bionic (3) tmpnam.3.gz

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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).

       ┌───────────┬───────────────┬──────────────────────────┐
       │InterfaceAttributeValue                    │
       ├───────────┼───────────────┼──────────────────────────┤
       │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

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                                                   2017-09-15                                          TMPNAM(3)