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From: Jay@deepthot.UUCP (Jay Denebeim)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: HELP with Independant Children Processes
Message-ID: <Jay.9138@deepthot.UUCP>
Date: 5 Feb 91 15:20:03 GMT
References: <1991Feb4.171549.28531@nntp-server.caltech.edu>
Organization: The Software Distillery
Lines: 85

In article <1991Feb4.171549.28531@nntp-server.caltech.edu> tll@nntp-server.caltech.edu (Tal Lewis Lancaster) writes:
>I have the following requiremnts:
>
>A parent process that starts up children processes and waits for them
>before continuing.  The child might require up to 50 arguments.  These
>arguments concatenated togther could total 1000 characters.  The parent
>needs to know if the child succeeded or failed (ie. returns 0 if okay,
>anything else if failed).  Here's the catch the child must be an independant
>program capable of being run on its own from CLI (just like COPY, MAKEDIR, etc.)

Under 2.0 you've got two choices:
  System()
  Execute()
  
System executes syncronously, and returns the return code of the child
task to the caller.

Execute executes asyncronously, and returns success of the launching of
the program.

So, if you need to launch several processes at the same time, execute
is your only choice.  If only one process is needed, System will do
what you want.

As far as passing parameters go, I would suggest concidering opening
up a public port, and have the child ask for the parameters.  You have
to open a port anyway in the execute case, as there is no mechinism 
defined to return the return code in the Execute case.

If I was writing the code, it would go something like this:

Parent:
  Open port
  Execute child (either passing the address of the port on the command
    line, or the name of the port if public)
  Forever
    Wait on Port
    While message available
      Process message
      If message=child complete break;
    end
  end
  
Child:
  Find Port
  Ask for Parms
  Do my thing
  Tell parent byebye
  exit
  
In the system case:
Parent:
  rc = System child
  
Child:
  do my thing
  return rc
  
It all depends on what you want to do.  Since I like multi-tasking, I'd
probably start the child and then do more work while the child was doing
its thing.

>
>Which Amiga function will I need to call in the parent program to start up
>the child to accomplish this?  It can be either 1.3 or 2.0.  
>
>Does anybody know the string length limit for the 2.0 System() call?  Is it the
>same as a CLI command 256?
Sorry, don't know for sure.  Reading between the lines of the autodoc,
I'd say same limitations as the CLI, but I'm not sure that the 256 byte
limit in the CLI is still there.  Its not BCPL anymore.
>
>Thanks in advance,
>
>Tal Lancaster
>tll@tybalt.caltech.edu

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