Question

我正在研究cpu heavy单线程控制台实用程序。我在一个同步调用中做cpu繁重的工作（即没有像这样的回调和废话），但是，显然，节点，出于某些疯狂的原因正异步输出到终端。有没有办法解决这个问题？我正在尝试显示一个进度条，但它完全没用，因为它在cpu工作完成后显示它，节点除了后面的打印之外什么都不做（在那一点没有意义，也延迟退出）。

以下是我正在使用的进度条的代码：

function ProgressBar(total, displayLen, prompt) { /**class*/
    this.prompt = prompt;
    this.total = total;
    this.displayLen = displayLen;
    this.perctf = 100.0 / total;
    this.displayf = 100.0 / displayLen;
    this.percprog = 0;
    this.displayprog = 0;

    this.laststr = "";
    this.dots = "";
    this.cpgrinc = 0;
    this.lastdisplayc = 0;
}

ProgressBar.prototype.update = function() {
    this.percprog += this.perctf;
    this.displayprog += this.perctf;
    if (this.displayprog > this.displayf) {
        this.dots += ".";
        this.displayprog = 0;
    }
    this.cpgrinc = (this.cpgrinc + 1) % 4;

    this.clear();
    this.laststr = this.prompt + " [" + this.dots;
    this.write(this.laststr + " " +
        this.percprog.toFixed() + "%] " + this.indicator());
};

ProgressBar.prototype.clear = function() {
    var str = "";
    for (var i = 0; i < this.lastdisplayc; i++) {
        str += "\b";
    }
    process.stdout.write(str);
};

ProgressBar.prototype.write = function(data) {
    process.stdout.write(data);
    this.lastdisplayc = data.length;
};

ProgressBar.prototype.indicator = function() {
    switch (this.cpgrinc) {
        case 0:
            return "-";
        case 1:
            return "\\";
        case 2:
            return "|";
        case 3:
            return "/";
    }
};

ProgressBar.prototype.run = function(callback) {
    var that = this;
    callback(function() {
        that.update();
    });
    this.clear();
    process.stdout.write(this.laststr + "] 100% Finished\n");
};

ProgressBar.prototype.runAsync = function(callback) {
    var that = this;
    callback(function() {
        that.update();
    }, function() {
        that.clear();
        process.stdout.write(that.laststr + "] 100% Finished\n");
    });
};

Answer 1

如果您想立即查看，可以写入process.stderr。

请参阅doc：https://nodejs.org/api/process.html#process_process_stderr

Answer 2

找出最佳方法：

var _fs = require('fs');
process.stdout.write = function(data) {
    try {
        _fs.writeSync(1, data);
    } catch (e) {
        process.stdout.write(data);
    }
};

如何同步写入process.stdout？

2 个答案: