Question

我有一个奇怪的问题。对于家庭作业，我正在创建自己的基本bash脚本，但是当运行execv（）来运行我的cp命令时，它不起作用。它适用于ls和组，但不适用于cp。我搞乱了我的cp程序以隔离错误，它确实是execv命令。

func createAlertView() -> UIAlertController {

    let view = UIView(frame: CGRect(x: CGFloat(0), y: CGFloat(0), width: CGFloat(250), height: CGFloat(100)))
    let itemName = UITextField(frame: CGRect(x: CGFloat(10), y: CGFloat(0), width: CGFloat(252), height: CGFloat(25)))
    itemName.borderStyle = .RoundedRect
    itemName.placeholder = "Item Name"
    itemName.keyboardAppearance = .Alert
    itemName.delegate = self
    view.addSubview(itemName)

    let itemPrice = UITextField(frame: CGRect(x: CGFloat(10), y: CGFloat(30), width: CGFloat(252), height: CGFloat(25)))
    itemPrice.placeholder = "Item Price"
    itemPrice.borderStyle = .RoundedRect
    itemPrice.keyboardAppearance = .Alert
    itemPrice.delegate = self
    view.addSubview(itemPrice)

    let itemQuantity = UITextField(frame: CGRect(x: CGFloat(10), y: CGFloat(60), width: CGFloat(252), height: CGFloat(25)))
    itemQuantity.placeholder = "Item Quantity"
    itemQuantity.borderStyle = .RoundedRect
    itemQuantity.keyboardAppearance = .Alert
    itemQuantity.delegate = self
    view.addSubview(itemQuantity)

    let alertController = UIAlertController(title: "Add Item", message: nil, preferredStyle: .Alert)
    alertController.view.addSubview(view)

    return alertController
}

func createAlertViewItem(alertController: UIAlertController, itemName: String, itemStringPrice: String) {

    let managedContext = self.bill.managedObjectContext
    let entity = NSEntityDescription.entityForName("Item", inManagedObjectContext: managedContext!)
    let newItem = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)

    if let itemName = alertController.textFields?.first?.text {

        newItem.setValue(itemName, forKey: "name")

    }
    if let itemPriceString = alertController.textFields?[1].text {

        let itemPriceNumber = Int(itemPriceString)

        newItem.setValue(itemPriceNumber, forKey: "price")
    }

    do {
        try managedContext!.save()
    }
    catch let error as NSError {
        print("Core Data save failed: \(error)")
    }

    let currentItems = self.bill.mutableSetValueForKey("items")
    currentItems.addObject(newItem)

    self.tableView.reloadData()
}

@IBAction func addNewItem(sender: UIButton) {

    let alertController = createAlertView()

    let itemName = alertController.textFields![0].text
    let itemPrice = alertController.textFields?[1].text
    let itemQuantity: Int!

    if alertController.textFields![2].text == "" {
        itemQuantity = 0
    } else {
        itemQuantity = Int((alertController.textFields?[2].text)!)!
    }

    let okAction = UIAlertAction(title: "OK", style: .Default, handler: { (action) -> Void in
        if itemQuantity == 0 || itemQuantity == 1 {
            print(2)
            self.createAlertViewItem(alertController, itemName: itemName!, itemStringPrice: itemPrice!)
        } else {
            for _ in 0...itemQuantity {
                print(3)
                self.createAlertViewItem(alertController, itemName: itemName!, itemStringPrice: itemPrice!)
            }
        }
    })

    alertController.addAction(okAction)

    let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)
    alertController.addAction(cancelAction)

    presentViewController(alertController, animated: true, completion: nil)
}

我觉得这个片段应该没问题。我的代码正确地访问了execv，它只是因为某些原因而没有执行它。 ls和groups工作正常，但cp没有。我的主要是调用输入

Answer 1

我根据有限的信息猜测，作为参数发送的数组只包含您要发送给cp的两件事之一。通过在调用cp之前打印数组，验证是否将源和目标都发送到execv。还要确保数组的最后一个元素是一个空指针。

Answer 2

这对我有用：

char* args[] = { "/bin/cp", "/etc/passwd", "passwd-copy", 0 };
pid_t pid; 
if(0>(pid=fork())){
    perror(0); 
    return -1;
}
if(0==pid){
    execv(args[0], args);
    perror(0);
    _exit(127);
}
siginfo_t info;
if(0>waitid(P_PID, pid, &info, WEXITED)){
    perror(0);
    return -1;
}
return info.si_status;

execv（）无法正常工作

2 个答案: