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163 lines
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163 lines
8.1 KiB
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4 years ago
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>mktemp (The Red Hat newlib C Library)</title>
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<body lang="en">
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<a name="mktemp"></a>
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<div class="header">
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<p>
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Next: <a href="open_005fmemstream.html#open_005fmemstream" accesskey="n" rel="next">open_memstream</a>, Previous: <a href="getwchar.html#getwchar" accesskey="p" rel="prev">getwchar</a>, Up: <a href="Stdio.html#Stdio" accesskey="u" rel="up">Stdio</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="mktemp_002c-mkstemp_002c-mkostemp_002c-mkstemps_002c"></a>
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<h3 class="section">4.42 <code>mktemp</code>, <code>mkstemp</code>, <code>mkostemp</code>, <code>mkstemps</code>,</h3>
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<a name="index-mktemp"></a>
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<a name="index-mkdtemp"></a>
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<a name="index-mkstemp"></a>
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<a name="index-mkstemps"></a>
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<a name="index-mkostemp"></a>
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<a name="index-mkostemps"></a>
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<a name="index-_005fmktemp_005fr"></a>
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<a name="index-_005fmkdtemp_005fr"></a>
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<a name="index-_005fmkstemp_005fr"></a>
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<a name="index-_005fmkstemps_005fr"></a>
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<a name="index-_005fmkostemp_005fr"></a>
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<a name="index-_005fmkostemps_005fr"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <stdlib.h>
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char *mktemp(char *<var>path</var>);
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char *mkdtemp(char *<var>path</var>);
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int mkstemp(char *<var>path</var>);
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int mkstemps(char *<var>path</var>, int <var>suffixlen</var>);
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int mkostemp(char *<var>path</var>, int <var>flags</var>);
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int mkostemps(char *<var>path</var>, int <var>suffixlen</var>, int <var>flags</var>);
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char *_mktemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
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char *_mkdtemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
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int *_mkstemp_r(struct _reent *<var>reent</var>, char *<var>path</var>);
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int *_mkstemps_r(struct _reent *<var>reent</var>, char *<var>path</var>, int <var>len</var>);
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int *_mkostemp_r(struct _reent *<var>reent</var>, char *<var>path</var>,
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int <var>flags</var>);
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int *_mkostemps_r(struct _reent *<var>reent</var>, char *<var>path</var>, int <var>len</var>,
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int <var>flags</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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<code>mktemp</code>, <code>mkstemp</code>, and <code>mkstemps</code> attempt to generate a file name
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that is not yet in use for any existing file. <code>mkstemp</code> and <code>mkstemps</code>
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create the file and open it for reading and writing; <code>mktemp</code> simply
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generates the file name (making <code>mktemp</code> a security risk). <code>mkostemp</code>
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and <code>mkostemps</code> allow the addition of other <code>open</code> flags, such
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as <code>O_CLOEXEC</code>, <code>O_APPEND</code>, or <code>O_SYNC</code>. On platforms with a
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separate text mode, <code>mkstemp</code> forces <code>O_BINARY</code>, while <code>mkostemp</code>
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allows the choice between <code>O_BINARY</code>, <code>O_TEXT</code>, or 0 for default.
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<code>mkdtemp</code> attempts to create a directory instead of a file, with a
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permissions mask of 0700.
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</p>
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<p>You supply a simple pattern for the generated file name, as the string
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at <var>path</var>. The pattern should be a valid filename (including path
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information if you wish) ending with at least six ‘<code>X</code>’
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characters. The generated filename will match the leading part of the
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name you supply, with the trailing ‘<code>X</code>’ characters replaced by some
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combination of digits and letters. With <code>mkstemps</code>, the ‘<code>X</code>’
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characters end <var>suffixlen</var> bytes before the end of the string.
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</p>
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<p>The alternate functions <code>_mktemp_r</code>, <code>_mkdtemp_r</code>, <code>_mkstemp_r</code>,
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<code>_mkostemp_r</code>, <code>_mkostemps_r</code>, and <code>_mkstemps_r</code> are reentrant
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versions. The extra argument <var>reent</var> is a pointer to a reentrancy
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structure.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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<code>mktemp</code> returns the pointer <var>path</var> to the modified string
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representing an unused filename, unless it could not generate one, or
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the pattern you provided is not suitable for a filename; in that case,
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it returns <code>NULL</code>. Be aware that there is an inherent race between
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generating the name and attempting to create a file by that name;
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you are advised to use <code>O_EXCL|O_CREAT</code>.
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</p>
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<p><code>mkdtemp</code> returns the pointer <var>path</var> to the modified string if the
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directory was created, otherwise it returns <code>NULL</code>.
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</p>
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<p><code>mkstemp</code>, <code>mkstemps</code>, <code>mkostemp</code>, and <code>mkostemps</code> return a file
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descriptor to the newly created file, unless it could not generate an
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unused filename, or the pattern you provided is not suitable for a
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filename; in that case, it returns <code>-1</code>.
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</p>
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<br>
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<p><strong>Notes</strong><br>
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Never use <code>mktemp</code>. The generated filenames are easy to guess and
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there’s a race between the test if the file exists and the creation
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of the file. In combination this makes <code>mktemp</code> prone to attacks
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and using it is a security risk. Whenever possible use <code>mkstemp</code>
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instead. It doesn’t suffer the race condition.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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ANSI C does not require either <code>mktemp</code> or <code>mkstemp</code>; the System
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V Interface Definition requires <code>mktemp</code> as of Issue 2. POSIX 2001
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requires <code>mkstemp</code>, and POSIX 2008 requires <code>mkdtemp</code> while
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deprecating <code>mktemp</code>. <code>mkstemps</code>, <code>mkostemp</code>, and <code>mkostemps</code>
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are not standardized.
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</p>
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<p>Supporting OS subroutines required: <code>getpid</code>, <code>mkdir</code>, <code>open</code>, <code>stat</code>.
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</p>
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<br>
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<hr>
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<div class="header">
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<p>
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Next: <a href="open_005fmemstream.html#open_005fmemstream" accesskey="n" rel="next">open_memstream</a>, Previous: <a href="getwchar.html#getwchar" accesskey="p" rel="prev">getwchar</a>, Up: <a href="Stdio.html#Stdio" accesskey="u" rel="up">Stdio</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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