bash script stops execution in while loop - why?

问题

I have this bash script for converting .mp4 video to .mp3 audio. It runs, but does the loop only once, though there are more mp4 files in /home/myname/mp4dir. The script converts the first .mp4 file it finds to .mp3, unless there is already an .mp3 file. This should be done in a loop, but after the first call to ffmpeg the script stops. Why?

#!/bin/bash
find /home/myname/mp4dir -name "*.mp4" | while read f
do
        fOut=`echo $f | sed s/mp4/mp3/`
        echo "convert $f => $fOut"
        if ! test -f $fOut
        then
                ffmpeg -i $f -vn -f mp3 $fOut
        fi
done

回答1:

From the comments we got that there actually are input files you are looping over (of what kind soever) and that ffmpeg at least starts once. Then, you are stuck.

Add

&> ffmpeg.outerr < /dev/null

to your ffmpeg command and monitor the file ffmpeg.outerr while your "loop", i.e. ffmpeg, executes. It will tell you what the problem is. Either you can solve this problem yourself, or you come back to stackoverflow with this ffmpeg-specific problem using the tag ffmpeg.

回答2:

try this in terminal

create bash nohup.sh and paste in this

#!/bin/sh
while true
do
 /var/www/bash/Someother-bash-script-goes-here.sh
 sleep 60
done

in terminal type where nohup.sh is located

nohup sh nohup.sh >/dev/null 2>&1 &

nohup, will execute every 60 seconds, you can grep service check like this

 #!/bin/sh
SERVICE='ffmpeg'

if ps ax | grep -v grep | grep $SERVICE > /dev/null
then
    echo "$SERVICE service running, will not bother ffmpeg yet"
else
    echo "$SERVICE is not running"
    echo "$SERVICE is not running!" | /var/www/bash/start_service.sh
fi

回答3:

The answer is to add '-nostdin' to ffmpeg (wouldn't answer to an old question like this, but still tops on related Google searches).

来源：https://stackoverflow.com/questions/12543628/bash-script-stops-execution-in-while-loop-why

标签

bash

loops

while-loop