qx and stderr

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

i am using the following bit of code:

     my $return = qx/$cmd/;
[download]

this works wonderfully for stdout of the system command contained in $cmd. however, i also need to cature stderr. imbedding 2>&1 into $cmd isn't working. i am aware of ipc::open3 but am not having any luck convincing him-who-installs-perl-modules to take any action.

are there any alternatives or suggestions? - d

20050224 Janitored by Corion: Added code tags, formatting

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Re: qx and stderr by Fletch (Bishop) on Feb 23, 2005 at 18:50 UTC
Erm, IPC::Open3 is core (i.e. ships with perl) and has been for a while now (see `perldoc perlmodlib`). You shouldn't need to convince anyone to install it unless you've got a broked install of perl itself. Update: Oh, and the alternative is to use `2>tmpfile` and let the shell redirect stderr to a file. You then check if `-s "tmpfile"` and handle whatever error output if necessary.	[reply] [d/l] [select]
Re: qx and stderr by RazorbladeBidet (Friar) on Feb 23, 2005 at 18:46 UTC
are you using strict? is the definition of command declared in single or double quotes? $output = `ls -? 2>&1` works fine for me Update: Hmm.. I thought that defining in double quotes using &1 would possible cause problems - hence the strict question - no matter. But: `my $cmd = "ls -? 2>&1"; $output = qx/$cmd/; print "-" x 50, "\n", $output, "\n", "-" x 50, "\n"` [download] works fine for me -------------- It's sad that a family can be torn apart by such a such a simple thing as a pack of wild dogs	[reply] [d/l] [select]
Re^2: qx and stderr by Anonymous Monk on Feb 23, 2005 at 18:53 UTC
no, i'm not using strict. but your inquiry about quoting may be my problem. this is how i'm putting a value into $cmd: qq/remsh $ctm_server -l ctmsrv "ctmshout -dest ECS -message '$msg'"/ i've got quotes on top of quotes on top of quotes (sigh). perhaps 2>&1 should be inbetween the last single and double (literal) quotes? - d	[reply]
Re^3: qx and stderr by RazorbladeBidet (Friar) on Feb 23, 2005 at 19:00 UTC
Ohh... well, not sure what NIX you're using, but the -a flag for remsh might help (as will the -n flag). Have you tried those? -------------- It's sad that a family can be torn apart by such a such a simple thing as a pack of wild dogs*	[reply]
Re: qx and stderr by dragonchild (Archbishop) on Feb 23, 2005 at 18:52 UTC
How are you embedding "2>&1" into $cmd? You might have to use single-quotes for that part. I would look at IPC::Cmd as well as IPC::Open3. The former provides the STDERR/STDOUT streams as lists where the latter requires filehandles. You can install them yourself, even by just cut'n'pasting the code - they're both PurePerl modules. Being right, does not endow the right to be rude; politeness costs nothing. Being unknowing, is not the same as being stupid. Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence. Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.	[reply]
Re^2: qx and stderr by amw1 (Friar) on Feb 23, 2005 at 21:43 UTC
Agreed. IPC::Open3 or IPC::Cmd should do it. Re: IPC::Open3 woes has a decent open3 example.	[reply]
Re: qx and stderr by perlfan (Parson) on Feb 23, 2005 at 18:45 UTC
You can use "eval" in a try/catch sort of way......	[reply]