sed not working from java program, but the input line works from terminal

Question

When I enter the line:

sed -i 's/DNS1="8.8.8.8"/DNS1="8.8.4.4"/' /etc/sysconfig/network-scripts/ifcfg-eth0

I get the desired result (i.e. 8.8.8.8 is replaced with 8.8.4.4), however, I have a jave program that passes the same command as shown here:

public static void swapDns() throws IOException, InterruptedException 
{
    Runtime rt = Runtime.getRuntime();
    Process ps;

    String cmd[] = {"sed","-i","'s/DNS1=\"8.8.8.8\"/DNS1=\"8.8.4.4\"/'","/etc/sysconfig/network-scripts/ifcfg-eth0"};
    ps = rt.exec(cmd);
}

and it doesn't work. It doesn't change anything. Is there an issue with sed/java, or am I missing something...

GL2014 · Accepted Answer · 2013-08-01 20:20:33Z

2

Does the Java program perhaps run with a different environment, perhaps one where sed is not in the path? Otherwise perhaps it runs as a user who does not have write permission to the network scripts?

answered Aug 1, 2013 at 20:20

GL2014

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5 Comments

GL2014 Over a year ago

Great!, you could make it setUID root, but running it as sudo is probably better practice. Please accept the answer if it works for you.

cHam Over a year ago

scratch that, i'm an idiot. it didn't work. I was running the sed command instead of the java program (facepalm)

GL2014 Over a year ago

So running the java program with sudo makes no difference?

cHam Over a year ago

Nope. I can always change the file with java completely but I do this fairly often in my current programs and sed would make thing easier.

GL2014 Over a year ago

Why dont you redirect STDERR to a file so you can see if there are errors? You could try running strace -f on your program and search for write calls to the file.

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