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This article mainly introduces how to use the xargs command on Linux, the article is very detailed, has a certain reference value, interested friends must read it!

When using Linux, have you ever encountered a situation where you need to string some commands together, but one of them does not accept pipe input? In this case, we can use the xargs command. Xargs can send the output of one command as an argument to another command.

In Linux, all standard applications have three data streams associated with them. They are standard input stream (stdin), standard output stream (stdout) and standard error stream (stderr). These streams are run as text, and we use text to send the input (stdin) to the command, and then the response (stdout) will be displayed as text on the terminal window. The error message is also displayed as text on the terminal window (stderr).

A major feature of Linux and Unix-like operating systems is the ability to pass the standard output stream of one command to the standard input stream of another command. The first command does not care whether its output is written to the terminal window, and the second command does not care whether its input comes from the keyboard.

Although all Linux commands have three standard streams, not all commands accept the standard output of another command as input to its standard input stream. So we can't pipe the input to these commands.

Xargs is a command that uses standard data streams to build execution pipes. By using the xargs command, we can make commands such as echo,rm and mkdir accept standard input as their parameters.

Xargs command

Xargs accepts pipe input, as well as input from a file. Xargs uses this input as an argument to the command we specify. If we do not specify a specific command for xargs, we use echo by default. Xargs always generates single-line output, even if the input data is multiple rows.

If we use the-1 (list one file per line) option of ls, we get a list of file names:

$ls-1. / * .sh

This command lists the Shell script files in the current directory.

What would happen if we piped the output to xargs?

$ls-1. / * .sh | xargs

As you can see, the output is written to the terminal in the form of a long string of text. Thus, xargs can pass the output as an argument to other commands.

Use xargs with the wc command

We can use the xargs command to easily let the wc command count the number of words, characters, and lines in multiple files

$ls * .c | xargs wc

The implementation results are as follows:

The result of the command run shows the statistics and the total for each file.

This command does the following:

Ls lists all the .page files and passes the list to xargs.

Xargs passes all file names to wc.

Wc treats these file names as command-line arguments.

Use xargs with confirmation messages

We can use the-p (interaction) option to have xargs prompt us if we want to take the next step.

If we pass a string of file names to the touch command through xargs, touch will create these files.

$echo 'one two three' | xargs-p touch

The command to be executed is displayed on the terminal, and xargs waits for us to type y or Y, n or N and press Enter to respond. If only Enter is pressed, it is considered n. This command is executed only when we enter y or Y.

We press y and Enter, and then use ls to check whether the file has been created.

$ls one two three

Use xargs with multiple commands

We can use the-I (initial parameter) option to use xargs with multiple commands. This option defines the replacement string. Wherever the replacement string appears on the command line, the value we provided to xargs is inserted.

It's a little abstract, let's explain it with an example.

Let's first look at the subdirectories in the current directory with the tree command. This-d (directory) option causes the tree command to ignore files and output only directories.

$tree-d

Now there is only one subdirectory images.

In the directories.txt file, we have some names of the directories we want to create. Let's first look at the contents of it with cat.

$cat directories.txt

We pass this to xargs as input data and execute the following command:

$cat directories.txt | xargs-I% sh-c 'echo%; mkdir%'

This command does the following:

Cat directories.txt: pass the contents of the directrories.txt file (all directory names to be created) to xargs.

Xargs-I%: the replacement string% is defined.

Sh-c: start a new child shell. -c (commond) lets shell read the command.

'echo%; mkdir%': each% is replaced with the directory name passed by xargs. The echo command prints the directory name, and the mkdir command creates the directory.

The result of the command execution:

We can use tree to verify that a directory has been created.

$tree-d

Copy files to multiple locations

We can use the xargs command to copy files to multiple locations with one command.

First, pipe the names of the two directories to xargs. And have xargs pass only one of the parameters to the command in use at a time.

To call cp twice, each time using one of the two directories as a command-line argument, we can do this by setting the-n (max number) option of xargs to 1.

The-v (verbose details) option is also used here to have cp give feedback on what is being done.

$echo ~ / dir1/ ~ / dir2/ | xargs-n 1 cp-v. / * .c

We copied the files to two directories, one at a time. Cp gave back the details so that we can see what has been done.

Delete files in a nested directory

If the file name contains spaces or other special characters, such as newline characters, xargs will not interpret the file names correctly. We can use the-0 (null Terminator) option to solve this problem. At this point, xargs will use the null character as the final delimiter for the file name.

Here we take the find command as an example. Find has its own options to handle spaces and special characters in file names, that is, the-print0 (full name, empty character) option.

$find. -name "* .png"-type f-print0 | xargs-0 rm-v-rf "{}"

This command does the following:

Find. -name "* .png": find will search the current directory for objects whose names match * .png, and type-f specifies that only files will be searched.

-print0: the name ends with an empty character and preserves spaces and special characters.

Xargs-0:xargs will also consider that the file name ends with a null value, and spaces and special characters do not cause problems.

Rm-v-rf "{}": rm will feed back the ongoing operation (- v), recursively perform the operation (- r), and delete the file directly (- f) without sending an error prompt. Replace "{}" with each file name.

After the command is executed, all subdirectories are searched and the matching files are deleted.

Delete nested directories

Suppose we want to delete a set of nested subdirectories and first look at them with tree.

$tree-d

$find. -name "level_one"-type d-print0 | xargs-0 rm-v-rf "{}"

This command uses find to search recursively in the current directory, searching for a directory named level_one, and then passing the directory name to rm via xargs.

The difference between this command and the previous command is that the search item is the name of the top-level directory, and-type d indicates the directory to look for, not the file.

The name of each directory is printed when it is deleted. We can use tree to check the results again:

$tree-d

All nested subdirectories have been deleted.

Delete all files except one file type

We can use find, xargs, and rm to delete all types of files and keep only one type of file that we want to keep. This requires providing the type of file you want to keep.

The-not option causes find to return all file names that do not match the search pattern. We use the-I (initial parameter) option of xargs again at this time. The replacement string defined this time is {}. This has the same effect as the replacement string% we used earlier.

$find. -type f-not-name "* .sh"-print0 | xargs-0-I {} rm-v {}

After the command is executed, we confirm the result through ls. As you can see, only the files that match * .sh are left in the directory.

$ls-l

Create a compressed file using Xargs

We can use the find command to search for files and pass the file name to the tar command through xargs to create a compressed file.

We will search the current directory for the * .sh file.

$find. /-name "* .sh"-type f-print0 | xargs-0 tar-cvzf script_files.tar.gz

The result of the command execution lists all .sh files and creates a compressed file.

The above is all the contents of the article "how to use xargs commands on Linux". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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