How can I tell matlab it's running in the background?

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Leo Simon 2013-3-11

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评论： Leo Simon 2014-4-14

I'd like to be able to run a job either in the background or in the foreground. My program runs fine in the foreground but crashes in the background, presumably because it's not seeing some environment variable. The command that causes the crash is useful only for foreground applications (it relates to screen output) so I could easily avoid this problem if I could flag whether or not the program is running in the foreground. So my question is: does matlab know if it's being run as a foreground or background application, and if yes, what variable would indicate this?

Thanks for any advice

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Jason Ross 2013-3-11

Can you clarify which operating system you are using?

And say exactly how are you get getting "foreground" and "background", e.g. you hit control-z, use nohup, launch from the command line with switches, use a job scheduler, etc.

Leo Simon 2013-3-31

Hi Jason, Sorry somehow I missed your response. Sorry for the lack of clarity.

I'm running on linux.

sometimes I run using nohup, other times using the -r flag.

I want to distinguish either case from when I'm running a command from within matlab.

In particular, I have a program that I sometimes run as a batch job, other times from within a matlab session. If the former I want to quit out of it, if the latter I want simply to return to the caller workspace

Thanks

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Answer 1

Jason Ross 2013-4-1

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I would run "system(env)" in both modes, put the output to a file, and diff them.

I have a sneaking suspicion that the difference is tied to the DISPLAY environment variable.

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Leo Simon 2014-4-14

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Thanks very much Jason, you're quite right! I don't know why I didn't try your suggestion before now. But it works beautifully, at least for linux, haven't tried it on anything else.

In case anybody else cares about this (doesn't seem that way!) here's some code that does the check

%Checks whether a program is running the foreground or background.
%It's in the foreground iff there's a line in system('env') that says
%   DISPLAY=:0
function isBg = bgfg;
isBg    = 1;
[~,myEnv] = system('env');
startString=findstr('DISPLAY',myEnv);
for ii=1:numel(startString);
    endString=startString(ii)+8;
    if strcmp(myEnv(endString:endString+1),':0');
        isBg=0;
        break;
    end;
end;