tempnam

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



NAME
       tempnam - create a name for a temporary file

SYNOPSIS
       #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

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() fails 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.

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

COLOPHON
       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
       https://www.kernel.org/doc/man-pages/.



                                   2017-09-15                         TEMPNAM(3)