Question

I’ve been working on a script to generate .tbn files for my home videos. If I run the script, it only seems to process every other file.

#!/bin/bash

find ~/Movies/Home\ Movies/Canada\ Trip -type f | egrep '\.mp4$|\.avi$|\.mkv$' | while read file ; do

    if [ ! -f "${file:0:${#file}-3}tbn" ]; then
        # .tbn not found
        echo "$file"
        ffmpeg  -itsoffset -13  -i "$file" -vcodec mjpeg -vframes 1 -s 400x224 -an -f rawvideo "${file:0:${#file}-3}tbn"
    fi

done

And here is my data set:

Canada.Trip.S01E01.avi
Canada.Trip.S01E02.avi
Canada.Trip.S01E03.avi
Canada.Trip.S01E04.avi
Canada.Trip.S01E05.avi
Canada.Trip.S01E06.avi
Canada.Trip.S01E07.avi
Canada.Trip.S01E08.avi
Canada.Trip.S01E09.avi
Canada.Trip.S01E10.avi
Canada.Trip.S01E11.avi
Canada.Trip.S01E12.avi
Canada.Trip.S01E13.avi
Canada.Trip.S01E14.mp4
Canada.Trip.S01E15.mp4
Canada.Trip.S01E16.mp4
Canada.Trip.S01E17.mp4
Canada.Trip.S01E18.avi
Canada.Trip.S01E19.mkv
Canada.Trip.S01E20.mp4

So the first time I run it, it generates tbn’s for 1,3,5,7 etc.. The even numbered files fail with vies/Canada Trip/Canada.Trip.S01E16.mp4: No such file or directory
(note the truncated start of the file name)

If I run the script again it generates the even numbered files .tbn files. I’ve never used Bash before so I’m finding the whole situation confusing!

Answer 1

ffmpeg reads stdin. Also, you should always use read -r.