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`tmpfile'--create a temporary file

     #include <stdio.h>
     FILE *tmpfile(void);
     FILE *_tmpfile_r(void *REENT);
Create a temporary file (a file which will be deleted automatically),
using a name generated by `tmpnam'.  The temporary file is opened with
the mode `"wb+"', permitting you to read and write anywhere in it as a
binary file (without any data transformations the host system may
perform for text files).
   The alternate function `_tmpfile_r' is a reentrant version.  The
argument REENT is a pointer to a reentrancy structure.
`tmpfile' normally returns a pointer to the temporary file.  If no
temporary file could be created, the result is NULL, and `errno'
records the reason for failure.
Both ANSI C and the System V Interface Definition (Issue 2) require
   Supporting OS subroutines required: `close', `fstat', `getpid',
`isatty', `lseek', `open', `read', `sbrk', `write'.
   `tmpfile' also requires the global pointer `environ'.