[AWS] *NIX daemons using AWS

[Jacob Sparre Andersen]

Peter Fedorow wrote:

> How much of what should be done when writing a *nix daemon
> in C, Pascal, or Perl, applies to writing one in Ada?

The visible effect should be the same, but you don't have to 
code it the same way.

> How should a process written in Ada fork?

I do it with '&' when the Ada program is launched.  This is
of course a little bit cheating, but it is much simpler and
works quite well. - And you will typically have a script to
control the launch of the daemon anyway.

> Are there any already written libraries or code examples
> to do this?

I don't know of any.

> > From The Linux Daemon Writing HOWTO:
> > ---
> > When a daemon starts up, it has to do some low-level housework to get
> > itself ready for its real job. This involves a few steps:
> > 
> >     * Fork off the parent process

Using `ada_program &` in the launch control script.  
Alternatively one can call "daemon()".  It should be pretty
trivial to create a binding to that function.

> >     * Change file mode mask (umask)

I don't get the point, but this is again something you can
do from the launch control script.

> >     * Open any logs for writing

"Open (Mode => Append_File, ...);" or, if you want to be
fancy, binding to syslog.  Another alternative is to use 
Standard_Output and Standard_Error for logging:

   ada_program 1>>/var/log/ada_program/log \
               2>>/var/log/ada_program/errors &

> >     * Create a unique Session ID (SID)

I'll have to read the full text to figure out what this 
means.

> >     * Change the current working directory to a safe
> >       place

I don't think this is of much real use, but `cd /safe/place`
in the daemon control script will do the job.

> >     * Close standard file descriptors

"daemon()" does this.  So does `ada_program
1>>/var/log/ada_program/log 2>>/var/log/ada_program/errors
&` effectively.

Greetings,

Jacob
-- 
"You've got to build bypasses!"