How to understand this input/output code?

[fishwater00]

I need to read parameters from a file called "params.c", the following is the 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" I have:

#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) ;
   }

}

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.

[Ancient Dragon]

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

That line is definately incorrect -- strcmp() only takes two parameters, not thread. Maybe it should have been strncmp() which has 3 parameters ?

mystrcmp() is missing the closing function brace -- }

line 20: where is buff declared?

[Salem]

> /* what is "%*s" mean? */
The * suppresses assignment. So this scans a string, but doesn't store it anywhere.

Like you have
hello 123
in the file, and you want to skip hello and store 123

[fishwater00]

Thank you.

I should use strncmp and define char *buff, then it works.

[ssharish2005]

You indentation is OK but not perfect. You present your code in a good way, .you expect can expect more help. Take me an example I totally ignored your post when I just looked at your at start. I had a look at it again. This applied to all newbies. But i have sorted it out for now.

#include "systems.h"   
 
int mystrcmp(const char *tag, char *buff) 
{
  int l = strlen(tag) ;

  return( strcmp(tag, buff, l) ) ; 
}

int params( const char *file, int *nx,  int *ny ) 
{
  FILE *fd ;
  char buff[256];

  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 );   
      
      if ( mystrcmp("ny", buff) == 0 ) 
	     sscanf(buff, "%*s %d", ny );
   }
   
   fclose(fd) ; // This part of the code should be outside the loop.
   return 0 ;
}

I have changed few thing in your code. So that the clarify of your code improves. Perhaps the code which is highlighted in blue was must ;).

ssharish