Shell by Example: Comments POSIX 

#!/bin/sh

Comments in shell scripts start with the # character. Everything after # on a line is ignored by the shell.

 

echo "This line runs" # This comment is ignored

Comments are essential for documenting your scripts. They help others (and future you) understand what the code does.

You can use comments to:

  • Explain complex logic
  • Document function purposes
  • Leave TODO notes
  • Temporarily disable code

Multi-line comments don’t have special syntax. You simply start each line with #.

Here’s an example of documenting a section:

 

# ==========================================
# Configuration Section
# ==========================================

CONFIG_FILE="/etc/myapp.conf"
LOG_DIR="/var/log/myapp"

You can also use comments to disable code temporarily. This is sometimes called “commenting out” code.

 

echo "This runs"
# echo "This doesn't run"
echo "This also runs"

Note: There’s no block comment syntax in shell. Some people use here-documents for multi-line comments, but that’s a hack - just use #.

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by Jose Diaz-Gonzalez | inspired by Go by Example | source