Zsh

Zsh is a shell imperative and scripting language first appearing in 1990.

Hello World

#!/usr/bin/env zsh

echo "Hello World!"

Coding Guide

Language Version

zsh (Z Shell) - Advanced shell with many interactive features

Execution Model

• Interpreted shell script
• Code executes directly from source
• Scripts run line-by-line from top to bottom
• Compatible with bash but with enhanced features

Key Characteristics

• Advanced shell with many extensions beyond POSIX
• Case-sensitive
• Variables: VAR=value (no spaces around =)
• Command substitution: `command` or $(command)
• String interpolation: "$VAR" or "${VAR}"
• Arrays: ARRAY=(item1 item2 item3) (indexed from 1, not 0)
• Associative arrays: typeset -A MAP
• Arithmetic expansion: $((expression))
• Pattern matching: [[ string =~ pattern ]]
• Extended globbing: **/*.txt (recursive), *.txt~*.old (exclusion)
• Parameter expansion: ${VAR:-default}, ${VAR#pattern}, etc.

Fragment Authoring

Write valid zsh shell commands. Your fragment becomes the script body. The fragment code will execute as part of the shell script.

Available Commands

Standard Unix utilities and zsh built-ins are available:

• echo - Print text
• printf - Formatted output
• test / [ / [[ - Conditional tests
• if, while, for, until - Control structures
• grep, sed, awk - Text processing
• jq - JSON processing (if installed)
• Standard Unix utilities

Common Patterns

• Output: echo "message" or printf "%s\n" "message"
• Variables: NAME="value" and echo "$NAME"
• Arrays: ARRAY=(1 2 3) and echo "${ARRAY[@]}" (indexed from 1)
• Conditionals: if [[ condition ]]; then ... fi
• Loops: for i in {1..5}; do echo "$i"; done or for i in {1..5}; echo "$i"
• Command substitution: RESULT=$(command)
• Arithmetic: $((A + B)) or let "result = A + B"
• Functions: function_name() { ... }
• Here documents: cat <<EOF ... EOF
• Parameter expansion: ${VAR:-default}, ${VAR#prefix}, ${VAR%suffix}

Examples

# Simple output
echo "Hello from fragment!"

# Variables
NAME="Alice"
echo "Hello, $NAME!"

# Arithmetic
A=5
B=10
SUM=$((A + B))
echo "Sum: $SUM"

# Arrays (indexed from 1)
FRUITS=("apple" "banana" "cherry")
for fruit in "${FRUITS[@]}"; do
    echo "Fruit: $fruit"
done
echo "First fruit: ${FRUITS[1]}"

# Conditionals
if [[ "$1" == "test" ]]; then
    echo "Testing mode"
else
    echo "Normal mode"
fi

# Functions
greet() {
    local name="$1"
    echo "Hello, $name!"
}

greet "World"

# Command substitution
DATE=$(date)
echo "Current date: $DATE"

# Arithmetic loops
for i in {1..5}; do
    echo "Count: $i"
done

# Associative arrays
typeset -A colors
colors[red]="#FF0000"
colors[green]="#00FF00"
echo "Red: ${colors[red]}"

# Parameter expansion
VAR=""
echo "Value: ${VAR:-default}"

# Extended globbing (if enabled)
# files=(**/*.txt)  # recursive glob
# echo "Found ${#files[@]} files"

# String manipulation
TEXT="Hello World"
echo "${TEXT#Hello }"  # Remove prefix
echo "${TEXT% World}"  # Remove suffix

Caveats

• Variable assignment: no spaces around =
• Use [[ for zsh-specific tests, [ for POSIX compatibility
• Quote variables to prevent word splitting: "$VAR"
• Arrays are indexed from 1, not 0: ${ARRAY[1]} is the first element
• Arrays require proper quoting: "${ARRAY[@]}" for all elements
• Case-sensitive variable names
• Arithmetic expansion: $((expression)) (no $ inside)
• Function definitions: function_name() { ... } or function function_name { ... }
• Use local keyword inside functions to avoid global variable pollution
• Associative arrays use typeset -A declaration
• Extended globbing may need setopt extendedglob (usually enabled by default in scripts)

Fraglet Scripts

Echo Args

#!/usr/bin/env -S fragletc --vein=zsh
echo "Args: $*"

Stdin Echo

#!/usr/bin/env -S fragletc --vein=zsh
while read -r line; do echo "$line"; done

Stdin Upper

#!/usr/bin/env -S fragletc --vein=zsh
while read -r line; do echo "$line" | tr "a-z" "A-Z"; done

Test

#!/usr/bin/env -S fragletc --vein=zsh

echo "Hello World!"

Connections

Container Info