Method 2: Match text with white space characters If your string is in the starting then you can just use (^) # grep -E '^abcd' /tmp/somefile abcd some text

This does not work if you have to find anything somewhere in the middle of line.Since there was only one such occurrence where the line starts with ' a' and ends with ' d', there was single output.You have to understand, when we define regex to look for beginning (^) and end ($) character, it means first and last character on the entire line.But if you observe, this command failed to capture other lines containing ' abcd'.Since we are planning to grep for ' abcd', our command would be: # grep -E '^abcd$' /tmp/somefile abcd We can grep an exact match by putting a regex match of beginning( ^) and ending( $) char. Method 1: grep for first and last character Word-constituent characters are letters, digits, and the underscore.

Similarly, it must be either at the end of the line or followed by a non-word constituent character. Substring must either be at the beginning of the line, or preceded by a non-word constituent character. Select only those lines containing matches that form whole words. From the man page of grep: -w, -word-regexp

# grep -w abcd /tmp/somefileĪs you observe, it did filtered the output by removing non-relevant match although the grep was not 100% successful. Now with grep we have an argument ( -w) which is used to grep for exact match of whole word from a file. Below is my sample file to demonstrate all the examples and scenarios from this tutorial.

Grep regexp