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cfor-loopeofgetchar

getchar() in a for loop condition

Consider following code:

int main()
{
    char c;
    for(;(c=getchar())+1;)
        printf("%c\n",c);
}

It gets characters what I enter in terminal and prints them. When I remove +1 in condition, program works but it doesnt stop when EOF (Ctrl+D) signal. When I change it to +2 same problem.

My question is how that +1 work? Is it something related to getchar() or for loop?

Solution

  • That is because the int value of EOF is -1, so what you're doing is loop until the expression(c=getchar())+1) gets the value 0 which is when you read EOF (where value of exrpession is: -1+1=0). Also as wll pointed out in the comments you should declare c as int since getchar() returns int.