Unique values separated by semicolons (thumbnailers)

The file /usr/share/thumbnailers/totem.thumbnailer contains:

[Thumbnailer Entry]
TryExec=/usr/bin/totem-video-thumbnailer
Exec=/usr/bin/totem-video-thumbnailer -s %s %u %o
MimeType=application/mxf;application/ram;application/sdp;application/vnd.apple.mpegurl;application/vnd.ms-asf;application/vnd.ms-wpl;application/vnd.rn-realmedia;application/vnd.rn-realmedia-vbr;application/x-extension-m4a;application/x-extension-mp4;application/x-flash-video;application/x-matroska;application/x-netshow-channel;application/x-quicktimeplayer;application/x-shorten;image/vnd.rn-realpix;image/x-pict;misc/ultravox;text/x-google-video-pointer;video/3gp;video/3gpp;video/3gpp2;video/dv;video/divx;video/fli;video/flv;video/mp2t;video/mp4;video/mp4v-es;video/mpeg;video/mpeg-system;video/msvideo;video/ogg;video/quicktime;video/vivo;video/vnd.divx;video/vnd.mpegurl;video/vnd.rn-realvideo;video/vnd.vivo;video/webm;video/x-anim;video/x-avi;video/x-flc;video/x-fli;video/x-flic;video/x-flv;video/x-m4v;video/x-matroska;video/x-mjpeg;video/x-mpeg;video/x-mpeg2;video/x-ms-asf;video/x-ms-asf-plugin;video/x-ms-asx;video/x-msvideo;video/x-ms-wm;video/x-ms-wmv;video/x-ms-wmx;video/x-ms-wvx;video/x-nsv;video/x-ogm+ogg;video/x-theora;video/x-theora+ogg;video/x-totem-stream;audio/x-pn-realaudio;audio/3gpp;audio/3gpp2;audio/aac;audio/ac3;audio/AMR;audio/AMR-WB;audio/basic;audio/dv;audio/eac3;audio/flac;audio/m4a;audio/midi;audio/mp1;audio/mp2;audio/mp3;audio/mp4;audio/mpeg;audio/mpg;audio/ogg;audio/opus;audio/prs.sid;audio/scpls;audio/vnd.rn-realaudio;audio/wav;audio/webm;audio/x-aac;audio/x-aiff;audio/x-ape;audio/x-flac;audio/x-gsm;audio/x-it;audio/x-m4a;audio/x-m4b;audio/x-matroska;audio/x-mod;audio/x-mp1;audio/x-mp2;audio/x-mp3;audio/x-mpg;audio/x-mpeg;audio/x-ms-asf;audio/x-ms-asx;audio/x-ms-wax;audio/x-ms-wma;audio/x-musepack;audio/x-opus+ogg;audio/x-pn-aiff;audio/x-pn-au;audio/x-pn-wav;audio/x-pn-windows-acm;audio/x-realaudio;audio/x-real-audio;audio/x-s3m;audio/x-sbc;audio/x-shorten;audio/x-speex;audio/x-stm;audio/x-tta;audio/x-wav;audio/x-wavpack;audio/x-vorbis;audio/x-vorbis+ogg;audio/x-xm;application/x-flac;

The file /usr/share/thumbnailers/ffmpegthumbnailer.thumbnailer contains:

[Thumbnailer Entry]
TryExec=ffmpegthumbnailer
Exec=ffmpegthumbnailer -i %i -o %o -s %s -f
MimeType=video/jpeg;video/mp4;video/mpeg;video/quicktime;video/x-ms-asf;video/x-ms-wm;video/x-ms-wmv;video/x-ms-asx;video/x-ms-wmx;video/x-ms-wvx;video/x-msvideo;video/x-flv;video/x-matroska;application/mxf;video/3gp;video/3gpp;video/dv;video/divx;video/fli;video/flv;video/mp2t;video/mp4v-es;video/msvideo;video/ogg;video/vivo;video/vnd.divx;video/vnd.mpegurl;video/vnd.rn-realvideo;application/vnd.rn-realmedia;video/vnd.vivo;video/webm;video/x-anim;video/x-avi;video/x-flc;video/x-fli;video/x-flic;video/x-m4v;video/x-mpeg;video/x-mpeg2;video/x-nsv;video/x-ogm+ogg;video/x-theora+ogg

I want the values of the MimeType field of the file /usr/share/thumbnailers/ffmpegthumbnailer.thumbnailer to not be contained in the MimeType field of the file /usr/share/thumbnailers/totem.thumbnailer.

The resulting file (handmade) is as follows (the modified totem.thumbnailer):

[Thumbnailer Entry]
TryExec=/usr/bin/totem-video-thumbnailer
Exec=/usr/bin/totem-video-thumbnailer -s %s %u %o
MimeType=application/ram;application/sdp;application/vnd.apple.mpegurl;application/vnd.ms-asf;application/vnd.ms-wpl;application/vnd.rn-realmedia-vbr;application/x-extension-m4a;application/x-extension-mp4;application/x-flash-video;application/x-matroska;application/x-netshow-channel;application/x-quicktimeplayer;application/x-shorten;image/vnd.rn-realpix;image/x-pict;misc/ultravox;text/x-google-video-pointer;video/3gpp2;video/mpeg-system;video/x-mjpeg;video/x-ms-asf-plugin;video/x-theora;video/x-totem-stream;audio/x-pn-realaudio;audio/3gpp;audio/3gpp2;audio/aac;audio/ac3;audio/AMR;audio/AMR-WB;audio/basic;audio/dv;audio/eac3;audio/flac;audio/m4a;audio/midi;audio/mp1;audio/mp2;audio/mp3;audio/mp4;audio/mpeg;audio/mpg;audio/ogg;audio/opus;audio/prs.sid;audio/scpls;audio/vnd.rn-realaudio;audio/wav;audio/webm;audio/x-aac;audio/x-aiff;audio/x-ape;audio/x-flac;audio/x-gsm;audio/x-it;audio/x-m4a;audio/x-m4b;audio/x-matroska;audio/x-mod;audio/x-mp1;audio/x-mp2;audio/x-mp3;audio/x-mpg;audio/x-mpeg;audio/x-ms-asf;audio/x-ms-asx;audio/x-ms-wax;audio/x-ms-wma;audio/x-musepack;audio/x-opus+ogg;audio/x-pn-aiff;audio/x-pn-au;audio/x-pn-wav;audio/x-pn-windows-acm;audio/x-realaudio;audio/x-real-audio;audio/x-s3m;audio/x-sbc;audio/x-shorten;audio/x-speex;audio/x-stm;audio/x-tta;audio/x-wav;audio/x-wavpack;audio/x-vorbis;audio/x-vorbis+ogg;audio/x-xm;application/x-flac;

How do I achieve this using a bash command?

If you switch to zsh in place of bash, you could make use of its array difference operator :| to manipulate the entries:

#!/usr/bin/zsh

# read the `MimeType=` lists into semicolon-delimited arrays
IFS=';' read -A totemArr < <(sed -n 's|^MimeType=||p' totem.thumbnailer)
IFS=';' read -A ffmpegArr < <(sed -n 's|^MimeType=||p' ffmpeg.thumbnailer)

# write back a semicolon-delimited string of the array difference
sed -i.bak 's|^MimeType=.*|MimeType='${(j/;/)${totemArr:|ffmpegArr}}';|' totem.thumbnailer

(the ; on the RHS of the substitution replaces the implied empty element which is common to both arrays and hence was removed), resulting in

