> For the complete documentation index, see [llms.txt](https://42-guide.gitbook.io/42-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://42-guide.gitbook.io/42-guide/piscine-life/c03/ft_strcmp.md).

# ft\_strcmp

**Objective:**

Recreate the behavior of the `strcmp` function (refer to `man strcmp`).

* **Turn-in Directory:** `ex00/`
* **Files to Turn In:** `ft_strcmp.c`
* **Allowed Functions:** None

**Prototype:**

```c
int ft_strcmp(char *s1, char *s2);
```

***

#### **Detailed Explanation:**

* The function compares two strings `s1` and `s2` character by character.
* It returns:
  * `0` if the strings are identical.
  * A **positive value** if `s1` is lexicographically greater than `s2`.
  * A **negative value** if `s1` is lexicographically smaller than `s2`.

***

#### **Code Implementation:**

```c
int ft_strcmp(char *s1, char *s2)
{
	while (*s1 == *s2 && *s1)  // Continue as long as characters are equal and not at the end of the string
	{
		s1++;  // Move to the next character in s1
		s2++;  // Move to the next character in s2
	}
	return (*s1 - *s2);  // Return the ASCII difference of the first differing characters
}
```

***

#### **Example Usage:**

```c
#include <stdio.h>

int ft_strcmp(char *s1, char *s2);

int main(void)
{
    printf("Comparison 1: %d\n", ft_strcmp("hello", "hello"));  // Output: 0
    printf("Comparison 2: %d\n", ft_strcmp("hello", "hell"));   // Positive value
    printf("Comparison 3: %d\n", ft_strcmp("hell", "hello"));   // Negative value
    printf("Comparison 4: %d\n", ft_strcmp("abc", "abd"));      // Negative value
    printf("Comparison 5: %d\n", ft_strcmp("xyz", "xy"));       // Positive value

    return 0;
}
```

***

#### **Edge Cases to Consider:**

* **Identical Strings:** `"hello", "hello"` → Returns `0`
* **One String is a Prefix:** `"hello", "hell"` → Returns a positive value
* **Different Characters in Between:** `"abc", "abd"` → Returns a negative value
* **Empty String Comparisons:** `"" , ""` → Returns `0`
* **Comparing With an Empty String:** `"hello", ""` → Returns a positive value

#### **Limitations of `ft_strcmp`:**

* **Case Sensitivity:** It performs case-sensitive comparisons (`"Hello"` is different from `"hello"`).
* **No Bounds Checking:** If given non-null-terminated strings, it may lead to undefined behavior.
* **Lexicographical Order:** The function doesn’t return `1` or `-1`, but rather the ASCII difference, which might not always be intuitive.


---

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