Slip_no_28_a.js

var fs = require("fs");
var buf = new Buffer(1024);
console.log("Going to open an existing file");
fs.open('input.txt', 'r+', function(err, fd) {
if (err) {
return console.error(err);
}
console.log("File opened successfully!");
console.log("Going to truncate the file after 10 bytes");
// Truncate the opened file.
fs.ftruncate(fd, 10, function(err){
if (err){
console.log(err);
}
console.log("File truncated successfully.");
console.log("Going to read the same file");
fs.read(fd, buf, 0, buf.length, 0, function(err, bytes){if (err){
console.log(err);
}
// Print only read bytes to avoid junk.
if(bytes > 0){
console.log(buf.slice(0, bytes).toString());
}
// Close the opened file.
fs.close(fd, function(err){
if (err){
console.log(err);
}
console.log("File closed successfully.");
});
});
});
});