How to use tempfile() in C

The tmpfile() function in C creates a temporary file that is automatically deleted when the program terminates.

The created file opens in binary update (wb+) mode.

To use the tmpfile() function, the program needs to include the stdio.h header file as shown below:

#include <stdio.h>

Parameters and Return Value

The tmpfile() function accepts no parameters.

tmpfile() returns a pointer to the file upon its successful creation, otherwise it returns NULL.

Examples

The following code demonstrates how to create a temporary file, read from it, and write to a temporary file:

#include <stdio.h>
int main()
{
  FILE* ptr;
  ptr = tmpfile();
  char input[] = "Educative.io";
  int i = 0;
  //checks for successful creation of file
  if(ptr == NULL)
  {
    printf("The file pointer is NULL");
    return 0;
  }
  else
  {
    printf("The file has been created\n");
  }
  while(input[i] != '\0')
  {
    //writes to file
    fputc(input[i] , ptr);
    i++;
  }
  //positions pointer at the start of file
  rewind(ptr);
  // check for end of file
  while(!feof(ptr))
  {
    //reads from file
    printf("%c",fgetc(ptr));
  }
}

Explanation

  • In the above example, a temporary file is created and stored in the pointer ptr
  • The program checks ptr for NULL value to detect unsuccessful creation of the file
  • The fputc() function writes one character of “Educative.io” to the file at a time until the end of the string is reached
  • The fgetc() function reads one character at a time until the end of the file is reached as identified by feof()

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