我正在开发一个Swift应用程序,该程序与外部二进制文件进行交互(通过NSTask),并针对每一行将输出作为字符串数组返回。
当多次调用executeCommand函数时,命令开始无法返回期望的数据。
在下面的示例Playground中,我在diskutil中轮询卷名。
在调试区域中,我得到的第一个响应是:
只需重新运行Playground即可:
无法获取卷名
import Cocoa
func executeCommand(launchPath: String, arguments: [String], additionalDelay: Int=0) -> [String] {
let outputPipe = NSPipe()
var outputArray = [String]()
let task = NSTask()
task.launchPath = launchPath
task.arguments = arguments
task.standardOutput = outputPipe
outputPipe.fileHandleForReading.waitForDataInBackgroundAndNotify()
NSNotificationCenter.defaultCenter().addObserverForName(NSFileHandleDataAvailableNotification, object: outputPipe.fileHandleForReading , queue: nil) {
notification in
let output = outputPipe.fileHandleForReading.availableData
let outputString = String(data: output, encoding: NSUTF8StringEncoding) ?? ""
outputArray = outputString.componentsSeparatedByCharactersInSet(.newlineCharacterSet())
outputPipe.fileHandleForReading.waitForDataInBackgroundAndNotify()
}
task.launch()
sleep(UInt32(additionalDelay)) // Additional delay
task.waitUntilExit()
// Remove last empty line from output array.
if outputArray.count > 0 {
outputArray.removeLast()
}
return outputArray
}
// Example usage
// Output volume name from provided disk identifier
func volumeName(identifier: String) -> String {
let volumeNameCommand = "/usr/sbin/diskutil info \(identifier) | awk '/Volume Name:/' | sed 's/Volume Name://g'| sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'"
let volumeNameOutput = executeCommand("/bin/bash", arguments: ["-c", volumeNameCommand])
var volumeName = "Unable to obtain volume name"
if volumeNameOutput.count > 0 {
volumeName = volumeNameOutput[0]
}
return volumeName
}
let identifiers = ["/dev/disk0","/dev/disk1","/dev/disk2","/dev/disk3","/dev/disk4"]
for identifier in identifiers {
print(volumeName(identifier))
}
我确实需要一致的结果,但不了解我要去哪里。
任何帮助将不胜感激!
我认为任务的异步执行会导致结果不一致。下面是一个按预期工作的新功能:
func executeCommand(launchPath: String, arguments: [String]) -> [String] {
let task: NSTask = NSTask()
let pipe: NSPipe = NSPipe()
task.launchPath = launchPath
task.arguments = arguments
task.standardOutput = pipe
task.launch()
task.waitUntilExit()
let handle = pipe.fileHandleForReading
let data = handle.readDataToEndOfFile()
let outputString = String(data: data, encoding: NSUTF8StringEncoding) ?? ""
var outputArray = [String]()
outputArray = outputString.componentsSeparatedByCharactersInSet(.newlineCharacterSet())
return outputArray
}
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我来说两句