mkstemp

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
       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 5.04 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)