TIL: Reading stdin to a BASH variable

Today I wanted to read stdin to a BASH script variable for additional processing. It's not completely straightforward, but it's pretty easy once you know the syntax:

YOUR_VARIABLE=$(</dev/stdin)

A full example:

	#!/bin/bash
	# Usage:
	# echo 'hello!' | ./read-stdin-to-variable.sh
	# https://stackoverflow.com/a/15269128
	STD_IN=$(</dev/stdin)
	echo "Echoing stdin:"
	echo "$STD_IN"
	echo "Echoing again:"
	echo "$STD_IN"

view raw read-stdin-to-variable.sh hosted with ❤ by GitHub

With this, you can easily make pipe-able BASH script files. For instance, with these two files using this technique:

	#!/bin/bash
	STD_IN=$(</dev/stdin)
	# https://stackoverflow.com/a/27480719
	echo $STD_IN | awk '{print toupper($0)}'

view raw to-uppercase.sh hosted with ❤ by GitHub

	#!/bin/bash
	STD_IN=$(</dev/stdin)
	echo $STD_IN | sed 's/-/_/g'

view raw to-snakecase.sh hosted with ❤ by GitHub

You can do:

echo some-text | ./to-uppercase.sh | ./to-snake-case.sh

For:

SOME_TEXT

Shoutout to StackOverflow user Ingo Karkat for explaining this. It's a very handy little trick for making BASH scripts more flexible and reusable!