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

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NAME

       regsub - Perform substitutions based on regular expression pattern matching

SYNOPSIS

       regsub ?switches? exp string subSpec varName
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DESCRIPTION

       This command matches the regular expression exp against string, and it copies string to the variable whose name is given by varName.  (Reg-
       ular expression matching is described in the re_syntax reference page.)	If there is a match, then while copying string to varName the por-
       tion  of  string that matched exp is replaced with subSpec.  If subSpec contains a ``&'' or ``'', then it is replaced in the substitution
       with the portion of string that matched exp.  If subSpec contains a ``
'', where n is a digit between 1 and 9, then it is replaced in  the
       substitution  with  the	portion of string that matched the n-th parenthesized subexpression of exp.  Additional backslashes may be used in
       subSpec to prevent special interpretation of ``&'' or ``'' or ``
'' or backslash.  The use of backslashes in subSpec tends  to  interact
       badly with the Tcl parser's use of backslashes, so it's generally safest to enclose subSpec in braces if it includes backslashes.

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

       -all	 All  ranges  in string that match exp are found and substitution is performed for each of these ranges.  Without this switch only
		 the first matching range is found and substituted.  If -all is specified, then ``&'' and ``
'' sequences are	handled  for  each
		 substitution using the information from the corresponding match.

       -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 METASYNTAX, below).

       -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 METASYNTAX, below).

       -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 METASYNTAX, below).

       -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 METASYNTAX, below).

       -nocase	 Upper-case characters in string will be converted to lower-case before matching against exp;  however, substitutions specified by
		 subSpec use the original unconverted form of string.										   |

       -start index																   |
		 Specifies a character index offset into the string to start matching the regular expression at.  When using this switch, `^' will |
		 not  match the beginning of the line, and A will still match the start of the string at index.  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 -.

       The command returns a count of the number of matching ranges that were found and replaced.  See the manual entry for regexp for details	on
       the interpretation of regular expressions.

SEE ALSO

       regexp(n), re_syntax(n)

KEYWORDS

       match, pattern, regular expression, substitute

Tcl									8.3								 regsub(n)