libgo/go/os/example_test.go

   1 // Copyright 2016 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package os_test
   6
   7 import (
   8         "fmt"
   9         "log"
  10         "os"
  11         "time"
  12 )
  13
  14 func ExampleOpenFile() {
  15         f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0755)
  16         if err != nil {
  17                 log.Fatal(err)
  18         }
  19         if err := f.Close(); err != nil {
  20                 log.Fatal(err)
  21         }
  22 }
  23
  24 func ExampleChmod() {
  25         if err := os.Chmod("some-filename", 0644); err != nil {
  26                 log.Fatal(err)
  27         }
  28 }
  29
  30 func ExampleChtimes() {
  31         mtime := time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC)
  32         atime := time.Date(2007, time.March, 2, 4, 5, 6, 0, time.UTC)
  33         if err := os.Chtimes("some-filename", atime, mtime); err != nil {
  34                 log.Fatal(err)
  35         }
  36 }
  37
  38 func ExampleFileMode() {
  39         fi, err := os.Stat("some-filename")
  40         if err != nil {
  41                 log.Fatal(err)
  42         }
  43
  44         switch mode := fi.Mode(); {
  45         case mode.IsRegular():
  46                 fmt.Println("regular file")
  47         case mode.IsDir():
  48                 fmt.Println("directory")
  49         case mode&os.ModeSymlink != 0:
  50                 fmt.Println("symbolic link")
  51         case mode&os.ModeNamedPipe != 0:
  52                 fmt.Println("named pipe")
  53         }
  54 }
  55
  56 func ExampleIsNotExist() {
  57         filename := "a-nonexistent-file"
  58         if _, err := os.Stat(filename); os.IsNotExist(err) {
  59                 fmt.Printf("file does not exist")
  60         }
  61         // Output:
  62         // file does not exist
  63 }
  64
  65 func init() {
  66         os.Setenv("USER", "gopher")
  67         os.Setenv("HOME", "/usr/gopher")
  68         os.Unsetenv("GOPATH")
  69 }
  70
  71 func ExampleExpandEnv() {
  72         fmt.Println(os.ExpandEnv("$USER lives in ${HOME}."))
  73
  74         // Output:
  75         // gopher lives in /usr/gopher.
  76 }
  77
  78 func ExampleLookupEnv() {
  79         show := func(key string) {
  80                 val, ok := os.LookupEnv(key)
  81                 if !ok {
  82                         fmt.Printf("%s not set\n", key)
  83                 } else {
  84                         fmt.Printf("%s=%s\n", key, val)
  85                 }
  86         }
  87
  88         show("USER")
  89         show("GOPATH")
  90
  91         // Output:
  92         // USER=gopher
  93         // GOPATH not set
  94 }
  95
  96 func ExampleGetenv() {
  97         fmt.Printf("%s lives in %s.\n", os.Getenv("USER"), os.Getenv("HOME"))
  98
  99         // Output:
 100         // gopher lives in /usr/gopher.
 101 }
 102
 103 func ExampleUnsetenv() {
 104         os.Setenv("TMPDIR", "/my/tmp")
 105         defer os.Unsetenv("TMPDIR")
 106 }