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():
           _XOPEN_SOURCE >= 500
               || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
               || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

       mkostemp(): _GNU_SOURCE
       mkstemps():
           /* Glibc since 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
       mkostemps(): _GNU_SOURCE

DESCRIPTION
       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
       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  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
       open(2).

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

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       allbox; lbw23 lb lb l l  l.   Interface Attribute Value  T{  mkstemp(),
       mkostemp(),
       mkstemps(), mkostemps() T}   Thread safety  MT-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 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
       0600.

       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()).

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

COLOPHON
       This  page  is  part of release 4.16 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
       https://www.kernel.org/doc/man-pages/.



GNU                               2017-09-15                        MKSTEMP(3)