Regular Expressions

The grep command supports regular expressions that are combinations of one or more of the following:

• The following expressions match a single character:

  c	Any ordinary character, other than one of the special pattern-matching characters, matches itself.
  .	A . (period) matches any single character.
  [string]	A string enclosed in square brackets matches any one character in the string.
  [.-.]	A range is two characters separated by a dash and enclosed in square brackets. It matches any character that is within the range.
  [^string]	A string (or range) enclosed in square brackets and preceeded by a ^ (circumflex) matches any character except for the characters in the string (or range). Strings and ranges may be combined as needed, as in: [a-m0-9xyz], which matches a through m, 0 through 9, x, y, or z.
  \c	The \ (backslash) followed by any character matches that character. This is useful for matching the following special characters: . * [ ] { } ^ $ \

• The single-character expressions can be combined into regular expressions as follows:

  *	Matches zero or more occurences of the previous character.
  {m}	Matches exactly m occurrences of the previous character.
  {m,}	Matches at least m occurrences of the previous character.
  {m,n}	Matches at least m but no more than n occurrences of the previous character. m and n must be integers from 0 to 255, inclusive.

• A regular expression can be restricted to match a string that begins on the first character of the line, ends on the last character of the line, or both, as follows:

  ^pattern	The pattern matches a string that begins on the first character of a line.
  pattern$	The pattern matches a string that ends on the last character of a line.
  ^pattern$	The pattern matches an entire line.