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

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

       #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)):

           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L

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

       The mkstemp() function generates a unique temporary filename from  tem-
       plate,  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 creates 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

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

       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  tem-
              plate were not XXXXXX; now template is unchanged.

              For  mkstemps() and mkostemps(): template is less than (6 + suf-
              fixlen) 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

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

       For   an   explanation   of   the  terms  used  in  this  section,  see

       |Interface               | Attribute     | Value   |
       |mkstemp(), mkostemp(),  | Thread safety | MT-Safe |
       |mkstemps(), mkostemps() |               |         |
       mkstemp(): 4.3BSD, POSIX.1-2001.

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

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

       In glibc versions 2.06 and earlier, the file is  created  with  permis-
       sions  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  programs.
       POSIX.1-2008 adds a requirement that the  file  be  created  with  mode

       More  generally, the POSIX specification of mkstemp() does not say any-
       thing 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()).

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

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GNU                               2015-03-02                        MKSTEMP(3)
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