View source for Search text files using regular expressions

==Creating a simple regular expression==
A basic regular expression to match email addresses:
\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Z|a-z]{2,}\b

This pattern matches:

    One or more word characters, dots, underscores, or plus signs before the @ symbol

    One or more word characters or dots after the @ symbol

    A dot followed by two or more letters for the top-level domain

    Using regular expression tools for searches:

==grep: Basic regular expression searching==
Example: grep "^[A-Z].*[0-9]$" file.txt
*This searches for lines in file.txt that start with an uppercase letter and end with a digit.

==egrep (or grep -E): Extended regular expression searching==
Example: egrep "apple|orange|banana" fruits.txt
*This searches for lines in fruits.txt containing either "apple", "orange", or "banana".

==fgrep (or grep -F): Fixed string searching (no regex interpretation)==
Example: fgrep "C++" programming_languages.txt
*This searches for the exact string "C++" in programming_languages.txt, without interpreting + as a regex quantifier