How to add null terminator to char pointer, when using strcpy

Question

I have a program that's attempting to use the strcpy() function. I know that when one uses a char array such as: char array[10] the null terminator can be set by: array[0] = '\0'; However, how would I go about setting the null terminator(s) when using char pointers?

EDIT: The program compiles, but gives garbage as output

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void)
{
    char *target;
    char *src = "Test";

    target = malloc(sizeof(char));
    src = malloc(sizeof(char));

     strcpy(target,src);
     printf("%c\n",target); 

    return 0;
}

Answer 1

You don't need to. Second argument of strcpy() needs to be nul terminated, and the first needs to fit the number of characters in source + the nul terminator.

The problems in your code are:

1. You are using sizeof operator in wrong way and you are overwriting the src pointer by allocating memory again to it.

   To get the length of a string you need strlen() and you don't need to call malloc() on every pointer.

   You are getting garbage value because you are copying from uninitialized data since src points to a newly allocated space, because of

   src = malloc(sizeof(char));
   

   you should not do that.

2. sizeof(char) == 1 by definition, so you are allocating space for just 1 byte, which if it was to be a valid C string, has to be '\0' because there is room for just 1 character.

3. The correct printf() specifier for a string is "%s", you are using "%c" which is for a character.

The correct way to do it is

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void)
{
    char       *target;
    const char *src;

    src    = "Test"; /* point to a static string literal */
    target = malloc(1 + strlen(src)); /* allocate space for the copy of the string */
    if (target == NULL) /* check that nothing special happened to prevent tragedy  */
        return -1;

    strcpy(target, src);
    printf("%s\n", target);
    /* don't forget to free the malloced pointer */
    free(target);

    return 0;
}