C# Access Permission Check on Linux System

using System;
using System.Diagnostics;

//  start bash with redirected output
//  pass ls -l + the path to the file or directory as argument
//  find the line with the name of the file or directory at the end
//  and last check if the 2nd/3rd/4th char of that line is r/w/x

namespace access_test
{
   class Program {

      static void Main(string[] args) {
         if (args.Length > 1) {
            if (args[0] == "-r") {
               if (HasPermission(Permission.Read, args[1]))
                  Console.WriteLine("YAY!");
               else
                  Console.WriteLine("NEY!");
            }
            else if (args[0] == "-w") {
               if (HasPermission(Permission.Write, args[1]))
                  Console.WriteLine("YAY!");
               else
                  Console.WriteLine("NEY!");
            }
            else if (args[0] == "-x") {
               if (HasPermission(Permission.Excecute, args[1]))
                  Console.WriteLine("YAY!");
               else
                  Console.WriteLine("NEY!");
            }
         }
      }

      static bool HasPermission(Permission permission, string path) {
         if (path[path.Length - 1] == '/')
            path = path.Remove(path.Length - 1);

         string p, f;
         if (path.LastIndexOf('/') != -1) {
            p = path.Remove(path.LastIndexOf('/'));
            f = path.Substring(path.LastIndexOf('/') + 1);
         }
         else {
            p = "";
            f = path;
         }

         string cmd = "ls -l \"" + p + "\"";
         string output = Bash(cmd);

         if (output.Length < 4)
            return false;

         if (output.Substring(0, 2) == "ls")
            return false;

         string result;
         do {
            int br = output.IndexOf("\n");
            if (br == -1)
               result = output;
            else
               result = output.Substring(0, br);
            if (result.Length > (f.Length + 1)) {
               if (result.Substring(result.Length - (f.Length + 1), f.Length + 1) == " " + f)
                  break;
               else
                  output = output.Remove(0, br + 1);
            }
            else
               output = output.Remove(0, br + 1);
         } while (output.Contains("\n"));

         if (result.Substring(result.Length - (f.Length + 1), f.Length + 1) != " " + f)
            return false;

         if (result.Length < 4)
            return false;

         if (result.Substring(0, 2) == "ls")
            return false;

         switch (permission) {
            case Permission.Read:
               return (result[1] == 'r');
            case Permission.Write:
               return (result[2] == 'w');
            case Permission.Excecute:
               return (result[3] == 'x');
            default:
               return false;
         }
      }

      static string Bash(string cmd) {
         string args = cmd.Replace("\"", "\\\"");

         Process p = new Process();
         p.StartInfo.FileName = "/bin/bash";
         p.StartInfo.Arguments = $"-c \"{args}\"";
         p.StartInfo.RedirectStandardOutput = true;
         p.StartInfo.RedirectStandardError = true;
         p.StartInfo.UseShellExecute = false;
         p.StartInfo.CreateNoWindow = true;

         p.Start();
         string result = p.StandardOutput.ReadToEnd();
         p.WaitForExit();
         return result;
      }
   }
   public enum Permission { Read, Write, Excecute }
}