42 lines
1.4 KiB
Markdown
42 lines
1.4 KiB
Markdown
---
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title: "CLI flag handling in Bash using getopts"
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date: 2021-08-04T20:49:37+01:00
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draft: false
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tags:
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- bash
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images:
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- 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
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---
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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.
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`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`)
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Example usage:
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```sh
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#!/bin/bash
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NAME="World"
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FORCE=false
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showHelp() {
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echo "Usage: example.sh [args]"
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exit 0
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}
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while getopts 'hfn:' FLAG
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do
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case $FLAG in
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h) showHelp ;;
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f) FORCE=true ;;
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n) NAME=$OPTARG ;;
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*) echo "Unsupported argument flag passed" ;;
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esac
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done
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echo "Hello, $NAME"
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```
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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. |