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https://github.com/golang/go
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443 lines
12 KiB
HTML
<!-- Getting Started -->
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<h2 id="introduction">Introduction</h2>
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<p>Go is an open source project, distributed under a
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<a href="/LICENSE">BSD-style license</a>.
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This document explains how to check out the sources,
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build them on your own machine, and run them.
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</p>
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<div class="detail">
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<p>
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There are two distinct ways to experiment with Go.
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This document focuses on the <code>gc</code> Go
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compiler and tools (<code>6g</code>, <code>8g</code> etc.).
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For information on how to use <code>gccgo</code>, a more traditional
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compiler using the GCC back end, see
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<a href="gccgo_install.html">Setting up and using gccgo</a>.
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</p>
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<p>
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The Go compilers support three instruction sets.
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There are important differences in the quality of the compilers for the different
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architectures.
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</p>
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<dl>
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<dt>
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<code>amd64</code> (a.k.a. <code>x86-64</code>); <code>6g,6l,6c,6a</code>
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</dt>
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<dd>
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The most mature implementation. The compiler has an effective optimizer
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(registerizer) and generates good code (although <code>gccgo</code>
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can do noticeably better sometimes).
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</dd>
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<dt>
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<code>386</code> (a.k.a. <code>x86</code> or <code>x86-32</code>); <code>8g,8l,8c,8a</code>
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</dt>
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<dd>
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Comparable to the <code>amd64</code> port.
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</dd>
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<dt>
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<code>arm</code> (a.k.a. <code>ARM</code>); <code>5g,5l,5c,5a</code>
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</dt>
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<dd>
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Incomplete.
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It only supports Linux binaries, the optimizer is not enabled,
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and floating point is performed entirely in software.
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However, all tests pass.
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Work on the optimizer and use of the VFP hardware
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floating point unit is underway.
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Tested against a Nexus One.
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</dd>
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</dl>
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<p>
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Except for things like low-level operating system interface code, the runtime
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support is the same in all ports and includes a mark-and-sweep garbage collector
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(a fancier one is in the works), efficient array and string slicing,
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support for segmented stacks, and a strong goroutine implementation.
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</p>
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<p>
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The compilers can target the FreeBSD, Linux, Native Client,
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and OS X (a.k.a. Darwin) operating systems.
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(A port to Microsoft Windows is in progress but incomplete. See the
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<a href="http://code.google.com/p/go/wiki/WindowsPort">Windows Port</a>
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page for details.)
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The full set of supported combinations is listed in the discussion of
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<a href="#environment">environment variables</a> below.
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</p>
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</div>
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<h2 id="ctools">Install C tools, if needed</h2>
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<p>The Go tool chain is written in C.
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To build it, you need these programs installed:
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<ul>
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<li>GCC,
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<li>the standard C libraries,
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<li>the parser generator Bison,
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<li><tt>make</tt>,
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<li><tt>awk</tt>, and
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<li>the text editor <tt>ed</tt>.
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</ul>
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</p>
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<p>On OS X, they can be
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installed as part of
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<a href="http://developer.apple.com/TOOLS/Xcode/">Xcode</a>.
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</p>
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<p>On Ubuntu/Debian, use <code>sudo apt-get install bison ed gawk gcc libc6-dev make</code>.
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</p>
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<h2 id="mercurial">Install Mercurial, if needed</h2>
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<p>
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To perform the next step you must have Mercurial installed. (Check that you have an <code>hg</code> command.) This suffices to install Mercurial on most systems:
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</p>
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<pre>
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sudo easy_install mercurial
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</pre>
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(On Ubuntu/Debian, you might try <code>apt-get install python-setuptools
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python-dev build-essential</code> first. The Mercurial in your distribution's
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package repository will most likely be old and broken.)
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</p>
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<p>
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If that fails, try installing manually from the <a href="http://mercurial.selenic.com/wiki/Download">Mercurial Download</a> page.</p>
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</p>
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<h2 id="fetch">Fetch the repository</h2>
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<p>
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<p>Go will install to a directory named <code>go</code>.
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Change to the directory that will be its parent
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and make sure the <code>go</code> directory does not exist.
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Then check out the repository:</p>
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<pre>
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$ hg clone -r release https://go.googlecode.com/hg/ go
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</pre>
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<h2 id="install">Install Go</h2>
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<p>
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To build the Go distribution, run
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</p>
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<pre>
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$ cd go/src
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$ ./all.bash
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</pre>
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<p>
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If all goes well, it will finish by printing output like:
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</p>
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<pre>
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--- cd ../test
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N known bugs; 0 unexpected bugs
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---
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Installed Go for linux/amd64 in /home/you/go.
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Installed commands in /home/you/go/bin.
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*** You need to add /home/you/go/bin to your $PATH. ***
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The compiler is 6g.
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</pre>
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<p>
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where <var>N</var> is a number that varies from release to release
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and the details on the last few lines will reflect the operating system,
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architecture, and root directory used during the install.
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</p>
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<div class="detail">
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<p>For more information about ways to control the build,
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see the discussion of <a href="#environment">environment variables</a> below.</p>
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</div>
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<h2 id="writing">Writing programs</h2>
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<p>
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Given a file <code>file.go</code>, compile it using
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</p>
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<pre>
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$ 6g file.go
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</pre>
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<p>
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<code>6g</code> is the Go compiler for <code>amd64</code>; it will write the output
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in <code>file.6</code>. The ‘<code>6</code>’ identifies
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files for the <code>amd64</code> architecture.
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The identifier letters for <code>386</code> and <code>arm</code>
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are ‘<code>8</code>’ and ‘<code>5</code>’.
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That is, if you were compiling for <code>386</code>, you would use
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<code>8g</code> and the output would be named <code>file.8</code>.
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</p>
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<p>
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To link the file, use
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</p>
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<pre>
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$ 6l file.6
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</pre>
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<p>
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and to run it
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</p>
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<pre>
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$ ./6.out
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</pre>
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<p>A complete example:
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</p>
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<pre>
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$ cat >hello.go <<EOF
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package main
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import "fmt"
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func main() {
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fmt.Printf("hello, world\n")
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}
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EOF
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$ 6g hello.go
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$ 6l hello.6
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$ ./6.out
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hello, world
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$
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</pre>
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<p>
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There is no need to list <code>hello.6</code>'s package dependencies
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(in this case, package <code>fmt</code>) on the <code>6l</code>
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command line.
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The linker learns about them by reading <code>hello.6</code>.
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</p>
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<div class="detail">
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<p>
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To build more complicated programs, you will probably
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want to use a
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<code>Makefile</code>.
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There are examples in places like
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<code>go/src/cmd/godoc/Makefile</code>
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and <code>go/src/pkg/*/Makefile</code>.
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The
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<a href="contribute.html">document</a>
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about contributing to the Go project
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gives more detail about
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the process of building and testing Go programs.
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</p>
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</div>
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<h2 id="next">What's next</h2>
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<p>
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Start by reading the <a href="go_tutorial.html">Go Tutorial</a>.
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</p>
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<p>
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Build a web application by following the <a href="codelab/wiki/">Wiki
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Codelab</a>.
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</p>
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<p>
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Read <a href="effective_go.html">Effective Go</a> to learn about writing
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idiomatic Go code.
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</p>
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<p>
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For the full story, consult Go's extensive
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<a href="docs.html">documentation</a>.
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</p>
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<h2 id="releases">Keeping up with releases</h2>
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<p>New releases are announced on the <a href="http://groups.google.com/group/golang-nuts">Go Nuts</a> mailing list.
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To update an existing tree to the latest release, you can run:
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</p>
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<pre>
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$ cd go/src
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$ hg pull
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$ hg update release
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$ ./all.bash
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</pre>
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<h2 id="community">Community resources</h2>
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<p>
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For real-time help, there may be users or developers on
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<code>#go-nuts</code> on the <a href="http://freenode.net/">Freenode</a> IRC server.
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</p>
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<p>
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The official mailing list for discussion of the Go language is
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<a href="http://groups.google.com/group/golang-nuts">Go Nuts</a>.
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</p>
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<p>
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Bugs can be reported using the <a href="http://code.google.com/p/go/issues/list">Go issue tracker</a>.
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</p>
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<p>
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For those who wish to keep up with development,
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there is another mailing list, <a href="http://groups.google.com/group/golang-checkins">golang-checkins</a>,
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that receives a message summarizing each checkin to the Go repository.
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</p>
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<h2 id="environment">Environment variables</h2>
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<p>
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The Go compilation environment can be customized by environment variables.
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None are required by the build, but you may wish to set them
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to override the defaults.
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</p>
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<dl>
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<dt>
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<code>$GOROOT</code>
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</dt>
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<dd>
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The root of the Go tree, often <code>$HOME/go</code>.
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This defaults to the parent of the directory where <code>all.bash</code> is run.
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If you choose not to set <code>$GOROOT</code>, you must
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run <code>gomake</code> instead of <code>make</code> or <code>gmake</code>
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when developing Go programs using the conventional makefiles.
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</dd>
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<dt>
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<code>$GOROOT_FINAL</code>
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</dt>
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<dd>
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The value assumed by installed binaries and scripts when
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<code>$GOROOT</code> is not set.
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It defaults to the value used for <code>$GOROOT</code>.
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If you want to build the Go tree in one location
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but move it elsewhere after the build, set
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<code>$GOROOT_FINAL</code> to the eventual location.
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</dd>
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<dt>
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<code>$GOOS</code> and <code>$GOARCH</code>
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</dt>
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<dd>
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The name of the target operating system and compilation architecture.
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These default to the values of <code>$GOHOSTOS</code> and
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<code>$GOHOSTARCH</code> respectively (described below).
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<p>
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Choices for <code>$GOOS</code> are <code>linux</code>,
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<code>freebsd</code>,
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<code>darwin</code> (Mac OS X 10.5 or 10.6),
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and <code>nacl</code> (Native Client, an incomplete port).
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Choices for <code>$GOARCH</code> are <code>amd64</code> (64-bit x86, the most mature port),
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<code>386</code> (32-bit x86), and
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<code>arm</code> (32-bit ARM, an incomplete port).
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The valid combinations of <code>$GOOS</code> and <code>$GOARCH</code> are:
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<table cellpadding="0">
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<tr>
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<th width="50"><th align="left" width="100"><code>$GOOS</code></th> <th align="left" width="100"><code>$GOARCH</code></th> <th align="left"></th>
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</tr>
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<tr>
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<td></td><td><code>darwin</code></td> <td><code>386</code></td>
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</tr>
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<tr>
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<td></td><td><code>darwin</code></td> <td><code>amd64</code></td>
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</tr>
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<tr>
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<td></td><td><code>freebsd</code></td> <td><code>386</code></td>
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</tr>
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<tr>
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<td></td><td><code>freebsd</code></td> <td><code>amd64</code></td>
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</tr>
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<tr>
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<td></td><td><code>linux</code></td> <td><code>386</code></td>
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</tr>
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<tr>
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<td></td><td><code>linux</code></td> <td><code>amd64</code></td>
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</tr>
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<tr>
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<td></td><td><code>linux</code></td> <td><code>arm</code></td> <td><i>incomplete</i></td>
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</tr>
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<tr>
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<td></td><td><code>nacl</code></td> <td><code>386</code></td>
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</tr>
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<tr>
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<td></td><td><code>windows</code></td> <td><code>386</code></td> <td><i>incomplete</i></td>
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</tr>
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</table>
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</dd>
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<dt>
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<code>$GOHOSTOS</code> and <code>$GOHOSTARCH</code>
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</dt>
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<dd>
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The name of the host operating system and compilation architecture.
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These default to the local system's operating system and
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architecture.
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<p>
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Valid choices are the same as for <code>$GOOS</code> and
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<code>$GOARCH</code>, listed above.
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The specified values must be compatible with the local system.
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For example, you should not set <code>$GOHOSTARCH</code> to
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<code>arm</code> on an x86 system.
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</dd>
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<dt>
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<code>$GOBIN</code>
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</dt>
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<dd>
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The location where binaries will be installed.
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The default is <code>$GOROOT/bin</code>.
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After installing, you will want to arrange to add this
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directory to your <code>$PATH</code>, so you can use the tools.
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</dd>
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<dt>
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<code>$GOARM</code> (arm, default=6)
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</dt>
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<dd>
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The ARM architecture version the runtime libraries should target.
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ARMv6 cores have more efficient synchronization primitives. Setting
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<code>$GOARM</code> to 5 will compile the runtime libraries using
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just SWP instructions that work on older architectures as well.
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Running v6 code on an older core will cause an illegal instruction trap.
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</dd>
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</dl>
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<p>
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Note that <code>$GOARCH</code> and <code>$GOOS</code> identify the
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<em>target</em> environment, not the environment you are running on.
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In effect, you are always cross-compiling.
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By architecture, we mean the kind of binaries
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that the target environment can run:
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an x86-64 system running a 32-bit-only operating system
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must set <code>GOARCH</code> to <code>386</code>,
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not <code>amd64</code>.
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</p>
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<p>
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If you choose to override the defaults,
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set these variables in your shell profile (<code>$HOME/.bashrc</code>,
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<code>$HOME/.profile</code>, or equivalent). The settings might look
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something like this:
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</p>
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<pre>
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export GOROOT=$HOME/go
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export GOARCH=386
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export GOOS=linux
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</pre>
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