RE: [Dev-C++] how to use strings

[Michael C. <jd...@ho...>]

Hi Johannes,

I believe that fprintf() does move the file pointer it just looks as though 
it isn't, try using ftell() to print the file position.

I believe that because there is a struct being written to the file via 
fread() and then a string via fprintf() this is causing the problem as you 
suggested.

These functions generally should never be mixed as the problems we are 
seeing are caused. Also when reading files between different systems there 
are problems concerning the endianess (big endian/little endian) for the 
file, allignment, etc. For example, the allignment of an int on one machine 
may be different for another. One would have to define a common alligned 
struct for writing, similar to the way X11, sockets, and other network 
protocols do it.

However, we are only using one os in this case so this shouldn't be a 
problem.

I also used fgets() and feof() to test for EOF. The output is only "Hallo 
World", and it doesn't see the number on the next line but reports EOF.

     char line [256];
     while (fgets (line, 256, fhandle) != NULL)
     {
       printf ("%s", line);
     }

     if (feof (fhandle))
     {
       printf ("EOF for fhandle.\n");
     }

However, I have also used fscanf()with the field specifier and the 
circumflex symbol to ignore upto the newline, etc. This works in certain 
circumstances, i.e. only when I specify two scanf() commands as opposed to 
one.

     fseek (fhandle, 0L, SEEK_SET);

     char c1[100];
     char c2[100];
     char c3[100];
     char c4[100];
     char c5[100];

/*
     // doesn't work - only sees first line

     printf ("pos %d\n", ftell (fhandle));
     fscanf (fhandle, "%s%s%*[^\n]%*[^'O']%s%s%s", c1, c2, c3, c4, c5);
     printf ("%s %s %s %s %s\n", c1, c2, c3, c4, c5);
     printf ("pos %d\n", ftell (fhandle));
*/

     // works well

     printf ("pos %d\n", ftell (fhandle));
     fscanf (fhandle, "%s%s%*[^\n]", c1, c2);
     printf ("%s %s\n", c1, c2);

     fscanf (fhandle, "%*[^'O']%s%s%s", c3, c4, c5);
     printf ("pos %d\n", ftell (fhandle));
     printf ("%s %s %s\n", c3, c4, c5);


You will notice that the file position is over 200 at the end of the 
program. This leads me to conclude that because of the 'crap' after the 
first string this causes problems for the string functions, we therefore 
need to ignore this stuff.

This doesn't explain why I need two fscanf()s to do this. Although I have 
been testing on a HPUX compiler and this should work.

Regards,

Michael



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