Added retry for SysProcess EINTR. Added Dir.workingDir

Author: kjessup

Sources/PerfectLib/Dir.swift

@@ -44,7 +44,21 @@ public struct Dir {
     public var exists: Bool {
 		return exists(realPath)
 	}
+	
+	public func setAsWorkingDir() throws {
+		let res = chdir(self.internalPath)
+		guard res == 0 else {
+			try ThrowFileError()
+		}
+	}
 
+	public static var workingDir: Dir {
+		let buffer = Array(repeating: 0 as UInt8, count: 2049)
+		let _ = getcwd(UnsafeMutablePointer<Int8>(buffer), 2048)
+		let path = String(validatingUTF8: UnsafeMutablePointer<Int8>(buffer)) ?? "."
+		return Dir(path)
+	}
+	
 	func exists(_ path: String) -> Bool {
 		return access(path, F_OK) != -1
 	}

Sources/PerfectLib/SysProcess.swift

@@ -177,10 +177,16 @@ public class SysProcess {
 	/// Determine if the process has completed running and retrieve its result code.
 	public func wait(hang: Bool = true) throws -> Int32 {
 		var code = Int32(0)
-		let status = waitpid(self.pid, &code, WUNTRACED | (hang ? 0 : WNOHANG))
-        guard status != -1 else {
-            try ThrowSystemError()
-        }
+		while true {
+			let status = waitpid(self.pid, &code, WUNTRACED | (hang ? 0 : WNOHANG))
+			if status == -1 && errno == EINTR {
+				continue
+			}
+			guard status != -1 else {
+				try ThrowSystemError()
+			}
+			break
+		}
 		self.pid = -1
 		close()
 		return code