Understanding the `command` Command in Linux
In Linux and other Unix-like operating systems, the command command is a shell
builtin that allows you to execute a simple command with a specified name. It
can be especially helpful when you want to bypass any function or alias that
might override the actual command. This article will guide you through the
syntax, options, and examples to help you master the use of the command
command in Linux.
Syntax
The basic syntax for the command command is as follows:
command [options] command_name [arguments]
Here, command_name is the name of the command you want to run, and arguments
are any additional parameters or options you want to pass to that command.
Options
The command command supports a few options, which can be quite handy in
various scenarios. Here is a table summarizing these options:
| Option | Shorthand | Description |
|---|---|---|
--help | N/A | Display a help message. |
--version | N/A | Display version information. |
-p | N/A | Use a default value for PATH that guarantees to find all of the standard utilities. |
-v | N/A | Verbose mode. Writes a string to stdout that contains the command name and the command arguments. |
-V | N/A | Writes a string to stdout that contains the command name and how it was resolved. |
Examples of Usage
1. Simple Execution
To simply execute a command without any interference from aliases or functions, you can use:
command ls
2. Bypassing an Alias
Imagine you have an alias for ls that looks like this:
alias ls='ls -al'
Using the command command, you can bypass this alias:
command ls
This will execute the plain ls command, without the -al options.
3. Using the -p Option
The -p option ensures that you run the command with a standard PATH,
bypassing any custom paths that could interfere with the default behavior. For
example:
command -p ls
4. Verbose Output with -v
This will show the verbose output, describing the command name and its arguments:
command -v ls
5. Detailed Description with -V
This will print a description of how the ls command is being interpreted:
command -V ls
6. Combining Options
You can also combine different options, although not all combinations are logically meaningful:
command -p -v ls
Conclusion
The command command in Linux is a powerful utility to execute commands while
bypassing shell functions and aliases. Understanding its syntax and options can
help you in scenarios where you need to ensure that a command runs in its
original form without any custom alterations. With this guide, you should have a
robust understanding of how to use the command command effectively in Linux.
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