FFmpeg in a bash script ( quotes )

Question

I'm working on a script that open a text file with some ffmpeg commands. ( about 10 command generated from an other project ) Each command are working when i copy paste than into the terminal manually, but when the script run, simple commands work but I am stuck on a " No such filter : ..." error.

Here is my command : -i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.mp4 -i 5.mp4 -i 6.mp4 -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1][3:0][3:1][4:0][4:1][5:0][5:1]concat=n=6:v=1:a=1:unsafe=1 [v] [a]' -map '[v]' -map '[a]' -aspect 16:9 -s 1280x720 -c:v mpeg4 -c:a libmp3lame -y track_0.mp4

I think all the problem is in the " ' " i try to escape them with " \' " but ffmpeg is telling me No such filter: '''

Here is my script assuming that the variable ARGS is set dynamically ( for the example I have set it manually ) :

#!/bin/bash
ARGS="-i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.mp4 -i 5.mp4 -i 6.mp4 -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1][3:0][3:1][4:0][4:1][5:0][5:1]concat=n=6:v=1:a=1:unsafe=1 [v] [a]' -map '[v]' -map '[a]' -aspect 16:9 -s 1280x720 -c:v mpeg4 -c:a libmp3lame -y track_0.mp4"
ffmpeg ${ARGS}

EDIT 1:

Well I forgot to precise that my text file is like that :

-loop 1 -f image2 -c:v png -i FILE_0.data -i sample.wav -map 0:v -map 1:a -t 20 -s 1280x720 -c:v mpeg4 -c:a libmp3lame  -pix_fmt yuv420p -y 4.mp4
-loop 1 -f image2 -c:v png -i black.png -i sample.wav -map 0:v -map 1:a -t 14 -s 1280x720 -c:v mpeg4 -c:a libmp3lame  -pix_fmt yuv420p -y 5.mp4
-loop 1 -f image2 -c:v png -i FILE_1.data -i sample.wav -map 0:v -map 1:a -t 20 -s 1280x720 -c:v mpeg4 -c:a libmp3lame  -pix_fmt yuv420p -y 6.mp4
-i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.mp4 -i 5.mp4 -i 6.mp4 -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1][3:0][3:1][4:0][4:1][5:0][5:1]concat=n=6:v=1:a=1:unsafe=1 [v] [a]' -map '[v]' -map '[a]' -aspect 16:9 -s 1280x720 -c:v mpeg4 -c:a libmp3lame -y track_0.mp4

And in this file I read each line and I pass the line to ffmpeg to process what i want

Can you help me ?

that other guy · Accepted Answer · 2015-03-20 21:02:12Z

4

Well, let's have a look:

$ shellcheck yourscript
ARGS="-i 1.mp4 -i 2.mp4 -i 3.mp4 -i 4.mp4 -i 5.mp4 -i 6.mp4 -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1][3:0][3:1][4:0][4:1][5:0][5:1]concat=n=6:v=1:a=1:unsafe=1 [v] [a]' -map '[v]' -map '[a]' -aspect 16:9 -s 1280x720 -c:v mpeg4 -c:a libmp3lame -y track_0.mp4"
      ^-- SC2089: Quotes/backslashes will be treated literally. Use an array.

In yourscript line 3:
ffmpeg ${ARGS}
       ^-- SC2090: Quotes/backslashes in this variable will not be respected.

As suggested, let's use an array:

#!/bin/bash
args=(
  -i "1.mp4"
  -i "2.mp4" ... 
  -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1][3:0][3:1][4:0][4:1][5:0][5:1]concat=n=6:v=1:a=1:unsafe=1 [v] [a]' 
  -map '[v]' 
  -map '[a]' 
  -aspect 16:9
  ....
)
ffmpeg "${args[@]}"

Obviously this works equally well if you build the array dynamically, e.g. with

args=()
for f in 1.mp4 2.mp4
do
  args+=(-i "$f")
done
...

To explain why this works, here's what you expected would happen:

Bash sees ffmpeg $ARGS
Bash substitutes the variable, giving ffmpeg -i 'my arg'
Bash interprets the new command, giving the argument list

ffmpeg, -i, my arg
Bash runs ffmpeg with these two arguments

This is what actually happens:

Bash sees ffmpeg $ARGS
Bash interprets it and splits it into the arguments

ffmpeg $ARGS
Bash sees that one of the arguments is an unquoted variable, so it splits the value of the variable on spaces and puts each word into a separate argument:

ffmpeg, -i, 'my, file'
Bash runs ffmpeg with these three arguments, which now contain garbage single quotes.

edited Mar 20, 2015 at 21:02

answered Mar 20, 2015 at 20:48

that other guy

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5 Comments

Guillaume Villena Over a year ago

I forgot one thing look my first post and you will understand

that other guy Over a year ago

@GuillaumeVillena What thing?

Guillaume Villena Over a year ago

As I said, I read a text file with all the args that I need to pass to ffmpeg, and I just post an example of my file.

that other guy Over a year ago

@GuillaumeVillena That's a fragile and insecure way to do it. If you really, seriously want to do it anyways, you can use eval "ffmpeg $ARGS".

Guillaume Villena Over a year ago

sorry, I did not understand what you said because I misread your very good explanation ( sorry I am french and I have some difficulties with english )

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