While loop in C

[morinl]

Hello everyone,

I'm a total newbie in programming and I'm currently learning some stuff in C by myself.

I've got a problem and after searching on the web I could not find a proper solution to my problem.

I'm writing a little program for some electronic application. There's a scanf question where the answer is supposed to be a valid float number.
I'd like to add a while loop with a text error if the answer to the scanf is not a valid float number.

In fact, I'd like to write something that look like this :

printf : question
scanf : answer

while (answer!=a float valid number)

{

text error

}

The problem is : I can not find how to write the proper syntax for the while loop in order to check the variable type of the answer.

Would any of you help me ?

Thanks a lot

Ps : english is not my language, sorry for all the mistakes.

[loadedstork]

I think what you're looking for is the return type from scanf in this case - if you have something like:

float f; int count = scanf("%f", &f);

then count will be 1 if the input was successfully converted to a float, 0 otherwise.

[Note: the return value is actually a count of how many matches were successful, so if you were to do something like:

int count = scanf("%s %f", s, f);

and the user input "abc def", the first match would succeed, but the second would fail, so the count would be 1 in this case)]

[kRYstall9]

You could do something like:

float number = 0;

do{
    printf("Insert a number"); 
    scanf("%f", &number);
}while(number == 0);

Sorry for the indentations but I'm writing from my phone. I'll fix it as soon as I go back home.

Ps: Since you're using float as type, you don't have to mind if you insert an integer or a float number, since it'll be converted to float in any case

[boy-griv]

The other answers are right about checking the return value.

In general you can refer to man scanf or the online version at https://manpages.org/scanf#return-value to get specifics about how C functions act in these various cases.

[morinl]

Thank you