Usage of GREP command with examples.

Grep is a command-line utility widely used in Linux/Unix that uses in searching data sets of specific files for lines that match a regular expression of plain texts.
Syntax: grep PATTERN [FILE]

Examples:

1. The below command will find all of the words in the files that matched the word ‘error’ in the error.log file

grep 'error' error.log

1. Case insensitive search : The -i option enables to search for a string case insensitively in the given file. This searches for the word 'Anush', 'AnuSh', 'aNUsH' etc.

grep -i 'Anush' Anush.txt

3.Displaying the count of number of matches : -c is find the number of lines that matches the given string/pattern

grep -c 'Anush' Anush.txt

4.Display the file names that matches the pattern : -l will just display the files that contains the given string/pattern.

** grep -l "Anush"* **

5.Checking for the whole words in a file : By default, grep matches the given string/pattern even if it is found as a substring in a file. The -w option to grep makes it match only the whole words.

grep -w "Training" Anush.txt

6.Displaying only the matched pattern : By default, grep displays the entire line which has the matched string. We can make the grep to display only the matched string by using the -o option.

grep -o "unix" geekfile.txt