146 lines
2.9 KiB
Go
146 lines
2.9 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package os_test
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import (
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"fmt"
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"log"
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"os"
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"time"
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)
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func ExampleOpenFile() {
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f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0755)
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if err != nil {
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log.Fatal(err)
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}
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if err := f.Close(); err != nil {
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log.Fatal(err)
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}
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}
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func ExampleOpenFile_append() {
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// If the file doesn't exist, create it, or append to the file
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f, err := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
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if err != nil {
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log.Fatal(err)
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}
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if _, err := f.Write([]byte("appended some data\n")); err != nil {
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f.Close() // ignore error; Write error takes precedence
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log.Fatal(err)
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}
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if err := f.Close(); err != nil {
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log.Fatal(err)
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}
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}
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func ExampleChmod() {
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if err := os.Chmod("some-filename", 0644); err != nil {
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log.Fatal(err)
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}
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}
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func ExampleChtimes() {
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mtime := time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC)
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atime := time.Date(2007, time.March, 2, 4, 5, 6, 0, time.UTC)
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if err := os.Chtimes("some-filename", atime, mtime); err != nil {
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log.Fatal(err)
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}
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}
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func ExampleFileMode() {
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fi, err := os.Lstat("some-filename")
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if err != nil {
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log.Fatal(err)
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}
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fmt.Printf("permissions: %#o\n", fi.Mode().Perm()) // 0400, 0777, etc.
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switch mode := fi.Mode(); {
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case mode.IsRegular():
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fmt.Println("regular file")
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case mode.IsDir():
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fmt.Println("directory")
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case mode&os.ModeSymlink != 0:
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fmt.Println("symbolic link")
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case mode&os.ModeNamedPipe != 0:
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fmt.Println("named pipe")
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}
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}
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func ExampleIsNotExist() {
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filename := "a-nonexistent-file"
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if _, err := os.Stat(filename); os.IsNotExist(err) {
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fmt.Println("file does not exist")
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}
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// Output:
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// file does not exist
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}
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func ExampleExpand() {
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mapper := func(placeholderName string) string {
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switch placeholderName {
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case "DAY_PART":
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return "morning"
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case "NAME":
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return "Gopher"
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}
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return ""
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}
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fmt.Println(os.Expand("Good ${DAY_PART}, $NAME!", mapper))
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// Output:
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// Good morning, Gopher!
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}
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func ExampleExpandEnv() {
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os.Setenv("NAME", "gopher")
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os.Setenv("BURROW", "/usr/gopher")
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fmt.Println(os.ExpandEnv("$NAME lives in ${BURROW}."))
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// Output:
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// gopher lives in /usr/gopher.
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}
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func ExampleLookupEnv() {
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show := func(key string) {
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val, ok := os.LookupEnv(key)
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if !ok {
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fmt.Printf("%s not set\n", key)
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} else {
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fmt.Printf("%s=%s\n", key, val)
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}
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}
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os.Setenv("SOME_KEY", "value")
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os.Setenv("EMPTY_KEY", "")
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show("SOME_KEY")
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show("EMPTY_KEY")
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show("MISSING_KEY")
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// Output:
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// SOME_KEY=value
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// EMPTY_KEY=
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// MISSING_KEY not set
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}
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func ExampleGetenv() {
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os.Setenv("NAME", "gopher")
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os.Setenv("BURROW", "/usr/gopher")
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fmt.Printf("%s lives in %s.\n", os.Getenv("NAME"), os.Getenv("BURROW"))
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// Output:
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// gopher lives in /usr/gopher.
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}
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func ExampleUnsetenv() {
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os.Setenv("TMPDIR", "/my/tmp")
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defer os.Unsetenv("TMPDIR")
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}
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