executing shell commands programmatically in Android

Question

I have two commands to execute and get back the data My .sh file as two commands and it looks like this

su dhcpcd eth0

when I try to execute the .sh command in my Android terminal by typing as sh filename.sh It does not give me output but when I do execute it by typing individual line it works. SO when I program as

nativeProcess = Runtime.getRuntime().exec("su");
nativeProcess = Runtime.getRuntime().exec("dhcpcd eth0");
while ((line = br.readLine()) != null) 
{
    contents.append(line + "\n");
}

What is wrong in this? I get the output contents as null

check this out tech-papers.org/executing-shell-command-android-application — Balwinder SIngh
– Balwinder SIngh, Commented Jan 11, 2015 at 10:24

nneonneo · Accepted Answer · 2013-02-11 17:04:34Z

3

exec in Java starts a new process. So the first line makes a new su process, which is going to simply sit there and wait for your input. The second line starts a new dhcpcd process, which won't be privileged and so won't produce useful output.

What you want is to run dhcpcd using su, typically like this:

exec("su -c dhcpcd eth0")

answered Feb 11, 2013 at 17:04

nneonneo

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2 Comments

user1810931 Over a year ago

It works when I type in terminal and I can see the result. nativeProcess = Runtime.getRuntime().exec("su -c dhcpcd eth0"); InputStream is = nativeProcess.getInputStream(); InputStreamReader isr = new InputStreamReader(is); BufferedReader br = new BufferedReader(isr); StringBuilder contents = new StringBuilder(); while ((line = br.readLine()) != null) { contents.append(line + "\n"); } I still get as null

user1810931 Over a year ago

@nneoneo- Actually the problem is when I execute that command the output I get is in the form of "fork to background, child pid type". DO you know anything about it, I was thinking it runs on background and connects to child process. SO to catch the response of the command "su -c dhcpcd eth0", there should be another way. If you know of it please do share your info

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