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| <section id="multiple-nsh-sessions"> |
| <h1>Multiple NSH Sessions<a class="headerlink" href="#multiple-nsh-sessions" title="Permalink to this heading"></a></h1> |
| <div class="admonition warning"> |
| <p class="admonition-title">Warning</p> |
| <p>Migrated from: |
| <a class="reference external" href="https://cwiki.apache.org/confluence/display/NUTTX/Multiple+NSH+Sessions">https://cwiki.apache.org/confluence/display/NUTTX/Multiple+NSH+Sessions</a></p> |
| </div> |
| <dl class="simple"> |
| <dt>Q:</dt><dd><p>I would like to run the NuttShell on multiple serial ports, but haven’t |
| figured it out yet; can you point me in the right direction?</p> |
| </dd> |
| <dt>A:</dt><dd><p>Easy. Don’t use <code class="docutils literal notranslate"><span class="pre">apps/examples/nsh_main.c</span></code>. Create your own main function |
| something like this (with all error handling omitted for simplicity). By the |
| way, this is all standard POSIX stuff that you can get detailed information |
| about by just Googling <cite>dup2</cite> or maybe <cite>I/O redirection</cite>:</p> |
| </dd> |
| </dl> |
| <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="kt">int</span><span class="w"> </span><span class="nf">my_main</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">argc</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="o">**</span><span class="n">argv</span><span class="p">)</span> |
| <span class="p">{</span> |
| <span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="n">tty</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">];</span> |
| <span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">fd</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">open</span><span class="p">(</span><span class="n">tty</span><span class="p">,</span><span class="w"> </span><span class="n">O_RDWR</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="p">)</span><span class="n">dup2</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="p">)</span><span class="n">dup2</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="p">)</span><span class="n">dup2</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">close</span><span class="p">(</span><span class="n">fd</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">...</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <p>And the rest is just like the original <code class="docutils literal notranslate"><span class="pre">nsh_main()</span></code> function (in fact, |
| perhaps the existing <code class="docutils literal notranslate"><span class="pre">nsh_main()</span></code> function could be optionally extended to |
| accept a console device string?). Then you can start a new NSH session on any |
| TTY like:</p> |
| <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nsh> mynsh /dev/ttyS2 & |
| </pre></div> |
| </div> |
| <p>This should cause a new NSH session to appear on <code class="docutils literal notranslate"><span class="pre">ttyS2</span></code>. That session will |
| persist until you do the following from the new session:</p> |
| <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nsh> exit |
| </pre></div> |
| </div> |
| <p>Then the new session, i.e., <code class="docutils literal notranslate"><span class="pre">my_main()</span></code> will exit.</p> |
| <p>If you were to do something like:</p> |
| <div class="highlight-none notranslate"><div class="highlight"><pre><span></span>nsh> mynsh /dev/console |
| </pre></div> |
| </div> |
| <p>then you would get nested NSH sessions on the same console. The first session |
| would halt and wait for the second session to take control of the console until |
| it exits. Then the first session will take over console again.</p> |
| <section id="nutty"> |
| <h2>NuTTY<a class="headerlink" href="#nutty" title="Permalink to this heading"></a></h2> |
| <p>In a previous discussion, there was talk about implementing the moral equivalent |
| of getty in NuttX (of course, it would be called “nutty”). A simple |
| implementation of nutty would work like this:</p> |
| <ol class="arabic simple"> |
| <li><p>It would wait on <code class="docutils literal notranslate"><span class="pre">poll()</span></code> on every (configured) serial device.</p></li> |
| <li><p>Whenever it is awakened, it would start something like <code class="docutils literal notranslate"><span class="pre">my_main()</span></code> above |
| on the active serial port.</p></li> |
| <li><p>NSH has an option to enable logins, but it would be better to remove the |
| existing login information from NSH and centralize it in nutty.</p></li> |
| </ol> |
| <p>That way, you could connect to any TTY, hit enter, and you would get an NSH |
| session. Hmm… it is not clear how nutty would get the TTY back after the |
| session is closed. That part may require some additional thought.</p> |
| </section> |
| <section id="other-ideas"> |
| <h2>Other Ideas<a class="headerlink" href="#other-ideas" title="Permalink to this heading"></a></h2> |
| <p>There are other ways to get multiple NSH sessions:</p> |
| <ul class="simple"> |
| <li><p>Telnet already supports multiple sessions.</p></li> |
| <li><p>Implement the existing NSH as an ELF program, then you can get multiple NSH |
| sessions with <code class="docutils literal notranslate"><span class="pre">posix_spawn</span></code> by simply redirecting I/O.</p></li> |
| <li><p>Using the tiny NxWM window managers, multiple NSH windows are already |
| supported.</p></li> |
| </ul> |
| </section> |
| </section> |
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