[fpc-pascal] Executing another program from Pascal

[Elio Cuevas Gómez]

El Mar 28 Mar 2006 13:40, Hans Mårtensson escribió:
> In good old days the Turbo Pascal had an EXEC procedure that could
> execute another program by invoking the DOS command interpreter.

I think that function is in the DOS unit. And it even works in Linux!

>
> In better new days the FPC does not seem to have such an option, or I
> couldn’t find it in the docs.
> Now I am particularly interested in doing such a thing in a Linux system.
>
> I have found in the unix unit a function FPEXECV(path, pp) that may be
> used for it, but it leaves a few questions to me.
>
> According to the docs the function does not return (if it succeeds). Is
> there no way of calling another program and then continue the calling
> program? Could it be done by starting a new thread, putting the call
> into that thread and let that thread not return while the main program
> continues? Will it leave allocated memory, that is never freed?
>

You must call fork() first an then call execv from the child process.

> If the function does not return, why is there a return integer value
> defined?
> (Or: why is it called a function, when it does not return?)

Who knows?

>
> In the doc’s example the FPEXECV(path, pp) has the same pchar in the
> path and as the first pchar of the pchar array that pp points to. I have
> tried similar examples, and they always seem to work with the same phar
> in the two places, but not otherwise. Is there some deeper philosophy in
> having the program-name in both path and in the first phar of the array?
>
> Hans Maartensson
>
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