grep command in unix/linux

Grep: grep is one of many standard UNIX utilities. It searches files for specified words or patterns. First clear the screen, then type

% grep college  college.txt
As you can see, grep has printed out each line containg the word college.

% grep College college.txt
The grep command is case sensitive; it distinguishes between College and college. To ignore upper/lower case distinctions, use the -i option, 

% grep -i College college.txt
To search for a phrase or pattern, you must enclose it in single quotes (the apostrophe symbol). For example to search for spinning top,

% grep -i ‘spinning top’ college.txt

Some of the other options of grep are:

-v display those lines that do NOT match

-n precede each matching line with the line number

-c print only the total count of matched lines  You can use more than one option at a time. For example, the number of lines without the words college or College is
% grep -ivc college college.txt

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