[SOLVED] bash/awk: What is going on here?

tmerriam · 04-16-2012, 03:52 PM

I have a problem with a line in a bash script I am working on, but I'm not really sure what the problem is. The command works, but my script breaks when the one of the variable names has spaces.

I found this command to use ffmpeg to find the length of a movie in seconds.

Code:

MOVIE=${1}
TIME=$(ffmpeg -i ${MOVIE} 2>&1 | grep "Duration"| cut -d ' ' -f 4 | sed s/,// | awk '{ split($1, A, ":"); split(A[3], B, "."); print 3600*A[1] + 60*A[2] + B[1] }')

echo "Duration: $TIME"

When $MOVIE has spaces in it, it seems that the line TIME=... is completely ignored. I know this because when it works correctly, there is some output from ffmpeg. Instead, bash quits later on because $TIME is not set.

What the heck is going wrong?

colucix · 04-16-2012, 04:06 PM

You have to use quotes to prevent the positional parameter (argument) from being splitted in two or more space separated fields:

Code:

MOVIE="${1}"
TIME=$(ffmpeg -i "${MOVIE}" 2>&1 | blah blah blah

An aside note: so many piped commands are not really necessary when awk can do it all! Example:

Code:

TIME=$(ffmpeg -i "${MOVIE}" 2>&1 | TZ=UTC0 awk '/Duration/{gsub(/[,:]/," ",$2); print mktime("1970 01 01 " $2)}')

tmerriam · 04-16-2012, 04:38 PM

That helped a little bit, but it still doesn't work. The line runs now, but ffmpeg just prints out the first word of the filename, complains that it doesn't exist, and quits. So the spaces are still tripping it up somehow.

colucix · 04-16-2012, 04:45 PM

Please, can you post an example of your shell session? I'll try to reproduce the error to see what's going on. A working example:

Code:

$ cat test.sh
#!/bin/bash
#
MOVIE="${1}"
TIME=$(ffmpeg -i "${MOVIE}" 2>&1 | TZ=UTC0 awk '/Duration/{gsub(/[,:]/," ",$2); print mktime("1970 01 01 " $2)}')
echo $TIME
$ ./test.sh "video name with spaces.avi"
3102
$ ffmpeg -i "video name with spaces.avi" 2>&1 | grep Duration
  Duration: 00:51:42.76, start: 0.000000, bitrate: 1353 kb/s

tmerriam · 04-16-2012, 05:06 PM

Actually, I take that back, it does work. I was misreading a different error from further on in the script. I fixed that and it works now.

Thank you so much!

colucix · 04-16-2012, 05:18 PM

Nice! You can mark this thread as SOLVED if you wish.

syg00 · 04-16-2012, 06:19 PM

And maybe also thank the man.
Every time I read a post from colucix I learn something new ...