Re: C question (linux)
I am going to throw my 2 cents in here.
I am with you Derek.
An example of A correct syntax (of many you could be used use)
that I use when I am writing Import programs for Appgen:
(Note: there are many ways to skin this cat)
/* Somewhere in your Program */
/* Lets allocate a buffer for 256 characters */
char a_buffer [256] ;
/* Now let us define what our INCOMING record will look like.
THIS DOES NOT allocate space, but simple defines what a
TYPE called foreign should look like.
*/
struct foreign {
char CUSTOMERCODE [8] ; /* 8 bytes of data */
char DOCNUMBER [7] ; /* 7 Bytes of data */
char PONUMBER [15] ; /* 15 Bytes of data */
char SALESREP [2] ; /* 2 bytes of data */
char TERMSCODE ; /* 1 byte of data */
char NEWLINE ; /* gotta have the EOL terminator */
};
/* Now let us define just how many characters
that the structure of "foreign" occupies.
We store that number in FBUFFER.
*/
# define FBUFFER (sizeof (struct foreign))
/* Allocated some space for stuff that looks like
the TYPE STRUCTURE of foreign and we call this space
infile. This DOES the actual allocation in memory.
*/
struct foreign infile ;
/* I like to use this method for "pointing". This is done
for clarity's sake. All we are saying is:
"fptr" is a POINTER to stuff in a structure TYPE
called foreign. It points to nothing right now, all
we are doing is defining this variable.
*/
struct foreign *fptr ;
/* stdio file descriptor for a file
Now, we have define a pointer of type FILE to
a variable called "a_file"
*/
FILE *a_file;
/* Assign to the FILE pointer, where our file is.
If the value returned is zero, then
"Houston, we have a problem" and we cannot
open our file, so we bail out */
if (!(a_file = fopen("MYFILENAME", "r"))) {
printf("This is Bogus, I cannot open this file: %s", "MYFILENAME") ;
exit(1);
}
/* **** BIG NOTE:
we could have easily programmed this to look like:
a_file = fopen("MYFILENAME", "r") ;
if( a_file == 0 ) {
printf("This is Bogus, I cannot open this file: %s", "MYFILENAME") ;
exit(1);
}
*/
/* Now everything is looking good, so we are going to assign
a pointer that gives us the "address of" the area we
allocated to the record we NOW call infile */
fptr = &infile ;
/* Ok, things get a little more complicated here:
We are going to a while loop and read our input file.
The fgets says:
Read characters from "a_file" until either the
size defined of FBUFFER - 1 or we get a "newline",
whichever occurs first. The incoming character
stream gets stored in the character array pointed to
by "the address of" infile.
(ED's Notes: I am a little rusty, is the following
true statements/information ?)
Since we are using the "address of", which is an integer,
and we DO NOT want C to complain, we "typecast"
with the "(char *)" the address of infile, so that
C will say "Oh yeah, the "address of" you are giving me
is a pointer to a character array, so I am cool"
THIS simple means we are telling C "(char *) &infile"
is the buffer we want to put stuff in.
Now fgets will also store the "NEWLINE" character it
has read as well.
*/
while ( fgets( (char *) &infile, FBUFFER, a_file )) {
/* Ok , we are going to "string print" into a_buffer,
a string (%s) of "dot eight" (.8), which says only
take 8 BYTES of data (otherwise we would ALL of the data
until a NULL is encountered starting at our pointer)
with the "pointer" fptr-> (Must have the "->") which
is "pointing to" the area called "infile" and the
LOCATION inside of "infile" called CUSTOMERCODE.
(FWIW - Could as well been "PONUMBER" of any other
names we defined in TYPE STRUCTURE called foreign).
I do this so I can pass "a_buffer" to various functions
that scrub (clean up) the data held in "a_buffer"
sprintf( a_buffer, "%.8s\0", fptr->CUSTOMERCODE ) ;
-BLAH - BLAH - BLAH Do some processing
} ; /* The end of our WHILE loop */
/* Close the file(s) */
fclose(a_file);
/* Be cute */
printf("Conversion is now complete...\n") ;
exit(0);
-------------------- End of Example --------------------
Now, I know this a LOT of information, I only hope it helps
you. I dunno what your C expertise is, and this IS NOT meant
to demean you or your abilities in anyway, but if helps you
or anyone else to understand a little bit more than they did,
then I have done my duty.
Thanks ...
Derek Parnell wrote:
>
> I'm sorry Matt. I just have to respond to this one.
>
> !!!DO NOT DO WHAT MATT HAS SUGGESTED!!!
>
> It will only bring you bugs and more bugs. An integer is not a pointer.
> Forcing C to convert (read: 'change') a pointer into an int, just to stop warning
> messages is plain stupid (IMNSHO). If you are going to do something, at least do
> a good job of it.
>
> Why do you want your code to return an int? Or is it just that you wish to use
> fopen()?
>
--
Ben Duncan Phone (601)-355-2574 Fax (601)-355-2573 Cell (601)-946-1220
Business Network Solutions
336 Elton Road Jackson MS, 39212
"Software is like Sex, it is better when it's free" - Linus Torvalds
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