Shell Script Debugging

Question

Level 4

3,011 points

Shell Script Debugging

I was wanting to set a debugging option in a script where the commands would get printed out instead of being executed. At the moment I have every command in an 'if' statement...

if [ $debugOn ] ; then
debugmessage touch $target/test
else
touch $target/test
fi

There must be a better way to do this 🙂

Any suggestions?

Ta.
-david

Server 10.4.8

Posted on Feb 17, 2007 10:39 AM

Answer 1

Feb 17, 2007 11:07 AM in response to David_x

Try running this command before running your script:

set -x

Answer 2

David_x Author

Level 4

3,011 points

Feb 17, 2007 11:48 AM in response to Ken Nellis

That's a usefull one to know for tracing through the whole script, thanks!

However, I was looking for something whereby I can selectively control what get printed out. Also, I don't actually want to run some of the commands in the script, just print out what 'would' have run. The 'set -x' still actually proceeds and executes the various script statements.

I've so far got a slightly better version...

debugmessage() { if [ $debugOn ] ; then
echo "$@"
else
$@
fi
}

Then, I can have the following command in the script...

debugmessage rm -rf $dir

and if debug is on, it will not actually run the 'rm' command, just print it out.

However, the above gives me an error... "line 34: debug:: command not found", which relates to the line after the 'else' with "$@" on it

Almost there but possibly a much better way?

Ta.
-david

Answer 3

David_x Author

Level 4

3,011 points

Feb 17, 2007 12:04 PM in response to David_x

OK, getting better (& simpler!)...

if [ "_$1" = "_--debug" ] ; then
debugOn=echo
else
debugOn=
fi

Then, I can have this line in the script...

$debugOn rm -rf /$dir

and if debug is ON, then it gets echoed, else it gets executed 🙂

Anyone see any probs with this?

-david

Answer 4

Feb 17, 2007 9:13 PM in response to David_x

It looks reasonable, though if you had a command named '-n' you'd be in trouble. Also, if you redirect I/O you'll end up with command names written into files.

Answer 5

Feb 19, 2007 8:08 AM in response to David_x

Hello,

You might want to look at the getopts function:
<pre style="overflow: auto;font-size:small; font-family: Monaco, 'Courier New', Courier, monospace; color: #222; background: #ddd; padding: .3em .8em .3em .8em; font-size: 10px;">DEBUG=0

while getopts 'd' option ; do
case "$option" in

'd')
DEBUG=1
;;

?)
usage # (function that prints help message for unknow options)
exit 0
;;
esac
done
shift `expr $OPTIND - 1`</pre>
Then for debug mode:
your_script -d

--
Cole

15 PB Mac OS X (10.3.9)