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<a name="mktemp_002c-mkstemp_002c-mkostemp_002c-mkstemps_002c"></a>
<h3 class="section">4.42 <code>mktemp</code>, <code>mkstemp</code>, <code>mkostemp</code>, <code>mkstemps</code>,</h3>
<a name="index-mktemp"></a>
<a name="index-mkdtemp"></a>
<a name="index-mkstemp"></a>
<a name="index-mkstemps"></a>
<a name="index-mkostemp"></a>
<a name="index-mkostemps"></a>
<a name="index-_005fmktemp_005fr"></a>
<a name="index-_005fmkdtemp_005fr"></a>
<a name="index-_005fmkstemp_005fr"></a>
<a name="index-_005fmkstemps_005fr"></a>
<a name="index-_005fmkostemp_005fr"></a>
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<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;stdlib.h&gt;
char *mktemp(char *<var>path</var>);
char *mkdtemp(char *<var>path</var>);
int mkstemp(char *<var>path</var>);
int mkstemps(char *<var>path</var>, int <var>suffixlen</var>);
int mkostemp(char *<var>path</var>, int <var>flags</var>);
int mkostemps(char *<var>path</var>, int <var>suffixlen</var>, int <var>flags</var>);

char *_mktemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
char *_mkdtemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
int *_mkstemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
int *_mkstemps_r(struct _reent *<var>reent</var>, char *<var>path</var>, int <var>len</var>);
int *_mkostemp_r(struct _reent *<var>reent</var>, char *<var>path</var>,
    int <var>flags</var>);
int *_mkostemps_r(struct _reent *<var>reent</var>, char *<var>path</var>, int <var>len</var>,
    int <var>flags</var>);

</pre></div>
<p><strong>Description</strong><br>
<code>mktemp</code>, <code>mkstemp</code>, and <code>mkstemps</code> attempt to generate a file name
that is not yet in use for any existing file.  <code>mkstemp</code> and <code>mkstemps</code>
create the file and open it for reading and writing; <code>mktemp</code> simply
generates the file name (making <code>mktemp</code> a security risk).  <code>mkostemp</code>
and <code>mkostemps</code> allow the addition of other <code>open</code> flags, such
as <code>O_CLOEXEC</code>, <code>O_APPEND</code>, or <code>O_SYNC</code>.  On platforms with a
separate text mode, <code>mkstemp</code> forces <code>O_BINARY</code>, while <code>mkostemp</code>
allows the choice between <code>O_BINARY</code>, <code>O_TEXT</code>, or 0 for default.
<code>mkdtemp</code> attempts to create a directory instead of a file, with a
permissions mask of 0700.
</p>
<p>You supply a simple pattern for the generated file name, as the string
at <var>path</var>.  The pattern should be a valid filename (including path
information if you wish) ending with at least six &lsquo;<code>X</code>&rsquo;
characters.  The generated filename will match the leading part of the
name you supply, with the trailing &lsquo;<code>X</code>&rsquo; characters replaced by some
combination of digits and letters.  With <code>mkstemps</code>, the &lsquo;<code>X</code>&rsquo;
characters end <var>suffixlen</var> bytes before the end of the string.
</p>
<p>The alternate functions <code>_mktemp_r</code>, <code>_mkdtemp_r</code>, <code>_mkstemp_r</code>,
<code>_mkostemp_r</code>, <code>_mkostemps_r</code>, and <code>_mkstemps_r</code> are reentrant
versions.  The extra argument <var>reent</var> is a pointer to a reentrancy
structure.
</p>
<br>
<p><strong>Returns</strong><br>
<code>mktemp</code> returns the pointer <var>path</var> to the modified string
representing an unused filename, unless it could not generate one, or
the pattern you provided is not suitable for a filename; in that case,
it returns <code>NULL</code>.  Be aware that there is an inherent race between
generating the name and attempting to create a file by that name;
you are advised to use <code>O_EXCL|O_CREAT</code>.
</p>
<p><code>mkdtemp</code> returns the pointer <var>path</var> to the modified string if the
directory was created, otherwise it returns <code>NULL</code>.
</p>
<p><code>mkstemp</code>, <code>mkstemps</code>, <code>mkostemp</code>, and <code>mkostemps</code> return a file
descriptor to the newly created file, unless it could not generate an
unused filename, or the pattern you provided is not suitable for a
filename; in that case, it returns <code>-1</code>.
</p>
<br>
<p><strong>Notes</strong><br>
Never use <code>mktemp</code>.  The generated filenames are easy to guess and
there&rsquo;s a race between the test if the file exists and the creation
of the file.  In combination this makes <code>mktemp</code> prone to attacks
and using it is a security risk.  Whenever possible use <code>mkstemp</code>
instead.  It doesn&rsquo;t suffer the race condition.
</p>
<br>
<p><strong>Portability</strong><br>
ANSI C does not require either <code>mktemp</code> or <code>mkstemp</code>; the System
V Interface Definition requires <code>mktemp</code> as of Issue 2.  POSIX 2001
requires <code>mkstemp</code>, and POSIX 2008 requires <code>mkdtemp</code> while
deprecating <code>mktemp</code>.  <code>mkstemps</code>, <code>mkostemp</code>, and <code>mkostemps</code>
are not standardized.
</p>
<p>Supporting OS subroutines required: <code>getpid</code>, <code>mkdir</code>, <code>open</code>, <code>stat</code>.
</p>
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