How to Write Self-Contained AWK Scripts

August 29, 2025

A Quick Why

I won’t try to sell AWK in this post, I’ve done it before.

Over time, I’ve migrated most of my utility scripts to AWK; it’s my default choice when I write new scripts.

The “classic” way, though simple, forces you to live inside a bash string. We can do better.

The “Classic” Way

Let’s write a simple script, to show line-length along with content.

This isn’t about AWK programming; the focus is on packaging your script. Also, most scripts would be longer and multi-line.

Create a new file, call it len (for example), and paste this

#!/bin/bash

awk '{print length, $0}' "$@"

Make it executable with chmod +x len. Run it on a file, on the script itself for example:

# run it on a file
> ./len len
# 11 #!/bin/bash
# 0
# 29 awk '{print length, $0}' "$@"

# or run it as a filter
> cat len | ./len
# 11 #!/bin/bash
# 0
# 29 awk '{print length, $0}' "$@"

# find the largest line, a common use-case
> ./len len | sort -nr | head -n1
# 29 awk '{print length, $0}' "$@"

Pros

simple or, at least, familiar
could be combined with other command-line tools (e.g. sort -n …)

Cons

bash process wrapper
all AWK logic crammed in single quotes…

A Simpler Way

Edit the len script down to this

#!/usr/bin/env -S awk -f

{print length, $0}

It works the same as the bash-wrapper version

# run it on a file
> ./len len
# 24 #!/usr/bin/env -S awk -f
# 0
# 18 {print length, $0}

# or run it as a filter
> cat len | ./len
# 24 #!/usr/bin/env -S awk -f
# 0
# 18 {print length, $0}

Pros

slightly simpler
native-AWK execution, without process wrapper
native-AWK syntax highlighting in your editor

The only real sticking point is the env line…

A Full env shebang

Why is the shebang line so complicated?

You can’t run #!/usr/bin/env awk because you need the -f flag.

You can’t run #!/usr/bin/env awk -f because some versions of env only take one argument.

You need #!/usr/bin/env -S awk -f to work around most of these problems.

But now that I’ve given it to you, you’re all set. (and this might come in useful in other circumstances)

A Longer Example

If you’re going to write longer scripts, the “native-AWK syntax highlighting” is the major benefit.

For example, this script that converts hiragana to romaji runs at around 150 lines.