Question

see

char str[] = "hello world";
printf("%s",str);  

printf statement prints the all character in string before reaching '\0'

so what if i want to print just 4 1st character of str on stdout?

Answer 1

You can just specify the field width in the printf format string:

#include <stdio.h>

int main(void)
{
    const char *s = "Hello world !";

    printf("%.4s\n", s);
    return 0;
}

or, if you want to specify the field width at run-time:

#include <stdio.h>

int main(void)
{
    const char *s = "Hello world !";
    const int fw = 4;

    printf("%.*s\n", fw, s);
    return 0;
}

In either case the output will be:

Hell