The **`tmpnam` function** is a C library function that creates a unique name for temporary files. The function generates a different filename each time we call the function, up to `TMP_MAX` times. 

>TMP_MAX is the maximum number of filenames that the `tmpnam` function can create. It is greater than or equal to `25`. 

The `tmpnam` function and `TMP_MAX` are declared in the `stdio.h` header file as shown below:
```C
#include stdio.h
```

# Syntax 
The basic syntax of the function is:

# Parameters 
The `tmpnam` function takes a single `char pointer` which points to the array of characters. The filename is a C string. 
>The size of the array of characters is at least equal to `L_tmpnam`, defined in the `stdio.h` header file. 


# Return Value 
The `tmpnam` function returns a pointer to a C string that contains the valid filename: 

* If the parameter *s* is a `NULL` pointer, the return value will point to the `tmpnam's` internal buffer, which the subsequent calls to the function will overwrite.

* If the parameter *s* is *not* `NULL`, the function returns s. A `NULL` pointer is returned in case a suitable filename is not found. 


# Example
The following code example shows the generation of a temporary filename stored in the array of characters. The `tmpnam` function returns a different filename when it is called the second time in `line 14`, as we see below:

>The warning generated in the code below indicates that there is a possibility of two files having the same name while using the `tmpnam` function. Therefore, the `mkstemp` function is preferred as it creates a file while the `tmpnam` function only returns the filename. 

#include <stdio.h>

int main() {

  //Define the array of characters and its size 
  char arr[L_tmpnam + 1]; 
  char *s; 

  //Call the tmpnam fucntion
  s = tmpnam(arr);
  printf ("The temporary filename is: %s\n", s);

  //Call the tmpnam function
  s = tmpnam(NULL);
  printf ("The temporary filename is: %s\n", s);

  return 0;
}

What is tmpnam() in C?

Generates unique temporary filenames, up to TMP_MAX. Use mkstemp instead to avoid duplicate names.