Instructions for using the fs.ftruncate method in node.js_node.js

Method description:

File content interception operation.

Grammar:

Copy code The code is as follows:

fs.ftruncate(fd, len, [callback(err)])

Since this method belongs to the fs module, the fs module needs to be introduced before use (var fs= require(“fs”) )

Receive parameters:

path File path

len truncates the length, retaining only the characters within the character length, and the excess will be cleared.

callback Callback, passing an exception parameter err

Example:

Copy code The code is as follows:

var fs = require('fs');
fs.ftruncate('126.txt', 2, function(err){
if(err){
throw err;
}
console.log('File content truncated successfully');
})

Source code:

Copy code The code is as follows:

fs.ftruncate = function(fd, len, callback) {
if (util.isFunction(len)) {
​ callback = len;
len = 0;
} else if (util.isUndefined(len)) {
len = 0;
}
binding.ftruncate(fd, len, makeCallback(callback));
};