sh

Overview

The Bourne Shell (sh) is the original Unix shell, developed by Stephen Bourne at Bell Labs in 1979. Today, /bin/sh typically points to a POSIX-compliant shell like dash or bash. It serves as the standard for portable shell scripting.

Who Should Use sh?

• Script writers - Maximum portability across systems
• System programmers - System initialization scripts
• Embedded developers - Minimal resource environments
• POSIX compliance needs - Standards-compliant scripting

Installation

sh is available on all Unix-like systems.

# Check what sh points to
ls -la /bin/sh

# On Ubuntu/Debian, sh is usually dash
# On macOS, sh is bash (in POSIX mode)
# On FreeBSD, sh is ash

# Run a script with sh
sh script.sh

# Or use shebang
#!/bin/sh

Basic Usage

POSIX shell scripting basics.

#!/bin/sh

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

# No arrays in POSIX sh!
# Use space-separated strings instead
fruits="apple banana cherry"
for fruit in $fruits; do
    echo "$fruit"
done

# Conditionals
if [ -f "file.txt" ]; then
    echo "File exists"
fi

# Functions
greet() {
    echo "Hello, $1!"
}
greet "User"

Configuration

sh configuration is minimal.

# ~/.profile - Read by login shells

# Set PATH
PATH="$HOME/bin:$PATH"
export PATH

# Set environment variables
export EDITOR=vim

# Note: sh has limited interactive features
# For interactive use, consider bash or zsh

Key Features

FAQ

Summary

Key takeaways for sh:

• Standard POSIX shell for maximum portability
• Available on all Unix-like systems
• Best choice for system scripts and cross-platform compatibility
• Limited interactive features compared to modern shells