Testing exam exercise, ./a.out " " returns USER=username

test_exam2_first_word.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <stdarg.h>

/*
Assignment name  : first_word
Expected files   : first_word.c
Allowed functions: write
--------------------------------------------------------------------------------

Write a program that takes a string and displays its first word, followed by a
newline.

A word is a section of string delimited by spaces/tabs or by the start/end of
the string.

If the number of parameters is not 1, or if there are no words, simply display
a newline.

Examples:

$> ./first_word "FOR PONY" | cat -e
FOR$
$> ./first_word "this        ...    is sparta, then again, maybe    not" | cat -e
this$
$> ./first_word "   " | cat -e
$
$> ./first_word "a" "b" | cat -e
$
$> ./first_word "  lorem,ipsum  " | cat -e
lorem,ipsum$
$>
 */

int good_char(int c)
{
	if (c == ' ' || c == '\t' || c == '\0')
		return 0;
	return (1);
}

int main(int argc, char **argv)
{
	if (argc != 2 || !argv[1] || !argv[1][0])
	{
		write(1, "\n", 1);
		return 0;
	}
	int i = 0;

	while (!good_char(argv[1][i])) // skip first
		i++;
	while (argv[1][i])
	{
		if (!good_char(argv[1][i]))
		{
			write(1, "\n", 1);
			return 0;
		}
		write(1, &argv[1][i], 1);
		i++;
	}

	return (0);
}