haxe linux/mac shell commands with pipes

Shell.hx

package;

import sys.io.Process;
using StringTools;

class Shell
{
    public static function main() {
        trace(exec('ioreg -c IOSerialBSDClient | grep usbmodem | grep IODialinDevice | cut -d " -f 4'));
    }

    public static function exec(command:String):String{
        var cmdArr = command.split("|");
        var tp:Process = null;
        var p:Process = null;

        for(cmd in cmdArr){
            var arr:Array<String> = cmd.ltrim().rtrim().split(" ");            
            p = new Process(arr.shift(), [].concat(arr));
            if(tp != null){
                p.stdin.writeInput(tp.stdout);
                p.stdin.close();
                tp.close();
                tp.exitCode();
            }
            tp = p;            
        }

        var s = p.stdout.readAll().toString();
        p.close();
        p.exitCode();

        return s;
    }
}