Example of how to edit subtitles in a video / media file

edit-subtitles.sh

#!/bin/sh

# the below command exports only the subtitles/text from the mkv video to a plain-text srt file
ffmpeg -i video.mkv -an -vn -map 0:2 -c:s:0 srt sub.srt

# this command replaces any text in the subtitles matching "some text to change" with "new text"
sed -E 's/(some text to change)/new text/g' -i sub.srt

# this command mixes the subtitles back in with the video and audio into a new media file
ffmpeg -i video.mkv -i sub.srt -map 0:0 -map 0:1 -map 1:0 -c:v copy -c:a copy -c:s copy video-new-subtitles.mkv