Hi,

When I use the %[...] input field with scanf(), I run into several major
problems.  Sometimes, all inputs after the input to %[] are ignored.  Most
of the time, the *next* scanf() statement is skipped over -- sometimes
several scanf()'s are skipped, depending on how many inputs were "ignored"
after the %[].  Can you tell me what I'm doinf wrong -- or is this a known
bug with the scanf() function?

main()
{
        float  x, y, z;
        char  mod[ 10], fmt[ 25], str1[ 80], str2[ 80];
        int  num;

        printf( "Part I\n------\nString/String = ");
        num = scanf( "%[^/]/%[^\n]", str1, str2);
        printf( "[%d]\t%s\n\t%s\n\n", num, str1, str2);

        /* So the user should enter blablalbla#1/blablabla#2.  But why
           did can't I specify %[^/]%[^\n] without the repetition of the
           extra slash in %[^/]/%[^\n] ?  I tried this, and my second
           input was either ignored or a slash was appended to it */    

        printf( "Part II\n-------\nFloat/String/Float = ");
        num = scanf( "%f/%[^/]/%f", &x, str1, &y);
        printf( "[%d]  %s (%f, %f)\n\n", num, str1, x, y);

        /* The second floating-point number is ignored and the next
           scanf() is interfered with -- it "jumps over it"... */

        printf( "Part III\n--------\nFormat = ");
        gets( mod);
        sprintf( fmt, "%%*d%%*%s%%*f%%f%%f%%f%%*d", mod);
        printf( "Input {%s} = ", fmt);
        num = scanf( fmt, &x, &y, &z);
        printf( "[%d]  x= %f,  y= %f,  z= %f\n", num, x, y, z);

Thanks in advance!  E-mail preferred.

- Eskandar

--
-------------------------------------------------------------------------
G o d l e s s   f e e l i n g   i n   m e
B o r n   o f   t h e i r   l i e s . . .                         Danzig
-------------------------------------------------------------------------

Your main problem is that %[] must match at least one character.  If
there are no matching character, the conversion fails and scanf stops;
that's why the following inputs are ignored.  Since you haven't
processed the remaining character, following scanf calls try to process
them and they don't match, so those scanfs fail as well.  You should
always check the return value from scanf -- if it's not what you expect,
you're in serious trouble.  Trying to recover from this situation is
usually not easy.
----
Larry Jones, SDRC, 2000 Eastman Dr., Milford, OH  45150-2789  513-576-2070

Everything's gotta have rules, rules, rules! -- Calvin

Which points up the biggest problem with scanf(). It doesn't handle
unexpected input gracefully.  Personally, I always fgets() into a buffer
and sscanf() the buffer.  Even for the quick'n'dirty stuff.

Someone on c.l.c once posted their usual compiler defines, and my two
favorites were -Dscanf=DONT_USE_SCANF and -Dgets=DONT_USE_GETS.
--

                 "Be careful... or be roadkill"
                                                 -- Calvin