Hi can anyone tell me what is the paramter of isatty() in c. I have following code, but I don't understand the first output three number would be 1 and all the left is 0.
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int main(){
for(int i=0;i<100;i++){
int t=isatty(i);
printf("%d",t);
}
return 0;
}
A quick look at your man pages would reveal:
int isatty(int fildes);
DESCRIPTION
The isatty() function tests whether fildes, an open file
descriptor, is associated with a terminal device.
Further investigation would lead you to the discovery that file descriptors 0, 1 and 2 (aka STDIN_FILENO, STDOUT_FILENO and STDERR_FILENO) are by convention set up to point to your terminal when your program is running from a terminal.