NAME
tempnam - create a name for a temporary file SYNOPSIS
#include
char *tempnam(const char *dir, const char *pfx); Feature Test Macro Requirements for glibc (see featuretestmacros(7)): tempnam(): BSDSOURCE || SVIDSOURCE 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 temp‐ nam() 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, Ptmpdir (as defined in
) is used when appropri‐ ate. 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 succes, the tempnam() function returns a pointer to a unique tempo‐ rary 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) OEXCL 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 TMPMAX (defined in
) times. If it is called more than TMPMAX 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. SEE ALSO mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3) COLOPHON This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2013-04-19 TEMPNAM(3)