bash_built-in_list.md

NR	Command	Description	Example
01	.	Executes commands from a file.	.bashrc (loads the bash configuration file)
02	:	Does nothing (useful as a placeholder).	true ; echo "This will be printed" (only the second command executes)
03	[ (or test )	Evaluates expressions for conditional statements.	[ -f filename ] && echo "File exists" (checks if a file exists)
04	alias	Creates or manages aliases (shorter names for commands).	alias ll='ls -l' (creates an alias for ls -l)
05	bg	Sends a suspended job to the background.	bg %1 (sends job number 1 to the background)
06	bind	Defines key bindings for specific actions.	bind '"\C-p":history -p' (binds Ctrl+P to previous history command)
07	break	Exits a loop or switch statement.	for i in {1,2,3}; do if [[ $i -eq 2 ]]; then break; fi; done (loops from 1 to 3, breaks on 2)
08	builtin	Runs a command as a built-in, even if it's also defined as a function.	builtin cd .. (ensures cd is the built-in version)
09	caller	Shows the call stack for the current function.	function f { caller; } ; f (shows the call hierarchy)
10	cd	Changes the current working directory.	cd /home/user (changes directory to user's home)
11	command	Runs the actual command, bypassing aliases or functions.	command ls (runs the original ls command)
12	compgen	Generates completion suggestions for arguments.	compgen -A file myprogram (provides filename completions for myprogram)
13	complete	Defines or displays command completion behavior.	complete -f git (enables filename completion for git)
14	continue	Skips the rest of the current loop iteration and moves to the next.	for i in {1,2,3}; do if [[ $i -eq 2 ]]; then continue; fi; echo $i; done (skips 2 and prints 3)
15	declare	Declares and manipulates shell variables.	declare -i var=10 (declares var as an integer)
16	dirs	Shows a list of previously visited directories.	dirs -v (shows timestamps for visited directories)
17	disown	Removes a background job from the job list, but lets it continue running.	disown %1 (removes job number 1 from the job list)
18	echo	Prints text to the standard output.	echo Hello, world! (prints the message)
19	enable	Enables a previously disabled shell built-in.	enable history (enables the history command)
20	eval	Evaluates a string as a shell command.	eval var="ls -l"; $var (evaluates "ls -l" and executes it)
21	exec	Replaces the current shell process with a new process.	exec ls -l (replaces the shell with ls -l)
22	exit	Terminates the shell.	exit 0 (exits the shell with success code 0)
23	export	Makes a shell variable available to child processes.	export MYVAR="some value" (exports MYVAR to child processes)
24	false	Always exits with a non-zero exit code (failure).	false && echo "This won't print" (the second command won't run)
25	fc	Manipulates the command history.	fc -l -5 (lists the last 5 history entries)
26	fg	Brings a suspended job to the foreground.	fg %1 (brings job number 1 to the foreground)
27	getopts	Parses command-line options.	while getopts ":hf:" opt; do case $opt in h) echo "help message"; exit 0; ;; f) file="$OPTARG";; esac; done
28	hash	Manages the command lookup cache for faster execution.	hash (rebuilds the command hash table)
29	help	Provides help information for shell commands.	help cd (shows help for the cd command)
30	history	Displays the command history.	history -c (clears the command history)
31	jobs	Shows information about background jobs.	jobs (lists running and stopped background jobs)
32	kill	Sends a signal to a process or job.	kill %1 (sends SIGTERM to job number 1)
33	let	Performs arithmetic operations on shell variables.	let x=5+3 (assigns 8 to variable x)
34	local	Declares a variable with local scope (limited to the current shell).	local var="value" (creates a variable var only in this shell)
35	logout	Exits the shell (same as exit).	logout (terminates the shell session)
36	popd	Removes the top directory from the directory stack and changes the working directory to it.	pushd /tmp ; popd (changes to /tmp then back to previous directory)
37	printf	Similar to echo but offers more control over formatting output.	printf "Number: %d\n" 10 (prints "Number: 10" with a newline)
38	pushd	Saves the current directory on a stack and changes the working directory to a new one.	pushd /tmp (changes directory to /tmp and saves the previous directory)
39	pwd	Prints the current working directory.	pwd (shows the absolute path of the current directory)
40	read	Reads input from the standard input and assigns it to a variable.	read name ; echo "Hello, $name!" (reads input and greets the user)
41	readonly	Makes a variable read-only (cannot be modified).	readonly PI=3.14159 (makes PI a constant)
42	return	Exits a function and optionally sets a return code.	return 0 (exits the function with success code 0)
43	set	Manipulates shell settings and arguments.	set -x (enables command echoing for debugging)
44	shift	Shifts positional parameters to the left.	shift 2 (removes the first two positional parameters)
45	shopt	Enables or disables shell options.	shopt -s histappend (enables appending commands to the history file)
46	source (or .)	Reads and executes commands from a file.	see .
47	suspend	Suspends the current shell process.	suspend (sends SIGTSTP to the shell, use fg to resume)
48	test (or [)	Evaluates expressions for conditional statements.	see [
49	times	Reports elapsed time, user CPU time, and system CPU time used by a process.	time sleep 5 (measures the time spent sleeping for 5 seconds)
50	trap	Sets traps (actions) to be taken upon receiving signals.	trap "echo 'Program interrupted' ; exit" SIGINT (runs the command when Ctrl+C is pressed)
51	true	Always exits with a zero exit code (success).	true ; echo "This will always print" (the second command always executes)
52	type	Identifies the type of a shell command.	type pwd (shows whether pwd is a builtin, alias, function, or external command)
53	typeset	Similar to declare for managing shell variables.	typeset -i var (declares var as an integer, same as declare -i var)
54	ulimit	Sets or inquires about resource limits.	ulimit -n 1024 (sets the open file limit to 1024)
55	umask	Sets the file mode creation mask.	umask 022 (sets the umas
56	unalias	Removes an alias definition.	unalias ll (removes the alias for ls -l)
57	unset	Undefines a shell variable.	unset MYVAR (removes the variable MYVAR)
58	wait	Waits for background jobs to finish.	wait %1 %2 (waits for job number 1 and 2 to finish)