tempnam - create a name for a temporary file

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────┬───────────────┬─────────────┐
       │ Interface                                                               │ Attribute     │ Value       │
       ├─────────────────────────────────────────────────────────────────────────┼───────────────┼─────────────┤
       │ tempnam()                                                               │ Thread safety │ MT-Safe env │
       └─────────────────────────────────────────────────────────────────────────┴───────────────┴─────────────┘

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

Neverusethisfunction.  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).

ENOMEM Allocation of storage failed.

       SVr4, 4.3BSD, POSIX.1-2001.  Obsoleted in POSIX.1-2008.

       Standard C library (libc, -lc)

       tempnam - create a name for a temporary file

       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.

       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 error.

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

Linux man-pages 6.9.1                              2024-05-02                                         tempnam(3)

       POSIX.1-2008.

#include<stdio.h>char*tempnam(constchar*dir,constchar*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