ft_strdup

Subject

STRDUP(3) (simplified)

NAME
    strdup -- save a copy of a string
SYNOPSIS
    char *strdup(const char *s1);
DESCRIPTION
    The strdup() function allocates sufficient memory for a copy of the string s1, does the copy, and returns a pointer to it. The pointer may subsequently be used as an argument to the function free(3).
    If insufficient memory is available, NULL is returned and errno is set to ENOMEM.

Understandable explanation

For once, the man is really clear on what the function does. So I don't think I need to explain it with more details.

Hints

We have to use malloc for this since the returned value of this function must be 'freeable' with the free function.

ft_strdup.c

char *ft_strdup(const char *s1)
{
    /* use malloc to allocate enough space for s1 
     * we will have to copy it completely
     * so we need enough space for it
     */
     /* loop over s1 and copy each character in the new string you
      * just allocated
      */
     /* return the allocated and copied string */
}

Commented solution

ft_strdup

ft_strdup.c

#include "libft.h"

char *ft_strdup(const char *s1)
{
    char *dest;
    size_t i;
    
    /* allocating enough memory for s1 + 1 character
     * for the NUL-terminating character
     */
    dest = (char *) malloc(ft_strlen(s1) + 1);
    if (!dest)
        return (NULL);
    i = 0;
    /* looping over the whole s1 string */
    while (s1[i])
    {
        /* copying the current s1 character into the same
         * position in the dest string we allocated above
         */
        dest[i] = s1[i];
        i++;
    }
    /* setting the NUL-terminating character */
    dest[i] = 0;
    /* finally, we return the newly created string */
    return (dest);
}