42 lines
1.2 KiB
Markdown
42 lines
1.2 KiB
Markdown
|
---
|
||
|
|
layout: post.html
|
||
|
|
title: "T.I.L. CLI flag handling in Bash using getopts"
|
||
|
|
summary: "Today I Learnt: CLI flag handling in Bash using getopts"
|
||
|
|
date: 2021-08-04T20:49:37+01:00
|
||
|
|
tags: til bash
|
||
|
|
|
||
|
|
---
|
||
|
|
|
||
|
|
I'm not sure how I've never come across this before but while looking through the [Scaleway Kosmos](https://www.scaleway.com/en/betas/#kuberneteskosmos) multi-cloud init script I dicovered the [`getopts`](https://www.man7.org/linux/man-pages/man1/getopts.1p.html) utility.
|
||
|
|
|
||
|
|
`getopts` makes it easier to parse arguments passed to a shell script by defining which letters your script supports. It supports both boolean and string style arguments but only supports single letter flags. (e.g. `-h` and not `--help`)
|
||
|
|
|
||
|
|
Example usage:
|
||
|
|
|
||
|
|
```sh
|
||
|
|
#!/bin/bash
|
||
|
|
|
||
|
|
NAME="World"
|
||
|
|
FORCE=false
|
||
|
|
|
||
|
|
showHelp() {
|
||
|
|
echo "Usage: example.sh [args]"
|
||
|
|
exit 0
|
||
|
|
}
|
||
|
|
|
||
|
|
while getopts 'hfn:' FLAG
|
||
|
|
do
|
||
|
|
case $FLAG in
|
||
|
|
h) showHelp ;;
|
||
|
|
f) FORCE=true ;;
|
||
|
|
n) NAME=$OPTARG ;;
|
||
|
|
*) echo "Unsupported argument flag passed" ;;
|
||
|
|
esac
|
||
|
|
done
|
||
|
|
|
||
|
|
echo "Hello, $NAME"
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
Notice the `:` following the `n`? That indicates that a value should follow the argument flag (`n` in this example) and will be made available as the `OPTARG` variable.
|