Bash comments are lines in a Bash script that are not executed as part of the script but serve as explanatory or informational notes. Comments are useful for documenting the purpose, behavior, or usage of the script, making it easier for others (including yourself) to understand the code.
In Bash, there are two ways to write comments:
- Single-line comments: To add a comment that spans a single line, you can use the
#(hash) symbol. Anything written after the
#symbol on the same line is considered a comment and will be ignored by the shell when executing the script.Here’s an example:
# This is a single-line comment. echo "This is a command."
In this example, the comment
# This is a single-line comment. is ignored, and only the
echo command is executed.
2. Multi-line comments: Bash does not have a built-in syntax for multi-line comments like some other programming languages. However, you can achieve a similar effect by enclosing multiple lines within a pair of opening
: ' (colon followed by a single quote) and closing
' (single quote) characters. The shell treats the enclosed lines as a single command substitution, which is a no-op (no operation) and has no effect. Here’s an example:
: ' This is a multi-line comment. It spans multiple lines. ' echo "This is a command."
In this example, the lines between
: ' and
' are considered a comment block and are effectively ignored by the shell.
Comments are not executed and do not affect the behaviour of the script. They are solely for providing explanations and annotations to make the code more understandable. Properly commenting your Bash scripts is a good practice for maintainability and collaboration.