On 6/13/2016 03:20, pit wrote:
Am Mittwoch, 8. Juni 2016 17:22:34 UTC+2 schrieb pit:
Hi Folks,
whats the best way to open documents with several filetypes from a perl/tk-program under windows.
Thanks
Pit
I mean open it with the app that is intended to process that type of file as in 'start' from command line.
Still not much detail. Do you want to do multiple of these and
background the apps? Do you want to do them one at a time? Do
you know what apps are to process the files or do you want to
use the default process? Etc, etc, etc.
You could use `` or 'system' or 'fork' and 'exec' or read perlipc
man page for other possible solutions.
On Windoze, I would probably use 'system' with a start command and
possibly background it with & if you don't need to wait for it.
But you really should describe what you're doing for a proper response.
Your OS would in a large part determine how you would want do it -
you didn't state that either.
perlfaq8 says:
How do I start a process in the background?
(contributed by brian d foy)
There's not a single way to run code in the background so you don't have to
wait for it to finish before your program moves on to other tasks. Process
management depends on your particular operating system, and many of the
techniques are covered in perlipc.
Several CPAN modules may be able to help, including IPC::Open2 or
IPC::Open3, IPC::Run, Parallel::Jobs, Parallel::ForkManager, POE,
Proc::Background, and Win32::Process. There are many other modules you might
use, so check those namespaces for other options too.
If you are on a Unix-like system, you might be able to get away with a
system call where you put an "&" on the end of the command:
system("cmd &")
You can also try using "fork", as described in perlfunc (although this is
the same thing that many of the modules will do for you).
STDIN, STDOUT, and STDERR are shared
Both the main process and the backgrounded one (the "child" process)
share the same STDIN, STDOUT and STDERR filehandles. If both try to
access them at once, strange things can happen. You may want to close or
reopen these for the child. You can get around this with "open"ing a
pipe (see "open" in perlfunc) but on some systems this means that the
child process cannot outlive the parent.
Signals
You'll have to catch the SIGCHLD signal, and possibly SIGPIPE too.
SIGCHLD is sent when the backgrounded process finishes. SIGPIPE is sent
when you write to a filehandle whose child process has closed (an
untrapped SIGPIPE can cause your program to silently die). This is not
an issue with "system("cmd&")".
Zombies
You have to be prepared to "reap" the child process when it finishes.
$SIG{CHLD} = sub { wait };
$SIG{CHLD} = 'IGNORE';
You can also use a double fork. You immediately "wait()" for your first
child, and the init daemon will "wait()" for your grandchild once it
exits.
unless ($pid = fork) {
unless (fork) {
exec "what you really wanna do";
die "exec failed!";
}
exit 0;
}
waitpid($pid, 0);
See "Signals" in perlipc for other examples of code to do this. Zombies
are not an issue with "system("prog &")".
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