xargs linux command

The xargs utility reads space, tab, newline and end-of-file delimited strings from the standard input and executes utility with the strings as arguments.

Why xargs?

Some commands like grep can accept input from stdin, but others can’t, this is place where xargs came into picture.

In layman’s terms, output of one command can be transfed to another command as a arguments. Piping outputs to some programs work (like grep, awk, sort, uniq, etc) but, it doesn’t work always (e.g. kill, mkdir, touch, etc).

Examples

Examples are always a best way to learn about CLI programs. Let’s dive into it.

Simple use case

Make folder using output from other command. If nothing is given it’ll pass input to echo.

$ echo "my-direcory" | xargs mkdir

-t switch

• -t switch will show what xargs is doing.

$ echo "my-directory-1 my-directory-2" | xargs -t mkdir
mkdir my-directory-1 my-directory-2

• Pass outputs one by one.

$ echo "my-directory-1 my-directory-2" | xargs -t -n 1 mkdir
mkdir my-directory-1
mkdir my-directory-2

-0 switch

If input items are terminated by null character instead of white spaces.

$ echo "file1\0file2\0" | xargs -0 touch

Manipulate input before passing to program

-I can be used to do this. Let’s say you want to bulk rename all files in a folder.

$ ls | xargs -I @@ mv @@ @@.sh

@@ used in above example is just a variable, you can use any other symbols.

Wait before executing next command

-P allows to do this. You can specify number of parellel executions.

Below command executes echo on each 1,2,3,4 one by one with 1 sec sleep in between. Number after -P is used to specify number of parallel executions.

$ echo "1 2 3 4" | xargs -n 1 -P 1 bash -c 'sleep 1; echo $0'

Let’s say, you want to execute 2 commands simultaneity and wait 1 sec before next 2.

$ echo "1 2 3 4" | xargs -n 1 -P 2 bash -c 'sleep 1; echo $0'