os操作

os操作的简单例子

// os_mytest project main.go
package main

// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.ExampleChmod()

import (
    "fmt"
    "log"
    "os"
    "time"
)

func ExampleOpenFile() {
    f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0755)
    if err != nil {
        log.Fatal(err)
    }

    if err := f.Close(); err != nil {
        log.Fatal(err)
    }
}

func ExampleOpenFile_append() {
    // If the file doesn't exist, create it, or append to the file
    f, err := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
    if err != nil {
        log.Fatal(err)
    }
    if _, err := f.Write([]byte("appended some data\n")); err != nil {
        log.Fatal(err)
    }
    if err := f.Close(); err != nil {
        log.Fatal(err)
    }
}

func ExampleChmod() {
    if err := os.Chmod("notes.txt", 0644); err != nil {
        log.Fatal(err)
    }
}

func ExampleChtimes() {
    mtime := time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC)
    atime := time.Date(2007, time.March, 2, 4, 5, 6, 0, time.UTC)
    if err := os.Chtimes("notes.txt", atime, mtime); err != nil {
        log.Fatal(err)
    }
}

func ExampleFileMode() {
    fi, err := os.Lstat("notes.txt")
    if err != nil {
        log.Fatal(err)
    }

    switch mode := fi.Mode(); {
    case mode.IsRegular():
        fmt.Println("regular file")
    case mode.IsDir():
        fmt.Println("directory")
    case mode&os.ModeSymlink != 0:
        fmt.Println("symbolic link")
    case mode&os.ModeNamedPipe != 0:
        fmt.Println("named pipe")
    }
}

func ExampleIsNotExist() {
    filename := "a-nonexistent-file"
    if _, err := os.Stat(filename); os.IsNotExist(err) {
        fmt.Printf("file does not exist")
    }
    // Output:
    // file does not exist
}

func init() {
    os.Setenv("USER", "gopher")
    os.Setenv("HOME", "/usr/gopher")
    os.Unsetenv("GOPATH")
}

func ExampleExpandEnv() {
    fmt.Println(os.ExpandEnv("$USER lives in ${HOME}."))

    // Output:
    // gopher lives in /usr/gopher.
}

func ExampleLookupEnv() {
    show := func(key string) {
        val, ok := os.LookupEnv(key)
        if !ok {
            fmt.Printf("%s not set\n", key)
        } else {
            fmt.Printf("%s=%s\n", key, val)
        }
    }

    show("USER")
    show("GOPATH")

    // Output:
    // USER=gopher
    // GOPATH not set
}

func ExampleGetenv() {
    fmt.Printf("%s lives in %s.\n", os.Getenv("USER"), os.Getenv("HOME"))

    // Output:
    // gopher lives in /usr/gopher.
}

func ExampleUnsetenv() {
    os.Setenv("TMPDIR", "/my/tmp")
    defer os.Unsetenv("TMPDIR")
}

func main() {
    ExampleOpenFile()
    ExampleOpenFile_append()
    ExampleChmod()
    ExampleChtimes()
    ExampleFileMode()
    ExampleIsNotExist()
    fmt.Println()
    ExampleExpandEnv()
    ExampleLookupEnv()
    ExampleGetenv()
    ExampleUnsetenv()
}

结果
[root@hadoop1 os]# ./os_mytest 
regular file
file does not exist
gopher lives in /usr/gopher.
USER=gopher
GOPATH not set
gopher lives in /usr/gopher.
[root@hadoop1 os]#