$ diff totem.thumbnailer{.bak,} | fold -w 80
4c4
< MimeType=application/mxf;application/ram;application/sdp;application/vnd.apple
.mpegurl;application/vnd.ms-asf;application/vnd.ms-wpl;application/vnd.rn-realme
dia;application/vnd.rn-realmedia-vbr;application/x-extension-m4a;application/x-e
xtension-mp4;application/x-flash-video;application/x-matroska;application/x-nets
how-channel;application/x-quicktimeplayer;application/x-shorten;image/vnd.rn-rea
lpix;image/x-pict;misc/ultravox;text/x-google-video-pointer;video/3gp;video/3gpp
;video/3gpp2;video/dv;video/divx;video/fli;video/flv;video/mp2t;video/mp4;video/
mp4v-es;video/mpeg;video/mpeg-system;video/msvideo;video/ogg;video/quicktime;vid
eo/vivo;video/vnd.divx;video/vnd.mpegurl;video/vnd.rn-realvideo;video/vnd.vivo;v
ideo/webm;video/x-anim;video/x-avi;video/x-flc;video/x-fli;video/x-flic;video/x-
flv;video/x-m4v;video/x-matroska;video/x-mjpeg;video/x-mpeg;video/x-mpeg2;video/
x-ms-asf;video/x-ms-asf-plugin;video/x-ms-asx;video/x-msvideo;video/x-ms-wm;vide
o/x-ms-wmv;video/x-ms-wmx;video/x-ms-wvx;video/x-nsv;video/x-ogm+ogg;video/x-the
ora;video/x-theora+ogg;video/x-totem-stream;audio/x-pn-realaudio;audio/3gpp;audi
o/3gpp2;audio/aac;audio/ac3;audio/AMR;audio/AMR-WB;audio/basic;audio/dv;audio/ea
c3;audio/flac;audio/m4a;audio/midi;audio/mp1;audio/mp2;audio/mp3;audio/mp4;audio
/mpeg;audio/mpg;audio/ogg;audio/opus;audio/prs.sid;audio/scpls;audio/vnd.rn-real
audio;audio/wav;audio/webm;audio/x-aac;audio/x-aiff;audio/x-ape;audio/x-flac;aud
io/x-gsm;audio/x-it;audio/x-m4a;audio/x-m4b;audio/x-matroska;audio/x-mod;audio/x
-mp1;audio/x-mp2;audio/x-mp3;audio/x-mpg;audio/x-mpeg;audio/x-ms-asf;audio/x-ms-
asx;audio/x-ms-wax;audio/x-ms-wma;audio/x-musepack;audio/x-opus+ogg;audio/x-pn-a
iff;audio/x-pn-au;audio/x-pn-wav;audio/x-pn-windows-acm;audio/x-realaudio;audio/
x-real-audio;audio/x-s3m;audio/x-sbc;audio/x-shorten;audio/x-speex;audio/x-stm;a
udio/x-tta;audio/x-wav;audio/x-wavpack;audio/x-vorbis;audio/x-vorbis+ogg;audio/x
-xm;application/x-flac;
---
> MimeType=application/ram;application/sdp;application/vnd.apple.mpegurl;applica
tion/vnd.ms-asf;application/vnd.ms-wpl;application/vnd.rn-realmedia-vbr;applicat
ion/x-extension-m4a;application/x-extension-mp4;application/x-flash-video;applic
ation/x-matroska;application/x-netshow-channel;application/x-quicktimeplayer;app
lication/x-shorten;image/vnd.rn-realpix;image/x-pict;misc/ultravox;text/x-google
-video-pointer;video/3gpp2;video/mpeg-system;video/x-mjpeg;video/x-ms-asf-plugin
;video/x-theora;video/x-totem-stream;audio/x-pn-realaudio;audio/3gpp;audio/3gpp2
;audio/aac;audio/ac3;audio/AMR;audio/AMR-WB;audio/basic;audio/dv;audio/eac3;audi
o/flac;audio/m4a;audio/midi;audio/mp1;audio/mp2;audio/mp3;audio/mp4;audio/mpeg;a
udio/mpg;audio/ogg;audio/opus;audio/prs.sid;audio/scpls;audio/vnd.rn-realaudio;a
udio/wav;audio/webm;audio/x-aac;audio/x-aiff;audio/x-ape;audio/x-flac;audio/x-gs
m;audio/x-it;audio/x-m4a;audio/x-m4b;audio/x-matroska;audio/x-mod;audio/x-mp1;au
dio/x-mp2;audio/x-mp3;audio/x-mpg;audio/x-mpeg;audio/x-ms-asf;audio/x-ms-asx;aud
io/x-ms-wax;audio/x-ms-wma;audio/x-musepack;audio/x-opus+ogg;audio/x-pn-aiff;aud
io/x-pn-au;audio/x-pn-wav;audio/x-pn-windows-acm;audio/x-realaudio;audio/x-real-
audio;audio/x-s3m;audio/x-sbc;audio/x-shorten;audio/x-speex;audio/x-stm;audio/x-
tta;audio/x-wav;audio/x-wavpack;audio/x-vorbis;audio/x-vorbis+ogg;audio/x-xm;app
lication/x-flac;

