java and system calls
 

Hi everyone, every time I try to do a system call that has inside some variable e.g:

helloWorld6Today is a C compiled program, imagine I have one for each day of the month.

String day=new String();
giveMeDay(day); --say it gives 6

Process egin=r.exec("/home/aizkorri/froga/helloWorld"+day+"Today");
egin.waitFor();

It just doesn't do anything, but If I do:

Process egin1=r.exec("/home/aizkorri/froga/helloWorld6Today");
egin1.waitFor();

It works.
And I think that it's pretty usual to use variables in that kind of calls, so do you have any idea what could be the problem?.

Try putting spaces in the string and see if it works


Process egin=r.exec("/home/aizkorri/froga/helloWorld "+day+" " +Today);

hi, well, but the file name doesn't have spaces, anyway, it doesn't even try to execute anything.

I see what you mean - I was reading it as two different parameters rather than one.

Only thing I can think of is giveMeDay is return a value you aren't expecting but I guess you've already checked that

I take it in the first example egin.WaitFor() returns a non-zero value showing there's been an error and at least it's tried to execute it.

thanks a lot, I found the error, it returns 1 but I forgot to put an important thing in the example: it does not work if I do:

Process egin=r.exec("/home/aizkorri/froga/helloWorld"+day+"*Today");
egin.waitFor();

Without the * it works fine, I was trying to execute more than one application at the same time but the * gives an error, I don't understand why, but it does.

I guess that's because the Java Virtual Machine does no use a shell to execute your command. The interpretation ("expansion") of wildcards ( * ? [a-z] ...) is always done by a shell.

thanks for the explanation