tmpfile (CRT)

tmpfile

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Microsoft Visual Studio 2005/.NET Framework 2.0

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Run-Time Library Reference

tmpfile

Creates a temporary file. This function is deprecated because a more secure version is available; see tmpfile_s.

FILE *tmpfile( void );

Return Value

If successful, tmpfile returns a stream pointer. Otherwise, it returns a NULL pointer.

Remarks

The tmpfile function creates a temporary file and returns a pointer to that stream. The temporary file is created in the root directory. To create a temporary file in a directory other than the root, use tmpnam or tempnam in conjunction with fopen.

If the file cannot be opened, tmpfile returns a NULL pointer. 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 does not change. The temporary file is opened in w+b (binary read/write) mode.

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

Requirements

Routine	Required header	Compatibility
tmpfile	<stdio.h>	ANSI, Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_tmpfile.c
// compile with: /W3
// This program uses tmpfile 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;

   // Create temporary files.
   for( i = 1; i <= 3; i++ )
   {
      if( (stream = tmpfile()) == NULL ) // C4996
      // Note: tmpfile is deprecated; consider using tmpfile_s instead
         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() );
}

Output

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

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

Reference

Stream I/O
_rmtmp
_tempnam, _wtempnam, tmpnam, _wtmpnam

(one day later)

I managed to fix it by creating my own tmpfile() function to replace the faulty default one (running Win7/build7100, Visual C++ 2008SP1):

FILE *myTmpFile()
// Creates a temp file in a more readable location than tmpfile() on Win32
// (which writes in root, not allowed in Vista/Win7)
{
  char  buf[1024],buf2[1024],bufN[256];
  int   n;
  FILE *fp;

  GetTempPath(1024,buf);
  for(n=_getpid();;n++)
  {
    strcpy_s(buf2,sizeof(buf2),buf);
    sprintf_s(bufN,sizeof(bufN),"jpeg_rvg_%d",n);
    strcat_s(buf2,sizeof(buf2),bufN);
    fp=0;
    // Exists?
    fp=fopen(buf2,"rb");
    if(fp)
    {
      fclose(fp);
      continue;
    }
    // Clear file and allow reads
    fopen_s(&fp,buf2,"wb+");
    if(fp)return fp;
  }
  // We'll never get here
  return 0;
}

Not sure if tmpfile() would create auto-deleting files, but this function just creates (but never deletes) the temp file.