c Programming/C Reference/stdio.h/tmpfile
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Template:C Standard library
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.[1][2][3]
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.[1]
Error conditions
In addition to returning NULL, tmpfile sets errno on failure. The permissible values of errno, if tmpfile fails, are:[1]
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.[4][5]
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".
See also
- mkstemp
- fopen
- fclose
- stdio.h
References
- 1 2 3 tmpfile by OpenGroup
- ↑ Temporary Files by GNU C Library
- ↑ tmpfile by HMUG
- ↑ TMPNAM-TMPFILE Vulnerability by Build Security In
- ↑ VOID FI039-C. Create temporary files securely by CERT