Error checking using sscanf

[Raxicori]

Im using sscanf to scan in a number of run time arguments and convert the strings to ints.It works fine when all the arguments are ints but wont detect when the arguments supplied are words instead of numbers.It just seems to ignore them.

I want it to detect when its not supplied a valid string (eg 3 is ok but three is wrong), and then output an error message, however I dont know how to detect this error when using sscanf.

Any help is appreciated.

[weaknessforcats]

scanf() can't detect anything. All it can do is process what you tell is. That is, if you use %s YOU MUST have a string. If you use %d YOU MUST have an int.

You will have to use getch() to get a character. Test it and decide what to do and then ungetch() to put it back in the inoutbuffer before you continue.

[AdrianH]

Im using sscanf to scan in a number of run time arguments and convert the strings to ints.It works fine when all the arguments are ints but wont detect when the arguments supplied are words instead of numbers.It just seems to ignore them.

I want it to detect when its not supplied a valid string (eg 3 is ok but three is wrong), and then output an error message, however I dont know how to detect this error when using sscanf.

Any help is appreciated.

For this case you can use the return value which is how many of the arguments have been assigned to a variable.

int value;
printf("Variables assigned: %d\n", scanf("%d", &value));
 

INPUT: 3
OUTPUT: Variables assigned: 1

INPUT: three
OUTPUT: Variables assigned: 0


Adrian

[Banfa]

Or you could use the functions strtoul or strtol (Google them for a definition).

These function skip leading space and convert any digits to a unsigned long or long and then return a pointer to the character the conversion stopped on allowing you to tell what caused the conversion to halt. If it was a letter then you can raise an error of some sort.

For a string with multiple integers in it just call the function multiple times until you get to the terminator (or an error).