> ## Content Index > Fetch the complete content index at: https://linuxhandbook.com/llms.txt > Use this file to discover other available public pages before exploring further. # Shell Built-in Commands - URL: https://linuxhandbook.com/shell-builtin-commands/ - Published: 2023-07-05T04:15:50.000Z - Updated: 2025-01-18T05:00:52.000Z - Description: In Linux, there are shell built-in commands which you are already using but never paid attention to. Learn more about them in this tutorial. - Author: Sagar Sharma - Tags: Commands In Linux, there are commands and then there are shell built-ins. Linux purists refrain from calling them commands or shell built-in commands. So, what's so special about these shell built-ins and how are they different from other Linux commands? You'll learn about them in this tutorial. ## What is a shell built-in? When you run a Linux command, it is run from a binary in a sub-shell by forking the existing process. However, a shell built-in is contained in the shell itself. It runs in the same shell without creating a new process. Thus, shell built-ins are faster. cd, [pwd](https://linuxhandbook.com/pwd-command/), exit, export, alias are some of the commonly used shell built-ins. Want to know what other shell built-in commands are there, why, and how they are used? In this tutorial, I'm going to answer all such questions. ## List of shell builtin commands To list all the builtin bash commands, all you have to do is execute the `help` command in the terminal: ``` help ``` ![list bash builtin commands in Linux](https://linuxhandbook.com/content/images/2023/06/list-bash-builtin-commands-in-Linux.png) A long list of commands. Isn't it? Now, let's have a look at why they are used in the first place: | Command | Description | | ----------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | alias | Used to create a shortcut or an alternative name for a command. | | bg | Moves suspended or stopped jobs in the background. | | bind | It is used to show or modify the keybindings. | | break | Used within loops to terminate the loop and continue the execution outside the loop. | | builtin | If you have built-in and external commands with the same name, using builtin, you can prioritize the internal command for the execution. | | caller | Used in the script to get more information about that specific code block. | | case | It allows you to create multiple conditions and their outcomes based on a specific block. | | cd | Change directory. | | command | Used to execute external commands by bypassing any alias or functions having the same name.\` | | compgen | It will generate completions for command options, files, directories, and other items based on the current context. | | complete | Allows you to modify the command completions for specific commands. | | compopt | It allows you to modify argument completion for a specific command. | | continue | Used in loops to skip the execution of the remaining iteration and move to the next iteration of the given code, | | coproc | Creates a co-process to establish communication between the script and the background process. | | declare | Used to define variables and their properties. | | dirs | It shows the list of the commands that you went through recently. | | disown | By using it, you can detach currently running jobs from the shell, allowing you to continue their execution even after closing the shell. | | echo | Used to print output. | | enable | Used to enable or disable the built-in shell commands and functions. | | eval | It treats the given arguments as a command and executes it in such it was written in as script or executed directly in the terminal. | | exec | It is used to replace the current process with the new one. | | exit | Used to terminate the current shell session or the script. | | export | It allows you to create or modify the environment variables. | | false | Used to return a non-zero exit status that indicates a false condition or failure. | | fc | By using it, you can list, modify and re-execute previously used commands. | | fg | Used to bring suspended, or the background processes, to the foreground. | | for \[condition\]; do\[execution\]; | A for loop is used in the shell script to execute repetitive tasks. | | function name { COMMANDS ; } | Used to create a function that can be used multiple times in a shell session or the shell script. | | getopts | Allows you to parse the command-line options and arguments inside a script. | | hash | It helps the shell to remember the location of the executables. | | help | Gives information about built-in commands in the shell. | | history | Provides a list of previously executed commands. | | if COMMANDS; then COMMANDS; | A condition statement that executed the command if the condition is true. | | jobs | Displays the status of the background jobs running in the background. | | kill | Sends a signal to kill to terminate the process. | | let arg \[arg ...