Bash while loop wait until task has completed

问题

I have a bash script that I created to process videos from within a folder and it's subfolders:

find . -type f -name '*.mkv' | while read file;
do
  ffmpeg -i $file ...
done

The problem: Instead of the while loop waiting ffmpeg to complete, it continues iterate through the loop. The end result is, files not getting processed. I need a way to have the current while loop iteration to wait until ffmpeg is complete before continuing to the next. Or alternatively a way to queue these items.

Edit: So The solution when iterating over a set of files is to pass the -nostdin param to ffmpeg. Hope this helps anyone else who might have a similar issue.

Also file --> $file was a copy/paste typo.

回答1:

I realize I posted this a while ago but I found the solution. Thanks for all of the responses. Providing the -nostdin param to ffmpeg will do the trick. It will process only the current file before moving onto the next file for processing.

ffmpeg's -nostdin option avoids attempting to read user input from stdin otherwise the video file itself is interpreted.

ffmpeg -i <filename> ... -nostdin

The best part about using the above is that you can continue to use verbosity in case an error is thrown in the output:

ffmpeg -i <filename> ... -nostdin -loglevel panic

OR if you would rather report the output to a file do so this way:

# Custom log name (optional). Helpful when multiple files are involved.
# FFREPORT=./${filename}-$(date +%h.%m.%s).log
ffmpeg -i <filename> ... -nostdin -report

You can also use a combination of the two as well. Also thanks @Barmar for the solution!

回答2:

I think that this is as simple as you missing the $ before file.

find . -type f -name '*.mkv' | while read file;
do
    ffmpeg -i $file ...
done

回答3:

This is good for you?

find . -type f -name '*.mkv' -exec ffmpeg -i {} \;

回答4:

I'm a vicious answer snatcher. I found one:

ffmpeg -i $file &
wait $!

Thanks to puchu, here: apply ffmpeg to many files

来源：https://stackoverflow.com/questions/13995715/bash-while-loop-wait-until-task-has-completed

标签

bash

ffmpeg

while-loop