print_hex

Subject

Assignment name  : print_hex
Expected files   : print_hex.c
Allowed functions: write
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Write a program that takes a positive (or zero) number expressed in base 10,
and displays it in base 16 (lowercase letters) followed by a newline.

If the number of parameters is not 1, the program displays a newline.

Examples:

$> ./print_hex "10" | cat -e
a$
$> ./print_hex "255" | cat -e
ff$
$> ./print_hex "5156454" | cat -e
4eae66$
$> ./print_hex | cat -e
$

Commented solution

print_hex.c

print_hex.c

#include <unistd.h>

// Simple atoi to convert the parameter to unsigned int
// You might need to manage negative numbers and all of
// that, it isn't specified in the subject if they could
// be sent to your program or not
unsigned int ft_atoi(char *str)
{
    unsigned int res = 0, i = 0;

    while (str[i] && str[i] >= '0' && str[i] <= '9')
    {
        res *= 10;
	res += str[i++] - '0';
    }
    return (res);
}

void put_hex(int nbr)
{
    char *digits = "0123456789abcdef";

    if (nbr >= 16)
        put_hex(nbr / 16);
    // choosing the char corresponding to the number we want
    // and writing it to the screen
    nbr = digits[nbr % 16];
    write(1, &nbr, 1);
}

int main(int ac, char **av)
{
    // if there is an argument, send it directly to the
    // put_hex function via ft_atoi
    if (ac == 2)
        put_hex(ft_atoi(av[1]));
    write(1, "\n", 1);
    return (0);
}