C Programming/stdio.h/tmpfile

In computing, tmpfile is an ISO C/POSIX function for creating a temporary file, a computer file which ceases to exist when the program, which opened the file, closes it or terminates.

Usage

Inclusion

C

#include <stdio.h>

C++

#include <cstdio>

Declaration

FILE* tmpfile(void);

Semantics

The function tmpfile reports a pointer to a valid file stream on success; on failure, it returns NULL.

Error conditions

In addition to returning NULL, tmpfile sets errno on failure. The permissible values of errno, if tmpfile fails, are:

• EINTR - if a signal was caught during the execution of tmpfile.
• EMFILE - if the maximum number of file descriptors and/or the maximum number of file streams has been reached (in the process).
• ENFILE - if the maximum allowable number of files is currently open (in the system).
• ENOSPC - if there is no space in the file system for creating the temporary file.
• EOVERFLOW - if the file is a regular file and the size of the file cannot be represented correctly in an object of type off_t.
• ENOMEM - if there is insufficient memory for allocating the file stream.

Caveats

The tmpfile function is susceptible to a number of security vulnerabilities; use the non-portable mkstemp (UNIX) or tmpfile_s (MSVCRT) functions, instead, to avoid these issues.

The implementation of this function in Microsoft C run-time library tries to create the file in the root directory of the current drive and typically fails reporting "Access denied".

External links

• C++ reference for std::tmpfile