| // 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. |
| |
| package os_test |
| |
| import ( |
| "errors" |
| "fmt" |
| "io/fs" |
| "log" |
| "os" |
| "path/filepath" |
| "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 { |
| f.Close() // ignore error; Write error takes precedence |
| log.Fatal(err) |
| } |
| if err := f.Close(); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleChmod() { |
| if err := os.Chmod("some-filename", 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("some-filename", atime, mtime); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleFileMode() { |
| fi, err := os.Lstat("some-filename") |
| if err != nil { |
| log.Fatal(err) |
| } |
| |
| fmt.Printf("permissions: %#o\n", fi.Mode().Perm()) // 0400, 0777, etc. |
| switch mode := fi.Mode(); { |
| case mode.IsRegular(): |
| fmt.Println("regular file") |
| case mode.IsDir(): |
| fmt.Println("directory") |
| case mode&fs.ModeSymlink != 0: |
| fmt.Println("symbolic link") |
| case mode&fs.ModeNamedPipe != 0: |
| fmt.Println("named pipe") |
| } |
| } |
| |
| func ExampleErrNotExist() { |
| filename := "a-nonexistent-file" |
| if _, err := os.Stat(filename); errors.Is(err, fs.ErrNotExist) { |
| fmt.Println("file does not exist") |
| } |
| // Output: |
| // file does not exist |
| } |
| |
| func ExampleExpand() { |
| mapper := func(placeholderName string) string { |
| switch placeholderName { |
| case "DAY_PART": |
| return "morning" |
| case "NAME": |
| return "Gopher" |
| } |
| |
| return "" |
| } |
| |
| fmt.Println(os.Expand("Good ${DAY_PART}, $NAME!", mapper)) |
| |
| // Output: |
| // Good morning, Gopher! |
| } |
| |
| func ExampleExpandEnv() { |
| os.Setenv("NAME", "gopher") |
| os.Setenv("BURROW", "/usr/gopher") |
| |
| fmt.Println(os.ExpandEnv("$NAME lives in ${BURROW}.")) |
| |
| // 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) |
| } |
| } |
| |
| os.Setenv("SOME_KEY", "value") |
| os.Setenv("EMPTY_KEY", "") |
| |
| show("SOME_KEY") |
| show("EMPTY_KEY") |
| show("MISSING_KEY") |
| |
| // Output: |
| // SOME_KEY=value |
| // EMPTY_KEY= |
| // MISSING_KEY not set |
| } |
| |
| func ExampleGetenv() { |
| os.Setenv("NAME", "gopher") |
| os.Setenv("BURROW", "/usr/gopher") |
| |
| fmt.Printf("%s lives in %s.\n", os.Getenv("NAME"), os.Getenv("BURROW")) |
| |
| // Output: |
| // gopher lives in /usr/gopher. |
| } |
| |
| func ExampleUnsetenv() { |
| os.Setenv("TMPDIR", "/my/tmp") |
| defer os.Unsetenv("TMPDIR") |
| } |
| |
| func ExampleReadDir() { |
| files, err := os.ReadDir(".") |
| if err != nil { |
| log.Fatal(err) |
| } |
| |
| for _, file := range files { |
| fmt.Println(file.Name()) |
| } |
| } |
| |
| func ExampleMkdirTemp() { |
| dir, err := os.MkdirTemp("", "example") |
| if err != nil { |
| log.Fatal(err) |
| } |
| defer os.RemoveAll(dir) // clean up |
| |
| file := filepath.Join(dir, "tmpfile") |
| if err := os.WriteFile(file, []byte("content"), 0666); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleMkdirTemp_suffix() { |
| logsDir, err := os.MkdirTemp("", "*-logs") |
| if err != nil { |
| log.Fatal(err) |
| } |
| defer os.RemoveAll(logsDir) // clean up |
| |
| // Logs can be cleaned out earlier if needed by searching |
| // for all directories whose suffix ends in *-logs. |
| globPattern := filepath.Join(os.TempDir(), "*-logs") |
| matches, err := filepath.Glob(globPattern) |
| if err != nil { |
| log.Fatalf("Failed to match %q: %v", globPattern, err) |
| } |
| |
| for _, match := range matches { |
| if err := os.RemoveAll(match); err != nil { |
| log.Printf("Failed to remove %q: %v", match, err) |
| } |
| } |
| } |
| |
| func ExampleCreateTemp() { |
| f, err := os.CreateTemp("", "example") |
| if err != nil { |
| log.Fatal(err) |
| } |
| defer os.Remove(f.Name()) // clean up |
| |
| if _, err := f.Write([]byte("content")); err != nil { |
| log.Fatal(err) |
| } |
| if err := f.Close(); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleCreateTemp_suffix() { |
| f, err := os.CreateTemp("", "example.*.txt") |
| if err != nil { |
| log.Fatal(err) |
| } |
| defer os.Remove(f.Name()) // clean up |
| |
| if _, err := f.Write([]byte("content")); err != nil { |
| f.Close() |
| log.Fatal(err) |
| } |
| if err := f.Close(); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func NoExampleReadFile() { |
| data, err := os.ReadFile("testdata/hello") |
| if err != nil { |
| log.Fatal(err) |
| } |
| os.Stdout.Write(data) |
| |
| // Output: |
| // Hello, Gophers! |
| } |
| |
| func ExampleWriteFile() { |
| err := os.WriteFile("testdata/hello", []byte("Hello, Gophers!"), 0666) |
| if err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleMkdir() { |
| err := os.Mkdir("testdir", 0750) |
| if err != nil && !os.IsExist(err) { |
| log.Fatal(err) |
| } |
| err = os.WriteFile("testdir/testfile.txt", []byte("Hello, Gophers!"), 0660) |
| if err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| func ExampleMkdirAll() { |
| err := os.MkdirAll("test/subdir", 0750) |
| if err != nil && !os.IsExist(err) { |
| log.Fatal(err) |
| } |
| err = os.WriteFile("test/subdir/testfile.txt", []byte("Hello, Gophers!"), 0660) |
| if err != nil { |
| log.Fatal(err) |
| } |
| } |