tempnam (3)
Leading comments
Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the L...
NAME
tempnam - create a name for a temporary fileSYNOPSIS
#include <stdio.h> char *tempnam(const char *dir, const char *pfx);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
tempnam(): _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
Never use this function. Use mkstemp(3) or tmpfile(3) instead.The tempnam() function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist when tempnam() checked. The filename suffix of the pathname generated will start with pfx in case pfx is a non-NULL string of at most five bytes. The directory prefix part of the pathname generated is required to be "appropriate" (often that at least implies writable).
Attempts to find an appropriate directory go through the following steps:
- a)
- In case the environment variable TMPDIR exists and contains the name of an appropriate directory, that is used.
- b)
- Otherwise, if the dir argument is non-NULL and appropriate, it is used.
- c)
- Otherwise, P_tmpdir (as defined in <stdio.h>) is used when appropriate.
- d)
- Finally an implementation-defined directory may be used.
The string returned by tempnam() is allocated using malloc(3) and hence should be freed by free(3).
RETURN VALUE
On success, the tempnam() function returns a pointer to a unique temporary filename. It returns NULL if a unique name cannot be generated, with errno set to indicate the cause of the error.ERRORS
- ENOMEM
- Allocation of storage failed.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
tempnam() | Thread safety | MT-Safe env |
CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001. POSIX.1-2008 marks tempnam() as obsolete.NOTES
Although tempnam() generates names that are difficult to guess, it is nevertheless possible that between the time that tempnam() returns a pathname, and the time that the program opens it, another program might create that pathname using open(2), or create it as a symbolic link. This can lead to security holes. To avoid such possibilities, use the open(2) O_EXCL flag to open the pathname. Or better yet, use mkstemp(3) or tmpfile(3).SUSv2 does not mention the use of TMPDIR; glibc will use it only when the program is not set-user-ID. On SVr4, the directory used under d) is /tmp (and this is what glibc does).
Because it dynamically allocates memory used to return the pathname, tempnam() is reentrant, and thus thread safe, unlike tmpnam(3).
The tempnam() function generates a different string each time it is called, up to TMP_MAX (defined in <stdio.h>) times. If it is called more than TMP_MAX times, the behavior is implementation defined.
tempnam()
uses at most the first five bytes from
pfx.
The glibc implementation of
tempnam()
will fail with the error
EEXIST
upon failure to find a unique name.