regexp(n)						       Tcl Built-In Commands							 regexp(n)

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NAME

       regexp - Match a regular expression against a string

SYNOPSIS

       regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar ...?
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DESCRIPTION

       Determines  whether  the regular expression exp matches part or all of string and returns 1 if it does, 0 if it does not, unless -inline is
       specified (see below).  (Regular expression matching is described in the re_syntax reference page.)

       If additional arguments are specified after string then they are treated as the names of variables in which  to	return	information  about
       which part(s) of string matched exp.  MatchVar will be set to the range of string that matched all of exp.  The first subMatchVar will con-
       tain the characters in string that matched the leftmost parenthesized subexpression within exp, the next subMatchVar will contain the char-
       acters that matched the next parenthesized subexpression to the right in exp, and so on.

       If the initial arguments to regexp start with - then they are treated as switches.  The following switches are currently supported:

       -about	      Instead  of  attempting to match the regular expression, returns a list containing information about the regular expression.
		      The first element of the list is a subexpression count.  The second element is a list of property names that describe  vari-
		      ous attributes of the regular expression. This switch is primarily intended for debugging purposes.

       -expanded      Enables use of the expanded regular expression syntax where whitespace and comments are ignored.	This is the same as speci-
		      fying the (?x) embedded option (see the re_syntax manual page).

       -indices       Changes what is stored in the subMatchVars.  Instead of storing the matching characters from string, each variable will con-
		      tain  a  list  of two decimal strings giving the indices in string of the first and last characters in the matching range of
		      characters.

       -line	      Enables newline-sensitive matching.  By default, newline is a completely ordinary character with no special  meaning.   With
		      this  flag, "[^" bracket expressions and "."  never match newline, "^" matches an empty string after any newline in addition
		      to its normal function, and "$" matches an empty string before any newline in addition to its normal function.  This flag is
		      equivalent to specifying both -linestop and -lineanchor, or the (?n) embedded option (see the re_syntax manual page).

       -linestop      Changes the behavior of "[^" bracket expressions and "."	so that they stop at newlines.	This is the same as specifying the
		      (?p) embedded option (see the re_syntax manual page).

       -lineanchor    Changes the behavior of "^" and "$" (the "anchors") so they match the beginning and end of a line respectively.  This is the
		      same as specifying the (?w) embedded option (see the re_syntax manual page).

       -nocase	      Causes upper-case characters in string to be treated as lower case during the matching process.

       -all	      Causes  the  regular expression to be matched as many times as possible in the string, returning the total number of matches
		      found.  If this is specified with match variables, they will contain information for the last match only.

       -inline	      Causes the command to return, as a list, the data that would otherwise be placed in match variables.   When  using  -inline,
		      match  variables may not be specified.  If used with -all, the list will be concatenated at each iteration, such that a flat
		      list is always returned.	For each match iteration, the command will append the overall match data,  plus  one  element  for
		      each subexpression in the regular expression.  Examples are:
		      regexp -inline -- {w(w)} " inlined "
			    -> in n
		      regexp -all -inline -- {w(w)} " inlined "
			    -> in n li i ne e

       -start index   Specifies  a  character index offset into the string to start matching the regular expression at.  The index value is inter- |
		      preted in the same manner as the index argument to string index.	When using this switch, "^" will not match  the  beginning
		      of  the  line,  and  A  will  still  match the start of the string at index.  If -indices is specified, the indices will be
		      indexed starting from the absolute beginning of the input string.  index will be constrained to  the  bounds  of	the  input
		      string.

       --	      Marks the end of switches.  The argument following this one will be treated as exp even if it starts with a -.

       If  there  are  more  subMatchVars than parenthesized subexpressions within exp, or if a particular subexpression in exp does not match the
       string (e.g. because it was in a portion of the expression that was not matched), then the corresponding subMatchVar will be set to "-1 -1"
       if -indices has been specified or to an empty string otherwise.

EXAMPLES

       Find the first occurrence of a word starting with foo in a string that is not actually an instance of foobar, and get the letters following
       it up to the end of the word into a variable:
	      regexp {mfoo(?!barM)(w*)} $string -> restOfWord
       Note that the whole matched substring has been placed in the variable "->", which is a name chosen to look nice given that we are not actu-
       ally interested in its contents.

       Find the index of the word badger (in any case) within a string and store that in the variable location:
	      regexp -indices {(?i)mbadgerM} $string location
       This  could also be written as a basic regular expression (as opposed to using the default syntax of advanced regular expressions) match by
       prefixing the expression with a suitable flag:
	      regexp -indices {(?ib)<badger>} $string location

       This counts the number of octal digits in a string:
	      regexp -all {[0-7]} $string

       This lists all words (consisting of all sequences of non-whitespace characters) in a string, and is useful as a more  powerful  version	of
       the split command:
	      regexp -all -inline {S+} $string

SEE ALSO

       re_syntax(n), regsub(n), string(n)													   |

KEYWORDS

       match, parsing, pattern, regular expression, splitting, string

Tcl									8.3								 regexp(n)