yeray/gobyexample
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
gobyexample/public/string-formatting
Oleg Butuzov 646c8b39da bugfix (mmcgrana/gobyexample#294) sha1 sum calculator 
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.
2019-10-22 14:27:02 +03:00

465 lines
19 KiB
Plaintext
Generated
Raw Blame History

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: String Formatting</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'string-functions';
}
if (e.key == "ArrowRight") {
window.location.href = 'regular-expressions';
}
}
</script>
<body>
<div class="example" id="string-formatting">
<h2><a href="./">Go by Example</a>: String Formatting</h2>
<table>
<tr>
<td class="docs">
<p>Go offers excellent support for string formatting in
the <code>printf</code> tradition. Here are some examples of
common string formatting tasks.</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/L6BkGeaN_p4"><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">&quot;fmt&quot;</span>
<span class="s">&quot;os&quot;</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">type</span> <span class="nx">point</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">x</span><span class="p">,</span> <span class="nx">y</span> <span class="kt">int</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>Go offers several printing &ldquo;verbs&rdquo; designed to
format general Go values. For example, this prints
an instance of our <code>point</code> struct.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">p</span> <span class="o">:=</span> <span class="nx">point</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%v\n&quot;</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>If the value is a struct, the <code>%+v</code> variant will
include the struct&rsquo;s field names.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%+v\n&quot;</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>The <code>%#v</code> variant prints a Go syntax representation
of the value, i.e. the source code snippet that
would produce that value.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%#v\n&quot;</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To print the type of a value, use <code>%T</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%T\n&quot;</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Formatting booleans is straight-forward.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%t\n&quot;</span><span class="p">,</span> <span class="kc">true</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>There are many options for formatting integers.
Use <code>%d</code> for standard, base-10 formatting.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%d\n&quot;</span><span class="p">,</span> <span class="mi">123</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>This prints a binary representation.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%b\n&quot;</span><span class="p">,</span> <span class="mi">14</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>This prints the character corresponding to the
given integer.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%c\n&quot;</span><span class="p">,</span> <span class="mi">33</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p><code>%x</code> provides hex encoding.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%x\n&quot;</span><span class="p">,</span> <span class="mi">456</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>There are also several formatting options for
floats. For basic decimal formatting use <code>%f</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%f\n&quot;</span><span class="p">,</span> <span class="mf">78.9</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p><code>%e</code> and <code>%E</code> format the float in (slightly
different versions of) scientific notation.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%e\n&quot;</span><span class="p">,</span> <span class="mf">123400000.0</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%E\n&quot;</span><span class="p">,</span> <span class="mf">123400000.0</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>For basic string printing use <code>%s</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%s\n&quot;</span><span class="p">,</span> <span class="s">&quot;\&quot;string\&quot;&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To double-quote strings as in Go source, use <code>%q</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%q\n&quot;</span><span class="p">,</span> <span class="s">&quot;\&quot;string\&quot;&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>As with integers seen earlier, <code>%x</code> renders
the string in base-16, with two output characters
per byte of input.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%x\n&quot;</span><span class="p">,</span> <span class="s">&quot;hex this&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To print a representation of a pointer, use <code>%p</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%p\n&quot;</span><span class="p">,</span> <span class="o">&amp;</span><span class="nx">p</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>When formatting numbers you will often want to
control the width and precision of the resulting
figure. To specify the width of an integer, use a
number after the <code>%</code> in the verb. By default the
