[FFmpeg-trac] #9752(undetermined:new): ffmpeg is affecting the parent shell's file stream

[FFmpeg]

#9752: ffmpeg is affecting the parent shell's file stream
-------------------------------------+-------------------------------------
             Reporter:  rgovostes    |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 I am invoking ffmpeg from within a bash loop like this:

 {{{
 while IFS="" read -r PLAYLIST; do
     ...
     ffmpeg -f concat -i concat.txt -i chapters.txt -map_metadata 1 \
         -c copy merged.mp4
     ....
 done < <(head -n 3 playlists.txt)
 }}}

 Each iteration of this loop, it should read one line from `playlists.txt`
 into the variable `PLAYLIST`. However, the lines are being unexpectedly
 truncated. Each line should start `{"ie_key": "YoutubeTab"` but when the
 truncation occurs the first 7 bytes are skipped and the loop reads `y":
 "YoutubeTab"`.

 This *only* happens when ffmpeg is invoked within the loop. I wasn't aware
 a child process could affect the parent like this but maybe ffmpeg is
 inheriting a file descriptor and inadvertently seeking it?

 {{{
 ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
 built with Apple clang version 13.1.6 (clang-1316.0.21.2)
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9752>
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