Search text files using regular expressions
From Mintarc Forge
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
