[[linux_wiki:use_grep_and_regular_expressions_to_analyze_text]]

Use Grep And Regular Expressions To Analyze Text

General Information

Pattern matching with grep.


Filter lines that start with (^) a comment (#) in myfile.txt

grep "^#" myfile.txt


Filter for “auth”, ignore case

grep -i "auth" /etc/ssh/ssh_config


Common Grep Options

  • -i ⇒ ignore case
  • -v ⇒ invert match (show non-matching lines)
  • -c ⇒ output the count of matches (or count of non-matching if used with -v)
  • -o ⇒ print only the matched parts of the matching line
  • -n ⇒ prefix each line of output with the line number


Regular Expression Matching

  • ^ ⇒ starts with
  • $ ⇒ ends with
  • [ab] ⇒ match a or b
  • [^ab] ⇒ do not match a or b
  • ? ⇒ previous item optional (match 0 or 1 time)
  • * ⇒ previous item matched zero or more times
  • + ⇒ previous item matched one or more times
  • . ⇒ match any single character (the period)
  • {x} ⇒ previous item matched exactly x times
  • {x,} ⇒ previous item matched x or more times
  • {,y} ⇒ previous item matched at max y times
  • {x,y} ⇒ previous item matched at least x times, but not more than y times

  • linux_wiki/use_grep_and_regular_expressions_to_analyze_text.txt
  • Last modified: 2019/05/26 03:50
  • (external edit)