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<div class="refentry">
<a name="cockpit-spawn"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>cockpit.js: Spawning Processes</h2>
<p>cockpit.js: Spawning Processes — Spawning processes or scripts</p>
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<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<p>This is the API for spawning a process and receiving its output, as well
as exit codes.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-spawn"></a><h2>cockpit.spawn()</h2>
<pre class="programlisting">
process = cockpit.spawn(args, [options])
</pre>
<p>Spawns a process on the system.</p>
<p>The <code class="code">args</code> should be an array starting with the executable and
containing all the arguments to pass on the command line. If <code class="code">args</code>
is a string then it is interpreted as an executable name. The optional
<code class="code">options</code> argument is a javascript plain object and can contain
any of the following fields:
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><code class="code">"binary"</code></span></p></td>
<td><p>If set to <code class="code">true</code> then handle the input and output
of the process as arrays of binary bytes.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"directory"</code></span></p></td>
<td><p>The directory to spawn the process in.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"err"</code></span></p></td>
<td><p>Controls where the standard error is sent. By default it is logged
to the journal. If set to <code class="code">"out"</code> it is included in with the
output data. If set to <code class="code">"ignore"</code> then the error output is discarded.
If set to <code class="code">"message"</code>, then it will be returned as the error message.
When the <code class="code">"pty"</code> field is set, this field has no effect.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"host"</code></span></p></td>
<td><p>The remote host to spawn the process on. If an alternate user or port is
required it can be specified as <code class="code">"user@myhost:port"</code>. If no host is
specified then the correct one will be automatically selected based on the page
calling this function.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"environ"</code></span></p></td>
<td><p>An optional array that contains strings to be used as
additional environment variables for the new process. These are
<code class="code">"NAME=VALUE"</code> strings.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"pty"</code></span></p></td>
<td><p>Launch the process in its own PTY terminal, and send/receive
terminal input and output.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"batch"</code></span></p></td>
<td><p>Batch data coming from the process in blocks of at least this
size. This is not a guarantee. After a short timeout the data will be sent
even if the data doesn't match the batch size. Defaults to zero.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"latency"</code></span></p></td>
<td><p> The timeout for flushing any cached data in milliseconds.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">"superuser"</code></span></p></td>
<td>
<p>Set to <code class="code">"require"</code> to spawn the process as root instead of
the logged in user. If the currently logged in user is not permitted to become root
(eg: via <code class="code">pkexec</code>) then the <code class="code">client</code> will immediately be
<a class="link" href="cockpit-dbus.html#cockpit-dbus-onclose" title="client.onclose">closed</a> with a <code class="code">"access-denied"</code>
problem code.</p>
<p>Set to <code class="code">"try"</code> to try to run the process as root, but if that fails,
fall back to an unprivileged process.</p>
</td>
</tr>
</tbody>
</table></div>
<p>The spawned process is a
<a class="ulink" href="https://www.promisejs.org/" target="_top">promise</a>
that will complete if the process exits successfully, or fail if there's a problem.
Some additional methods besides the standard promise methods are documented
below.</p>
<p>The standard output of the process is made available via the spawned process
object. Any non-UTF8 output from the process will be coerced into textual form.
It is highly recommended that only textual output be produced by the command.
The standard error is logged to the journal.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-script"></a><h2>cockpit.script()</h2>
<pre class="programlisting">
process = cockpit.script(script, [args], [options])
</pre>
<p>Run a shell script on the system.</p>
<p>This function <a class="link" href="cockpit-spawn.html#cockpit-spawn-spawn" title="cockpit.spawn()">spawns</a> a Bourne shell script
process. The full text of the <code class="code">/bin/sh</code> shell script should be passed in as
the first argument. The <code class="code">args</code> can be an array of arguments, not including
the executable, which are passed to the script as <code class="code">$1</code>, <code class="code">$2</code> and
so on. Shebang options are not used or respected.</p>
<p>The <code class="code">options</code> is an optional javascript plain object and can include
any of the fields listed for the
<a class="link" href="cockpit-spawn.html#cockpit-spawn-spawn" title="cockpit.spawn()"><code class="code">cockpit.spawn()</code></a> function.</p>
<p>The spawned process is a
<a class="ulink" href="https://www.promisejs.org/" target="_top">promise</a>
that will complete if the script exits successfully, or fail if there's a problem.
Some additional methods besides the standard promise methods are documented
below.</p>
<p>The standard output of the process is made available via the spawned process
object. Any non-UTF8 output from the process will be coerced into textual form.
It is highly recommended that only textual output be produced by the command.
The standard error is logged to the journal by default.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-done"></a><h2>process.done()</h2>
<pre class="programlisting">
process.done(function(data[, message]) { ... })
</pre>
<p>This is a standard
<a class="ulink" href="https://www.promisejs.org/" target="_top">promise</a>
method. It sets up a handler to be called when the process finishes successfully.</p>
<p>The <code class="code">data</code> argument contains the standard output of the process.
If it a string, unless the process was opened in binary mode, in which case the
<code class="code">data</code> is an array of bytes. If a
<code class="code"><a class="link" href="cockpit-spawn.html#cockpit-spawn-stream" title="process.stream()">process.stream()</a></code>
handler is set up, then any standard output data consumed by the handler will not
be included in the <code class="code">data</code> argument.</p>
<p>If the process was spawned with the <code class="code">"err"</code> option set to
<code class="code">"message"</code> then the second argument will contain the standard error
output of the process.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-fail"></a><h2>process.fail()</h2>
<pre class="programlisting">
process.fail(function(exception[, data]) { ... })
</pre>
<p>This is a standard
<a class="ulink" href="http://api.jquery.com/category/deferred-object/" target="_top">jQuery promise</a> method.
It sets up a handler to be called when the process fails, terminates or exits.</p>
<p>The <code class="code">exception</code> object passed to the handler can have the
following fields:</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><code class="code">message</code></span></p></td>
<td><p>A message describing the exception. If the process was spawned with
the <code class="code">"err"</code> option set to <code class="code">"message"</code> then the second argument
will contain the standard error output of the process.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">problem</code></span></p></td>
<td><p>A <a class="link" href="cockpit-error.html#cockpit-problems" title="Problem Codes">problem code</a> string when
a problem occurred starting or communicating with the process. This is <code class="code">null</code>
if the process exited or was terminated.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">exit_status</code></span></p></td>
<td><p>The numeric exit status of the process. This is <code class="code">null</code> if
the process did not exit.</p></td>
</tr>
<tr>
<td><p><span class="term"><code class="code">exit_signal</code></span></p></td>
<td><p>A string representing a unix signal that caused the process to terminate.
This is <code class="code">null</code> if the process did not terminate because of a signal.</p></td>
</tr>
</tbody>
</table></div>
<p>If the process actually ran and produced output before failing, it will be available in
the <code class="code">data</code> argument. Otherwise this argument will be <code class="code">undefined</code>.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-always"></a><h2>process.always()</h2>
<pre class="programlisting">
process.always(function() { ... })
</pre>
<p>This is a standard
<a class="ulink" href="http://api.jquery.com/category/deferred-object/" target="_top">jQuery promise</a> method.
It sets up a handler to be called when the process completes, whether it exits successfully,
fails, terminates, or exits with a failure.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-stream"></a><h2>process.stream()</h2>
<pre class="programlisting">
process.stream(function(data) { ... })
</pre>
<p>This sets up a handler to be called when the process has standard output. The
handler will be called multiple times. The handler will be called regardless of
whether the process ends up exiting successfully or not.</p>
<p>Only one handler may be registered at a time. Registering an additional handler
replaces the previous one. The handler receives either string <code class="code">data</code> or
an array of binary bytes as its argument. A stream handler may return a number, which
indicates the number of characters or bytes consumed from <code class="code">data</code>. Any data
not consumed will be included again the next time the handler is called.</p>
<p>If a <code class="code">process.stream()</code> handler is set up, then the
<code class="code"><a class="link" href="cockpit-spawn.html#cockpit-spawn-done" title="process.done()">process.done()</a></code> handlers will
only get any remaining data not consumed by the stream handler.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-input"></a><h2>process.input()</h2>
<pre class="programlisting">
process.input(data, [stream])
</pre>
<p>This method writes <code class="code">data</code> to the standard input of the process.
If <code class="code">data</code> is <code class="code">null</code> or <code class="code">undefined</code> it is not sent.
The <code class="code">data</code> should be a string or an array of bytes if the process was
opened in binary mode.</p>
<p>If <code class="code">stream</code> is set to <code class="code">true</code> then this function may be
called again with further input. Otherwise the standard input of the process
is closed.</p>
</div>
<div class="refsection">
<a name="cockpit-spawn-close"></a><h2>process.close()</h2>
<pre class="programlisting">
process.close([problem])
</pre>
<p>Close the process by closing its standard input and output. If <code class="code">problem</code> is
specified it should be a standard
<a class="link" href="cockpit-error.html#cockpit-problems" title="Problem Codes">problem code</a> string. In this case the
process will be terminated with a signal.</p>
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