redirect output

Sun751 has asked for the wisdom of the Perl Monks concerning the following question:

I am writing a script which execute some commands and also runs third party script.
I am trying to redirect the output generated my 3rd party script and I came through this command,

perl test.pl >/dev/null
[download]

But if I do this, this will redirect the output I want to generate too,
for example I want "Processing going on..."
So can any one suggest me how can I redirect any output generate by script to >/dev/null rather than "Processing going on...". Any suggestion?Please.
Cheers,
Update.. For example,
I don't want any output generated by following commands,

open(EMAIL, "| $cmd")|| exe_err($cmd,'0','Email script');
[download]

And I want this output

 print "Please Check Log: 'log.log' file\n";
 exit;
[download]

Any suggestion? Cheers,

Comment on redirect output Select or Download Code

Replies are listed 'Best First'.
Re: redirect output by ELISHEVA (Prior) on Jul 17, 2009 at 07:11 UTC
The output you are "generating" is also getting redirected because both the output you want to "generate" and the output you want to throw away (to >/dev/null>) are being sent to STDOUT (standard out). The only reliable way to send output to two different places is to send it to two different places. You'll need to set up your script so that the output want to throw away is being sent to a different place, e.g. STDERR. If you aren't sure how to do this, you might want to update your original post with a bit of your code showing how the third party script and your other commands are being called. Be sure to add comments indicating the parts you consider "generated" and the parts you'd like to throw away to `/dev/null` Best, beth	[reply] [d/l]
Re: redirect output by moritz (Cardinal) on Jul 17, 2009 at 07:01 UTC
`perl test.pl \| grep 'Processing going on'` [download] Something along these lines?	[reply] [d/l]
Re: redirect output by llancet (Friar) on Jul 17, 2009 at 08:47 UTC
You should use the STDERR handle, which is pre-opened in every script. Generally, you may use it directly, and there is no need to open it. `print STDERR "processing..\n"; print $result; print STDERR "done\n";` [download]	[reply] [d/l]
Re: redirect output by Bloodnok (Vicar) on Jul 17, 2009 at 11:31 UTC
As both ELISHEVA & llancet have pointed out, you _could_ use an alternate file handle/stream to receive the unwanted output, but IMO, this would have the dual disadvantages of... Going against the grain and using STDERR for non error/warning output Not being future proof - who knows what/which output my, or may not, be dispensable at some later point whereas moritzs `grep` based suggestion has neither disadvantage - at the notional cost of an additional run-time process. Just my 2 penn'orth :-) A user level that continues to overstate my experience :-))	[reply] [d/l]
Re: redirect output by ig (Vicar) on Jul 18, 2009 at 16:39 UTC
I would redirect the output of the sub-command rather than the calling script. `use strict; use warnings; print "about to open cat in a sub-process\n"; open(CAT, '\|-', "cat") or die "open cat failed: $!"; print CAT "This was written to cat without output redirected\n"; close(CAT); open(CAT, '\|-', "cat > /dev/null") or die "open cat failed: $!"; print CAT "This was written to cat with output redirected\n"; close(CAT); print "all done\n";` [download] produces `about to open cat in a sub-process This was written to cat without output redirected all done` [download]	[reply] [d/l] [select]


Perl-Sensitive Sunglasses
	PerlMonks