tmpnam(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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NOTES

35       The  tmpnam()  function  generates  a  different string each time it is
36       called, up to TMP_MAX times. If it is called more than  TMP_MAX  times,
37       the behaviour is implementation defined.
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39       Although  tmpnam(3)  generates names that are difficult to guess, it is
40       nevertheless possible that between the time that  tmpnam(3)  returns  a
41       pathname, and the time that the program opens it, another program might
42       create that pathname using open(2), or create it as  a  symbolic  link.
43       This  can lead to security holes.  To avoid such possibilities, use the
44       open(2)  O_EXCL  flag  to  open  the  pathname.   Or  better  yet,  use
45       mkstemp(3) or tmpfile(3).
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47       Portable  applications  that use threads cannot call tmpnam() with NULL
48       parameter if either _POSIX_THREADS or  _POSIX_THREAD_SAFE_FUNCTIONS  is
49       defined.
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51       A POSIX draft proposed to use a function tmpnam_r() defined by
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53            char *tmpnam_r(char *s) {
54                return s ? tmpnam(s) : NULL;
55            }
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57       apparently  as  a warning not to use NULL.  A few systems implement it.
58       To get a glibc prototype for  this  function,  define  _SVID_SOURCE  or
59       _BSD_SOURCE before including <stdio.h>.
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BUGS

62       Never use this function. Use mkstemp(3) or tmpfile(3) instead.
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CONFORMING TO

65       SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
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