Added getopts post

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Marcus Noble 2021-08-04 20:49:40 +00:00
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---
title: "CLI flag handling in Bash using getopts"
date: 2021-08-04T20:49:37+01:00
draft: false
tags:
- bash
images:
- https://opengraph.cluster.fun/opengraph/?siteTitle=Today%20I%20learnt...&title=CLI%20flag%20handling%20in%20Bash%20using%20getopts&tags=bash&image=https%3A%2F%2Fmarcusnoble.co.uk%2Fimages%2Fmarcus.jpg&twitter=Marcus_Noble_&github=AverageMarcus&website=www.MarcusNoble.co.uk
---
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.