Clovertech

Using a null value as part of a regular expression.

› Clovertech Forums › Read Only Archives › Cloverleaf › Cloverleaf › Using a null value as part of a regular expression.

  • Creator
    Topic
  • January 4, 2008 at 6:21 pm #49725
    Thomas Fortino
    Participant

      Hello Fellow Clovertechers,

         

        I’m trying to use an use the following regular expression in a tclproc to as part of if condition to continue a message. The values are IN and null {}. The regexp recognizes the IN but does not recognize the {} null.

      The regexp is below –

      if [regexp — IN|{} $vip] {

      I have tried escaping the {} using { } and “{}” but neither worked. I continue looking in the Brent Welch book but any help would be appreciated.

      AIX 5.1

      Platform V rev5.2

    • Creator
      Topic
    Viewing 5 reply threads
    • Author
      Replies
      • January 4, 2008 at 11:11 pm #63293
        Charlie Bursell
        Participant

          Tcl is iterpreting the {} as an empty string.  Pass the regular express to the parser with braces and Tcl will leave it alone.

          Try this:

          regexp — {IN|{}} $vip

          Works for me

        • January 4, 2008 at 11:31 pm #63294
          Chris Williams
          Participant

            regexp — {IN|^$} $vip

            Returns 1 for IN and null.

            Returns 0 for other non-null values.

            You need the curly braces surrounding the expression. The caret and dollar sign mark the beginning and end of a string (with nothing between them).

          • January 8, 2008 at 12:28 pm #63295
            Thomas Fortino
            Participant

              Thanks Charlie and Chris both examples worked great.

            • January 8, 2008 at 7:52 pm #63296
              Chris Williams
              Participant

                Thomas,

                Be aware of how you are representing a null string in your testing. Both regexp expressions will give you matches. However,

                ^$ will match a null (empty) string.

                00 will match a character that is a null.

                {} will match a pair of curly brace characters.

              • January 8, 2008 at 11:07 pm #63297
                Charlie Bursell
                Participant

                  What Chris is saying is true.  I was under the assumption you want to match a literal pair of braces

                • January 9, 2008 at 1:41 am #63298
                  Thomas Fortino
                  Participant

                    Thank, I used Chris’s code because I was looking for a null value. I tested the using both “IN” and a empty field in the data.

                    regexp — {IN|^$} $vip

                • Author
                  Replies
                Viewing 5 reply threads
                • The forum ‘Cloverleaf’ is closed to new topics and replies.