tmpnam

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



NAME
       tmpnam, tmpnam_r - create a name for a temporary file

SYNOPSIS
       #include <stdio.h>

       char *tmpnam(char *s);
       char *tmpnam_r(char *s);

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

       tmpnam_r()
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Up to and including glibc 2.19:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       Note: avoid using these functions; use mkstemp(3) or tmpfile(3) instead.

       The tmpnam() function returns a pointer to a string that is a valid
       filename, and such that a file with this name did not exist at some point
       in time, so that naive programmers may think it a suitable name for a
       temporary file.  If the argument s is NULL, this name is generated in an
       internal static buffer and may be overwritten by the next call to
       tmpnam().  If s is not NULL, the name is copied to the character array
       (of length at least L_tmpnam) pointed to by s and the value s is returned
       in case of success.

       The created pathname has a directory prefix P_tmpdir.  (Both L_tmpnam and
       P_tmpdir are defined in <stdio.h>, just like the TMP_MAX mentioned
       below.)

       The tmpnam_r() function performs the same task as tmpnam(), but returns
       NULL (to indicate an error) if s is NULL.

RETURN VALUE
       These functions return a pointer to a unique temporary filename, or NULL
       if a unique name cannot be generated.

ERRORS
       No errors are defined.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌─────────────────────────────┬───────────────┬──────────────────────────┐
       │Interface                    Attribute     Value                    │
       ├─────────────────────────────┼───────────────┼──────────────────────────┤
       │tmpnam()                     │ Thread safety │ MT-Unsafe race:tmpnam/!s │
       ├─────────────────────────────┼───────────────┼──────────────────────────┤
       │tmpnam_r()                   │ Thread safety │ MT-Safe                  │
       └─────────────────────────────┴───────────────┴──────────────────────────┘

CONFORMING TO
       tmpnam(): SVr4, 4.3BSD, C89, C99, POSIX.1-2001.  POSIX.1-2008 marks
       tmpnam() as obsolete.

       tmpnam_r() is a nonstandard extension that is also available on a few
       other systems.

NOTES
       The tmpnam() function generates a different string each time it is
       called, up to TMP_MAX times.  If it is called more than TMP_MAX times,
       the behavior is implementation defined.

       Although these functions generate names that are difficult to guess, it
       is nevertheless possible that between the time that the pathname is
       returned 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).

       Portable applications that use threads cannot call tmpnam() with a NULL
       argument if either _POSIX_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is
       defined.

BUGS
       Never use these functions.  Use mkstemp(3) or tmpfile(3) instead.

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

COLOPHON
       This page is part of release 5.12 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/.



                                   2021-03-22                          TMPNAM(3)