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Catalog / Zsh Scripting Cheatsheet

Zsh Scripting Cheatsheet

A handy reference for Zsh scripting, covering syntax, built-ins, options, and common patterns.

Zsh Basics & Syntax

Basic Syntax

Comments

# This is a comment

Variables

VAR_NAME="value"
echo $VAR_NAME or echo ${VAR_NAME}

String Concatenation

result="Hello, "$VAR_NAME
result="Hello, ${VAR_NAME}"

Command Substitution

output=$(ls -l) or output=ls -l

Exit Status

$? (Exit status of the last command)

Here Documents

cat <<EOF Multiline text EOF

Arrays

my_array=(item1 item2 item3)
echo ${my_array[0]}
echo ${#my_array[@]} (length)
echo ${my_array[@]} (all elements)`

Conditional Statements 

if [[ condition ]]; then
  # code
elif [[ condition ]]; then
  # code
else
  # code
fi

String Comparisons:
==, !=, <, >

File Tests:
-e file (exists), -f file (regular file), -d file (directory), -r file (readable), -w file (writable), -x file (executable)

Numeric Comparisons:
-eq, -ne, -lt, -gt, -le, -ge

Looping

For Loop:

for var in item1 item2 item3; do
  echo $var
done

While Loop:

while [[ condition ]]; do
  # code
done

Until Loop:

until [[ condition ]]; do
  # code
done

Looping through array:

for element in "${my_array[@]}"; do
  echo "Element: $element"
done

Functions & Builtins

Functions

Function Definition

 
my_function() {
  echo "Hello from my_function"
}

OR

function my_function {
  echo "Hello from my_function"
}

Calling a function

my_function

Passing Arguments

my_function arg1 arg2
Inside function: $1, $2, etc.

Return Value

return 0 (Success), return 1 (Failure). Use $? to check.

Local Variables

local my_var="value" (Scope is within the function)

Useful Built-in Commands

echo

Print text to standard output.

printf

Formatted output (similar to C’s printf).

read

Read input from standard input.
read -p "Prompt: " variable

exit

Exit the script.
exit 0 (Success), exit 1 (Failure).

source or .

Execute commands from a file in the current shell.
. ./my_script.sh

pwd

Print working directory.

cd

Change directory.

Parameter Expansion

${var:-word} - Use default value ‘word’ if var is unset or null.

${var:=word} - Assign default value ‘word’ to var if var is unset or null.

${var:?message} - Display error message and exit if var is unset or null.

${var:+word} - Use ‘word’ if var is set and not null.

${#var} - String length of var.

${var:offset:length} - Substring of var.

Zsh Options & Globbing

Setting Options

set -o option_name

Enable option.

set +o option_name

Disable option.

setopt option_name

Enable option (Zsh specific).

unsetopt option_name

Disable option (Zsh specific).

Useful Options

allexport: Automatically export all defined variables.

errexit: Exit immediately if a command exits with a non-zero status.

nounset: Treat unset variables as an error when substituting.

xtrace: Print commands and their arguments as they are executed.

noclobber: Prevent overwriting existing files with redirection.

Globbing (Filename Generation)

*

Matches any string of characters (except leading dots).

?

Matches any single character.

[abc]

Matches one of the characters a, b, or c.

[a-z]

Matches any character between a and z.

[^abc] or [!abc]

Matches any character except a, b, or c.

(foo|bar)

Matches either foo or bar.

**

Matches files recursively (Zsh specific, enable with setopt glob_star).

Advanced Zsh

Zsh Modules

zmodload zsh/module

Loads a specific Zsh module. Example: zmodload zsh/tcp

Available Modules

zmodload -l Lists available modules.

Common modules

zsh/tcp, zsh/datetime, zsh/mathfunc

Process Substitution

<(command)

Provides the output of command as a file.
diff <(ls dir1) <(ls dir2)

>(command)

Redirects standard output to command.
tee >(gzip > file.gz) > file.txt

Customizing the Prompt

PS1 is the primary prompt variable.

PS1="%n@%m %~> " (user@host current_directory> )

Common escape sequences: %n (username), %m (hostname), %~ (current directory), %d (current directory full path), %w (current time), %D{format} (date/time with format).

Example:

PS1='%F{blue}%n@%m%f:%F{green}%~%f$(git_prompt_info)'

For advanced prompt customization, use a Zsh theme manager like Oh My Zsh or Prezto.
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