exec method in java not able to execute command

Question

I am trying to execute command using exec method

proc3=Runtime.getRuntime().exec("umount "+m);

Where m is variable having directory location like /mnt, /media When i execute the command in command prompt it will work as expected, but with java exec method it's not working giving exit status 2. What may be the reason ?

One of the reason for this behaviour is that all the environment variables are not available to the java runtime, as a test can you indentify the absolute path of umount and use it. If that works, the PATH is not available. — ganaraj
– ganaraj, Commented May 28, 2014 at 10:19
You can try calling a script that redirects the error to a file, ie write a shell script which has the command umount $1 > out.log 2> out.err. This way you might be able to catch the error and get an idea of the underlying OS error — ganaraj
– ganaraj, Commented May 28, 2014 at 10:21

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Try with ProcessBuilder :

ProcessBuilder pb = new ProcessBuilder("umount",p1,p2);
pb.start();

You can pass to ProcessBuilder's constructor as many arguments as you want .

PS : Don't forget to check your permission.

edited Jun 20, 2020 at 9:12

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answered May 28, 2014 at 10:27

Mifmif

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user3153014 Over a year ago

I got to know problem is permission . I must be root user to execute the command. But servlet will run as nobody user

ganaraj · Accepted Answer · 2014-05-28 11:20:28Z

0

You have two option with you. 1) To start your server/servlet using su(not an ideal option). 2) Provide sudo access on umount to the user starting the servlet service, so that it can execute (might need a password). You might have to check this.

Steps to Identify the error: Write a shell script which has the command umount $1 > out.log 2> out.err. This will log any OS error onto a file which enables further debug.

answered May 28, 2014 at 11:20

ganaraj

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1 Comment

user3153014 Over a year ago

I solved this problem by creating small c++ program to execute the command and providing sticky bit to that program.

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