12 Useful Commands For Filtering Text for Effective File Operations in Linux

In this article, we will review a number of command line tools that act as filters in Linux. A filter is a program that reads standard input, performs an operation upon it and writes the results to standard output.

For this reason, it can be used to process information in powerful ways such as restructuring output to generate useful reports, modifying text in files and many other system administration tasks.

With that said, below are some of the useful file or text filters in Linux.

1. Awk Command

Awk is a remarkable pattern scanning and processing language, it can be used to build useful filters in Linux. You can start using it by reading through our Awk series Part 1 to Part 13.

Additionally, also read through the awk man page for more info and usage options:

$ man awk

2. Sed Command

sed is a powerful stream editor for filtering and transforming text. We’ve already written a two useful articles on sed, that you can go through it here:

1. How to use GNU ‘sed’ Command to Create, Edit, and Manipulate files in Linux
2. 15 Useful ‘sed’ Command Tips and Tricks for Daily Linux System Administration Tasks

The sed man page has added control options and instructions:

$ man sed

3. Grep, Egrep, Fgrep, Rgrep Commands

These filters output lines matching a given pattern. They read lines from a file or standard input, and print all matching lines by default to standard output.

Note: The main program is grep, the variations are simply the same as using specific grep options as below (and they are still being used for backward compatibility):

$ egrep = grep -E
$ fgrep = grep -F
$ rgrep = grep -r  

Below are some basic grep commands:

tecmint@TecMint ~ $ grep "aaronkilik" /etc/passwd
aaronkilik:x:1001:1001::/home/aaronkilik:
tecmint@TecMint ~ $ cat /etc/passwd | grep "aronkilik"
aaronkilik:x:1001:1001::/home/aaronkilik:

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