MKSTEMP(3)                          Linux Programmer's Manual                          MKSTEMP(3)



NAME
       mkstemp, mkostemp, mkstemps, mkostemps - create a unique temporary file

SYNOPSIS
       #include <stdlib.h>

       int mkstemp(char *template);

       int mkostemp(char *template, int flags);

       int mkstemps(char *template, int suffixlen);

       int mkostemps(char *template, int suffixlen, int flags);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       mkstemp():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L

       mkostemp(): _GNU_SOURCE
       mkstemps(): _BSD_SOURCE || _SVID_SOURCE
       mkostemps(): _GNU_SOURCE

DESCRIPTION
       The mkstemp() function generates a unique temporary filename from  template,  creates  and
       opens the file, and returns an open file descriptor for the file.

       The  last six characters of template must be "XXXXXX" and these are replaced with a string
       that makes the filename unique.  Since it will be modified, template must not be a  string
       constant, but should be declared as a character array.

       The  file  is created with permissions 0600, that is, read plus write for owner only.  The
       returned file descriptor provides both read and write access to the  file.   The  file  is
       opened with the open(2) O_EXCL flag, guaranteeing that the caller is the process that cre‐
       ates the file.

       The mkostemp() function is like mkstemp(), with the difference that  the  following  bits—
       with  the  same meaning as for open(2)—may be specified in flags: O_APPEND, O_CLOEXEC, and
       O_SYNC.  Note that when creating the file, mkostemp() includes the values O_RDWR, O_CREAT,
       and  O_EXCL  in  the  flags argument given to open(2); including these values in the flags
       argument given to mkostemp() is unnecessary, and produces errors on some systems.

       The mkstemps() function is like mkstemp(), except that the string in template  contains  a
       suffix of suffixlen characters.  Thus, template is of the form prefixXXXXXXsuffix, and the
       string XXXXXX is modified as for mkstemp().

       The mkostemps() function is to mkstemps() as mkostemp() is to mkstemp().

RETURN VALUE
       On success, these functions return the file descriptor of the temporary file.   On  error,
       -1 is returned, and errno is set appropriately.

ERRORS
       EEXIST Could  not  create  a  unique temporary filename.  Now the contents of template are
              undefined.

       EINVAL For mkstemp() and mkostemp(): The last six characters of template were not  XXXXXX;
              now template is unchanged.

              For  mkstemps()  and  mkostemps(): template is less than (6 + suffixlen) characters
              long, or the last 6 characters before the suffix in template were not XXXXXX.

       These functions may also fail with any of the errors described for open(2).

VERSIONS
       mkostemp() is available since glibc 2.7.  mkstemps() and mkostemps() are  available  since
       glibc 2.11.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The mkstemp(), mkostemp(), mkstemps(), and mkostemps() functions are thread-safe.

CONFORMING TO
       mkstemp(): 4.3BSD, POSIX.1-2001.

       mkstemps(): unstandardized, but appears on several other systems.

       mkostemp() and mkostemps(): are glibc extensions.

NOTES
       In  glibc  versions  2.06 and earlier, the file is created with permissions 0666, that is,
       read and write for all users.  This old behavior may be a security risk, especially  since
       other  UNIX  flavors  use  0600, and somebody might overlook this detail when porting pro‐
       grams.  POSIX.1-2008 adds a requirement that the file be created with mode 0600.

       More generally, the POSIX specification of mkstemp() does  not  say  anything  about  file
       modes,  so  the application should make sure its file mode creation mask (see umask(2)) is
       set appropriately before calling mkstemp() (and mkostemp()).

SEE ALSO
       mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)

COLOPHON
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2014-08-19                                 MKSTEMP(3)