What is the xargs command?

The xargs command constructs and executes commands provided through standard input. It takes input and converts it into command arguments for another command. This functionality is particularly useful in file management and can be combined with commands like rm, cp, mkdir, and others.

Using the xargs command

When used alone, the xargs command prompts the user to enter a text string and then passes it to the echo command.

This example demonstrates the input provided and the output of the echo command.

Combining xargs with find

The find command is often used in conjunction with xargs in a pipeline. It provides a file list to xargs for further processing. The syntax is as follows:

find [location] -name "[search-term]" -type f | xargs [command]

The above example demonstrates the use of the find command to locate all files with a .sh extension. The file list is then passed through a pipeline to xargs, which uses the rm command to delete them.

However, xargs does not automatically handle files with spaces in their names. To include these files as well, use the -print0 option with find and the -0 option with xargs:

find [location] -name "[search-term]" -type f -print0 | xargs -0 [command]

The rm command is now used to delete all files with the .sh extension.

Combining xargs with grep

xargs can be used with the grep command to search for a string in the file list provided by that command.

find . -name '[search-term]' | xargs grep '[string-to-find-in-files]'

The above example searches for all files with the .txt extension and pipes them to xargs, which then executes the grep command on them.

Multiple xargs commands

To run multiple commands with xargs, use the -I option. The syntax is as follows:

[command-providing-input] | xargs -I % sh -c '[command-1] %; [command-2] %'

In the example, the contents of file4.txt are displayed first. Then, mkdir is used to create a folder for each word in the file.

Reading content from a file

As mentioned earlier, xargs reads from standard input. Use the -a option to read the content of a file.

xargs -a [filename]

Combining find and tar

When used together with the tar command, xargs creates a tar.gz archive and populates it with the files provided by the find command.

find [location] -name "[search-term]" -type f -print0 | xargs -0 tar -cvzf [tar-gz-archive-name]

Printing commands

To view the commands being executed in the standard output by xargs, use the -t option.

[command-providing-input] | xargs -t [command]

In the above example, note that the entire string provided was used by xargs to execute the mkdir command.

Interactive execution of xargs commands

Some xargs operations, such as deleting files and folders, are irreversible. To control the execution of these commands, use the -p option.

[command-providing-input] | xargs -p [command]

When you use the -p option to execute a command, xargs displays a confirmation prompt before execution. Type 'y' to proceed or 'n' to cancel the operation.

Limiting output per line

Sometimes you need to control the number of arguments xargs accepts at a time. To do this, use the -n option followed by the number of arguments you want to limit xargs to.

[command-providing-input] | xargs -n [number] [command]

In the example below, xargs takes the string "echo" from the command and splits it into three parts. Then, it executes another "echo" for each part:

Specifying a delimiter

By default, the delimiter used by xargs is a space. To change the default delimiter, use the -d option followed by a single character or an escape character (such as 'n' for a new line) in the command.

[command-providing-input] | xargs -d [new-delimiter] | xargs [command]

In the example below, the xargs command instructs the system to use an asterisk (*) as a delimiter and applies it to mkdir for each parameter obtained.

Removing spaces from strings

Since xargs ignores spaces when parsing arguments, this command is useful for removing unnecessary spaces from a string.

echo "[string-with-unnecessary-spaces]" | xargs

Listing the line count/word count/character count in each file

xargs can be used with the wc command to display a file list along with the line count, word count, and character count.

ls | xargs wc

The example below instructs the ls command to only pass files containing the word "example" through the pipeline to xargs. xargs then applies wc to this list:

Copying files to multiple directories

To copy files to multiple directories using xargs, the syntax is straightforward:

echo [directory-1] [directory-2] | xargs -n 1 cp -v [filename]

The echo command provides the directory names, and xargs uses the cp command to copy the given file to each directory.

Reference: 如何使用 Linux xargs 命令