Error Handling.

SO I am humming right a long in my Learning C book and then my brain freezes on Chapter 9 Error handling. This line of code stopped me in my tracks, it's only part of the over all code.

Code:

    int     error;
	
    error = printf( "The title array takes up %ld bytes of memory.\n\n",  sizeof( title ) );
    
    if ( error < 0 )
        return kError_printf;

Now my brain is telling me that printf is the argument that is begin passed to error. But error is of type int and it is begin passed a char string? When I run this it is printing the printf line but also storing some int value in error to be evaluated by IF? Huh?

-Lars

 

Very cool. I did not know you could use terminal to get detailed explanations of the functions, Thanks!

I guess this line sums it up then from printf- " These functions return the number of characters printed (not including the trailing `\0' ) " I understand this now.

So without having to look at every function to check this I will ask. So printf does 2 things when it executes, it writes the string and returns an int value. Do all functions do to things for the most part, one being the the intended use of the function and the second being an error that is returned?

Example:
printf 1) writes the char string 2) returns a int value
fgets 1) reads the char stream 2) returns NULL if there was an error.

-Lars

 

Hummm.... This ads a new dimension of thinking. Pass one argument in and get multiple results back, unless it is the 'switch hitter'.

Cromulent - Thanks for the tip on the 'man 3 printf' I can easily research functions now. I will read up on the errno.

Lee210 - I understand that multiple results exist but will move forward in the book and not dig to deeply into that now. This simple code I wrote explained a lot to me in understanding what is happening.

Code:

#include <stdio.h>

int main () {
	
	int error;
	
	error = printf("Hello World");
	printf("error int is %d: ",error);
	
    return 0;
}

I was confused when I first saw error = printf(""); I have never seen anything in front of printf like that before.

So... when I see 'error =' in the future, or 'variable = function' I know the 'Variable =' is being passed the RETURN value of what ever return type it is supposed to return, and the MAIN call to the function is performing it's normal task as in printf writing out to the stdout. If I need error correction for code I need to read each one to see what it RETURNS for error correction, if it returns something that is not s 'Switch Hitter'.

Now if you will excuse me I am going to let my brain explode for the evening