> 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/c01/ft_strlen.md).

# ft\_strlen

**Objective:**

Create a function that counts and returns the number of characters in a string.

**Turn-in Directory:**`ex06/`

**Files to Turn In:** `ft_strlen.c`

**Allowed Functions:** None

**Prototype:**

```c
int ft_strlen(char *str);
```

***

#### **Detailed Explanation:**

**1. Functionality:**

* The `ft_strlen` function calculates the length of a string by counting the number of characters until it encounters the null terminator (`'\0'`).
* Strings in C are arrays of characters terminated by the special null character (`'\0'`), which marks the end of the string.

**2. Input:**

* A single parameter: `char *str`
  * This is a pointer to the first character of the string to be measured.

**3. Output:**

* An integer value representing the number of characters in the string, excluding the null terminator.

**4. Implementation Steps:**

1. Initialize a counter variable (e.g., `length`) to `0`.
2. Loop through the string using the pointer `str`:
   * Check if the current character is not `'\0'`.
   * Increment the counter for each character.
3. Stop the loop when `'\0'` is encountered.
4. Return the counter.

**5. Code Implementation:**

Here is the code for the `ft_strlen` function:

```c
int ft_strlen(char *str)
{
    int length = 0;

    while (str[length] != '\0') // Continue until the null character is found
    {
        length++; // Increment the length for each character
    }
    return length; // Return the total length of the string
}
```

***

#### **Example Usage:**

**Code Example:**

```c
#include <stdio.h>

int ft_strlen(char *str);

int main(void)
{
    char example[] = "Hello, 42!";
    printf("The length of the string is: %d\n", ft_strlen(example));
    return 0;
}
```

**Expected Output:**

```csharp
The length of the string is: 10
```

***

#### **Edge Cases to Test:**

1. **Empty String:**
   * Input: `""`
   * Expected Output: `0`
2. **String with One Character:**
   * Input: `"A"`
   * Expected Output: `1`
3. **String with Special Characters:**
   * Input: `"Hello\nWorld!"`
   * Expected Output: `12` (The newline  counts as a character)
4. **String with Spaces:**
   * Input: `" "`
   * Expected Output: `1`


---

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