646c8b39da
This bugfix implements correct way to calculate source sha1 hash, before it will changed, by propagation of unchanged sources. This commit will also include regenerated static files and *.hash files.
267 lines
12 KiB
Plaintext
Generated
267 lines
12 KiB
Plaintext
Generated
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta charset="utf-8">
|
|
<title>Go by Example: Spawning Processes</title>
|
|
<link rel=stylesheet href="site.css">
|
|
</head>
|
|
<script>
|
|
onkeydown = (e) => {
|
|
|
|
if (e.key == "ArrowLeft") {
|
|
window.location.href = 'http-servers';
|
|
}
|
|
|
|
|
|
if (e.key == "ArrowRight") {
|
|
window.location.href = 'execing-processes';
|
|
}
|
|
|
|
}
|
|
</script>
|
|
<body>
|
|
<div class="example" id="spawning-processes">
|
|
<h2><a href="./">Go by Example</a>: Spawning Processes</h2>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Sometimes our Go programs need to spawn other, non-Go
|
|
processes. For example, the syntax highlighting on this
|
|
site is <a href="https://github.com/mmcgrana/gobyexample/blob/master/tools/generate.go">implemented</a>
|
|
by spawning a <a href="http://pygments.org/"><code>pygmentize</code></a>
|
|
process from a Go program. Let’s look at a few examples
|
|
of spawning processes from Go.</p>
|
|
|
|
</td>
|
|
<td class="code empty leading">
|
|
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
<a href="http://play.golang.org/p/jUpRr-RcUKf"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
|
|
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
|
|
<span class="s">"fmt"</span>
|
|
<span class="s">"io/ioutil"</span>
|
|
<span class="s">"os/exec"</span>
|
|
<span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>We’ll start with a simple command that takes no
|
|
arguments or input and just prints something to
|
|
stdout. The <code>exec.Command</code> helper creates an object
|
|
to represent this external process.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">dateCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"date"</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p><code>.Output</code> is another helper that handles the common
|
|
case of running a command, waiting for it to finish,
|
|
and collecting its output. If there were no errors,
|
|
<code>dateOut</code> will hold bytes with the date info.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">dateOut</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">dateCmd</span><span class="p">.</span><span class="nx">Output</span><span class="p">()</span>
|
|
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
|
|
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> date"</span><span class="p">)</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">dateOut</span><span class="p">))</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Next we’ll look at a slightly more involved case
|
|
where we pipe data to the external process on its
|
|
<code>stdin</code> and collect the results from its <code>stdout</code>.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">grepCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"grep"</span><span class="p">,</span> <span class="s">"hello"</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Here we explicitly grab input/output pipes, start
|
|
the process, write some input to it, read the
|
|
resulting output, and finally wait for the process
|
|
to exit.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">grepIn</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">grepCmd</span><span class="p">.</span><span class="nx">StdinPipe</span><span class="p">()</span>
|
|
<span class="nx">grepOut</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">grepCmd</span><span class="p">.</span><span class="nx">StdoutPipe</span><span class="p">()</span>
|
|
<span class="nx">grepCmd</span><span class="p">.</span><span class="nx">Start</span><span class="p">()</span>
|
|
<span class="nx">grepIn</span><span class="p">.</span><span class="nx">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="s">"hello grep\ngoodbye grep"</span><span class="p">))</span>
|
|
<span class="nx">grepIn</span><span class="p">.</span><span class="nx">Close</span><span class="p">()</span>
|
|
<span class="nx">grepBytes</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">ReadAll</span><span class="p">(</span><span class="nx">grepOut</span><span class="p">)</span>
|
|
<span class="nx">grepCmd</span><span class="p">.</span><span class="nx">Wait</span><span class="p">()</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>We ommited error checks in the above example, but
|
|
you could use the usual <code>if err != nil</code> pattern for
|
|
all of them. We also only collect the <code>StdoutPipe</code>
|
|
results, but you could collect the <code>StderrPipe</code> in
|
|
exactly the same way.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> grep hello"</span><span class="p">)</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">grepBytes</span><span class="p">))</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Note that when spawning commands we need to
|
|
provide an explicitly delineated command and
|
|
argument array, vs. being able to just pass in one
|
|
command-line string. If you want to spawn a full
|
|
command with a string, you can use <code>bash</code>’s <code>-c</code>
|
|
option:</p>
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre> <span class="nx">lsCmd</span> <span class="o">:=</span> <span class="nx">exec</span><span class="p">.</span><span class="nx">Command</span><span class="p">(</span><span class="s">"bash"</span><span class="p">,</span> <span class="s">"-c"</span><span class="p">,</span> <span class="s">"ls -a -l -h"</span><span class="p">)</span>
|
|
<span class="nx">lsOut</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">lsCmd</span><span class="p">.</span><span class="nx">Output</span><span class="p">()</span>
|
|
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
|
|
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"> ls -a -l -h"</span><span class="p">)</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">lsOut</span><span class="p">))</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>The spawned programs return output that is the same
|
|
as if we had run them directly from the command-line.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="gp">$</span> go run spawning-processes.go
|
|
<span class="gp">></span> date
|
|
<span class="go">Wed Oct 10 09:53:11 PDT 2012</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="gp">></span> grep hello
|
|
<span class="go">hello grep</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre><span class="gp">></span> ls -a -l -h
|
|
<span class="go">drwxr-xr-x 4 mark 136B Oct 3 16:29 .</span>
|
|
<span class="go">drwxr-xr-x 91 mark 3.0K Oct 3 12:50 ..</span>
|
|
<span class="go">-rw-r--r-- 1 mark 1.3K Oct 3 16:28 spawning-processes.go</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
|
|
<p class="next">
|
|
Next example: <a href="execing-processes">Exec'ing Processes</a>.
|
|
</p>
|
|
|
|
<p class="footer">
|
|
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/spawning-processes">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
|
</p>
|
|
</div>
|
|
<script>
|
|
var codeLines = [];
|
|
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"io/ioutil\"\u000A \"os/exec\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' dateCmd := exec.Command(\"date\")\u000A');codeLines.push(' dateOut, err := dateCmd.Output()\u000A if err != nil {\u000A panic(err)\u000A }\u000A fmt.Println(\"\x3E date\")\u000A fmt.Println(string(dateOut))\u000A');codeLines.push(' grepCmd := exec.Command(\"grep\", \"hello\")\u000A');codeLines.push(' grepIn, _ := grepCmd.StdinPipe()\u000A grepOut, _ := grepCmd.StdoutPipe()\u000A grepCmd.Start()\u000A grepIn.Write([]byte(\"hello grep\\ngoodbye grep\"))\u000A grepIn.Close()\u000A grepBytes, _ := ioutil.ReadAll(grepOut)\u000A grepCmd.Wait()\u000A');codeLines.push(' fmt.Println(\"\x3E grep hello\")\u000A fmt.Println(string(grepBytes))\u000A');codeLines.push(' lsCmd := exec.Command(\"bash\", \"-c\", \"ls -a -l -h\")\u000A lsOut, err := lsCmd.Output()\u000A if err != nil {\u000A panic(err)\u000A }\u000A fmt.Println(\"\x3E ls -a -l -h\")\u000A fmt.Println(string(lsOut))\u000A}\u000A');codeLines.push('');codeLines.push('');codeLines.push('');
|
|
</script>
|
|
<script src="site.js" async></script>
|
|
</body>
|
|
</html>
|