Bash

Strap in for a bashful blast to the past as we revisit the command-line charisma of bash. Picture this: a cozy UNIX shell born in the late '80s that became the go-to language for scripting wizardry.

Bash, short for 'Bourne Again SHell,' is like the wise elder of the programming world, offering a warm welcome with its 'Hello World!' charm. Imagine early developers huddled around their terminals for warmth, laying the foundations for the scripting revolution.

Hello World

#!/usr/bin/env bash

echo "Hello World!"

Coding Guide

Language Version

bash (GNU Bash) - Full-featured shell

Execution Model

• Interpreted shell script
• Code executes directly from source
• Scripts run line-by-line from top to bottom
• Uses shebang #!/usr/bin/env bash for execution

Key Characteristics

• Full-featured 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)
• Associative arrays: declare -A MAP
• Arithmetic expansion: $((expression))
• Pattern matching: [[ string =~ pattern ]]

Fragment Authoring

Write valid bash 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 bash 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[@]}"
• Conditionals: if [[ condition ]]; then ... fi
• Loops: for i in {1..5}; do echo "$i"; done
• Command substitution: RESULT=$(command)
• Arithmetic: $((A + B)) or let "result = A + B"
• Functions: function_name() { ... }
• Here documents: cat <<EOF ... EOF

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
FRUITS=("apple" "banana" "cherry")
for fruit in "${FRUITS[@]}"; do
    echo "Fruit: $fruit"
done

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

Caveats

• Variable assignment: no spaces around =
• Use [[ for bash-specific tests, [ for POSIX compatibility
• Quote variables to prevent word splitting: "$VAR"
• Arrays require proper quoting: "${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

Fraglet Scripts

Echo Args

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

Stdin Upper

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

Test

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

echo "Hello World!"

Connections

Container Info