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 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
       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 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

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

       ┌────────────────────────┬───────────────┬─────────┐
       │Interface               │ Attribute     │ Value   │
       ├────────────────────────┼───────────────┼─────────┤
       │mkstemp(), mkostemp(),  │ Thread safety │ MT-Safe │
       │mkstemps(), mkostemps() │               │         │
       └────────────────────────┴───────────────┴─────────┘

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
       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 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 4.15 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/.