Re: Creating an executer

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I only skimmed this, but afaik the only way to get the child PID is to
"fork" rather than to "exec".

On Thu, May 24, 2007 10:10 am, lists@xxxxxxxxxxx wrote:
> Hi,
>
> Summary:
>
> 1. I execute script1 that will run in the background (daemon)
> 2. script1 needs to execute script2 and capture STDERR, STDOUT and
> exitcode from script2 if script2 exits before SIGTERM is received.
> 3. If I send SIGTERM to script1 it should kill script2, and write to
> DB (or log  file some information that it was stopped)
>
> Simple, isn't it? But I cannot seam to get it to work. Anyone with
> some example code that does the same thing?
>
>
> =========
>
> More complex description
>
> I have some scripts (perl, c, php, or anything else) that simple
> independent scripts that do some stuff and output STDOUT and STDERR
> and exit with an exitcode. There scripts will be kept like this, and
> will not change their behavior.
>
> Now I need to control them and also log their STDOUT, STDERR and
> exitcode. Ok, that far I have come, so that I am logging the STDOUT,
> STDERR and exitcode. What I am doing is that I have created an
> executer that takes care of this and writing it to DB.
>
> Now I need to add a functionality so that when the executer receives a
> SIGTERM signal it should kill the script (that was started with a
> exec() call, and then log some information to the DB (that the script
> was killed etc).
>
> I have registered the signal SIGTERM with pcntl_signal(SIGTERM,
> "sig_handler"). When I am testing I just write some info to a file
> when the signal is received. I created a simple testing script with a
> while(true) loop and then send the signal to the script and it
> successfully writes the information to the logflie.
>
> Ok, now I instead of a while(true) loop make an exec() call to a
> script (that is running for ever) and send the signal, then it does
> not write to the file as it is supposed to. I guess it is because the
> script is busy running the exec command.
>
> I tried to then exec() it in the background. The problem there is that
> it becomes a daemon and then I cannot know what that script is doing,
> and it will not send any SIGCHLD to the parent, or it does, but to
> init. Or actually there will be a SIGCHLD sent, as the exec() will
> open its own shell, and then the shell will exit and we get the
> SIGCHLD from the shell instead of the executed script.
>
> Is there any way to get the "child" process PID when you exec() and
> send it to the background? But then, how can I capture the exitcode?
> The STDERR and STDOUT is fine as I can direct it to a file and get it
> from there.
>
> I have a really ugly workarounds: I could append an dummy variable to
> the execution of the script and then do a grep of the ps -ef to get
> the PID of that script.
>
> /Peter
>
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>


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