1 // Copyright 2012 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 exec_test 6 7 import ( 8 "bytes" 9 "context" 10 "encoding/json" 11 "fmt" 12 "io" 13 "io/ioutil" 14 "log" 15 "os" 16 "os/exec" 17 "strings" 18 "time" 19 ) 20 21 func ExampleLookPath() { 22 path, err := exec.LookPath("fortune") 23 if err != nil { 24 log.Fatal("installing fortune is in your future") 25 } 26 fmt.Printf("fortune is available at %s\n", path) 27 } 28 29 func ExampleCommand() { 30 cmd := exec.Command("tr", "a-z", "A-Z") 31 cmd.Stdin = strings.NewReader("some input") 32 var out bytes.Buffer 33 cmd.Stdout = &out 34 err := cmd.Run() 35 if err != nil { 36 log.Fatal(err) 37 } 38 fmt.Printf("in all caps: %q\n", out.String()) 39 } 40 41 func ExampleCommand_environment() { 42 cmd := exec.Command("prog") 43 cmd.Env = append(os.Environ(), 44 "FOO=duplicate_value", // ignored 45 "FOO=actual_value", // this value is used 46 ) 47 if err := cmd.Run(); err != nil { 48 log.Fatal(err) 49 } 50 } 51 52 func ExampleCmd_Output() { 53 out, err := exec.Command("date").Output() 54 if err != nil { 55 log.Fatal(err) 56 } 57 fmt.Printf("The date is %s\n", out) 58 } 59 60 func ExampleCmd_Run() { 61 cmd := exec.Command("sleep", "1") 62 log.Printf("Running command and waiting for it to finish...") 63 err := cmd.Run() 64 log.Printf("Command finished with error: %v", err) 65 } 66 67 func ExampleCmd_Start() { 68 cmd := exec.Command("sleep", "5") 69 err := cmd.Start() 70 if err != nil { 71 log.Fatal(err) 72 } 73 log.Printf("Waiting for command to finish...") 74 err = cmd.Wait() 75 log.Printf("Command finished with error: %v", err) 76 } 77 78 func ExampleCmd_StdoutPipe() { 79 cmd := exec.Command("echo", "-n", `{"Name": "Bob", "Age": 32}`) 80 stdout, err := cmd.StdoutPipe() 81 if err != nil { 82 log.Fatal(err) 83 } 84 if err := cmd.Start(); err != nil { 85 log.Fatal(err) 86 } 87 var person struct { 88 Name string 89 Age int 90 } 91 if err := json.NewDecoder(stdout).Decode(&person); err != nil { 92 log.Fatal(err) 93 } 94 if err := cmd.Wait(); err != nil { 95 log.Fatal(err) 96 } 97 fmt.Printf("%s is %d years old\n", person.Name, person.Age) 98 } 99 100 func ExampleCmd_StdinPipe() { 101 cmd := exec.Command("cat") 102 stdin, err := cmd.StdinPipe() 103 if err != nil { 104 log.Fatal(err) 105 } 106 107 go func() { 108 defer stdin.Close() 109 io.WriteString(stdin, "values written to stdin are passed to cmd's standard input") 110 }() 111 112 out, err := cmd.CombinedOutput() 113 if err != nil { 114 log.Fatal(err) 115 } 116 117 fmt.Printf("%s\n", out) 118 } 119 120 func ExampleCmd_StderrPipe() { 121 cmd := exec.Command("sh", "-c", "echo stdout; echo 1>&2 stderr") 122 stderr, err := cmd.StderrPipe() 123 if err != nil { 124 log.Fatal(err) 125 } 126 127 if err := cmd.Start(); err != nil { 128 log.Fatal(err) 129 } 130 131 slurp, _ := ioutil.ReadAll(stderr) 132 fmt.Printf("%s\n", slurp) 133 134 if err := cmd.Wait(); err != nil { 135 log.Fatal(err) 136 } 137 } 138 139 func ExampleCmd_CombinedOutput() { 140 cmd := exec.Command("sh", "-c", "echo stdout; echo 1>&2 stderr") 141 stdoutStderr, err := cmd.CombinedOutput() 142 if err != nil { 143 log.Fatal(err) 144 } 145 fmt.Printf("%s\n", stdoutStderr) 146 } 147 148 func ExampleCommandContext() { 149 ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond) 150 defer cancel() 151 152 if err := exec.CommandContext(ctx, "sleep", "5").Run(); err != nil { 153 // This will fail after 100 milliseconds. The 5 second sleep 154 // will be interrupted. 155 } 156 } 157