\] | Using the let command, you can perform the arithmetic operations. | | local | It allows the user to define local variables within the specific function. | | logout | As the name suggests, it logs you out of the current user session. | | mapfile | Reads text from an input stream or a file and stores it in an array. | | popd | It is used to replace the top directory from the directory stack with the current directory. | | printf | Used to format and print the variable values or the text. | | pushd | Allows you to change the directory and stores the previous directory to the directory stack, by which you can easily navigate between multiple directories with the least effort. | | pwd | When executed, it shows the current working directory. | | read | Reads input from a file or user and assigns it to a variable. | | readarray | Used to read lines from the input file and turns it into an array variable. | | readonly | Used to declare and define read-only variables. | | return | It is used to exit a function and, optionally, you can also specify a return value. | | select | By using it, you can create a simple menu or interactive selection prompt for a user. | | set | Allows you to modify the shell settings and parameters. | | shift | By using it, you can drop the first argument and lower the remaining ones a step lower in the list of positional parameters. | | shopt | Provides various options to modify the behavior of the shell. | | source | It is used to reload config files and execute the script in the current shell. | | suspend | Used to suspend the current shell and returns the control to the parent shell. | | test | Used within the shell script, allowing you to check conditions and perform various tests. | | time | Used to measure the command or script execution time. | | times | It is used to measure the CPU usage of a shell session or a shell script. | | trap | It allows you to execute specific operations when received defined signals. | | true | Returns a successful exit status. | | type | Informs you about the type of the command. | | typeset | Allows you to define and control the behavior of the variables. | | ulimit | By using it, you can manage resources for shell sessions. | | umask | Allows you to control permissions given to newly created files and directories. | | unalias | Used to unset alias which was configured using the alias command. | | unset | It is used to unset variables and functions which were defined previously. | | until COMMANDS; do COMMANDS; done | It is a loop that will be iterated until the given conditions are met. | | variables | Provides names and descriptions of some shell variables. | | wait | Used to pause the execution until all the background tasks are complete. | | while COMMANDS; do COMMANDS; done | It is a loop that will be iterated till the specified conditions are true. | 🤚 Some Linux purists frown upon calling them shell built-in commands. They prefer not addressing them as commands. However, most Linux books call them built-in shell commands so I see no harm in using the 'command' word with shell built-ins. ## No man pages and binaries for shell built-in commands Regular or should I say external Linux commands come with a man page entry that gives information on how to use them. However, shell built-in commands don't have man pages. If you try using the man command, it will show an error like this: ``` Sagar@LHB:~$ man cd No manual entry for cd ``` You'll have to use the help command that you saw above: ``` help shell_built_in_command_name ``` And it will give you some hints on using the built-in command. Similarly, you won't see binaries for the shell built-ins with whereis and [which commands](https://linuxhandbook.com/which-command/). ## Identify the shell built-in command To identify which command is built-in, you can [use the type command](https://linuxhandbook.com/type-command/) as shown: ``` type -t Command ``` For example, if I want to check whether the `cd` is a built-in command or not, I will be using the following: ``` type -t cd ``` ![identify the built-in command using the type command in Linux](https://linuxhandbook.com/content/images/2023/06/identify-the-built-in-command-using-the-type-command-in-Linux.png) 💡 Sometimes you'll see a re-implementation of a shell built-in as an external command. [echo](https://linuxhandbook.com/echo-command/) is a common example. To identify, use `type -a` to see if there is any re-implementation of a built-in command. But what if the command is not built-in? So what output can you expect from the type command? Well, apart from the above output, it can give you four other types of output: - `alias`: If the command is an alias. - `file`: If the command is an executable file and is also configured with the PATH variable. - `function`: If the command is function. - `No output`: If the command is not of the above, then, it won't show you anything. [Use Type Command in Linux to Get More Info About CommandsThe type command tells you whether a Linux command is built-in shell command, where is its executable located and whether it is aliased to some other command. Here’s how to use the type command in Linux.![](https://linuxhandbook.com/content/images/size/w256h256/2021/08/Linux-Handbook-New-Logo.png)Linux HandbookChristopher Murray![](https://linuxhandbook.com/content/images/2020/06/type-command-1.png)](https://linuxhandbook.com/type-command/) ## More bash specials Bash also has some special variables that you may want to know about next. [Special Variables in Bash Shell \[With Script Examples\]The bash shell has some special variables that have specific usages and purposes. Learn more about them here.![](https://linuxhandbook.com/content/images/size/w256h256/2021/08/Linux-Handbook-New-Logo.png)Linux HandbookSagar Sharma![](https://linuxhandbook.com/content/images/2023/04/special-variables-in-bash-shell-scripting.png)](https://linuxhandbook.com/bash-special-variables/) Since we are discussing 'specials', how about [special file permissions](https://linuxhandbook.com/suid-sgid-sticky-bit/)? [What is SUID, GUID and Sticky Bit in Linux? How to Use Them?You see an s instead of x in the file permissions? Linux has some special file permissions called SUID, GUID and Sticky Bit. Know more about them.![](https://linuxhandbook.com/content/images/size/w256h256/2021/08/Linux-Handbook-New-Logo.png)Linux HandbookAbhishek Prakash![](https://linuxhandbook.com/content/images/2020/06/linux-special-permissions-explained-1.png)](https://linuxhandbook.com/suid-sgid-sticky-bit/) I hope you liked this article on shell built-ins. Let me know if you have questions or suggestions.