285 lines
9.7 KiB
HTML
285 lines
9.7 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>connect</title>
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<body bgcolor="white">
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<basefont size="3"> <a name="connect"></a> <a name="tag_03_85"></a><!-- connect -->
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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_85_01"></a>NAME</h4>
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<blockquote>connect - connect a socket</blockquote>
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<h4><a name="tag_03_85_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/sys/socket.h.html">sys/socket.h</a>><br>
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<br>
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int connect(int</tt> <i>socket</i><tt>, const struct sockaddr *</tt><i>address</i><tt>,<br>
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socklen_t</tt> <i>address_len</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_85_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>connect</i>() function shall attempt to make a connection on a socket. The function takes the following arguments:</p>
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<dl compact>
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<dt><i>socket</i></dt>
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<dd>Specifies the file descriptor associated with the socket.</dd>
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<dt><i>address</i></dt>
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<dd>Points to a <b>sockaddr</b> structure containing the peer address. The length and format of the address depend on the address
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family of the socket.</dd>
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<dt><i>address_len</i></dt>
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<dd>Specifies the length of the <b>sockaddr</b> structure pointed to by the <i>address</i> argument.</dd>
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</dl>
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<p>If the socket has not already been bound to a local address, <i>connect</i>() shall bind it to an address which, unless the
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socket's address family is AF_UNIX, is an unused local address.</p>
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<p>If the initiating socket is not connection-mode, then <i>connect</i>() shall set the socket's peer address, and no connection is
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made. For SOCK_DGRAM sockets, the peer address identifies where all datagrams are sent on subsequent <a href=
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"../functions/send.html"><i>send</i>()</a> functions, and limits the remote sender for subsequent <a href=
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"../functions/recv.html"><i>recv</i>()</a> functions. If <i>address</i> is a null address for the protocol, the socket's peer
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address shall be reset.</p>
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<p>If the initiating socket is connection-mode, then <i>connect</i>() shall attempt to establish a connection to the address
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specified by the <i>address</i> argument. If the connection cannot be established immediately and O_NONBLOCK is not set for the
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file descriptor for the socket, <i>connect</i>() shall block for up to an unspecified timeout interval until the connection is
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established. If the timeout interval expires before the connection is established, <i>connect</i>() shall fail and the connection
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attempt shall be aborted. If <i>connect</i>() is interrupted by a signal that is caught while blocked waiting to establish a
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connection, <i>connect</i>() shall fail and set <i>errno</i> to [EINTR], but the connection request shall not be aborted, and the
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connection shall be established asynchronously.</p>
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<p>If the connection cannot be established immediately and O_NONBLOCK is set for the file descriptor for the socket,
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<i>connect</i>() shall fail and set <i>errno</i> to [EINPROGRESS], but the connection request shall not be aborted, and the
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connection shall be established asynchronously. Subsequent calls to <i>connect</i>() for the same socket, before the connection is
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established, shall fail and set <i>errno</i> to [EALREADY].</p>
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<p>When the connection has been established asynchronously, <a href="../functions/select.html"><i>select</i>()</a> and <a href=
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"../functions/poll.html"><i>poll</i>()</a> shall indicate that the file descriptor for the socket is ready for writing.</p>
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<p>The socket in use may require the process to have appropriate privileges to use the <i>connect</i>() function.</p>
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</blockquote>
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<h4><a name="tag_03_85_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>connect</i>() shall return 0; otherwise, -1 shall be returned and <i>errno</i> set to indicate
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the error.</p>
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</blockquote>
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<h4><a name="tag_03_85_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>connect</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EADDRNOTAVAIL]</dt>
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<dd>
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The specified address is not available from the local machine.</dd>
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<dt>[EAFNOSUPPORT]</dt>
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<dd>
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The specified address is not a valid address for the address family of the specified socket.</dd>
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<dt>[EALREADY]</dt>
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<dd>A connection request is already in progress for the specified socket.</dd>
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<dt>[EBADF]</dt>
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<dd>The <i>socket</i> argument is not a valid file descriptor.</dd>
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<dt>[ECONNREFUSED]</dt>
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<dd>
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The target address was not listening for connections or refused the connection request.</dd>
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<dt>[EINPROGRESS]</dt>
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<dd>O_NONBLOCK is set for the file descriptor for the socket and the connection cannot be immediately established; the connection
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shall be established asynchronously.</dd>
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<dt>[EINTR]</dt>
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<dd>The attempt to establish a connection was interrupted by delivery of a signal that was caught; the connection shall be
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established asynchronously.</dd>
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<dt>[EISCONN]</dt>
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<dd>The specified socket is connection-mode and is already connected.</dd>
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<dt>[ENETUNREACH]</dt>
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<dd>
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No route to the network is present.</dd>
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<dt>[ENOTSOCK]</dt>
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<dd>The <i>socket</i> argument does not refer to a socket.</dd>
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<dt>[EPROTOTYPE]</dt>
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<dd>The specified address has a different type than the socket bound to the specified peer address.</dd>
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<dt>[ETIMEDOUT]</dt>
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<dd>The attempt to connect timed out before a connection was made.</dd>
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</dl>
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<p>If the address family of the socket is AF_UNIX, then <i>connect</i>() shall fail if:</p>
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<dl compact>
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<dt>[EIO]</dt>
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<dd>An I/O error occurred while reading from or writing to the file system.</dd>
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<dt>[ELOOP]</dt>
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<dd>A loop exists in symbolic links encountered during resolution of the pathname in <i>address</i>.</dd>
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<dt>[ENAMETOOLONG]</dt>
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<dd>
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A component of a pathname exceeded {NAME_MAX} characters, or an entire pathname exceeded {PATH_MAX} characters.</dd>
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<dt>[ENOENT]</dt>
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<dd>A component of the pathname does not name an existing file or the pathname is an empty string.</dd>
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<dt>[ENOTDIR]</dt>
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<dd>A component of the path prefix of the pathname in <i>address</i> is not a directory.</dd>
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</dl>
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<p>The <i>connect</i>() function may fail if:</p>
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<dl compact>
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<dt>[EACCES]</dt>
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<dd>Search permission is denied for a component of the path prefix; or write access to the named socket is denied.</dd>
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<dt>[EADDRINUSE]</dt>
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<dd>Attempt to establish a connection that uses addresses that are already in use.</dd>
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<dt>[ECONNRESET]</dt>
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<dd>Remote host reset the connection request.</dd>
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<dt>[EHOSTUNREACH]</dt>
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<dd>
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The destination host cannot be reached (probably because the host is down or a remote router cannot reach it).</dd>
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<dt>[EINVAL]</dt>
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<dd>The <i>address_len</i> argument is not a valid length for the address family; or invalid address family in the <b>sockaddr</b>
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structure.</dd>
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<dt>[ELOOP]</dt>
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<dd>More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the pathname in <i>address</i>.</dd>
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<dt>[ENAMETOOLONG]</dt>
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<dd>
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Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.</dd>
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<dt>[ENETDOWN]</dt>
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<dd>The local network interface used to reach the destination is down.</dd>
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<dt>[ENOBUFS]</dt>
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<dd>No buffer space is available.</dd>
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<dt>[EOPNOTSUPP]</dt>
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<dd>The socket is listening and cannot be connected.</dd>
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</dl>
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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_85_06"></a>EXAMPLES</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_85_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>If <i>connect</i>() fails, the state of the socket is unspecified. Conforming applications should close the file descriptor and
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create a new socket before attempting to reconnect.</p>
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</blockquote>
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<h4><a name="tag_03_85_08"></a>RATIONALE</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_85_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_85_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="accept.html"><i>accept</i>()</a> , <a href="bind.html"><i>bind</i>()</a> , <a href="close.html"><i>close</i>()</a> , <a
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href="getsockname.html"><i>getsockname</i>()</a> , <a href="poll.html"><i>poll</i>()</a> , <a href=
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"select.html"><i>select</i>()</a> , <a href="send.html"><i>send</i>()</a> , <a href="shutdown.html"><i>shutdown</i>()</a> , <a
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href="socket.html"><i>socket</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_85_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from the XNS, Issue 5.2 specification.</p>
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<p>The wording of the mandatory [ELOOP] error condition is updated, and a second optional [ELOOP] error condition is added.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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<center><font size="2"><!--footer start-->
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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