Special Symbols

When using grep -E (which enables Extended Regular Expressions), several characters are treated as special metacharacters. These include:

• . – Matches any single character (except newline).
• ^ – Matches the beginning of a line.
• $ – Matches the end of a line.
• * – Matches the preceding element zero or more times.
• + – Matches the preceding element one or more times.
• ? – Matches the preceding element zero or one time.
• { } – Specifies a repetition interval for the preceding element (e.g., {2,5}).
• ( ) – Groups subexpressions and captures matched text.
• | – Denotes alternation (logical OR between expressions).
• [ ] – Denotes a character class (matches any one character within the brackets).

If you need to match these symbols literally, you generally have to escape them with a backslash (e.g., \. to match a literal period).