[ "$1" == "--help" ] && { sed -n -e '/^# Usage:/,/^$/ s/^# \?//p' < $0; exit; }

display an embeded help message from bash script header

With this one liner you can easily output a standard help message using the following convention: Usage: is the start marker Stop at the last #
Sample Output
#!/bin/bash
#
# Usage: do someting really funny
#  --help      This message
#  --force     force be stronger
#  --remove    delete whatyou've done, be CAREFULL
#
# ex:  myfun  dosomething
#
# myfun --force dosomething_REALLY_DO_IT
#

[ "$1" == "--help" ] && { sed -n -e '/^# Usage:/,/^$/ s/^# \?//p' < $0; exit; }

echo really funny !

9
By: syladmin
2009-09-04 20:36:06
sed

These Might Interest You

  • A really fun vim oneliner for auto documenting your option's parsing in your script. # print the text embeded in the case that parse options from command line. # the block is matched with the marker 'CommandParse' in comment, until 'esac' extract_cmdl_options() { # use vim for parsing: # 1st grep the case block and copy in register @p + unindent in the buffer of the file itself # 2nd filter lines which start with --opt or +opt and keep comment on hte following lines until an empty line # 3rd discard changes in the buffer and quit vim -n -es -c 'g/# CommandParse/+2,/^\s\+esac/-1 d p | % d | put p | % -c 'g/^\([-+]\+[^)]\+\))/,/^\(\s\+[^- \t#]\|^$\)/-1 p' \ -c 'q!' $0 } example code:http://snipplr.com/view/25059/display-embeded-comments-for-every-opt-usefull-for-auto-documenting-your-script/ Show Sample Output


    0
    vim -n -es -c 'g/# CommandParse/+2,/^\s\+esac/-1 d p | % d | put p | %<' -c 'g/^\([-+]\+[^)]\+\))/,/^\(\s\+[^- \t#]\|^$\)/-1 p' -c 'q!' $0
    syladmin · 2009-12-19 08:32:00 0
  • echo "ls" > script.bash; This is my script, a simple 'ls'. gpg -c script.bash; Here I encrypt and passord-protect my script. This creates file script.bash.gpg. cat script.bash.gpg | gpg -d --no-mdc-warning | bash Here I open file script.bash.gpg, decrypt it and execute it.


    -2
    echo "ls" > script.bash; gpg -c script.bash; cat script.bash.gpg | gpg -d --no-mdc-warning | bash
    betsubetsu · 2013-03-10 09:34:12 1
  • Put this code in a bash script. The script expects the PDF file as its only parameter. It will add a header to the PDF containing the page numbers and output it to a file with the suffix "-header.pdf" Requires enscript, ps2pdf and pdftk.


    1
    enscript -L1 -b'||Page $% of $=' -o- < <(for i in $(seq "$(pdftk "$1" dump_data | grep "Num" | cut -d":" -f2)"); do echo; done) | ps2pdf - | pdftk "$1" multistamp - output "${1%.pdf}-header.pdf"
    captaincomic · 2012-01-27 12:26:33 2
  • (Please see sample output for usage) script.bash is your script, which will be crypted to script.secure script.bash --> script.secure You can execute script.secure only if you know the password. If you die, your script dies with you. If you modify the startup line, be careful with the offset calculation of the crypted block (the XX string). Not difficult to make script editable (an offset-dd piped to a gpg -d piped to a vim - piped to a gpg -c directed to script.new ), but not enough space to do it on a one liner. Show Sample Output


    5
    echo "eval \"\$(dd if=\$0 bs=1 skip=XX 2>/dev/null|gpg -d 2>/dev/null)\"; exit" > script.secure; sed -i s:XX:$(stat -c%s script.secure): script.secure; gpg -c < script.bash >> script.secure; chmod +x script.secure
    rodolfoap · 2013-03-09 11:16:48 5
  • In order to write bash-scripts, I often do the task manually to see how it works. I type ### at the start of my session. The function fetches the commands from the last occurrence of '###', excluding the function call. You could prefix this with a here-document to have a proper script-header. Delete some lines, add a few variables and a loop, and you're ready to go. This function could probably be much shorter...


    1
    quickscript () { filename="$1"; history | cut -c 8- | sed -e '/^###/{h;d};H;$!d;x' | sed '$d' > ${filename:?No filename given} }
    joedhon · 2014-02-09 12:19:29 0
  • will display typedefs, structs, unions and functions declared in 'stdio.h'(checkout _IO_FILE structure). It will be helpful if we want to know what a particular header file will offer to us. Command 'cpp' is GNU's C Preprocessor.


    4
    cpp /usr/include/stdio.h | grep -v '^#' | grep -v '^$' | less
    mohan43u · 2009-05-22 22:40:25 2

What Others Think

Why didn't I think of that? Elegant.
sufoo · 454 weeks and 4 days ago
This is pickier, but shorter: [ "$1" == "--help" ] && \ awk '/^#: / { print $0 }' $0 Start your help message with "#:". Also convenient for embedding other messages in scripts.
lbonanomi · 454 weeks ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands



Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: