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| <h4 class="subsection">16.5.2 Details of Local Namespace</h4> |
| |
| <p><a name="index-sys_002fsocket_002eh-1673"></a>To create a socket in the local namespace, use the constant |
| <code>PF_LOCAL</code> as the <var>namespace</var> argument to <code>socket</code> or |
| <code>socketpair</code>. This constant is defined in <samp><span class="file">sys/socket.h</span></samp>. |
| |
| <!-- sys/socket.h --> |
| <!-- POSIX --> |
| <div class="defun"> |
| — Macro: int <b>PF_LOCAL</b><var><a name="index-PF_005fLOCAL-1674"></a></var><br> |
| <blockquote><p>This designates the local namespace, in which socket addresses are local |
| names, and its associated family of protocols. <code>PF_Local</code> is the |
| macro used by Posix.1g. |
| </p></blockquote></div> |
| |
| <!-- sys/socket.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Macro: int <b>PF_UNIX</b><var><a name="index-PF_005fUNIX-1675"></a></var><br> |
| <blockquote><p>This is a synonym for <code>PF_LOCAL</code>, for compatibility's sake. |
| </p></blockquote></div> |
| |
| <!-- sys/socket.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Macro: int <b>PF_FILE</b><var><a name="index-PF_005fFILE-1676"></a></var><br> |
| <blockquote><p>This is a synonym for <code>PF_LOCAL</code>, for compatibility's sake. |
| </p></blockquote></div> |
| |
| <p>The structure for specifying socket names in the local namespace is |
| defined in the header file <samp><span class="file">sys/un.h</span></samp>: |
| <a name="index-sys_002fun_002eh-1677"></a> |
| <!-- sys/un.h --> |
| <!-- BSD --> |
| |
| <div class="defun"> |
| — Data Type: <b>struct sockaddr_un</b><var><a name="index-struct-sockaddr_005fun-1678"></a></var><br> |
| <blockquote><p>This structure is used to specify local namespace socket addresses. It has |
| the following members: |
| |
| <dl> |
| <dt><code>short int sun_family</code><dd>This identifies the address family or format of the socket address. |
| You should store the value <code>AF_LOCAL</code> to designate the local |
| namespace. See <a href="Socket-Addresses.html#Socket-Addresses">Socket Addresses</a>. |
| |
| <br><dt><code>char sun_path[108]</code><dd>This is the file name to use. |
| |
| <p><strong>Incomplete:</strong> Why is 108 a magic number? RMS suggests making |
| this a zero-length array and tweaking the following example to use |
| <code>alloca</code> to allocate an appropriate amount of storage based on |
| the length of the filename. |
| </dl> |
| </p></blockquote></div> |
| |
| <p>You should compute the <var>length</var> parameter for a socket address in |
| the local namespace as the sum of the size of the <code>sun_family</code> |
| component and the string length (<em>not</em> the allocation size!) of |
| the file name string. This can be done using the macro <code>SUN_LEN</code>: |
| |
| <!-- sys/un.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Macro: int <b>SUN_LEN</b> (<em>struct sockaddr_un *</em><var> ptr</var>)<var><a name="index-SUN_005fLEN-1679"></a></var><br> |
| <blockquote><p>The macro computes the length of socket address in the local namespace. |
| </p></blockquote></div> |
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