Printing pretty help/usage messages
October 22nd, 2007
I just came across a script that had a beautiful method of printing help messages. I am unsure why this method is not used more. Here is an example:
$ cat helpExample.sh
#!/bin/bash
usage()
{
echo "Usage: ${0##*/}
This is an example help message in BASH.
-x this option does nothing
" >&2
exit $1
}
usage 1
The script is using echo ” followed by a multi line help message redirected to standard error (" >&2). Output:
$ ./helpExample.sh
Usage: helpExample.sh
This is an example help message in BASH.
-x this option does nothing
October 22nd, 2007 at 11:41 am
Here Documents would work equally as well.
October 23rd, 2007 at 9:29 am
Hi Brock,
Can you please explain ${0##*/}
$0 - prints the command name
when i ran it with just $0 i got he following:
Usage: ./testt.sh ( i named the script testt.sh)
Yes $0 prints the command name. ${0#*/} removes everything up to the first forward slash in the command name. Here is an example:
$ cat scriptName.sh
#!/bin/bash
echo '$0 ' = $0
echo '${0#*/} ' = ${0#*/}
echo '${0##*/} ' = ${0##*/}
$ ./scriptName.sh
$0 = ./scriptName.sh
${0#*/} = scriptName.sh
${0##*/} = scriptName.sh
$ /home/noland/scriptName.sh
$0 = /home/noland/scriptName.sh
${0#*/} = home/noland/scriptName.sh
${0##*/} = scriptName.sh
Another resource is my 10 Steps to Beautiful Shell Scripts post.
Thanks,
Brock