See also

• Intersection of two arrays in BASH

In pure bash ... (Assuming MimeType is the last line in both files) ... You can do it like this:

#!/bin/bash

readarray -t arr1 < /usr/share/thumbnailers/ffmpegthumbnailer.thumbnailer
readarray -t arr2 < /usr/share/thumbnailers/totem.thumbnailer

IFS=';=' read -a arr1_1 <<< "${arr1[-1]}"
IFS=';=' read -a arr2_1 <<< "${arr2[-1]}"

m="MimeType="

for i in "${arr2_1[@]}";
  do
  [[ ! "${arr1_1[*]}" =~ "$i" ]] && m+="${i};"
  done
  
arr2[-1]="$m"
printf '%s\n' "${arr2[@]}"

And the output will be like this:

[Thumbnailer Entry]
TryExec=/usr/bin/totem-video-thumbnailer
Exec=/usr/bin/totem-video-thumbnailer -s %s %u %o
MimeType=application/ram;application/sdp;application/vnd.apple.mpegurl;application/vnd.ms-asf;application/vnd.ms-wpl;application/vnd.rn-realmedia-vbr;application/x-extension-m4a;application/x-extension-mp4;application/x-flash-video;application/x-matroska;application/x-netshow-channel;application/x-quicktimeplayer;application/x-shorten;image/vnd.rn-realpix;image/x-pict;misc/ultravox;text/x-google-video-pointer;video/3gpp2;video/mpeg-system;video/x-mjpeg;video/x-ms-asf-plugin;video/x-totem-stream;audio/x-pn-realaudio;audio/3gpp;audio/3gpp2;audio/aac;audio/ac3;audio/AMR;audio/AMR-WB;audio/basic;audio/dv;audio/eac3;audio/flac;audio/m4a;audio/midi;audio/mp1;audio/mp2;audio/mp3;audio/mp4;audio/mpeg;audio/mpg;audio/ogg;audio/opus;audio/prs.sid;audio/scpls;audio/vnd.rn-realaudio;audio/wav;audio/webm;audio/x-aac;audio/x-aiff;audio/x-ape;audio/x-flac;audio/x-gsm;audio/x-it;audio/x-m4a;audio/x-m4b;audio/x-matroska;audio/x-mod;audio/x-mp1;audio/x-mp2;audio/x-mp3;audio/x-mpg;audio/x-mpeg;audio/x-ms-asf;audio/x-ms-asx;audio/x-ms-wax;audio/x-ms-wma;audio/x-musepack;audio/x-opus+ogg;audio/x-pn-aiff;audio/x-pn-au;audio/x-pn-wav;audio/x-pn-windows-acm;audio/x-realaudio;audio/x-real-audio;audio/x-s3m;audio/x-sbc;audio/x-shorten;audio/x-speex;audio/x-stm;audio/x-tta;audio/x-wav;audio/x-wavpack;audio/x-vorbis;audio/x-vorbis+ogg;audio/x-xm;application/x-flac;