Extract subtitles from mkv movies

$ sudo pacman -S mkvtoolnix-cli

$ mkvmerge -i 5426d90fb609da53e52fdc31ce1180efb6e29430
File '5426d90fb609da53e52fdc31ce1180efb6e29430': container: Matroska
Track ID 0: audio (PCM)
Track ID 1: video (MPEG-4p10/AVC/h.264)
Track ID 2: subtitles (SubRip/SRT)
Global tags: 1 entries

$ mkvextract tracks 5426d90fb609da53e52fdc31ce1180efb6e29430 2:sub.srt
Extracting track 2 with the CodecID 'S_TEXT/UTF8' to the file 'sub.srt'. Container format: SRT text subtitles
Progress: 100%

Reference: http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge-gui.html