Thread: error handling[c]

hi.
i am learning about error handling as of now and i have a simple question.
when consider this program i made to test the error messages , what error should be used for the initial if no arguments are supplied to be correct. i did find the open groups definitions and read them all and i am trying them one by one this way but i dont seem to find the one that should be correct used in this context.
thanks.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

int main(int argc, char** argv)
{
	int i;
	/* if no argcs we get an error ?  */
	if( argc == 1)
	{
		fprintf(stderr,"%s %s\n",argv[0],strerror(EACCES));
		    	 exit(1);
	}
	

	   for(i=1;i < argc; i++)
	   if(strcmp(argv[i],"--version") == 0)
	            printf(" version 0.0.1\n");
	  
	        else if(strcmp(argv[i],"--error1")==0)
	           fprintf(stderr," EACCES:%s\n",strerror(EACCES));
			   
		else if(strcmp(argv[i],"--error2")==0)
	           fprintf(stderr,"EADDRINUSE:%s\n",strerror(EADDRINUSE));
		
		else if(strcmp(argv[i],"--error3") == 0)	   
	            fprintf(stderr,"E2BIG:%s\n",strerror(E2BIG));
		
		else if(strcmp(argv[i],"--error4")==0)		
	            fprintf(stdout,"EADDRNOTAVAIL:%s\n",strerror(EADDRNOTAVAIL));
	    
		else if(strcmp(argv[i],"--error5")==0)        
	            printf("EAGAIN:%s\n",strerror(EAGAIN));
	
	return 0;
}

thanks.
i sometimes use the get opt function so i might as well just use the same message as it gives if an invalid argument is been giving. i did however think there was a standard error code among all those others.

thanks for the time.

Originally Posted by brewbuck

The standard error code for invalid arguments is EINVAL, but the resulting error message is not very informative. Better to report something more specific yourself.

thanks.
i found all the error codes in linux using cat command and i figure there must be almost identical error codes for solaris and other *nix systems as the error codes should be same as in the open groups specifications.

so i just wrote a small sample i was going to post wiht the message that i had found something out. i assume the eagain is ok to use in this context .

thanks for the time.

Code:

/* i was checking for error codes using cat #include <asm-generic/errno-base.h> */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

void usage();

int main(int argc, char** argv)
{
	    if(argc == 1)
	    {
	        usage(argv[0]);
		    exit(11); 
		     /* #define	EAGAIN		11	 Try again */
	    }
	
	    if((argv[1][0] == '-' && argv[1][1] == 'h') == 0 )
	    {
		
	    
	 			      fprintf(stdout,"%s %s\n",argv[0],strerror(EINVAL));
	                  /* #define	EINVAL		22	 Invalid argument */
	    }
		else{
			
			   fprintf(stdout,"hello world\n");
		    }
		 
			
	return 0;
}

void usage(const char *progname)
{
	fprintf(stdout,"%s usage: [option]   \n"
	                          "--version   version \n"
				   "--help     this help\n"
				  "COPYRIGHT author \n"
				  "LICENSE	  BSD\n",progname);
}