5 Basic Regular Expressions for Efficient Text Manipulation in Linux Terminal

Are you struggling with finding patterns in your Linux terminal? Regular expressions (regex) and grep are powerful tools that can help you search and manipulate text. In this article, we’ll dive into the 5 regular expressions with grep and provide examples that you can use to practice.

Matching a word:

The most basic regular expression is matching a specific word or phrase. The syntax for this is straightforward:

grep "word" file.txt        

For example, let’s say we have a file named "article.txt" that contains the following text:

The quick brown fox jumps over the lazy dog        

To match the word “fox”, we can use the following command:

grep "fox" article.txt        

This will output:

The quick brown fox jumps over the lazy dog        

Matching multiple words:

To match multiple words or phrases, you can use the “OR” operator “|”. The syntax for this is:

grep "word1\|word2" file.txt        

Let’s say we want to match both “fox” and “dog” in the previous example. We can use the following command:

grep "fox\|dog" article.txt        

This will output:

The quick brown fox jumps over the lazy dog        

Matching a pattern:

Regular expressions can also be used to match patterns. For example, let’s say we have a file named "numbers.txt" that contains the following text:

123-456-7890
555-555-1234
888-999-0000        

We can use the following command to match all phone numbers:

grep "[0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\}" numbers.txt        

This will output:

123-456-7890
555-555-1234
888-999-0000        

Matching a range of characters:

To match a range of characters, you can use square brackets. For example, let’s say we have a file named "colors.txt" that contains the following text:

red
blue
green
yellow        

We can use the following command to match all colors that start with the letter “g”:

grep "g[a-z]*" colors.txt        

This will output:

green        

Matching the beginning or end of a line:

You can use the caret (^) to match the beginning of a line and the dollar sign ($) to match the end of a line. For example, let’s say we have a file named "names.txt" that contains the following text:

John Smith
Jane Doe
Michael Johnson        

We can use the following command to match all names that start with “J”:

grep "^J[a-zA-Z]*" names.txt        

This will output:

John Smith        

Practice text for the 5 regular expressions:

Foxes are quick and dogs are lazy. The quick brown fox jumps over the lazy dog.
The sky is blue and the grass is green. I love the color green.
My phone number is 123-456-7890. Call me anytime.
I like the colors red, blue, and green. Green is my favorite color.
John Smith is a great guy. Jane Doe and Michael Johnson are also nice people.        

In conclusion, understanding the basics of regular expressions and grep can greatly enhance your productivity and efficiency in the Linux terminal. The 5 regular expressions we covered in this article should be a good starting point for anyone who wants to improve their text searching and manipulation skills.

Remember that regular expressions are powerful tools and can be quite complex. It takes time and practice to master them. Therefore, I encourage you to keep practicing and experimenting with different regular expressions and grep commands.

Finally, if you want to learn more about regular expressions, I recommend checking out the documentation for grep and the regex library. There are also plenty of online resources and tutorials that can help you take your regex skills to the next level.