= sprintf +($i == 3 ? '%03d' : '%02d') . (':', ':', ',', q())[$i], $ms / (FACTORS)[$i]; $ms = $ms % (FACTORS)[$i]; } return $str; } my $diff = 1000 * shift; my $TIME_R = qr/[0-9]{2}:[0-9]{2}:[0-9]{2},[0-9]{3}/; while (<>) { if (my ($from, $to) = /($TIME_R) --> ($TIME_R)/) { my $i = 0; for my $time ($from, $to) { $time = time2ms($time) + $diff; print ms2time($time), (' --> ', "\n")[$i++]; } } else { print; } }