egrep

Additional Notes

egrep is the deprecated alias for grep -E. It runs grep with extended regular expression support, which adds +, ?, |, and () as metacharacters without needing backslash escaping. The name stands for "extended grep."

Modern scripts and documentation should use grep -E instead of egrep. The egrep name is provided for backward compatibility but may be removed in future versions. The behavior is identical to calling grep -E with the same options and arguments. See grep for a full description of options and behavior.

Syntax

egrep [options] PATTERN [file...]

Parameters

• PATTERN: Text or extended regular expression to search for.
• file: One or more files to search. If omitted, reads standard input.

Common Options

• -i, --ignore-case: Match without case sensitivity.
• -v, --invert-match: Show lines that do not match.
• -c, --count: Count matching lines.
• -l, --files-with-matches: List only filenames with matches.
• -n, --line-number: Show line numbers.
• -r, --recursive: Search directories recursively.
• -o: Print only the matching part of each line.
• -x, --line-regexp: Match entire lines only.

Examples

egrep "foo|bar" file.txt

Search for lines containing foo or bar using alternation.

egrep "^[A-Z]+:" config.txt

Match lines starting with one or more uppercase letters followed by a colon.

egrep -i "error|fail" log.txt

Search for error or fail case-insensitively.

Practical Notes

• egrep is equivalent to grep -E. Use grep -E in new scripts for portability.
• Extended regex adds + (one or more), ? (zero or one), | (alternation), and () (grouping) without backslashes.
• For basic regex behavior, use grep (or grep -G).
• The egrep binary may not be installed on minimal or newer systems; grep -E is always available.