tmpfile(), tmpfile64()

Create a temporary file


#include <stdio.h>

FILE* tmpfile( void );

FILE* tmpfile64( void );



Use the -l c option to qcc to link against this library. This library is usually included automatically.


The tmpfile() and tmpfile64() functions create a temporary file and open a corresponding FILE stream. The tmpfile64() function is a large-file support version of tmpfile().

Note: In QNX Neutrino 6.6 or later, the large-file support functions and data types appear in the name space only if you define _LARGEFILE64_SOURCE when you compile your code. For more information, see "Classification" in What's in a Function Description?

The file is automatically removed when it's closed or when the program terminates. The file is opened in update mode (as in fopen()'s w+ mode).

If the process is killed between file creation and unlinking, a permanent file may be left behind.

Note: When a stream is opened in update mode, both reading and writing may be performed. However, writing may not be followed by reading without an intervening call to fflush(), or to a file-positioning function (fseek(), fsetpos(), rewind()). Similarly, reading may not be followed by writing without an intervening call to a file-positioning function, unless the read resulted in end-of-file.


A pointer to the stream of the temporary file, or NULL if an error occurs (errno is set).


The calling process doesn't have permission to create the temporary file.
All file descriptors available to the process are currently open.
The system already has the maximum number of files open.
The filesystem for the temporary file is read-only.


#include <stdio.h>
#include <stdlib.h>

static FILE *TempFile;

int main( void )
    TempFile = tmpfile();
    fclose( TempFile );
    /* The temporary file will be removed when we exit. */
    return EXIT_SUCCESS;


tmpfile() is ANSI, POSIX 1003.1; tmpfile64() is Large-file support

Cancellation point Yes
Interrupt handler No
Signal handler No
Thread Yes