> 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/c02/ft_putstr_non_printable.md).

# ft\_putstr\_non\_printable

**Objective**

The function `ft_putstr_non_printable` displays a given string on the screen. If the string contains **non-printable characters**, they are displayed in **hexadecimal format**, preceded by a backslash (`\`).

***

### **Turn-in Requirements**

* **Directory:** `ex11/`
* **File:** `ft_putstr_non_printable.c`
* **Allowed Functions:** `write`

***

### **Prototype**

```c
void ft_putstr_non_printable(char *str);
```

***

### **Implementation**

```c
#include <unistd.h>

void	ft_putchar(char c)
{
	write(1, &c, 1);
}

void	ft_putstr_non_printable(char *str)
{
	int		i;
	char		*hex;

	hex = "0123456789abcdef"; // Hexadecimal characters
	i = 0;
	while (str[i] != '\0')
	{
		if (str[i] >= 32 && str[i] <= 126) // If the character is printable
			ft_putchar(str[i]);
		else
		{
			ft_putchar('\\'); // Print backslash
			ft_putchar(hex[(unsigned char)str[i] / 16]); // Print first hex digit
			ft_putchar(hex[(unsigned char)str[i] % 16]); // Print second hex digit
		}
		i++;
	}
}
```

***

### **Explanation**

#### **Input Parameter:**

* The function receives `str`, a **string** containing printable and non-printable characters.

#### **Processing Steps:**

1. **Loop through the string**
   * Iterate through each character until reaching `'\0'`.
2. **Check if the character is printable**
   * ASCII **printable characters** range from **32 (' ') to 126 ('\~')**.
   * If the character is printable, print it using `write()`.
3. **Handle non-printable characters**
   * If a character is **non-printable**, it is converted into a **hexadecimal format**:
     * Print a **backslash (`\`)**.
     * Extract the **first hex digit** using division by 16.
     * Extract the **second hex digit** using modulo 16.
4. **Print the formatted characters**
   * The `write()` function is used to output each character.

***

### **Example Usage**

```c
#include <stdio.h>

void ft_putstr_non_printable(char *str);

int main()
{
    char str1[] = "Coucou\ntu vas bien ?";
    char str2[] = "Hello\x01\x02\x7FWorld!";
    char str3[] = "";

    printf("Original: Coucou\\ntu vas bien ?\nOutput: ");
    ft_putstr_non_printable(str1);
    printf("\n");

    printf("Original: Hello\x01\x02\x7FWorld!\nOutput: ");
    ft_putstr_non_printable(str2);
    printf("\n");

    printf("Original: (empty string)\nOutput: ");
    ft_putstr_non_printable(str3);
    printf("\n");

    return 0;
}
```

#### **Expected Output**

```vbnet
Original: Coucou\ntu vas bien ?
Output: Coucou\0atu vas bien ?

Original: Hello\x01\x02\x7FWorld!
Output: Hello\01\02\7fWorld!

Original: (empty string)
Output: 
```

***

### **Edge Cases Considered**

✅ **Handles empty strings** (prints nothing).\
✅ **Handles all non-printable ASCII characters** (`0-31` and `127`).\
✅ **Preserves original string formatting** while replacing non-printable characters.

***

### **Complexity Analysis**

* **Time Complexity:** **O(n)** → Iterates through the string once.
* **Space Complexity:** **O(1)** → Uses only a small amount of additional memory for `hex`.


---

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