How to interpret this input problem?

[fishwater00]

I need to read parameters from a file called "params", the following is part of codes which can read parameters from that file. But I am not totally understand. Hope anyone can give detailed answers. Thanks.

In a file called "params.c"
[code=c]
#include "systems.h" /* it includes all .h codes I need */

int mystrcmp(const char *tag, char *buff)
{
int l = strlen(tag) ;

return( strcmp(tag, buff, l) ) ; /* why he uses 3 parameters? I think it should be 2 parameters in "strcmp" ? */

int params(char *file, int *nx, int *ny)
{
FILE *fd ;

fd = fopen(file,"r") ;
if ( fd == NULL )
{
fprintf(stderr, "cannot open %-s\n",file) ;
return(1) ;
}

while ( fgets(buff,256, fd ) )
{

if ( mystrcmp("nx", buff) == 0 )
sscanf(buff, "%*s %d", nx ); /* what is "%*s" mean? */

if ( mystrcmp("ny", buff) == 0 )
sscanf(buff, "%*s %d", ny );

fclose(fd) ;
return(0) ;
}

}
[/code]

After I compile it ( I do have main funtion, but the probem is here), it shows:
In function ‘mystrcmp’:
"error: too many arguments to function ‘strcmp’ "
warning: passing argument 1 of ‘fgets’ from incompatible pointer type
warning: passing argument 2 of ‘mystrcmp’ from incompatible pointer type
warning: passing argument 1 of ‘sscanf’ from incompatible pointer type

Thank you in advance.

[Laharl]

strcmp does indeed take two arguments, however, strncmp takes three. sscanf is complaining because your format string is essentially of the form <string> <int>, and the only pointer you're passing in for it to write to is an int*. The * means that the function will scan the data, but not read it in. As to the incompatibility warnings, I'm not completely sure...

[fishwater00]

strcmp does indeed take two arguments, however, strncmp takes three.

Thanks. it hsould be strncmp.

Do I need to define "buff", if I donot define buff, error message shows "‘buff’ undeclared (first use in this function)". if I define "*buff" as int or float, it will shows the message like:

warning: passing argument 1 of ‘fgets’ from incompatible pointer type
warning: passing argument 2 of ‘mystrcmp’ from incompatible pointer type
warning: passing argument 1 of ‘sscanf’ from incompatible pointer type

How can I define buff coreecty or fgets can give it memory?

[oler1s]

Do I need to define "buff"

Of course you do. Why otherwise?

if I define "*buff" as int or float

If you look up the documentation for fgets, you see that buff needs to be a char*. Actually, that translates to buff either pointed to a dynamically allocated char array, or a char array itself. (remember that when you pass a char array[], it decays to a char*)

[fishwater00]

If you look up the documentation for fgets, you see that buff needs to be a char*. Actually, that translates to buff either pointed to a dynamically allocated char array, or a char array itself. (remember that when you pass a char array[], it decays to a char*)

Thank you. I fix it.

char *buff

[Banfa]

Thank you. I fix it.

char *buff

If you are doing that I hope you are allocating some memory for the pointer before writing data to the place it points to.