How to use the grep command on Linux? See 4 practical examples

The grep command on Linux is the best way to search for files and patterns through lines of text within the operating system. Knowing how to manipulate this command is essential to facilitate the routine of users and professionals who work with Linux in their daily lives.

But when it comes to the grep command, many questions arise, such as: what is this control for? How to use it to resolve everyday impasses? And what are some practical examples of use?

Thinking of helping you with these questions, we developed this complete article, with everything you need to know about the subject, including examples of lines of code that you can use for various situations. Follow up!

What is the Grep command?

Grep, Global Expression Regular Print, simply refers to the command that searches for patterns or expressions within the text files present in the system, as requested by the user.

In more technical terms, grep can be considered an application that searches for specified strings (words) within all data content using regular expressions (called regex).

Syntax

The syntax of the Grep command boils down to:

• grep [options] regex [files];
• or even: command | grep [options] regex.

In this framework, it is important to identify what each segment means:

• grep: the command;
• options: such as the command filters;
• regex (or default): what needs to be found;
• files: the place where you want to find the search term.

Using these command syntaxes, grep reads every line of the files and, when it finds the information corresponding to the regular expression, selects it and “prints” it, or shows it, on the screen as a result.

Within each command, there are numerous options, each with a specific purpose, in order to filter searches for information.

To illustrate, know that there are options that display the number of lines, perform recursive searches, or even reverse the search mode, showing only file lines that do not match the desired pattern.

**And what is it for?

Like all Linux features, the Grep command makes it easier for users to search and filter information in the best possible way.

Thus, even in huge text files with many lines, expressions, and data, it is possible to find just the desired expression.

The opposite is also true: if a term is repeated a lot, it is possible to filter in order to return only the results that are different from it, using commands such as -v (minus symbol and letter V), responsible for this function of returning information that does not correspond to the regex.

But don’t worry: we’ll talk more about each of the main commands below, so that you better understand how to use them in your daily life in order to optimize time, processes, and resources.

And how to use the Grep command on Linux?

Photo: Pexels | How to use this function? You can use the Grep command on Linux whenever you want and need to identify a specific term in a file on your operating system.

If you want to identify, for example, all the places where your name appears, grep can make this possible.

Or, in a file that needs alteration, for example, the programmer or developer could apply the search name or term filter, in addition to activating the option that provides the line number in which the term appears.

To better understand the variety of options present in the Linux system, simply open the command terminal and search for “grep -help”. Thus, all available options and explanations will be shown.

This simple search will serve as a kind of glossary, so that you can learn about all the options available in the grep system on Linux.

Examples of using the Grep command

Photo: Freepik | Understanding Grep is totally useful. Now that you know how Grep works, and how it can be applied, let’s connect theoretical and practical knowledge, through interesting examples of the use of the Grep command.

You can reproduce the examples discussed here on your own Linux terminal for study and testing purposes. That way, it will be much easier to record the commands and truly understand.

Search word in text file

To identify a specific word in a text file, simply play the grep command with including the desired word and the location where the file is located.

Here, as an example, we’ll use the word “command” in the place “grep”:

Grep Command Grep

Search word ignoring uppercase and lowercase letters

To make sure that both words starting with uppercase and lowercase letters can be found, simply include the “-i” option (without the quotes), such as the template:

grep -i file request

Also following the example above, of the word “command”, the structure would look like this:

grep -i command grep

Thus, all lines containing the word “command”, regardless of whether they are written in uppercase or lowercase letters, will be shown in a different color to highlight.

Word counter

If you want to find out how many times the desired word or term appears in the text files in the chosen directory of your operating system, simply run the -c command.

With it, you can check the counting of the words searched in a simple and effective way. Just follow the structure below:

grep -c file request

Search for words in several files

In the case of broader searches, in which you need to consider where the searched word appears, regardless of the location of the file, simply include the -l option, according to the example structure below:

grep -l request. /*

These are just a few examples of how grep options and commands can be customized according to your file search and identification needs.

There is a multitude of content waiting for you to make your routine with the handling of the Linux system simpler and more efficient.

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Conclusion

Did you notice how useful the grep command is? Like this command, there are several other utilities that you only discover when you start studying the peculiarities of the Linux system.

If you want to learn more, the best option is to browse our Linux Certification course platform. You can choose the course that best meets your current needs and be guaranteed to learn with the most experienced teacher in the field!