Categories
Linux Tutorial Series

Linux Tutorial Series – 48 – The grep command

Here is the video version, if you prefer it:

The grep command is used to find text patterns within files. (Ward, 2014)⁠ Its usage is as follows:

grep pattern filename

grep outputs the lines which match the pattern. What is the pattern? The pattern is anything you want to match. You can use regular expressions here, but we are going to talk about that later. pattern, for our purposes right now, is a word or multiple words you want to find in a file. Say I had this file:

mislav@mislavovo-racunalo:~$ cat file.txt

Some line

Some other line

Here is what happens when I want to print out every line which contains the word (pattern) line:

mislav@mislavovo-racunalo:~$ grep line file.txt

Some line

Some other line

Here is the result if I want to print every line which contains the pattern other:

mislav@mislavovo-racunalo:~$ grep other file.txt

Some other line

If I wanted my pattern to be composed of multiple words, I would have to put them under single quotations, like this:

mislav@mislavovo-racunalo:~$ grep ‘other line’ file.txt

Some other line

If I wouldn’t I’d get an error. But you do know how to use Google for errors, do you?

Useful options are -i for case insensitive matches (no difference between capital letters and “small” letters) and -v for inverting matches (printing every line that does not contain a match).

Hope you found this helpful!

References

Ward, B. (2014). How Linux Works: What Every Superuser Should Know (2nd ed.). No Starch Press. Pages 18-19

NewsletterUpdates on interesting things I am doing

Subscribe to my newsletter to keep abreast of the interesting things I'm doing. I will send you the newsletter only when there is something interesting. This means 0% spam, 100% interesting content.

Leave a Reply

Your email address will not be published.