regexp man page on Archlinux

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


       regexp - Match a regular expression against a string

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

       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 contain
       the characters in string that matched the leftmost parenthesized subex‐
       pression	 within	 exp, the next subMatchVar will contain the characters
       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	subex‐
		      pression	count.	 The second element is a list of prop‐
		      erty names that describe various attributes of the regu‐
		      lar  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 specifying 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	 vari‐
		      able  will  contain 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 mean‐
		      ing.   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 subexpres‐
		      sion 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	 interpreted  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.

       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(?!bar\M)(\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)\mbadger\M} $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 pre‐
       fixing 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

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

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

Tcl				      8.3			     regexp(n)

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