DOKK / manpages / debian 10 / tcl8.6-doc / regsub.3tcl.en
regsub(3tcl) Tcl Built-In Commands regsub(3tcl) 







regsub - Perform substitutions based on regular expression pattern
    matching








regsub ?switches? exp string subSpec
    ?varName?










This command matches the regular expression exp against
    string, and either copies string to the variable whose name is
    given by varName or returns string if varName is not
    present. (Regular expression matching is described in the re_syntax
    reference page.) If there is a match, then while copying string to
    varName (or to the result of this command if varName is not
    present) the portion of string that matched exp is replaced
    with subSpec. If subSpec contains a “&” or
    “\0”, then it is replaced in the substitution with the portion
    of string that matched exp. If subSpec contains a
    “\n”, 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 “&”, “\0”,
    “\n” and backslashes. The use of backslashes in
    subSpec tends to interact badly with the Tcl parser's use of
    backslashes, so it is generally safest to enclose subSpec in braces
    if it includes backslashes.


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



  

  
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 “\n”
      sequences are handled for each substitution using the information from the
      corresponding match.

  

  
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).

  

  
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).

  

  
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).

  

  
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).

  

  
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.

  

  
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.
      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 varName is supplied, the command returns a count of the
    number of matching ranges that were found and replaced, otherwise the string
    after replacement is returned. See the manual entry for regexp for
    details on the interpretation of regular expressions.








Replace (in the string in variable string) every instance
    of foo which is a word by itself with bar:






regsub -all {\mfoo\M} $string bar string




or (using the “basic regular expression”
  syntax):






regsub -all {(?b)\<foo\>} $string bar string




Insert double-quotes around the first instance of the word
    interesting, however it is capitalized.






regsub -nocase {\yinteresting\y} $string {"&"} string




Convert all non-ASCII and Tcl-significant characters into \u
    escape sequences by using regsub and subst in combination:






# This RE is just a character class for almost everything "bad"
set RE {[][{};#\\\$ \r\t\u0080-\uffff]}
# We will substitute with a fragment of Tcl script in brackets
set substitution {[format \\\\u%04x [scan "\\&" %c]]}
# Now we apply the substitution to get a subst-string that
# will perform the computational parts of the conversion. Note
# that newline is handled specially through string map since
# backslash-newline is a special sequence.
set quoted [subst [string map {\n {\\u000a}} \


        [regsub -all $RE $string $substitution]]]










regexp(3tcl), re_syntax(3tcl), subst(3tcl), string(3tcl)








match, pattern, quoting, regular expression, substitution







  

    8.3
    Tcl