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() 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.

SEE ALSO

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

COLOPHON

   This  page  is  part of release 4.09 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/.

                              2016-03-15                        TEMPNAM(3)

---

Free and Open Source Software