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reading-files
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example မြန်မာဘာသာ: Reading Files</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'base64-encoding';
}
if (e.key == "ArrowRight") {
window.location.href = 'writing-files';
}
}
</script>
<body>
<div class="example" id="reading-files">
<h2><a href="./">Go by Example မြန်မာဘာသာ</a>: Reading Files</h2>
<table>
<tr>
<td class="docs">
<p>ဖိုင်များဖတ်ခြင်းနှင့် ရေးခြင်းသည် Go ပရိုဂရမ်များအတွက် အခြေခံလိုအပ်ချက်ဖြစ်သည်။
ပထမဦးစွာ ဖိုင်ဖတ်ခြင်းဥပမာအချို့ကို ကြည့်ကြမည်။</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://go.dev/play/p/Nzr4LHSAgZO"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"bufio"</span>
<span class="s">"fmt"</span>
<span class="s">"io"</span>
<span class="s">"os"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဖိုင်ဖတ်ခြင်းသည် အများအားဖြင့် အမှားစစ်ဆေးမှုလိုအပ်သည်။
ဤ helper function သည် အောက်ပါ အမှားစစ်ဆေးမှုများကို ရိုးရှင်းစေမည်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">check</span><span class="p">(</span><span class="nx">e</span> <span class="kt">error</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">e</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">e</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>အခြေခံကျဆုံး ဖိုင်ဖတ်ခြင်းလုပ်ငန်းမှာ ဖိုင်တစ်ခုလုံး၏အကြောင်းအရာကို
မှတ်ဉာဏ်ထဲ (memory) သို့ တစ်ခါတည်းဖတ်ယူခြင်းဖြစ်သည်။</p>
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">dat</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">ReadFile</span><span class="p">(</span><span class="s">"/tmp/dat"</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Print</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">dat</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဖိုင်၏မည်သည့်အပိုင်းကို မည်သို့ဖတ်မည်ကို ပိုမိုထိန်းချုပ်လိုကြောင်း သင်တွေ့ရလိမ့်မည်။
ဤလုပ်ငန်းများအတွက် ‘Open’ ဖြင့် ဖိုင်ကိုဖွင့်ပြီး ‘os.File’ တန်ဖိုးကို ရယူပါ။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">f</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">Open</span><span class="p">(</span><span class="s">"/tmp/dat"</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဖိုင်၏အစမှ byte အချို့ကိုဖတ်ပါ။
5 byte အထိဖတ်ခွင့်ပြုသော်လည်း အမှန်တကယ်ဖတ်မိသည့် အရေအတွက်ကိုလည်း မှတ်သားပါ။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">b1</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span>
<span class="nx">n1</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Read</span><span class="p">(</span><span class="nx">b1</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%d bytes: %s\n"</span><span class="p">,</span> <span class="nx">n1</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">b1</span><span class="p">[:</span><span class="nx">n1</span><span class="p">]))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>သင်သည် ဖိုင်ထဲတွင် သိထားသောနေရာသို့ ‘Seek’ လုပ်နိုင်ပြီး ထိုနေရာမှ ‘Read’ လုပ်နိုင်သည်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">o2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">b2</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="nx">n2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Read</span><span class="p">(</span><span class="nx">b2</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%d bytes @ %d: "</span><span class="p">,</span> <span class="nx">n2</span><span class="p">,</span> <span class="nx">o2</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%v\n"</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">b2</span><span class="p">[:</span><span class="nx">n2</span><span class="p">]))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>‘io’ package သည် ဖိုင်ဖတ်ခြင်းအတွက် အသုံးဝင်သော function များပေးသည်။
ဥပမာအားဖြင့် အထက်ပါကဲ့သို့ ဖတ်ခြင်းများကို ‘ReadAtLeast’ ဖြင့် ပိုမိုခိုင်မာစွာ အကောင်အထည်ဖော်နိုင်သည်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">o3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">b3</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="nx">n3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">io</span><span class="p">.</span><span class="nf">ReadAtLeast</span><span class="p">(</span><span class="nx">f</span><span class="p">,</span> <span class="nx">b3</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"%d bytes @ %d: %s\n"</span><span class="p">,</span> <span class="nx">n3</span><span class="p">,</span> <span class="nx">o3</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">b3</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ပါဝင်ပြီးသား rewind မရှိသော်လည်း ‘Seek(0, 0)’ သည် ဤလုပ်ငန်းကို ဆောင်ရွက်နိုင်သည်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Seek</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>‘bufio’ package သည် buffered reader ကို အကောင်အထည်ဖော်သည်။
၎င်းသည် အသေးစား ဖတ်ခြင်းများစွာအတွက် ထိရောက်မှုရှိခြင်းနှင့်
၎င်းပေးသော ထပ်ဆောင်းဖတ်ခြင်းနည်းလမ်းများကြောင့် အသုံးဝင်နိုင်သည်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">r4</span> <span class="o">:=</span> <span class="nx">bufio</span><span class="p">.</span><span class="nf">NewReader</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span>
<span class="nx">b4</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">r4</span><span class="p">.</span><span class="nf">Peek</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"5 bytes: %s\n"</span><span class="p">,</span> <span class="nb">string</span><span class="p">(</span><span class="nx">b4</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>အသုံးပြုပြီးပါက ဖိုင်ကိုပိတ်ပါ (ပုံမှန်အားဖြင့် ၎င်းကို ‘Open’ လုပ်ပြီးချက်ချင်း
‘defer’ ဖြင့် သတ်မှတ်လေ့ရှိသည်)။</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">f</span><span class="p">.</span><span class="nf">Close</span><span class="p">()</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="gp">$</span> echo "hello" > /tmp/dat
<span class="gp">$</span> echo "go" >> /tmp/dat
<span class="gp">$</span> go run reading-files.go
<span class="go">hello
</span><span class="go">go
</span><span class="go">5 bytes: hello
</span><span class="go">2 bytes @ 6: go
</span><span class="go">2 bytes @ 6: go
</span><span class="go">5 bytes: hello</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>နောက်တစ်ဆင့်အနေဖြင့်
ဖိုင်ရေးသားခြင်းကို လေ့လာကြမည်။</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
နောက်ဥပမာ: <a href="writing-files">Writing Files</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> နှင့် <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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