Question

I am loading matrix from file and here comes the question, how to treat if there will be fault in loading file if there will be letter instead of number? I am especially asking – how to determine, that I loaded letter?

Thx

Answer 1

If the input read by fscanf() does not match the expected type (as determined by the conversion specifier), this will be reported by the return value of fscanf() (which is equal to the number of coversion specifiers successfully read).

int x;   
if ( fscanf( file, "%d", &x ) != 1 )
{
    // input was not a number
}

More generally speaking, the whole scanf() family of functions is primarily aimed at reading whitespace-separated, trivial data. Usually it is more easy and reliable to read in a complete line (using fgets()), and then doing the parsing internally. (strtol() and strtod() can be of help here, but strtok() should be used with care, especially in a multithreaded environment.)