`tmpfile_s`

Article
02/13/2023

Creates a temporary file. It's a version of tmpfile with security enhancements as described in Security features in the CRT.

Syntax

errno_t tmpfile_s(
   FILE** pFilePtr
);

Parameters

pFilePtr
The address of a pointer to store the address of the generated pointer to a stream.

Return value

Returns 0 if successful, an error code on failure.

Error conditions

`pFilePtr`	Return value	Contents of `pFilePtr`
`NULL`	`EINVAL`	not changed

If the above parameter validation error occurs, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, errno is set to EINVAL, and the return value is EINVAL.

Remarks

The tmpfile_s function creates a temporary file and puts a pointer to that stream in the pFilePtr argument. The temporary file is created in the root directory. To create a temporary file in a directory other than the root, use tmpnam_s or tempnam with fopen.

If the file can't be opened, tmpfile_s writes NULL to the pFilePtr parameter. This temporary file is automatically deleted when the file is closed, when the program terminates normally, or when _rmtmp is called, assuming that the current working directory doesn't change. The temporary file is opened in w+b (binary read/write) mode.

Failure can occur if you attempt more than TMP_MAX_S (see STDIO.H) calls with tmpfile_s.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`tmpfile_s`	<stdio.h>

For more compatibility information, see Compatibility.

Example

Note

This example may require administrative privileges to run on Windows.

// crt_tmpfile_s.c
// This program uses tmpfile_s to create a
// temporary file, then deletes this file with _rmtmp.
//

#include <stdio.h>

int main( void )
{
   FILE *stream;
   char tempstring[] = "String to be written";
   int  i;
   errno_t err;

   // Create temporary files.
   for( i = 1; i <= 3; i++ )
   {
      err = tmpfile_s(&stream);
      if( err )
         perror( "Could not open new temporary file\n" );
      else
         printf( "Temporary file %d was created\n", i );
   }

   // Remove temporary files.
   printf( "%d temporary files deleted\n", _rmtmp() );
}

Temporary file 1 was created
Temporary file 2 was created
Temporary file 3 was created
3 temporary files deleted