File System
fs module is a encapsulation of file operations.
fs.readFile [Most commonly used]
fs.readFile(filename,[encoding],[callback(err,data)])
- filename: file name to read
- encoding: optional, for character encoding
- callback: to receive the content of the file.
If we encoding is omitted, datas will be passed as binar with Buffer style.
If we set a encoding, it will pass datas with given encoding
var fs = require('fs');
fs.readFile('content.txt', function(err, data) {
if (err) {
console.error(err);
} else {
console.log(data);
}
});
//<Buffer 54 65 78 74 20 e6 96 87 e6 9c ac e6 96 87 e4 bb b6 e7 a4 ba e4 be 8b>
fs.readFile('content.txt','utf-8', function(err, data) {
if (err) {
console.error(err);
} else {
console.log(data);
}
});
//Text 文本文件示例
fs.open
fs.open(path, flags, [mode], [callback(err, fd)])
flags:
-
r: read -
r+: read write -
w: write -
w+: read write -
a: add read -
a+: add read write
mode:
config the file authority, default is 0666, POSIX standard
callback function will pass a file descriptor fd
fs.read
fs.read(fd, buffer, offset, length, position, [callback(err, bytesRead, buffer)])
-
fd: file descriptor -
buffer: buffer to store read datas -
offset: offset to write to buffer -
length: bytes num to read -
position: beginning position of file to read, if position is null, it will read from current file pointer position (current offset) -
bytesRead: bytes num read -
buffer: buffer object to store read datas
var fs = require('fs');
fs.open('content.txt', 'r', function(err, fd) {
if (err) {
console.error(err);
return;
}
var buf = new Buffer(8);
fs.read(fd, buf, 0, 8, null, function(err, bytesRead, buffer) {
if (err) {
console.error(err); return;
}
console.log('bytesRead: ' + bytesRead);
console.log(buffer);
})
});
//result
//bytesRead: 8
//<Buffer 54 65 78 74 20 e6 96 87>
fs.close
fs.close(fd, [callback(err)])
