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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | BUGS | SEE ALSO | COLOPHON |
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tempnam(3) Library Functions Manual tempnam(3)
tempnam - create a name for a temporary file
Standard C library (libc, -lc)
#include <stdio.h>
char *tempnam(const char *dir, const char *pfx);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
tempnam():
Since glibc 2.19:
_DEFAULT_SOURCE
glibc 2.19 and earlier:
_BSD_SOURCE || _SVID_SOURCE
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).
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 error.
ENOMEM Allocation of storage failed.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────┬───────────────┬─────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────┼───────────────┼─────────────┤
│ tempnam() │ Thread safety │ MT-Safe env │
└─────────────────────────────────┴───────────────┴─────────────┘
POSIX.1-2008.
SVr4, 4.3BSD, POSIX.1-2001. Obsoleted in POSIX.1-2008.
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() fails with the error EEXIST
upon failure to find a unique name.
The precise meaning of "appropriate" is undefined; it is
unspecified how accessibility of a directory is determined.
mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 tempnam(3)
Pages that refer to this page: getpid(2), mkdtemp(3), mkstemp(3), mktemp(3), stdio(3), tmpfile(3), tmpnam(3), environ(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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