async system()?

[AJ ONeal]

How do I make a system call without waiting for it to finish?

I'm looking for something like

int pid = async_system(char*);

which I could then use with, say, libev's ev_child.


AJ ONeal

[Shawn]

On Dec 19, 2:53 pm, AJ ONeal <coola...@gmail.com> wrote:
> How do I make a system call without waiting for it to finish?

The normal approach is to use fork() to create the child process and
then the appropriate member of the exec*() family of functions to load
the appropriate program for the child.

If you need to do I/O with the child process, use popen(). It does
the fork and exec for you (actually it invokes a shell and has it
execute the string you provide), and returns a file handle that
represents stdin/stdout of the child process.

There are libraries that provide higher-level APIs for starting and
managing child processes, but fork(), exec*() and popen() are all
POSIX and therefore portable.

[AJ ONeal]

I haven't used exec before, but I'll try it out tomorrow and post back with a simple example if no-one else does first.

That was enough information to get me started down the right path.

AJ ONeal

http://en.wikipedia.org/wiki/Fork-exec
http://en.wikipedia.org/wiki/Exec_(operating_system)

On Sun, Dec 19, 2010 at 3:14 PM, Shawn Willden <shawnw...@gmail.com> wrote:

(I tried to reply to the list, but my messages keep bouncing.  I have to look into that.)

On Sun, Dec 19, 2010 at 2:53 PM, AJ ONeal <cool...@gmail.com> wrote:

How do I make a system call without waiting for it to finish?

The normal approach is to use fork() to create the child process and then the appropriate member of the exec*() family of functions to load the appropriate program for the child.

If you need to do I/O with the child process, use popen().  It does the fork and exec for you (actually it invokes a shell and has it execute the string you provide), and returns a file handle that represents stdin/stdout of the child process.

There are libraries that provide higher-level APIs for starting and managing child processes, but fork(), exec*() and popen() are all POSIX and therefore portable.

-- 

Shawn

[Shawn]

On Dec 19, 3:30 pm, AJ ONeal <coola...@gmail.com> wrote:
> I haven't used exec before, but I'll try it out tomorrow and post back with
> a simple example if no-one else does first.

There are some good examples at http://www.osix.net/modules/article/?id=641

It's pretty straightforward once you get your head around the idea of
the "duplicate myself, then replace one of me" approach to creating
child processes.

[Alex Esplin]

On Sun, Dec 19, 2010 at 15:22, Shawn <shawnw...@gmail.com> wrote:
> If you need to do I/O with the child process, use popen().  It does
> the fork and exec for you (actually it invokes a shell and has it
> execute the string you provide), and returns a file handle that
> represents stdin/stdout of the child process.

+1 for popen(). I've used it a lot and it's _incredibly_ handy.

--
Alex Esplin