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 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

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