Execute as new process?

perlpreben has asked for the wisdom of the Perl Monks concerning the following question:

I want a webpage(cgi script) to execute a perl script , but continue loading the webpage. Now it waits until the program is done, THEN continues.

I have read documentation on exec, system, backticks, and tried numerous examples but can make it work.

Its running on a unix system, so I also tried appending & at the end of the command, but that doesnt work either

Any clue?

Comment on Execute as new process?

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Re: Execute as new process? by jakobi (Pilgrim) on Sep 29, 2009 at 20:50 UTC
lower level approaches: system and qx// are synchronous and make perl wait until the syscall in question is done. You could try system("cmd&") to have the shell run the command and return to perl w/o waiting. An interesting question now is whether you want $? or the output of the command before finishing to send the page to the client. If that's the case: check out e.g. waitpid, perlipc and maybe also use something like the following sketch `if (not fork()) {system("cmd >cmd-out"); ... exit} ...additionalprocessing-in-parallel...; wait; # or a more specific waitpid...; # if you've a lot of forks and/or run a long time, # consider to reap your children: wait, SIG{CHLD} # -> man perlipc open(FH,"<cmd-out");... ...process the results of cmd and add them to the page... # (or consider a state file/sessions, if the background # command can and should run for more than the duration # of a single client request) finish the page` [download]	[reply] [d/l]
Re: Execute as new process? by Joost (Canon) on Sep 29, 2009 at 21:18 UTC
Either use system("whatever &") to let the shell do the lifting for you, or do a fork() then an exec() if you need more control. This is assuming you don't need any output or exit status from the child process. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re: Execute as new process? by Illuminatus (Curate) on Sep 29, 2009 at 20:49 UTC
I think you need to provide an example. In general, if you use `system` with a command that ends with a '&', the call should immediately return.	[reply] [d/l]
Re: Execute as new process? by corenth (Monk) on Sep 29, 2009 at 21:53 UTC
A long time ago, I played with POE (Perl Object Environment) to good effect. I don't recall much about it, and it may not be what you want, but it should give you the effect you're looking for.	[reply]
Re: Execute as new process? by Utilitarian (Vicar) on Sep 29, 2009 at 20:40 UTC
I think you should look at making the Perl produced content of the page load via AJAX	[reply]
Re: Execute as new process? by Anonymous Monk on Sep 30, 2009 at 04:46 UTC
Proc::Background, Watching long processes through CGI (Aug 02)	[reply]