💻 sh vs Zsh vs Bash Built-in Commands Comparison

This table compares the built-in commands available in the original Bourne Shell (sh), Z Shell (Zsh), and Bourne Again Shell (Bash). Commands are organized alphabetically with notes on key differences.

Command	sh	Bash	Zsh	Notes
. (dot)	✓	✓	✓	Sources a script file
: (colon)	✓	✓	✓	Null command (does nothing but returns success)
[	✓	✓	✓	Condition evaluation (alias for test)
alias	Limited	✓	✓	Create command aliases; limited in original sh
autoload	✗	✗	✓	Zsh-specific: load functions on demand
bg	✓	✓	✓	Resume jobs in the background
bind	✗	✓	✗	Bash-specific: display or set readline key bindings
bindkey	✗	✗	✓	Zsh-specific: display or set key bindings
break	✓	✓	✓	Exit from loops
builtin	✗	✓	✓	Execute built-in commands directly
caller	✗	✓	✗	Bash-specific: return context of subroutine call
cd	✓	✓	✓	Change directory
command	✓	✓	✓	Execute command bypassing any aliases
compdef	✗	✗	✓	Zsh-specific: define completion functions
compgen	✗	✓	✗	Bash-specific: generate possible completions
complete	✗	✓	✗	Bash-specific: specify how to complete arguments
compopt	✗	✓	✗	Bash-specific: modify completion options
compsys	✗	✗	✓	Zsh-specific: completion system initialization
continue	✓	✓	✓	Skip to next iteration of a loop
declare	✗	✓	✓	Declare variables with attributes
dirs	✗	✓	✓	Display directory stack
disown	✗	✓	✓	Remove jobs from current shell
echo	✓	✓	✓	Display arguments as text
enable	✗	✓	✗	Bash-specific: enable/disable shell built-ins
eval	✓	✓	✓	Evaluate arguments as shell commands
exec	✓	✓	✓	Replace current process with specified command
exit	✓	✓	✓	Exit the shell
export	✓	✓	✓	Set environment variables
false	✓	✓	✓	Return a failure status
fc	✗	✓	✓	Fix command (history editing)
fg	✓	✓	✓	Resume job in foreground
float	✗	✗	✓	Zsh-specific: declare floating-point variables
function	✗	✓	✓	Define a function (sh uses different syntax)
getopts	✓	✓	✓	Process command-line options
hash	✓	✓	✓	Remember command locations
help	✗	✓	✗	Bash-specific: display help for built-ins
history	✗	✓	✓	Display command history
if	✓	✓	✓	Conditional statement
integer	✗	✗	✓	Zsh-specific: declare integer variables
jobs	✓	✓	✓	List active jobs
kill	✓	✓	✓	Send signals to processes
let	✗	✓	✓	Evaluate arithmetic expressions
local	✗	✓	✓	Declare local variables
logout	✗	✓	✓	Exit a login shell
mapfile	✗	✓	✗	Bash-specific: read lines into array variable
popd	✗	✓	✓	Remove directories from directory stack
print	✗	✗	✓	Zsh-specific: more versatile version of echo
printf	✗	✓	✓	Format and print data
pushd	✗	✓	✓	Add directories to directory stack
pwd	✓	✓	✓	Print working directory
read	✓	✓	✓	Read from stdin into variables
readarray	✗	✓	✗	Bash-specific: read lines into array variable
readonly	✓	✓	✓	Mark variables as read-only
rehash	✗	✗	✓	Zsh-specific: rebuild command hash table
return	✓	✓	✓	Return from a function
set	✓	✓	✓	Set/unset shell options and positional parameters
setopt	✗	✗	✓	Zsh-specific: set shell options
shift	✓	✓	✓	Shift positional parameters
shopt	✗	✓	✗	Bash-specific: set/unset shell options
source	✗	✓	✓	Execute commands from file (sh only has .)
suspend	✗	✓	✓	Suspend shell execution
test	✓	✓	✓	Evaluate conditional expression
times	✓	✓	✓	Display process times
trap	✓	✓	✓	Trap signals and events
true	✓	✓	✓	Return a successful status
type	✓	✓	✓	Display command type
typeset	✗	✓	✓	Declare variables and their attributes
ulimit	✓	✓	✓	Set resource limits
umask	✓	✓	✓	Set file creation mask
unalias	Limited	✓	✓	Remove command aliases
unfunction	✗	✗	✓	Zsh-specific: remove function definitions
unhash	✗	✗	✓	Zsh-specific: remove command from hash table
unset	✓	✓	✓	Remove variables or functions
unsetopt	✗	✗	✓	Zsh-specific: unset shell options
wait	✓	✓	✓	Wait for job completion
whence	✗	✗	✓	Zsh-specific: describe command (similar to type)
which	✗	✗	✓	Zsh-specific: locate command
zcompile	✗	✗	✓	Zsh-specific: compile functions/scripts for faster loading
zformat	✗	✗	✓	Zsh-specific: format strings
zle	✗	✗	✓	Zsh-specific: zsh line editor commands
zmodload	✗	✗	✓	Zsh-specific: load zsh modules
zparseopts	✗	✗	✓	Zsh-specific: parse options
zpty	✗	✗	✓	Zsh-specific: pseudo terminal handling
zregexparse	✗	✗	✓	Zsh-specific: parsing based on regular expressions
zstyle	✗	✗	✓	Zsh-specific: set style for completion system

Shell Evolution and Feature Comparison

Bourne Shell (sh)

The original Unix shell developed by Stephen Bourne at Bell Labs in 1979:

• Minimalist design with essential shell functionality
• Focus on scripting rather than interactive use
• Limited job control
• No command history
• No command line editing
• Basic built-in commands only
• POSIX-compliant (original reference implementation)

Bash (Bourne Again Shell)

Developed by Brian Fox for the GNU Project in 1989:

• Direct extension of the Bourne shell
• Strong focus on POSIX compliance
• Enhanced scripting capabilities
• Command history and editing
• Job control
• Programmable completion
• Array support
• More advanced parameter expansion

Zsh (Z Shell)

Developed by Paul Falstad in 1990:

• Extended feature set beyond Bash
• Modular design with loadable modules
• Highly customizable
• Advanced pattern matching and globbing
• Theming capabilities
• Spelling correction
• Sophisticated tab completion system
• Floating point arithmetic
• More extensive string handling
• Better interactive features

Key Functional Differences

1. Core Commands:
   • sh: Provides minimalist but essential commands
   • Bash: Extends sh with interactive features
   • Zsh: Further extends with advanced customization
2. Variable Handling:
   • sh: Basic variable support
   • Bash: Added arrays and better variable manipulation
   • Zsh: Added specialized variable types (integer, float)
3. Command Completion:
   • sh: None or minimal
   • Bash: Programmable completion system
   • Zsh: Advanced, context-aware completion system
4. Scripting Capabilities:
   • sh: Basic scripting support
   • Bash: Enhanced scripting with more built-ins
   • Zsh: Most extensive scripting capabilities