Introduction to Pipes and Filters in Linux

Pipes and Filters in Linux

The use of pipes and filters is one of the most powerful and important concepts in the Linux command line. Pipes and filters allow commands to be combined and redirected in order to produce custom output. In Linux, a pipe is a way to redirect the standard output of one program to the input of another program. A filter is a program that takes standard input and produces standard output with some changes. This article will discuss how to use pipes and filters in the Linux command line.

Using Pipes in Linux

When two commands are separated by a pipe (|), the first command’s output is used as input to the second command. For example, if you want to list all the processes running on your machine, you could type:

ps -ef | grep bash

This would list all the processes running on your machine and then grep for any process that had “bash” in the command line. Pipes can also be used to redirect the output of one command to a file, like this:

ps -ef > processes.txt

This would create a file called “processes.txt” containing the list of all processes running on your machine.

Using Filters in Linux

Filters are programs that take standard input and change it before sending it to standard output. Common filters include head, tail, cut, sort, uniq and grep. For example, if you wanted to list the 5 most recently modified files in a directory, you could type:

 ls –l | head -n 5

This would list all the files in the current directory and then take the first five lines of output using head. Filters can also be chained together to produce more complex results. For example, if you wanted to sort the output of the previous command alphabetically, you could type:

 ls –l | head -n 5 | sort

This would take the first five lines of output from the ls command, sort them alphabetically, and display the result.

Conclusion

Pipes and filters are essential tools for creating powerful commands in the Linux command line. They allow you to combine multiple commands and filters to produce custom output tailored to your specific needs. Knowing how to use pipes and filters effectively is an invaluable skill for anyone who works with Linux.