Bash builtins help
Updated: 02/27/2019 by Computer Hope
Bash is the default shell of many Linux operating systems, and the Windows Subsystem for Linux in Windows 10. It has its own set of builtin commands, listed below.
Inherited and special builtin commands
Some of these commands are inherited from the original Bourne shell (sh). Commands marked as "inherited" below also work in the Bourne shell.
Some of the commands are designated as special commands under the POSIX standard. If bash is running in POSIX mode (e.g., set -o posix), they have these special behaviors:
- When you run a special command, it is guaranteed to run first, before other commands with the same name.
- If the command returns an error, and the shell was started in non-interactive mode, the shell will exit.
- Variable assignments that precede a special builtin command stays in effect after the special command is completed.
Index of bash builtin commands
| Builtin command | Inherited | Special | Description |
|---|---|---|---|
| : (a colon) | Yes | Yes | Returns an exit status of zero. |
| . (a period) | Yes | Yes | The same as source. Takes a file name as an argument, and executes the commands found in that file. |
| [ | Yes | The same as test. Evaluate a conditional expression, and a return a value of true or false. | |
| alias | Define, or display, the shell's command aliases. | ||
| bg | Resume a suspended job so that it runs in the background. | ||
| bind | Define, or display, the shell's key and function bindings. | ||
| break | Yes | Yes | Exit from a for, while, or select loop. |
| builtin | Run a builtin command, even if there is a bash function with the same name. | ||
| caller | Return the context (execution frame) of a running subroutine. Useful for performing examining the stack when debugging a bash script. | ||
| cd | Yes | Change the working directory. | |
| command | Run an external or builtin command, even if there is a bash function with the same name. | ||
| compgen | Generate auto-completion matches for the specified command. | ||
| complete | Specify how arguments should be auto-completed. | ||
| compopt | Modify or display options for auto-completion. | ||
| continue | Yes | Yes | Skip to the next, or to another, iteration in a for, while, until, or select loop. |
| declare | The same as typeset. Declare, display, or assign attributes to variables. | ||
| dirs | Display the shell's directory stack, which contains remembered directories. | ||
| disown | Remove specified jobs from the current shell. | ||
| echo | Write a string to the standard output. | ||
| enable | Enable or disable builtin shell commands. Useful when other commands on the system share a builtin command name. | ||
| eval | Yes | Yes | Evaluate arguments and execute them as a command. |
| exec | Yes | Yes | Execute a command which replaces the current shell, without creating a new process. |
| exit | Yes | Yes | Exit the shell with an optional numeric exit status. |
| export | Yes | Yes | Designate that shell variables or functions should be passed to child processes. |
| fc | Edit, or execute a range of, commands from the history list. | ||
| fg | Move a job to the foreground, making it the shell's current job. | ||
| getopts | Yes | Parse arguments passed to a shell script. | |
| hash | Yes | Forget, determine, or display the remembered locations of command executables. | |
| help | Display brief help information about what the shell builtin commands are, and how to use them. | ||
| history | Display or modify the history list. | ||
| jobs | Display the status of all jobs. | ||
| kill | Send a signal to a process. | ||
| let | Evaluate arithmetic expressions. | ||
| local | Declare a variable with local scope in a bash function. | ||
| logout | Exit a login shell with an optional exit status. | ||
| mapfile | Read lines from a file or from standard input, and map each line to an element in an array. | ||
| popd | Remove directories from the shell's directory stack. | ||
| printf | Print formatted text to standard output. | ||
| pushd | Add directories to the shell's directory stack. | ||
| pwd | Yes | Print the absolute path name of the current working directory. | |
| read | Read a line from a file or from standard input, split it into words, and assign each word to a variable. | ||
| readarray | Same as mapfile: read lines from a file or stdin, and assign each line to an array element. | ||
| readonly | Yes | Yes | Designate function or variables as read-only, so they cannot be changed. |
| return | Yes | Yes | Exit a bash function and return a value. |
| set | Yes | Yes | Modify the options of the current shell, changing its behavior. Display the names and values of shell functions and variables. |
| shift | Yes | Yes | Shift the positional parameters of the current command to the left. |
| shopt | Modify certain bash shell options. | ||
| source | Same as . (a period). Read commands from a file, and execute them. | ||
| test | Yes | Test file attributes and compare numeric values. | |
| times | Yes | Display the user and system CPU times of the shell process. | |
| trap | Yes | Yes | Specify a signal trap, to be executed when the shell receives a specific signal. |
| type | Determine how the shell will interpret a name: as an alias, function, builtin, file, or keyword. | ||
| typeset | The same as declare. Declare, display, or assign attributes to variables. | ||
| ulimit | Assign limits to the resources available to processes started by the shell. | ||
| umask | Yes | Set the file creation mask for files created by the shell. | |
| unalias | Remove aliases. | ||
| unset | Yes | Yes | Remove variable or function names. |
| wait | Yes | Wait for a process to exit, then display its return value. |