cin.get(char *, int, termination char) question

From: Peter Gordon (petergo_at__deleteme_.netspace.net.au)
Date: 02/28/05

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    Date: Mon, 28 Feb 2005 01:29:56 +0000 (UTC)

    I am exploring the iostream get method
    with three arguments. eg cin.get(buf, 80, ';')

    My reference says, "If a termination character is
    reached before the maximum number of characters is
    read, a null is written and the termination character
    is left in the buffer".
    Using the above exampe, to me this means that if
    a ';' is encountered before 79 characters are read,
    the string in buf will be null terminated. The
    reference does not mention empty fields.
    eg. If the buffer being read contains
    "abc;;def", how is the second field treated?

    I wrote some test code and have compiled it with
    both Cygwin g++ 3.3.3-3 and with bcc32, which is the
    command line compiler for Borland CBuilder4.
    They give different output. Thus, I am wondering
    if I have found a bug in g++ or if since the reference
    does not explicitly mention empty fields, the result is
    undefined. Any thoughs on this?

    I am working on Win XP and have tried it using bash from
    Cygwin and the MKS Korn shell. Both give the same result.

    The test file, called a.txt contains the line:
    abc;;def;ghi;jkl

    The command I give is:
    get.compiler.test < a.txt

    The output from the bcc32 compiled code is:
    abc
    Empty field
    def
    ghi
    jkl

    The output from the g++ compiled code is:
    abc

    In other words, g++ considers it an error.

    My test code in the file "get.compiler.test.cpp" is:

    #include <iostream>
    #include <cstring>

    using namespace std;

    int main(int argc, char *argv[]) {
        char *pstr[10], ch;
        int i, nfields;

        for(i = 0; i < 10; ++i)
            pstr[i] = new char(20);

        nfields = 0;

        for(i = 0; i < 10; ++i, ++nfields) {
            if( ! cin.get(pstr[i], 20, ';'))
                break;
            cin.ignore(1, ';');
        }

        for(i = 0; i < nfields; ++i)
                if( strlen(pstr[i]) )
                    cout << pstr[i] << endl;
            else
                    cout << "Empty field" << endl;

        return 0;
    }

    Be kind to me, it is only test code.

    Peter Gordon

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