C-如何检查是否输入了号码

Question

How to simply and correctly check if user enters a number and not a char or string in C language? I've tried to write some loops containing:

if (scanf("%d",&number)=1) 

but they never work or end. The loop should end when a number is entered.

Answer 1

It should be

if (scanf("%d", &number) == 1) // Notice the two ='s, not just one

A single = is the assignment operator, a double == is the equality test.

Answer 2

I think you want this:

for (scanf(" %d", &number); (number < -100 || number > 100); scanf(" %d", &number)) {
    printf("you didn't enter a valid number, try again >");
}

Answer 3

Your line should simply be: if (scanf("%d",&number)){

If anything other than a number is entered, it will result in: if(0){ , instead of if(1){

Answer 4

Does this suit your context:

char ch;int g;
for(ch=getc(stdin);isalpha(ch);ch=getc(stdin))
{
printf("\nenter numbers only");
while(isalpha(getc(stdin))){}
}
ungetc(ch,stdin);
scanf("%d",&g);
printf("number entered  %d",g);