Name
tempnam — create a name for a temporary file
Synopsis
#include <stdio.h>
char
*tempnam( |
const char *dir, |
const char *pfx); |
![[Note]](../stylesheet/note.png) |
Note | ||
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DESCRIPTION
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:
-
In case the environment variable
TMPDIRexists and contains the name of an appropriate directory, that is used. -
Otherwise, if the
dirargument is non-NULL and appropriate, it is used. -
Otherwise,
P_tmpdir(as defined in<stdio.h>is used when appropriate. -
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
The tempnam() function
returns a pointer to a unique temporary filename, or NULL if
a unique name cannot be generated.
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.
BUGS
The precise meaning of "appropriate" is undefined; it is unspecified how accessibility of a directory is determined.
Never use this function. Use mkstemp(3) or tmpfile(3) instead.
COLOPHON
This page is part of release 3.33 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
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Copyright (c) 1999 Andries Brouwer (aebcwi.nl) 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 Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |