『Golang』—— 标准库之 os

Posted 2020-09-09 纯原创，零转载

Golang 的 os 库基本承袭 Unix 下 C 语言的用法

path 库：

func Base(path string) string    //取文件名，不含目录部分
func Dir(path string) string    //取路径中的目录名部分，不含文件名
func Join(elem ...string) string    //拼接字段，中间自动添加 ‘/’

os 库：

  1 ackage main
  2 
  3 import "os"
  4 import "os/exec"
  5 
  6 import "time"
  7 import "fmt"
  8 import "log"
  9 import "errors"
 10 
 11 //    const (// {{{
 12 //        O_RDONLY int = syscall.O_RDONLY // open the file read-only.
 13 //        O_WRONLY int = syscall.O_WRONLY // open the file write-only.
 14 //        O_RDWR   int = syscall.O_RDWR   // open the file read-write.
 15 //        O_APPEND int = syscall.O_APPEND // append data to the file when writing.
 16 //        O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
 17 //        O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist
 18 //        O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
 19 //        O_TRUNC  int = syscall.O_TRUNC  // if possible, truncate file when opened.
 20 //    )
 21 //
 22 //    var (
 23 //        stdin  = newfile(uintptr(syscall.stdin), "/dev/stdin")
 24 //        Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
 25 //        Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
 26 //    )
 27 // }}}
 28 const (
 29     Unknown   int = -1
 30     Dir       int = 0
 31     Regular   int = 1
 32     Symlink   int = 2
 33     Socket    int = 3
 34     NamedPipe int = 4
 35 )
 36 
 37 var (
 38     path string = "/tmp/link_to_testfile"
 39     err  error
 40 )
 41 
 42 func main() {
 43     defer defer_printBye()
 44 
 45     cwd, _ := os.Getwd()
 46     fmt.Println("Work dir:", cwd)
 47     os.Chdir("/tmp")
 48     cwd, _ = os.Getwd()
 49     fmt.Println("New work dir:", cwd)
 50 
 51     hostname, _ := os.Hostname()
 52     pagesize := os.Getpagesize()
 53     fmt.Printf("hostname = %s\npagesize = %d\n", hostname, pagesize)
 54 
 55     if nil != os.Setenv("HISTSIZE", "1000") {
 56         log.Fatal("Can‘t set env HISTSIZE")
 57     }
 58 
 59     fmt.Println(os.Getenv("HISTSIZE"))
 60     os.Unsetenv("HISTSIZE")
 61     fmt.Println("After Unsetenv:", os.Getenv("HISTSIZE"))
 62 
 63     //for _, env := range os.Environ() {
 64     //    fmt.Println(env)
 65     //}
 66 
 67     os.Clearenv()
 68     fmt.Println("Env variables after os.Clearenv: ", os.Environ())
 69 
 70     groups, _ := os.Getgroups()
 71     fmt.Println("groups IDs:", groups)
 72     fmt.Println("uid:", os.Getuid(), "euid:", os.Geteuid(), "gid:", os.Getgid(), "egid:", os.Getegid(), "pid:", os.Getpid(), "ppid:", os.Getppid())
 73     // {{{
 74     /*
 75         type FileInfo interface {
 76               Name() string       // base name of the file
 77               Size() int64        // length in bytes for regular files; system-dependent for others
 78               Mode() FileMode     // file mode bits
 79               ModTime() time.Time // modification time
 80               IsDir() bool        // abbreviation for Mode().IsDir()
 81               Sys() interface{}   // underlying data source (can return nil)
 82         }
 83 
 84         const (
 85                 // The single letters are the abbreviations used by the String method‘s formatting.
 86                 ModeDir        FileMode = 1 << (32 - 1 - iota) // d: is a directory
 87                 ModeAppend                                     // a: append-only
 88                 ModeExclusive                                  // l: exclusive use
 89                 ModeTemporary                                  // T: temporary file (not backed up)
 90                 ModeSymlink                                    // L: symbolic link
 91                 ModeDevice                                     // D: device file
 92                 ModeNamedPipe                                  // p: named pipe (FIFO)
 93                 ModeSocket                                     // S: Unix domain socket
 94                 ModeSetuid                                     // u: setuid
 95                 ModeSetgid                                     // g: setgid
 96                 ModeCharDevice                                 // c: Unix character device, when ModeDevice is set
 97                 ModeSticky                                     // t: sticky
 98 
 99                 // Mask for the type bits. For regular files, none will be set.
100                 ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice
101 
102                 ModePerm FileMode = 0777 // Unix permission bits
103         )
104     */ // }}}
105 
106     ftype, fm := file_info(path)
107     fmt.Println("File type is:", file_type_string(ftype))
108 
109     fmt.Printf("permission: %s, %b\n", fm.String(), fm.Perm())
110     fm = fm & 0400
111     os.Chmod(path, fm)
112     fmt.Printf("After os.Chmod, permission: %s, %b\n", fm.String(), fm.Perm())
113 
114     err = os.Chown(path, 1000, -1)
115     print_err("Change owner to 1000/-1 failed!")
116     err = os.Lchown(path, 0, 0)
117     print_err("Change owner to 0/0 failed!")
