mjhjmtu

In my bash script I have a while loop as follows. What I don't understand is, why the call of HandBrakeCLI breaks the loop.
If the 'if' condition is false and 'else' is follwed, the loop continues. Here is my script:

FILES="xxx*.ts
yyy.ts"

for f in $FILES
do
 find /pathto -name $f -print | while IFS= read -r file; do
 echo "file found = $file"
 outputfile=$outputpath$(basename "$file")".mp4"

 if [[ ! -f $outputfile ]] then 
 HandBrakeCLI -i "$file" -o "$outputfile" -e x264 -q 22 -r 15 -B 64 -X 480 -O
 else echo "outputfile already exists: $outputfile"
 fi
 done
done

So I have three files, named xxx1.ts, xxx2.ts and yyy.ts.
All should be found and converted by HandBrakeCLI. But after the first conversion (of xxx1.ts) the while loop breaks and yyy.ts is processed.
If I start the script again, it finds the first file being already converted and enters the else branch. This time the while loop doesn't break and it processes xxx2.ts and then yyy.ts

Why does the HandBrakeCLI call breaks my loop and how can I prevent it?

while as written is not safe to use as standard input is here shared between processes so HandBrakeCLI is likely consuming standard input as well. This can be seen in a minimal example:

$ printf "anbncn" 
| while IFS= read -r x; do echo $x; sed 's/$/ sed was here/'; done
a
b sed was here
c sed was here

and thus the while loop exits early as there is nothing else to read from standard input after sed graffitied up the lines.

Workarounds are to hope and pray nothing else in the code is using some other file descriptor, say 3

while IFS= read -u 3 -r x; do
 echo $x
 sed 's/$/ sed read this line/'
done 3< <(printf "anbncn")

or to switch to a different programming language. (sed will now hang, unless you feed standard input to it, somehow.)

Another option would be to close standard input to your program, e.g.

HandBrakeCLI ... <&-

as that will prevent it from seeing the standard input the while loop needs.