Loading all env variables with processbuilder

Question

I want to load the variables I have defined in the .bashrc file prior to the execution of a script from a java code. The script is executed via the ProcessBuilder. On the web, I see that the command array should be started with bash -c as below:

String[] cmdline = {"/bin/bash", "-c", "python", "/home/mahmood/temp.py"};
final ProcessBuilder pb = new ProcessBuilder(cmdline);
pb.command(cmdline);
pb.redirectOutput(Redirect.INHERIT);
final Process p = pb.start();
int exitCode = p.waitFor();
if (exitCode != 0) {
   throw new IOException("... python failed :( \n");
}

Indeed the waitFor never returns! If I drop the bash -c, then the exitCode will be non-zero since the variables have not been loaded.

Please note that there is not a single variable in the .bashrc. Can I fix the problem with ProcessBuilder or there is a better option for that?

Answer 1

Bash has to be invoked as an interactive shell to read and execute commands from ~/.bashrc. When running bash -c command you're executing command in a non-interactive shell. To run interactively (and read .bashrc), just add -i:

String[] cmdline = {"/bin/bash", "-ic", "python /home/mahmood/temp.py"};

Also, note that the command string (python /path/to/file) has to be specified as a single word (notice single quotes when invoked from shell):

bash -ic 'python /home/mahmood/temp.py'

or otherwise, bash will execute python (the first word) interactively (not running the script) -- and that's the reason your waitFor never returns.

---

Since running an interactive shell just to load some environment variables from .bashrc might be an overkill, you could extract the variables of interest in a separate file, for example:

export var1=val1
export var2='val 2'
...

and then source that file just before running your python script:

String[] cmdline = {"/bin/bash", "-c", ". /path/to/envfile; python /home/mahmood/temp.py"};