The grep command in Linux

The grep command in UNIX-like operating systems is used to search for a given substring or regular expression in text files or the output of other commands.

What function does the grep command perform

The syntax of the grep command is as follows:

grep [options] sample [files]

Here, pattern is the substring or regular expression to be searched and [files] is the list of files to be searched. If [files] is not specified, grep will read input from standard input (usually meaning that you can pass the output of other commands to grep).

Some common grep options are:

-i - ignore character case when searching

-r - search recursively in all subdirectories

-n - output line numbers where a pattern is found

-v - output only lines that do not contain the pattern

For example, to find all lines in the file example.txt containing the word "apple", you can use the command:

grep apple example.txt

And to find all files in the current directory and its subdirectories containing the word "banana", you can use the command:

grep -r banana .

Here the dot stands for the current directory.