[sf-perl] Async or Sync

[Adam Morgan]

You can also open a FILEHANDLE that has it's input piped in from a
system process. This would allow you to do other things in your code and
return to the input when you or it the data is ready. I don't know if
this is truly asynchronous because the pipe will halt the system process
when it has some preset amount of data waiting on it.

eg. open(INDATA, "system_command |"); 

-----Original Message-----
From: sanfrancisco-pm-bounces+adam.morgan=safeway.com at pm.org
[mailto:sanfrancisco-pm-bounces+adam.morgan=safeway.com at pm.org] On
Behalf Of David Alban
Sent: Saturday, March 10, 2007 10:48 AM
To: San Francisco Perl Mongers User Group
Subject: Re: [sf-perl] Async or Sync

       system LIST
       system PROGRAM LIST
               Does exactly the same thing as "exec LIST", except that a
fork
               is done first, and the parent process waits for the child
               process to complete.  Note that argument processing
varies
               depending on the number of arguments.  If there is more
than
               one argument in LIST, or if LIST is an array with more
than one
               value, starts the program given by the first element of
the
               list with arguments given by the rest of the list.  If
there is
               only one scalar argument, the argument is checked for
shell
               metacharacters, and if there are any, the entire argument
is
               passed to the system's command shell for parsing (this is
               "/bin/sh -c" on Unix platforms, but varies on other
platforms).
               If there are no shell metacharacters in the argument, it
is
               split into words and passed directly to "execvp", which
is more
               efficient.

    [...]

On 3/10/07, Neil Heller <nheller at silcon.com> wrote:
> When I launch a program from within a Perl script via a "system" call,

> is the return asynchronous or synchronous?

I believe "waits for the child to complete" answers this question.

> Is there any way to specifically
> control that from within the calling script?

fork() and exec()?

Call system() with a command ending in ampersand (to get asynchronous
behavior)?

Call system() with a command that will itself call other things
asynchronously (and thus, has the potential to return right away)?

--
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"MMS <safeway.com>" made the following annotations.
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