118     os.Link(path, "tempfile_new")
119     os.Symlink(path, "tempfile_new_symlink")
120     os.Mkdir("/tmp/tempfile_dir", 0755)
121     os.MkdirAll("/tmp/tempfile_dir_All/teem", 0755)
122 
123     out, _ := exec.Command("/bin/ls", "/tmp").Output()
124     fmt.Printf("%s", out)
125     fmt.Println()
126 
127     os.Rename("/tmp/tempfile_dir", "/tmp/tempfiledir")
128     os.Remove("/tmp/tempfiledir")
129     os.RemoveAll("/tmp/tempfile_dir_All")
130     fmt.Println("Delete all tmp files")
131 
132     out, _ = exec.Command("/bin/ls", "/tmp").Output()
133     fmt.Printf("%s", out)
134     fmt.Println()
135 
136     realname, _ := os.Readlink(path)
137     tmp0, _ := os.Stat(realname)
138     tmp1, _ := os.Stat(path)
139     if os.SameFile(tmp0, tmp1) {
140         fmt.Println("SameFile")
141     }
142     os.Truncate(path, 1024)
143     fi, _ := os.Stat(path)
144     fmt.Println("New file size is:", fi.Size())
145 
146     //    type File struct {// {{{
147     //        *file // os specific
148     //    }
149     // }}}
150     fp, er := os.OpenFile("/tmp/xxxmyfile", os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0644)
151     err = er
152     print_err("Create /tmp/xxxmyfile failed!")
153     fp.Close()
154     os.Mkdir("/tmp/test", 0700)
155     fp, _ = os.Open("/tmp/test")
156     fp.Chdir()
157     cwd, _ = os.Getwd()
158     fmt.Printf("Current dir:%s \n", cwd)
159     fp.Chmod(0700)
160     fp.Chown(-1, -1)
161     fmt.Printf("%p, %s\n", fp.Fd(), fp.Name())
162     fr, fw, _ := os.Pipe()
163     in := []byte("aljkdflajs;lfjalsjfoawjlfkjaslkjflkashglhaklsjfjalsjfklasjklf")
164 
165     out = make([]byte, 100)
166 
167     go gofn(fw, in)
168 
169     fr.Read(out)
170     fmt.Println(string(out))
171 
172     go func() {
173         fw.WriteString("--------------------------------------------------------------")
174         fr.Read(out)
175         fmt.Println(string(out))
176     }()
177 
178     dirname, _ := fp.Readdirnames(-1)
179     for _, yy := range dirname {
180         fmt.Printf("--------%s\n", yy)
181     }
182 
183     fp.Seek(0, 0)
184 
185     fii, _ := fp.Readdir(-1)
186     for _, xx := range fii {
187         fmt.Printf("+++++++%s\n", xx.Name())
188     }
189 
190     //    type Process struct {// {{{
191     //        Pid int
192     //    }
193     //
194     //    type ProcAttr struct {
195     //        Dir string
196     //        Env []string
197     //        Files []*File
198     //        Sys *syscall.SysProcAttr
199     //    }
200     //
201     //    type ProcessState struct {}
202     // }}}
203 
204     pattr := os.ProcAttr{Files: []*os.File{os.Stdin, os.Stdout, os.Stderr}}
205     cmd := []string{"", "/tmp"}
206 
207     var ps *os.Process
208     go func() {
209         ps, _ = os.StartProcess("/bin/ls", cmd, &pattr)
210     }()
211 
212     go func() {
213         fmt.Println("Sleeping...3s...")
214         time.Sleep(time.Second * 3)
215 
216         ps.Kill()
217         ps.Signal(os.Interrupt)
218 
219     }()
220 
221     fmt.Println("Sleeping...3s...")
222     time.Sleep(time.Second * 3)
223 
224     procstat, _ := ps.Wait()
225     fmt.Println(procstat.String(), procstat.Exited(), procstat.Pid(), procstat.SystemTime(), procstat.UserTime())
226 
227     fp.Close()
228 }
229 
230 func defer_printBye() {
231     fmt.Println("Bye, thanks for CPU time")
232 }
233 
234 func print_err(info string) {
235     if nil != err {
236         fmt.Fprintln(os.Stderr, errors.New(info))
237     }
238 }
239 
240 func file_info(path string) (int, os.FileMode) {
241     var ftype int
242     var fm os.FileMode
243 
244     fi, err := os.Lstat(path)
245     if nil != err {
246         switch {
247         case os.IsNotExist(err):
248             print_err("IsNotExist")
249         case os.IsPermission(err):
250             print_err("IsPermission")
251         default:
252             print_err("Unknown errors")
253             break
254         }
255         os.Exit(1)
256     } else {
257         switch fm = fi.Mode(); {
258         case fm.IsDir():
259             ftype = Dir
260         case fm&os.ModeSymlink != 0:
261             ftype = Symlink
262         case fm.IsRegular():
263             ftype = Regular
264         case fm&os.ModeSocket != 0:
265             ftype = Socket
266         case fm&os.ModeNamedPipe != 0:
267             ftype = NamedPipe
268         default:
269             ftype = Unknown
270         }
271     }
272     return ftype, fm
273 }
274 
275 func file_type_string(ftype int) string {
276     var res string
277     switch ftype {
278     case Dir:
279         res = "Dir"
280     case Regular:
281         res = "Regular"
282     case Socket:
283         res = "Socket"
284     case NamedPipe:
285         res = "NamedPipe"
286     case Unknown:
287         res = "Unknown"
288     default:
289         res = "Symlink"
290     }
291     return res
292 }
293 
294 func gofn(fw *os.File, in []byte) {
295     num, _ := fw.Write(in)
296     if num != len(in) {
297         print_err("write failed")
298     }
299 } 

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