C Reference Control Character Test: iscntrl()

The iscntrl() function returns a non-zero if its argument is a control character. If there is no control character encountered, then zero is returned.

isalpha() source code example:

#include<stdio.h>
#include<ctype.h>

int main()
{
	int counter=0;

	char str[]="line one \n line two \n line three \n";
	while (!iscntrl(str[counter]))
	{
		putchar (str[counter]);
		counter++;
	}

	return 0;
}

Note: Only line one is printed because after line one there is a control character ‘\n’ (ASCII code 0x0a)