General :: How To Execute Command Shell Programmatically

i have made a kinda theme installer (for stockrom)..

so.. first of all i extract needed file from assets to sdcard

n on button click i add this line of code..

the code is work n sometimes not...

when execute the code, my phone hang for several time

"here is the line of execution code :

Code:

Process ppush;
try {
ppush = Runtime.getRuntime().exec("su");
DataOutputStream os = new DataOutputStream(ppush.getOutputStream());
os.writeBytes("mount -o remount,rw -t yaffs2 /dev/block/mtdblock4 /system
");
os.writeBytes("cp /mnt/sdcard/dys/SystemUI.apk /system/app
");

[code].....