bash loop droping a leading '.' character in the loop variable every other iteration

Question

So far I only have spaces and single quotes to deal with, so I put double quotes around it

#!/bin/bash
#ffmpeg -i Muppets\ Most\ Wanted_KBYUT_2017_07_08_18_56_00.wtv  -f ffmetadata metadata.txt
#ffmpeg -i Gene\ Roddenberry\'s\ Andromeda_COMET_2017_12_14_20_05_51.wtv  -f ffmetadata metadata1.txt
find . -type f | grep 'wtv$' | while read file; do
    echo "----"
    echo "----"
    echo "----"
    echo "$file"
    ls -alh "$file"
    echo "$file.txt"
    #ffmpeg -i "$file" -f ffmetadata "$file.txt"
done

prints out

stephen@B450-AORUS-M:~/Videos$ ./ffmetadata.sh 
./Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv
-rw------- 1 stephen stephen 7.9G Sep  6  2019 './Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv'
./Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv.txt
./Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv
-rw------- 1 stephen stephen 794M Dec 16  2017 "./Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv"
./Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv.txt

Looks ok, so I try letting ffmpeg do its thing, by uncommenting the one line, and I get

stephen@B450-AORUS-M:~/Videos$ ./ffmetadata.sh 
./Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv
-rw------- 1 stephen stephen 7.9G Sep  6  2019 './Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv'
./Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv.txt
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
  ...
Input #0, wtv, from './Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv':
  Metadata:
    WM/MediaClassPrimaryID: db9830bd-3ab3-4fab-8a371a995f7ff74
    WM/MediaClassSecondaryID: ba7f258a-62f7-47a9-b21f4651c42a000
    Title           : Muppets Most Wanted
    ...
Output #0, ffmetadata, to './Muppets Most Wanted_KBYUT_2017_07_08_18_56_00.wtv.txt':
  Metadata:
    WM/MediaClassPrimaryID: db9830bd-3ab3-4fab-8a371a995f7ff74
    WM/MediaClassSecondaryID: ba7f258a-62f7-47a9-b21f4651c42a000
    Title           : Muppets Most Wanted
    ...
Stream mapping:
Press [q] to stop, [?] for help
size=       2kB time=-577014:32:22.77 bitrate=N/A speed=N/A    
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded 
----
----
----
/Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv
ls: cannot access "/Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv": No such file or directory
/Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv.txt
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
...
  libpostproc    54.  7.100 / 54.  7.100
/Gene Roddenberry's Andromeda_COMET_2017_12_14_20_05_51.wtv: No such file or directory

The first file works, but the second file looses the leading dot, changing the relative path to an absolute path. I tried 3 file in the folder, and 2 work. 4 files 2 work. 6 files 3 work.

Stephen Kitt · Accepted Answer · 2020-03-20 14:13:21Z

2

The leading “.” is being consumed by ffmpeg (when it asks about the stream mapping), which shares its standard input with read.

You should use find’s capabilities instead:

find . -type f -name '*wtv' -ls -exec ffmpeg -i {} -f ffmetadata {}.txt \;

This finds files whose name ends with wtv, shows their detailed information (which is a GNU extension; use -print if your find doesn’t support ls), and runs ffmpeg on them.

answered Mar 20, 2020 at 14:13

Stephen Kitt

482k60 gold badges1.2k silver badges1.4k bronze badges

Oh, that's tricky. Passing -nostdin to ffmpeg works too.

Stephen
– Stephen

2020-03-20 16:15:43 +00:00
Commented Mar 20, 2020 at 16:15

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