How to create a temporary text file in C++?

This may be a little off-topic because the author wanted to create a tmp.txt and delete it after using it, but that is trivial - you can simple open() it and delete it (using boost::filesystem of course).

mkstemp() is UNIX-based. With Windows you use GetTempFileName() and GetTempPath() to generate a path to a temp file. Sample code from MSDN:

http://msdn.microsoft.com/en-us/library/aa363875%28VS.85%29.aspx

Maybe this will help

FILE * tmpfile ( void );

http://www.cplusplus.com/reference/clibrary/cstdio/tmpfile/

Open a temporary file

Creates a temporary binary file, open for update (wb+ mode -- see fopen for details). The filename is guaranteed to be different from any other existing file. The temporary file created is automatically deleted when the stream is closed (fclose) or when the program terminates normally.

See also

char * tmpnam ( char * str );

Generate temporary filename

A string containing a filename different from any existing file is generated. This string can be used to create a temporary file without overwriting any other existing file.

http://www.cplusplus.com/reference/clibrary/cstdio/tmpnam/

Here's a complete example:

#include <unistd.h>

int main(void) {
  char filename[] = "/tmp/mytemp.XXXXXX"; // template for our file.        
  int fd = mkstemp(filename);    // Creates and opens a new temp file r/w.
                                 // Xs are replaced with a unique number.
  if (fd == -1) return 1;        // Check we managed to open the file.
  write(fd, "abc", 4);           // note 4 bytes total: abc terminating '\0'
  /* ...
     do whatever else you want.
     ... */
  close(fd);
  unlink(filename);              // Delete the temporary file.
}

If you know the name of the file you want to create (and are sure it won't already exist) then you can obviously just use open to open the file.

tmpnam and tmpfile should probably be avoided as they can suffer from race conditions - see man tmpfile(3) for the details.