111–120 of 129 posts
This is only a convention and is entirely up to the calling program.
For example in bash scripts you can use `exec -a name ...` to pass "name" as the 0th argument.
If you are already using #!/bin/bash you might as well use ${BASH_SOURCE[0]} to get the path to the current script.
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You can also use add a hyphen ( https://linuxhint.com/bash-heredoc-tutorial/
I've always avoided that for fear that my or someone else's editor will accidentally replace the tabs with space. Mixed is not a common configuration, these days.
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I also really like the "flag" package for Go, it generates the help text for you and easily lets you set defaults as well as helps you type-check inputs.
I like https://github.com/jpillora/opts for Go arg parsing. It has better, sane defaults with long/short opts.
The power is out on your boat, again. It’s 3am. You suspect that, again, the alternator housing has come loose. You duct tape a flashlight to the bulkhead so you can work hands free and actually see what you are doing. All you have on you is a broken pocket knife but it’ll do because all you need to accomplish right now is to tighten the housing screws enough . You know this for a fact because you’ve done it three ti…
"Necessity is the mother of invention" must have been coined by a sailor.
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Or just a multiline string: #!/bin/bash USAGE="my-script — does one thing well Usage: my-script Options: Input file to read. Output file to write. Use '-' for stdout. -h Show this message. " help() { echo "$USAGE" } This is my standard approach which is cleaner for putting the documentation at the very top of the file like the linked article.
Thank you! I had no idea that multiline strings were valid bash.
git commit -m "First line of commit
Second line of commit"
That's a multi-line string in bash.
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Thank you for this really helpful comment. It's like an encyclopedia's worth of bash information in one go--much appreciated.
You're welcome! Shell scripting has a weird language, unsafe by default, and very prone to mistakes... but knowing it well pays off. People say that for complex things it's better to write Python, but that doesn't fly in embedded or Docker environments. Python is not even present in the default Ubuntu Docker images. Also if all you want to do is really write glue code between CLI programs, shell scripting is the way…
I learnt the same trick some years ago, from an article called Shell Scripts Matter : https://dev.to/thiht/shell-scripts-matter So I took some of the advice and tips offered in there, and wrote a template file to be used as a baseline when writing scripts for any project that might need one: https://github.com/j1elo/shell-snippets/blob/master/template... Other resources that I link in the readme of that repo, because…
A bash pitfall which I have experienced but didn’t see mentioned is the behavior of the `set -e` (errexit) option when using command substitution. If you expect failures within the command substitution to cause the script to exit, you’re gonna be confused. https://twitter.com/hellsmaddy/status/1273744824835796993?s=... Tl;dr use `shopt -s inherit_errexit`
# Cause command substitution to inherit the value of the `errexit` option.
# Introduced in Bash 4.4
if [ "${BASH_VERSINFO[0]}" -gt 4 ] ||
{ [ "${BASH_VERSINFO[0]}" -eq 4 ] && [ "${BASH_VERSINFO[1]}" -ge 4 ]; }; then
shopt -s inherit_errexit
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bash is everywhere
So is python
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Or just a multiline string: #!/bin/bash USAGE="my-script — does one thing well Usage: my-script Options: Input file to read. Output file to write. Use '-' for stdout. -h Show this message. " help() { echo "$USAGE" } This is my standard approach which is cleaner for putting the documentation at the very top of the file like the linked article.
Woah, I had no idea multiline strings were even a thing in Bash, I've been using heredocs for help messages since forever! Do you know if these are portable?
[1]https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...
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To expand on that pattern: while (( $# )); do case "$1" in -h|--help) usage exit ;; -v|--version) do_version exit ;; -d|--debug) debug=true ;; -a|--arg) arg_value="$2" shift ;; *) if [[ ! -v pos1 ]]; then pos1="$1" elif [[ ! -v pos2 ]]; then pos2="$1" else >&2 printf "%s: unrecognized argument\n" "$1" >&2 usage exit 1 fi esac shift done
The one downside of this is that it doesn't handle squeezing flags as in foo -da bar whereas getopts does. On the other hand, with (the Bash built-in) getopts you're limited to single character flags.
while (( $# )); do
case "$1" in
-*h*|--help)
do_help
exit
;;
-*v*|--version)
do_version
exit
;;
-*d*|--debug)
debug=true
;;&
-*a*|--arg)
value="$2"
shift
;;&
esac
shift
done