result will be right-justified and padded with
spaces.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;|%6d|%6d|\n&quot;</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">345</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>You can also specify the width of printed floats,
though usually you&rsquo;ll also want to restrict the
decimal precision at the same time with the
width.precision syntax.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;|%6.2f|%6.2f|\n&quot;</span><span class="p">,</span> <span class="mf">1.2</span><span class="p">,</span> <span class="mf">3.45</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To left-justify, use the <code>-</code> flag.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;|%-6.2f|%-6.2f|\n&quot;</span><span class="p">,</span> <span class="mf">1.2</span><span class="p">,</span> <span class="mf">3.45</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>You may also want to control width when formatting
strings, especially to ensure that they align in
table-like output. For basic right-justified width.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;|%6s|%6s|\n&quot;</span><span class="p">,</span> <span class="s">&quot;foo&quot;</span><span class="p">,</span> <span class="s">&quot;b&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To left-justify use the <code>-</code> flag as with numbers.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;|%-6s|%-6s|\n&quot;</span><span class="p">,</span> <span class="s">&quot;foo&quot;</span><span class="p">,</span> <span class="s">&quot;b&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>So far we&rsquo;ve seen <code>Printf</code>, which prints the
formatted string to <code>os.Stdout</code>. <code>Sprintf</code> formats
and returns a string without printing it anywhere.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">s</span> <span class="o">:=</span> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Sprintf</span><span class="p">(</span><span class="s">&quot;a %s&quot;</span><span class="p">,</span> <span class="s">&quot;string&quot;</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="nx">s</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>You can format+print to <code>io.Writers</code> other than
<code>os.Stdout</code> using <code>Fprintf</code>.</p>
</td>
<td class="code">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Fprintf</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stderr</span><span class="p">,</span> <span class="s">&quot;an %s\n&quot;</span><span class="p">,</span> <span class="s">&quot;error&quot;</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<div class="highlight"><pre><span class="gp">$</span> go run string-formatting.go
<span class="go">{1 2}</span>
<span class="go">{x:1 y:2}</span>
<span class="go">main.point{x:1, y:2}</span>
<span class="go">main.point</span>
<span class="go">true</span>
<span class="go">123</span>
<span class="go">1110</span>
<span class="go">!</span>
<span class="go">1c8</span>
<span class="go">78.900000</span>
<span class="go">1.234000e+08</span>
<span class="go">1.234000E+08</span>
<span class="go">&quot;string&quot;</span>
<span class="go">&quot;\&quot;string\&quot;&quot;</span>
<span class="go">6865782074686973</span>
<span class="go">0x42135100</span>
<span class="go">| 12| 345|</span>
<span class="go">| 1.20| 3.45|</span>
<span class="go">|1.20 |3.45 |</span>
<span class="go">| foo| b|</span>
<span class="go">|foo |b |</span>
<span class="go">a string</span>
<span class="go">an error</span>
</pre></div>
</td>
</tr>
</table>
<p class="next">
Next example: <a href="regular-expressions">Regular Expressions</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/string-formatting">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 \"os\"\u000A)\u000A');codeLines.push('type point struct {\u000A x, y int\u000A}\u000A');codeLines.push('func main() {\u000A');codeLines.push(' p := point{1, 2}\u000A fmt.Printf(\"%v\\n\", p)\u000A');codeLines.push(' fmt.Printf(\"%+v\\n\", p)\u000A');codeLines.push(' fmt.Printf(\"%#v\\n\", p)\u000A');codeLines.push(' fmt.Printf(\"%T\\n\", p)\u000A');codeLines.push(' fmt.Printf(\"%t\\n\", true)\u000A');codeLines.push(' fmt.Printf(\"%d\\n\", 123)\u000A');codeLines.push(' fmt.Printf(\"%b\\n\", 14)\u000A');codeLines.push(' fmt.Printf(\"%c\\n\", 33)\u000A');codeLines.push(' fmt.Printf(\"%x\\n\", 456)\u000A');codeLines.push(' fmt.Printf(\"%f\\n\", 78.9)\u000A');codeLines.push(' fmt.Printf(\"%e\\n\", 123400000.0)\u000A fmt.Printf(\"%E\\n\", 123400000.0)\u000A');codeLines.push(' fmt.Printf(\"%s\\n\", \"\\\"string\\\"\")\u000A');codeLines.push(' fmt.Printf(\"%q\\n\", \"\\\"string\\\"\")\u000A');codeLines.push(' fmt.Printf(\"%x\\n\", \"hex this\")\u000A');codeLines.push(' fmt.Printf(\"%p\\n\", &p)\u000A');codeLines.push(' fmt.Printf(\"|%6d|%6d|\\n\", 12, 345)\u000A');codeLines.push(' fmt.Printf(\"|%6.2f|%6.2f|\\n\", 1.2, 3.45)\u000A');codeLines.push(' fmt.Printf(\"|%-6.2f|%-6.2f|\\n\", 1.2, 3.45)\u000A');codeLines.push(' fmt.Printf(\"|%6s|%6s|\\n\", \"foo\", \"b\")\u000A');codeLines.push(' fmt.Printf(\"|%-6s|%-6s|\\n\", \"foo\", \"b\")\u000A');codeLines.push(' s := fmt.Sprintf(\"a %s\", \"string\")\u000A fmt.Println(s)\u000A');codeLines.push(' fmt.Fprintf(os.Stderr, \"an %s\\n\", \"error\")\u000A}\u000A');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink