xargs is a command-line tool. If you want to redirect the output of a command as the argument of another command, then xargs is the tool for you. It is a very useful tool for easily doing a lot of stuff on the command line. In this article, I am going to show you how to use xargs on Linux. So, let’s get started.
Let now see how xargs Works:
The format in which you use xargs command is:
$ command1 | xargs command2
You can also modify the behaviour of xargs with some options. In that case, the format of the xargs command will be:
$ command1 | xargs [options] command2
Here, the output of the command1 will be used as the argument of command2. The output of command1 is broken down into many arguments by xargs depending on a character called a delimiter. Then, xargs runs the command command2 for each of these arguments and that argument is passed as the argument of the command command2.
For example, let’s say, the output of command1 is as follows:
value1 value2 value3
Let’s say, the delimiter character is space. Now, the output of command1 will be broken into 3 arguments, value1, value2, and value3.
Now, xargs runs the command command2 for each of the 3 arguments once.
$ command2 value1 $ command2 value2 $ command2 value3
Here, value1, value2, and value3 are the arguments parsed by xargs from the output of the command command1.
You can achieve the same effect using loops in a shell script. But xargs is just an easier way to do things without loops, especially on the command line.
By default, the delimiter of xargs is newline/space character. But you can change the delimiter character with the -d or –delimiter option of xargs.
By default, xargs works with one argument at a time. If you want to run the command command2 with multiple arguments from the output of the command command1, then you can use the -n or –max-args option of xargs. Sometimes, you will have to tell xargs specifically to work with one argument at a time with the -n or –max-args option.
You can also append or prepend other strings to the arguments passed to the command command2 using the -I option of xargs.
Example 1: Creating and Removing Files Listed in a Text File
Let’s say, you have a list of filenames in a text file files.txt.
You can see the contents of the text file files.txt using the below.
$ cat files01.txt
Output: root@server: $ cat files01.txt I love Linux root@server:
Now, let’s say, you want to remove the files which are listed in the files.txt text file. You can use the rm command with xargs as follows:
$ cat files.txt | xargs rm -v
This is a very simple example of xargs.
Example 2: Redirect STDOUT to Commands that Don’t Support Pipe
You can redirect the STDOUT of a command command1 as the STDIN of another command command2 if command command2 supports Linux pipe. But if the command does not support pipe, you won’t be able to do that.
For example, the echo command does not support the pipe. Check with the following command:
$ date | echo
Output: root@server: $ date | echo root@server:
xargs command can help you to redirect the STDOUT of command1 (in this case date) to the STDIN of command2 (in this case echo).
$ date | xargs echo
Output: root@server: $ date | echo Mon Feb 17 17:24:15 IST 2020 root@server:
Example 3: Changing Delimiter of xargs
Here, I want to print a string 123-456-7890 (a dummy phone number) using xargs.
Output: 123-456-7890
Here, I’ve changed the delimiter to – using the -d option of xargs.
$ echo -n "123-456-789" | xargs -n 1 -d - echo
Output: 123 456 7890
Example 4: Appending or Prepending xargs Arguments
You can append (add to the end of the argument) or prepend (add to the front of the argument) string to the argument passed to the command command2 using xargs. Before I show you how to do this, I will show you how to use the -I option of xargs.
The -I option of xargs allows you to define a symbol for the xargs argument that is passed to the command command2. It works just like a variable.
For example,
$ echo -n "123-456-789" | xargs -d - -n 1 -I{} echo {}
Output: 123 456 7890
Here, -I option defines {} as the symbol for the argument that xargs is currently working on. Once the symbol {} is defined, the symbol can be used to pass the argument to the command command2, which (the symbol {}) will be replaced by the value of the argument.
Now, to append the string .txt (let’s say) to each argument, you can use xargs as follows:
$ echo -n "123-456-789" | xargs -d - -n 1 -I{} echo {}.txt
Output: 123.txt 456.txt 7890.txt
The same way, you can prepend the string hello (let’s say) to each argument as follows:
$ echo -n "123-456-789" | xargs -d - -n 1 -I{} echo "hello {}"
Output: hello 123 hello 456 hello 7890
Example 5: Changing Extensions of Specific Files
This one is a little bit tricky. But I will explain how it works. Don’t worry.
Let’s say, you have some files in your current working directory with different file extensions. Now, you want to change them all to png extension.
Output: root@server: $ ls -l file01.jpg file02.jpeg file03.png root@server:
You can change the file extension of all the files in your current working directory to png with xargs as follows:
$ ls | xargs -I{} bash -c 'FILE={} && mv -v $FILE ${FILE%%.*}.png'
Output: root@server: $ ls -l file01.png file02.png file03.png root@server:
As you can see, all the file extension has changed to png.
Here, xargs starts a bash subshell and runs the bash command
FILE={} && mv -v $FILE ${FILE%%.*}.png
First, FILE={} assigns the symbol {} value, which is the filename (the argument value of xargs) to the FILE shell variable.
Then, mv command is used to change the file extension.
The $FILE shell variable contains the original filename.
${FILE%%.*} remove the extension of the filename (including . character) and then .png string is appended to the stripped filename.
xargs can do a lot more complex kinds of stuff. Keep trying out new things with xargs. The sky is your limit.
If you need any help on xargs, you can check the man page of xargs as follows:
$ man xargs
So, that’s how you use xargs on Linux.
