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 ExampleOpenFile_append() {
  25         // If the file doesn't exist, create it, or append to the file
  26         f, err := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
  27         if err != nil {
  28                 log.Fatal(err)
  29         }
  30         if _, err := f.Write([]byte("appended some data\n")); err != nil {
  31                 log.Fatal(err)
  32         }
  33         if err := f.Close(); err != nil {
  34                 log.Fatal(err)
  35         }
  36 }
  37
  38 func ExampleChmod() {
  39         if err := os.Chmod("some-filename", 0644); err != nil {
  40                 log.Fatal(err)
  41         }
  42 }
  43
  44 func ExampleChtimes() {
  45         mtime := time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC)
  46         atime := time.Date(2007, time.March, 2, 4, 5, 6, 0, time.UTC)
  47         if err := os.Chtimes("some-filename", atime, mtime); err != nil {
  48                 log.Fatal(err)
  49         }
  50 }
  51
  52 func ExampleFileMode() {
  53         fi, err := os.Lstat("some-filename")
  54         if err != nil {
  55                 log.Fatal(err)
  56         }
  57
  58         switch mode := fi.Mode(); {
  59         case mode.IsRegular():
  60                 fmt.Println("regular file")
  61         case mode.IsDir():
  62                 fmt.Println("directory")
  63         case mode&os.ModeSymlink != 0:
  64                 fmt.Println("symbolic link")
  65         case mode&os.ModeNamedPipe != 0:
  66                 fmt.Println("named pipe")
  67         }
  68 }
  69
  70 func ExampleIsNotExist() {
  71         filename := "a-nonexistent-file"
  72         if _, err := os.Stat(filename); os.IsNotExist(err) {
  73                 fmt.Printf("file does not exist")
  74         }
  75         // Output:
  76         // file does not exist
  77 }
  78
  79 func init() {
  80         os.Setenv("USER", "gopher")
  81         os.Setenv("HOME", "/usr/gopher")
  82         os.Unsetenv("GOPATH")
  83 }
  84
  85 func ExampleExpandEnv() {
  86         fmt.Println(os.ExpandEnv("$USER lives in ${HOME}."))
  87
  88         // Output:
  89         // gopher lives in /usr/gopher.
  90 }
  91
  92 func ExampleLookupEnv() {
  93         show := func(key string) {
  94                 val, ok := os.LookupEnv(key)
  95                 if !ok {
  96                         fmt.Printf("%s not set\n", key)
  97                 } else {
  98                         fmt.Printf("%s=%s\n", key, val)
  99                 }
 100         }
 101
 102         show("USER")
 103         show("GOPATH")
 104
 105         // Output:
 106         // USER=gopher
 107         // GOPATH not set
 108 }
 109
 110 func ExampleGetenv() {
 111         fmt.Printf("%s lives in %s.\n", os.Getenv("USER"), os.Getenv("HOME"))
 112
 113         // Output:
 114         // gopher lives in /usr/gopher.
 115 }
 116
 117 func ExampleUnsetenv() {
 118         os.Setenv("TMPDIR", "/my/tmp")
 119         defer os.Unsetenv("TMPDIR")
 120 }