Eli Bendersky
Mark McGranaghan
parent
f9050decb5
commit
8219122e44
@ -56,6 +56,7 @@ SHA1 Hashes
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Base64 Encoding
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Base64 Encoding
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Reading Files
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Reading Files
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Writing Files
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Writing Files
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Temporary Files and Directories
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Line Filters
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Line Filters
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File Paths
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File Paths
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Directories
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Directories
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@ -0,0 +1,65 @@
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// Throughout program execution, we often want to create
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// data that isn't needed after the program exits.
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// *Temporary files and directories* are useful for this
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// purpose since they don't pollute the file system over
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// time.
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package main
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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)
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func check(e error) {
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if e != nil {
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panic(e)
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}
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}
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func main() {
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// The easiest way to create a temporary file is by
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// calling `ioutil.TempFile`. It creates a file *and*
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// opens it for reading and writing. We provide `""`
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// as the first argument, so `ioutil.TempFile` will
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// create the file in the default location for our OS.
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f, err := ioutil.TempFile("", "sample")
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check(err)
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// Display the name of the temporary file. On
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// Unix-based OSes the directory will likely be `/tmp`.
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// The file name starts with the prefix given as the
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// second argument to `ioutil.TempFile` and the rest
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// is chosen automatically to ensure that concurrent
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// calls will always create different file names.
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fmt.Println("Temp file name:", f.Name())
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// Clean up the file after we're done. The OS is
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// likely to clean up temporary files by itself after
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// some time, but it's good practice to do this
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// explicitly.
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defer os.Remove(f.Name())
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// We can write some data to the file.
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_, err = f.Write([]byte{1, 2, 3, 4})
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check(err)
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// If we intend to write many temporary files, we may
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// prefer to create a temporary *directory*.
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// `ioutil.TempDir`'s arguments are the same as
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// `TempFile`'s, but it returns a directory *name*
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// rather than an open file.
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dname, err := ioutil.TempDir("", "sampledir")
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fmt.Println("Temp dir name:", dname)
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defer os.RemoveAll(dname)
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// Now we can synthesize temporary file names by
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// prefixing them with our temporary directory.
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fname := filepath.Join(dname, "file1")
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err = ioutil.WriteFile(fname, []byte{1, 2}, 0666)
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check(err)
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}
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@ -0,0 +1,2 @@
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5f7d0c43988d7dce235adb06ec02f4d2026b7f83
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pxE20wGTFjv
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@ -0,0 +1,4 @@
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# The exact names printed out will likely be different.
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$ go run temporary-files-and-directories.go
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Temp file name: /tmp/sample610887201
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Temp dir name: /tmp/sampledir898854668
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@ -139,6 +139,8 @@
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<li><a href="writing-files">Writing Files</a></li>
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<li><a href="writing-files">Writing Files</a></li>
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<li><a href="temporary-files-and-directories">Temporary Files and Directories</a></li>
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<li><a href="line-filters">Line Filters</a></li>
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<li><a href="line-filters">Line Filters</a></li>
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<li><a href="file-paths">File Paths</a></li>
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<li><a href="file-paths">File Paths</a></li>
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232
public/temporary-files-and-directories
Normal file
232
public/temporary-files-and-directories
Normal file
@ -0,0 +1,232 @@
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Temporary Files and Directories</title>
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<link rel=stylesheet href="site.css">
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</head>
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<body>
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<div class="example" id="temporary-files-and-directories">
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<h2><a href="./">Go by Example</a>: Temporary Files and Directories</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Throughout program execution, we often want to create
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data that isn’t needed after the program exits.
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<em>Temporary files and directories</em> are useful for this
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purpose since they don’t pollute the file system over
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time.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/pxE20wGTFjv">
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<img title="Run code" class="run" src="data:image/png;base64,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" />
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</a>
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"io/ioutil"</span>
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<span class="s">"os"</span>
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<span class="s">"path/filepath"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">check</span><span class="p">(</span><span class="nx">e</span> <span class="kt">error</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">if</span> <span class="nx">e</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="nb">panic</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The easiest way to create a temporary file is by
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calling <code>ioutil.TempFile</code>. It creates a file <em>and</em>
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opens it for reading and writing. We provide <code>""</code>
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as the first argument, so <code>ioutil.TempFile</code> will
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create the file in the default location for our OS.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">f</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">TempFile</span><span class="p">(</span><span class="s">""</span><span class="p">,</span> <span class="s">"sample"</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Display the name of the temporary file. On
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Unix-based OSes the directory will likely be <code>/tmp</code>.
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The file name starts with the prefix given as the
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second argument to <code>ioutil.TempFile</code> and the rest
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is chosen automatically to ensure that concurrent
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calls will always create different file names.</p>
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</td>
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<td class="code leading">
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<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">"Temp file name:"</span><span class="p">,</span> <span class="nx">f</span><span class="p">.</span><span class="nx">Name</span><span class="p">())</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Clean up the file after we’re done. The OS is
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likely to clean up temporary files by itself after
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some time, but it’s good practice to do this
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explicitly.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">defer</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Remove</span><span class="p">(</span><span class="nx">f</span><span class="p">.</span><span class="nx">Name</span><span class="p">())</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>We can write some data to the file.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <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="nx">Write</span><span class="p">([]</span><span class="kt">byte</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="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">})</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>If we intend to write many temporary files, we may
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prefer to create a temporary <em>directory</em>.
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<code>ioutil.TempDir</code>’s arguments are the same as
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<code>TempFile</code>’s, but it returns a directory <em>name</em>
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rather than an open file.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">dname</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">TempDir</span><span class="p">(</span><span class="s">""</span><span class="p">,</span> <span class="s">"sampledir"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"Temp dir name:"</span><span class="p">,</span> <span class="nx">dname</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">defer</span> <span class="nx">os</span><span class="p">.</span><span class="nx">RemoveAll</span><span class="p">(</span><span class="nx">dname</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Now we can synthesize temporary file names by
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prefixing them with our temporary directory.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">fname</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">Join</span><span class="p">(</span><span class="nx">dname</span><span class="p">,</span> <span class="s">"file1"</span><span class="p">)</span>
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<span class="nx">err</span> <span class="p">=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">WriteFile</span><span class="p">(</span><span class="nx">fname</span><span class="p">,</span> <span class="p">[]</span><span class="kt">byte</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="mo">0666</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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<p>The exact names printed out will likely be different.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run temporary-files-and-directories.go
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<span class="go">Temp file name: /tmp/sample610887201</span>
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<span class="go">Temp dir name: /tmp/sampledir898854668</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="line-filters">Line Filters</a>.
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</p>
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<p class="footer">
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||||||
|
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/temporary-files-and-directories">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
||||||
|
</p>
|
||||||
|
</div>
|
||||||
|
</body>
|
||||||
|
</html>
|
||||||
@ -266,7 +266,7 @@ we’ve just seen to the <code>stdin</code> and <code>stdout</code> streams.
|
|||||||
|
|
||||||
|
|
||||||
<p class="next">
|
<p class="next">
|
||||||
Next example: <a href="line-filters">Line Filters</a>.
|
Next example: <a href="temporary-files-and-directories">Temporary Files and Directories</a>.
|
||||||
</p>
|
</p>
|
||||||
|
|
||||||
<p class="footer">
|
<p class="footer">
|
||||||
|
|||||||
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Reference in New Issue
Block a user