sscanf.rst

String Parsing (sscanf)

.. hoc:function:: sscanf


    Syntax:
        ``num = sscanf("string", "format", args)``


    Description:
        A subset of the c stdio sscanf function.
        The formats understood are %s, %[...], %c, %lf, %f, %d, %i, %o, %x, along with
        numbers and the * character. Explicit strings in the format are also understood.
        A great deal of error checking is done to make sure the args match the
        format string. The function returns the actual number of args that are
        assigned values.

        Note that %lf is always preferred to %f since the latter truncates to floating
        point accuracy. Hence

        .. code-block::
            none

            x=0
            sscanf("0.3","%f",&x)
            print x
            prints the value
            0.30000001


    Example:

        .. code-block::
            none

            strdef s
            double x[20]
            y=0

            sscanf("this is a test\n", "%s", s)
            print s

            sscanf("this is a test\n", "%[^\n]", s)
            print s

            sscanf("this is a test\n", "%*s%s", s)
            print s

            sscanf("this is a test\n", "%2s", s)
            print s

            sscanf("this is a test\n", "%10s", s)
            print s

            sscanf("this is a test\n", "%*3s%s", s)
            print s

            sscanf("this is a test\n", "%*s%s", s)
            sscanf("0xff 010 25", "%i%i%i", &x[0], &x[1], &x[2])
            print x[0], x[1], x[2]

            double x[20]
            sscanf("ff 10 25", "%x%o%d", &x[0], &x[1], &x[2])
            print x[0], x[1], x[2]

            sscanf("50.75", "%d.%d", &x[0], &x[1])
            print x[0], x[1]

            sscanf("30.987654321", "%f", &y)
            printf("%20.15g\n", y)

            sscanf("30.987654321", "%lf", &y)
            printf("%20.15g\n", y)

            sscanf("A", "%c", &y)
            printf("%c\n", y)

            sscanf("1 2 3 4 5 6 7 8 9 10", "%f%f%f%f%f%f%f%f%f%f%f", &x[0], &x[1], &x[2],\
                &x[3], &x[4], &x[5], &x[6], &x[7], &x[8], &x[9], &x[10], &x[11], &x[12])
            print "should only read ten of the following"
            for i=0,12 print i, x[i]

            print "error tests"

            execute1("sscanf(\"string\", \"%\", s)")
            execute1("sscanf(\"string\", \"%*\", s)")
            execute1("sscanf(\"string\", \"%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c%c\", &x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x)")
            execute1("sscanf(\"string\", \"%*5\", s)")

            execute1("sscanf(\"string\", \"%l[st]\", s)")
            execute1("sscanf(\"string\", \"%[\", s)")
            execute1("sscanf(\"string\", \"%[]\", s)")
            execute1("sscanf(\"string\", \"%[^]\", s)")
            execute1("sscanf(\"string\", \"%ls\", s)")
            execute1("sscanf(\"string\", \"%lc\", &y)")
            execute1("sscanf(\"string\", \"%5c\", &y)")
            execute1("sscanf(\"string\", \"%q\", &y)")

            execute1("sscanf(\"string\", \"%s\")")

            execute1("sscanf(\"string\", \"%s\", &y)")
            execute1("sscanf(\"25\", \"%d\", s)")


            execute1("sscanf(\"string\", \"%c%c%c%c%c%c%c%c%c%c%c%c%c\", &x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x,&x)")