tmpnam_r(3)

1TMPNAM(3)                  Linux Programmer's Manual                 TMPNAM(3)
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NAME

6       tmpnam, tmpnam_r - create a name for a temporary file
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SYNOPSIS

9       #include <stdio.h>
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11       char *tmpnam(char *s);
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DESCRIPTION

14       The  tmpnam()  function  returns  a pointer to a string that is a valid
15       filename, and such that a file with this name did  not  exist  at  some
16       point  in  time, so that naive programmers may think it a suitable name
17       for a temporary file.  If the argument s is NULL this name is generated
18       in an internal static buffer and may be overwritten by the next call to
19       tmpnam().  If s is not NULL, the name is copied to the character  array
20       (of  length  at  least  L_tmpnam)  pointed  to  by s and the value s is
21       returned in case of success.
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23       The pathname that is created, has a directory prefix  P_tmpdir.   (Both
24       L_tmpnam  and  P_tmpdir are defined in <stdio.h>, just like the TMP_MAX
25       mentioned below.)
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RETURN VALUE

28       The tmpnam() function returns a pointer to a unique temporary filename,
29       or NULL if a unique name cannot be generated.
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ERRORS

32       No errors are defined.
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ATTRIBUTES

35   Multithreading (see pthreads(7))
36       The  tmpnam()  function  is  thread-safe  with  exceptions.   It is not
37       thread-safe if called with a NULL parameter.
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39       The tmpnam_r() function is thread-safe.
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CONFORMING TO

42       SVr4, 4.3BSD, C89, C99, POSIX.1-2001.  POSIX.1-2008 marks  tmpnam()  as
43       obsolete.
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NOTES

46       The  tmpnam()  function  generates  a  different string each time it is
47       called, up to TMP_MAX times.  If it is called more than TMP_MAX  times,
48       the behavior is implementation defined.
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50       Although  tmpnam()  generates  names that are difficult to guess, it is
51       nevertheless possible that between the time  that  tmpnam()  returns  a
52       pathname, and the time that the program opens it, another program might
53       create that pathname using open(2), or create it as  a  symbolic  link.
54       This  can lead to security holes.  To avoid such possibilities, use the
55       open(2)  O_EXCL  flag  to  open  the  pathname.   Or  better  yet,  use
56       mkstemp(3) or tmpfile(3).
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58       Portable applications that use threads cannot call tmpnam() with a NULL
59       argument if either _POSIX_THREADS  or  _POSIX_THREAD_SAFE_FUNCTIONS  is
60       defined.
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62       A POSIX draft proposed to use a function tmpnam_r() defined by
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64           char *
65           tmpnam_r(char *s)
66           {
67               return s ? tmpnam(s) : NULL;
68           }
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70       apparently  as  a warning not to use NULL.  A few systems implement it.
71       To get a glibc prototype  for  this  function  from  <stdio.h>,  define
72       _SVID_SOURCE or _BSD_SOURCE (before including any header file).
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BUGS

75       Never use this function.  Use mkstemp(3) or tmpfile(3) instead.
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COLOPHON

81       This  page  is  part of release 3.53 of the Linux man-pages project.  A
82       description of the project, and information about reporting  bugs,  can
83       be found at http://www.kernel.org/doc/man-pages/.
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87                                  2013-06-21                         TMPNAM(3)