tempnam(3) — Linux manual page


TEMPNAM(3)                Linux Programmer's Manual               TEMPNAM(3)

NAME         top

       tempnam - create a name for a temporary file

SYNOPSIS         top

       #include <stdio.h>

       char *tempnam(const char *dir, const char *pfx);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           Since glibc 2.19:
           Glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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

       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

       c) Otherwise, P_tmpdir (as defined in <stdio.h>) is used when

       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         top

       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         top

       ENOMEM Allocation of storage failed.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface Attribute     Value       │
       │tempnam() │ Thread safety │ MT-Safe env │

CONFORMING TO         top

       SVr4, 4.3BSD, POSIX.1-2001.  POSIX.1-2008 marks tempnam() as

NOTES         top

       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.

BUGS         top

       The precise meaning of "appropriate" is undefined; it is unspecified
       how accessibility of a directory is determined.

SEE ALSO         top

       mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2017-09-15                       TEMPNAM(3)

Pages that refer to this page: getpid(2)getppid(2)mkdtemp(3)mkostemp(3)mkostemps(3)mkstemp(3)mkstemps(3)mktemp(3)stdio(3)tmpfile(3)tmpnam(3)tmpnam_r(3)environ(7)