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