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command

shell builtinsLinux/Unix
The command command is one of the most frequently used commands in Linux/Unix-like operating systems. command Run a command, ignoring shell functions and aliases
See ExamplesView Syntax

Quick Reference

Command Name:

command

Category:

shell builtins

Platform:

Linux/Unix

Basic Usage:

command [options] [arguments]

Common Use Cases

  • 1

    Command execution

    Execute commands with specific behavior

  • 2

    Shell scripting

    Control command execution in shell scripts

  • 3

    Builtin verification

    Check if a command is a shell builtin

  • 4

    Function bypass

    Bypass shell functions to execute original commands

Syntax

command [-pVv] command [arg ...]

Options

Option Description
-p Use a default value for PATH that is guaranteed to find all standard utilities
-v Print a description of the command (the path to the command)
-V Print a more verbose description of the command

Examples

How to Use These Examples

The examples below show common ways to use the command command. Try them in your terminal to see the results. You can copy any example by clicking on the code block.

Basic Examples:

Run a command bypassing any aliases or functions with the same name
command ls
Find the exact path of a command
command -v ls
Check if a command exists (returns 0 if found, 1 if not)
command -v non_existent_command >/dev/null 2>&1 && echo "Exists" || echo "Does not exist"
Display all details about a command
command -V ls

Advanced Examples:

Use in scripts to ensure running the actual command, not an alias
command grep "pattern" file.txt
Verify a command exists before using it in a script
if command -v curl >/dev/null 2>&1; then
curl -s https://example.com else echo "curl is not installed" exit 1 fi
Force the use of a program even if there's a shell function with the same name
function echo() { printf "Custom echo function\n"; }
echo "This uses the function" command echo "This uses the real echo command"
Use with PATH modification to find commands in specific locations
PATH=/custom/path:$PATH command -v program

Try It Yourself

Practice makes perfect! The best way to learn is by trying these examples on your own system with real files.

Understanding Syntax

Pay attention to the syntax coloring: commands, options, and file paths are highlighted differently.

Notes

The command utility allows you to run a command bypassing any shell functions or aliases with the same name. It's a shell builtin in most modern shells including bash, zsh, and ksh.

Key points about command:

  • It's primarily used to bypass aliases and shell functions
  • With -v option, it's commonly used to check if a command exists
  • Unlike 'which' or 'type', it's built into the shell and works more consistently across systems
  • It's particularly useful in shell scripts to ensure predictable behavior
  • The command follows the same rules as regular command lookups (searches PATH, etc.)

Common use cases:

  • Testing for the existence of a command in shell scripts
  • Bypassing aliases in interactive sessions or scripts
  • Finding the location of a command (similar to 'which')
  • Getting detailed information about a command (with -V)
  • Ensuring predictable behavior in scripts by ignoring user customizations

Comparison with similar commands:

  • type: Shows how a command would be interpreted if used, also a shell builtin
  • which: External command that finds executables in PATH
  • whereis: Locates the binary, source, and manual page files for a command
  • command -v: Preferred way to test for command existence in scripts (POSIX-compliant)

Note that command with the -p option uses a default, safe path to find standard system utilities, which can be useful in security-sensitive environments.

Common Use Cases

Command execution

Execute commands with specific behavior

Shell scripting

Control command execution in shell scripts

Builtin verification

Check if a command is a shell builtin

Function bypass

Bypass shell functions to execute original commands

Script portability

Ensure scripts work consistently across different shells

Related Commands

These commands are frequently used alongside command or serve similar purposes:

type
which
whereis
hash
alias
unalias
builtin
exec
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Use Cases

1

Command execution

Execute commands with specific behavior

2

Shell scripting

Control command execution in shell scripts

3

Builtin verification

Check if a command is a shell builtin

4

Function bypass

Bypass shell functions to execute original commands

5

Script portability

Ensure scripts work consistently across different shells

Learn By Doing

The best way to learn Linux commands is by practicing. Try out these examples in your terminal to build muscle memory and understand how the command command works in different scenarios.

See ExamplesTry Lab Exercises
$ command
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