Use It Anyway

A Shell Colon Does Nothing

Based on Hacker News Discussion

135 points

02

The Magic of the Colon

A command that does nothing, yet does everything

01

A Built-in Shell Command The colon (:) is a shell built-in that returns true (exit code 0)
02

Does Absolutely Nothing It executes no operation, no side effects, nothing happens
03

Also Known As 'True' Functionally equivalent to the 'true' command in most shells
04

Exists in Every Shell Available in Bash, Zsh, Fish, and all POSIX-compliant shells

shell-example.sh

# The colon command - does nothing, returns true
:

# Equivalent to 'true' command
: && echo "Success!"

# Exit status is always 0
: ; echo $?

The colon command executes successfully and returns exit code 0, making it perfect for control flow and placeholder scenarios.

05

Practical patterns that make the colon indispensable

sync

Create clean while loops: while :; do ...; done

edit_note

Default values syntax: : ${VAR:=default}

comment

Block comments: : 'comment text here'

settings

Stub functions and config file placeholders

code

Safe if-then syntax when you need no action

speed

Built-in command—no external process overhead

0

Operations executed by the colon command

Yet it's one of the most useful commands in shell scripting—elegance in simplicity

Sometimes the most powerful tools do the least

Source: refp.se/articles/your-shell-and-the-magic-colon