To debug a script you may:

    Add -x to interpreter line:  #!/usr/bin/sh -x

    Put command:	set -x
    close to the section of interest

    In suitable places, put "echo $VARIABLE" or "sleep 30" or similar statments
    to trace values or to give time for checking output.

    In pipelines put "tee debugfile" to check if data going down pipeline is
    what you expect.


Note the following coding problems which often cause problems:

    There is no white space around = on variable assignment.
    The arguments to all commands, inparticular, to test ([) must
    be space separated.

    ; is required between commands on the same line

    ;; is used in case statements to terminal statements matching a pattern

    When a VARIABLE could contain characters significant to the shell
    quote the value: "$VARIABLE" is usually best.