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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 ...?
____________________________________________________________________________________________________________


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 contain the characters in string
       that matched the leftmost parenthesized subexpression 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 subexpression
                      pression count.  The second element is a list of property names that describe  various
                      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 specifying the (?x) embedded option (see the re_syn-tax re_syntax
                      tax manual page).

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

       -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 -linean-chor, -lineanchor,
                      chor, or the (?n) embedded option (see the re_syntax manual page).

       -linestop      Changes the behavior of "[^" bracket expressions and "."  so that they  stop  at  new-lines. newlines.
                      lines.   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  vari-ables, variables,
                      ables, 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 interpreted in the same manner as the index argu- |
                      ment 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 speci-fied, specified,
                      fied, 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(?!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 actually interested in its contents.

       Find  the index of the word badger (in any case) within a string and store that in the variable loca-tion: location:
       tion:
              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 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)