Multi-line commands with comments in bash

As part of the last post I initially used a bash script to generate the commands to output the individual videos. As per usual, when I finally got fed up of the limitations and syntax issues in bash I switched to a proper programming language, perl. However this time I learnt a neat trick to doing multi-line commands in bash with comments embedded using the array feature of bash. A multi-line command typically looks like:

        melt \
            color:black \
                out=$audiolen \

However what if you want to add comments into the command? You can’t.

To solve this create an array:

        # Take black background track for same number of seconds as the MP3, then add 10 seconds of another image

and then use the following magic to execute it:


Using this you can also conditionally add in extra statements if you’re using a pipeline-type program such as imagemagick (convert) or melt:

        # Output to the file
        -consumer avformat
            f=mpeg acodec=mp2 ab=96k vcodec=mpeg2video vb=1000k

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