GO·NOTE

一份 Go 开发工程师的学习笔记

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os的文件操作

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os.OpenFile()

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// Open opens the named file for reading. If successful, methods on
// the returned file can be used for reading; the associated file
// descriptor has mode O_RDONLY.
// If there is an error, it will be of type *PathError.
func Open(name string) (*File, error) {
	return OpenFile(name, O_RDONLY, 0)
}

os.Create()

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// Create creates or truncates the named file. If the file already exists,
// it is truncated. If the file does not exist, it is created with mode 0666
// (before umask). If successful, methods on the returned File can
// be used for I/O; the associated file descriptor has mode O_RDWR.
// If there is an error, it will be of type *PathError.
func Create(name string) (*File, error) {
	return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
}

os.Open()

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// OpenFile is the generalized open call; most users will use Open
// or Create instead. It opens the named file with specified flag
// (O_RDONLY etc.). If the file does not exist, and the O_CREATE flag
// is passed, it is created with mode perm (before umask). If successful,
// methods on the returned File can be used for I/O.
// If there is an error, it will be of type *PathError.
func OpenFile(name string, flag int, perm FileMode) (*File, error) {
	testlog.Open(name)
	f, err := openFileNolog(name, flag, perm)
	if err != nil {
		return nil, err
	}
	f.appendMode = flag&O_APPEND != 0

	return f, nil
}

flag

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// Flags to OpenFile wrapping those of the underlying system. Not all
// flags may be implemented on a given system.
const (
	// Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
	O_RDONLY int = syscall.O_RDONLY // open the file read-only.
	O_WRONLY int = syscall.O_WRONLY // open the file write-only.
	O_RDWR   int = syscall.O_RDWR   // open the file read-write.
	// The remaining values may be or'ed in to control behavior.
	O_APPEND int = syscall.O_APPEND // append data to the file when writing.
	O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
	O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist.
	O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
	O_TRUNC  int = syscall.O_TRUNC  // truncate regular writable file when opened.
)

perm

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一般都文件属性标识如下： 

-rwxrwxrwx

第1位：文件属性，一般常用的是"-"，表示是普通文件；"d"表示是一个目录。

第2～4位：文件所有者的权限rwx (可读/可写/可执行)。

第5～7位：文件所属用户组的权限rwx (可读/可写/可执行)。

第8～10位：其他人的权限rwx (可读/可写/可执行)。

 

在golang中，可以使用os.FileMode(perm).String()来查看权限标识：

os.FileMode(0777).String()    //返回 -rwxrwxrwx

os.FileMode(0666).String()   //返回 -rw-rw-rw-

os.FileMode(0644).String()   //返回 -rw-r--r--

注意，golang中创建文件指定权限时，只能以"0XXX"的形式，不能省掉前面的"0"，否则指定的权限不是预期的