Pattern matching

regex & grep

Regex

• regex is a pattern template to filter text
• BRE: POSIX Basic Regular Expression engine
• ERE: POSIX Extended Regular Expression engine

Usage

• grep ‘pattern’ filename
• command | grep ‘pattern’
• Default engine: BRE
• Switch to use ERE:
  • egrep ‘pattern’ filename or...
  • grep -E ‘pattern’ filename

Special characters (BRE & ERE)