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      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 }
    107