160 lines
6.3 KiB
HTML
160 lines
6.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>ctermid</title>
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<body bgcolor="white">
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<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
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<basefont size="3"> <a name="ctermid"></a> <a name="tag_03_102"></a><!-- ctermid -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_102_01"></a>NAME</h4>
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<blockquote>ctermid - generate a pathname for the controlling terminal</blockquote>
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<h4><a name="tag_03_102_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br>
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<br>
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char *ctermid(char *</tt><i>s</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_102_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>ctermid</i>() function shall generate a string that, when used as a pathname, refers to the current controlling terminal
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for the current process. If <i>ctermid</i>() returns a pathname, access to the file is not guaranteed.</p>
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<p>If the application uses any of the _POSIX_THREAD_SAFE_FUNCTIONS or _POSIX_THREADS functions, it shall ensure that the
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<i>ctermid</i>() function is called with a non-NULL parameter.</p>
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</blockquote>
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<h4><a name="tag_03_102_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>If <i>s</i> is a null pointer, the string shall be generated in an area that may be static (and therefore may be overwritten by
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each call), the address of which shall be returned. Otherwise, <i>s</i> is assumed to point to a character array of at least
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L_ctermid bytes; the string is placed in this array and the value of <i>s</i> shall be returned. The symbolic constant L_ctermid is
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defined in <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a>, and shall have a value greater than 0.</p>
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<p>The <i>ctermid</i>() function shall return an empty string if the pathname that would refer to the controlling terminal cannot
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be determined, or if the function is unsuccessful.</p>
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</blockquote>
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<h4><a name="tag_03_102_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_102_06"></a>EXAMPLES</h4>
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<blockquote>
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<h5><a name="tag_03_102_06_01"></a>Determining the Controlling Terminal for the Current Process</h5>
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<p>The following example returns a pointer to a string that identifies the controlling terminal for the current process. The
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pathname for the terminal is stored in the array pointed to by the <i>ptr</i> argument, which has a size of L_ctermid bytes, as
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indicated by the <i>term</i> argument.</p>
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<pre>
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<tt>#include <stdio.h>
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...
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char term[L_ctermid];
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char *ptr;
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<br>
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ptr = ctermid(term);
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_102_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The difference between <i>ctermid</i>() and <a href="../functions/ttyname.html"><i>ttyname</i>()</a> is that <a href=
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"../functions/ttyname.html"><i>ttyname</i>()</a> must be handed a file descriptor and return a path of the terminal associated with
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that file descriptor, while <i>ctermid</i>() returns a string (such as <tt>"/dev/tty"</tt> ) that refers to the current controlling
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terminal if used as a pathname.</p>
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</blockquote>
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<h4><a name="tag_03_102_08"></a>RATIONALE</h4>
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<blockquote>
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<p>L_ctermid must be defined appropriately for a given implementation and must be greater than zero so that array declarations
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using it are accepted by the compiler. The value includes the terminating null byte.</p>
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<p>Conforming applications that use threads cannot call <i>ctermid</i>() with NULL as the parameter if either
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_POSIX_THREAD_SAFE_FUNCTIONS or _POSIX_THREADS is defined. If <i>s</i> is not NULL, the <i>ctermid</i>() function generates a
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string that, when used as a pathname, refers to the current controlling terminal for the current process. If <i>s</i> is NULL, the
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return value of <i>ctermid</i>() is undefined.</p>
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<p>There is no additional burden on the programmer-changing to use a hypothetical thread-safe version of <i>ctermid</i>() along
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with allocating a buffer is more of a burden than merely allocating a buffer. Application code should not assume that the returned
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string is short, as some implementations have more than two pathname components before reaching a logical device name.</p>
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</blockquote>
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<h4><a name="tag_03_102_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_102_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="ttyname.html"><i>ttyname</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/stdio.h.html"><i><stdio.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_102_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
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</blockquote>
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<h4><a name="tag_03_102_12"></a>Issue 5</h4>
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<blockquote>
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<p>The DESCRIPTION is updated for alignment with the POSIX Threads Extension.</p>
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</blockquote>
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<h4><a name="tag_03_102_13"></a>Issue 6</h4>
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<blockquote>
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<p>The DESCRIPTION is updated to avoid use of the term "must" for application requirements.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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