write the docs once

[Eli the Bearded]

Just a hack, no other content.

I have a habit, in small helper shell scripts / perl scripts, to
document what it is and how it is used right after the #! line. And then
sometimes I don't want to code up a usage() shell function with the same
document as in the comments.

For those cases, here's a fix.

Use the comments at the top of the script as the error usage help
message.

if usage_error_condition; then
echo "${0##*/}: usage error"
sed -e 's/^#!.*/ /;s/^# *$/ /; s/^# //; /^$/ q' < $0
exit 2
fi

Explained:
${0##*/} the script name, with the leading path component removed

sed < $0 read from the script making changes:
s/^#!.*/ / blank out the #! line
s/^# *$/ / blank out blank comments
s/^# // remove leading "# " from comments
/^$/ q stop printing upon reaching first blank line


Elijah
------
Buzz McCool shouldn't be the only one keeping the group alive