使用 NSTask 交互式访问命令答案

【问题标题】：Interactive access to command using NSTask使用 NSTask 交互式访问命令
【发布时间】：2017-03-13 20:14:37
【问题描述】：

我正在使用一个 NSTask 来运行一个交互式的 cli 应用程序。我用它通过 USB 连接提取数据。

我正在打开一个带有大纲和错误管道的 NSTask，但是当我发出命令时，它可以工作，但会在循环中旋转沙滩球，从输出中提取数据。

我希望能够混合执行帮助命令的 - (IBAction)clicked:(id)sender 按钮并返回输出：

NSTask *usbCommandTask;
NSPipe *outPipe;
NSPipe *inPipe;
NSPipe *errorPipe;
NSFileHandle *inFile;
NSFileHandle *outFile;
NSTimer *pollTimer;
dispatch_queue_t mtpTask;

@implementation AppDelegate


- (void)commandNotification:(NSNotification *)notification
{
    NSData *data = nil;

    while ((data = [outFile availableData]) && [data length]){
        NSString *myString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"Data: %@",myString);
        }
    NSLog(@"Execution never gets here");

}

-(void)checkTask
{
    if(usbCommandTask){
        if([usbCommandTask isRunning])NSLog(@"Task running"); else NSLog(@"Task dead");

    } else NSLog(@"Task is nil");


}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {



    usbCommandTask = [[NSTask alloc] init];
    [usbCommandTask setLaunchPath:@"/Applications/usb-debugger-cli"];
    [usbCommandTask setCurrentDirectoryPath:@"/"];
    [usbCommandTask setArguments:[NSArray arrayWithObject:@"-i"]];
    inPipe = [NSPipe pipe];
    [usbCommandTask setStandardInput:inPipe];




    outPipe = [NSPipe pipe];
    [usbCommandTask setStandardOutput:outPipe];
    errorPipe = [NSPipe pipe];
    [usbCommandTask setStandardError:errorPipe];

    outFile = [outPipe fileHandleForReading];
    inFile = [inPipe fileHandleForWriting];

     [outFile waitForDataInBackgroundAndNotify];



    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(commandNotification:)
                                                 name:NSFileHandleDataAvailableNotification
                                               object:nil];



    pollTimer=[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(checkTask) userInfo:nil repeats:TRUE];
    [usbCommandTask launch];
    NSLog(@"Launched");



}


- (void)applicationWillTerminate:(NSNotification *)aNotification {
    // Insert code here to tear down your application
    if(usbCommandTask)[usbCommandTask terminate];


}


- (IBAction)clicked:(id)sender {

    if(usbCommandTask){
    NSString *command=@"help\n";
    NSData *commandData=[NSData dataWithBytes:command.UTF8String length:command.length];

    [inFile writeData:commandData];
    }
    else
    {NSLog(@"Comamnd task dead");
    }
}

【问题讨论】：

标签： cocoa nstask nspipe

【解决方案1】：

[outFile availableData]

实际上是一个阻塞调用，没有数据或显式EOF，所以这总是会阻塞，而不是我使用：

data = [outFile availableData];
NSString *myString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"Data: %@",myString);
[outFile waitForDataInBackgroundAndNotify];

【讨论】：