Re^5: System command silent screen

No, it isn't perfect. It invokes an unknown shell with unquoted arguments. That's begging for trouble.

If you want your script to play safe, fork() manually, then open /dev/null (or even better the return value of File::Spec->devnull()) as STDOUT and STDERR in the child process, then call exec() with a list of program name and arguments. In the parent process, wait() or waitpid() for the PID returned by fork().

This way, no shell is involved, and all of those nasty quoting problems are magically gone.

Of course, this requires more typing and more thinking. Alternatively, you can use one of the CPAN modules that wraps open(), fork(), exec(), waitpid(). Look at IPC::Run and IPC::Run3.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

Comment on Re^5: System command silent screen Select or Download Code

Replies are listed 'Best First'.
Re^6: System command silent screen by ikegami (Patriarch) on Oct 10, 2010 at 21:20 UTC
No, it isn't perfect. It invokes an unknown shell with unquoted arguments. That's begging for trouble. If there is a non-zero number of arguments, the following remove the need for quoting: `use IPC::Open3 qw( open3 ); { open(local FR_NULL, '<', '/dev/null') or die; open(local TO_NULL, '>', '/dev/null') or die; my $pid = open3('<&FR_NULL', '>&TO_NULL', undef, $command, @arguments); waitpid($pid, 0) or die; }` [download]	[reply] [d/l]
Re^7: System command silent screen by sundialsvc4 (Abbot) on Oct 11, 2010 at 13:31 UTC
I nevertheless prefer afoken’s solution, because it would be a general one. (Also, as noted, it is something that has probably already been done.) In my book, it is well worth the “extra effort” to develop a solution that makes a problem go-away completely, in every case, and never come back under any (unforseen at the time it was written) circumstances. (The “suh-prize!”-es usually pop up at three o’clock in the morning.) Best to “whack that mole” such that it stays whacked.
Re^8: System command silent screen by ikegami (Patriarch) on Oct 11, 2010 at 18:24 UTC
I nevertheless prefer afoken’s solution Using fork and exec and pipe and dup2 yourself? You're talking about a substantial amount of code. (50 lines?) That's the solution of his I was replacing.	[reply]
Re^6: System command silent screen by chuckbutler (Monsignor) on Oct 10, 2010 at 23:52 UTC
I have a working example of IPC::Run3 included in the following node Re: Automating user input for a CLI-based program on windows. You are able to process the ouput as you need, including discarding it. Good luck. -c	[reply]


Just another Perl shrine
	PerlMonks