That works like a charm -- thanks!
"Chas. Owens" <chas.ow...@gmail.com> wrote on 07/05/2009 03:57:34 AM:
> From:
>
> "Chas. Owens" <chas.ow...@gmail.com>
>
> To:
>
> Eric Veith/Germany/i...@ibmde
>
> Cc:
>
> beginners@perl.org
>
> Date:
>
> 07/05/2009 03:58 AM
>
> Subject:
>
> Re: Redirecting STDOUT and STDERR for system()
>
> On Thu, Jul 2, 2009 at 04:36, Eric Veith<erve...@de.ibm.com> wrote:
> >
> > Hello List,
> >
> > as part of a Perl script of mine, I want to execute a program, get its
> > return code AND capture its output on both STDERR and STDOUT. I tried
> > IO::Handle, but that only gives me STDOUT and not the return code.
Using
> > qr//, I cannot read linewise and have to load the complete program's
output
> > into memory first, which I want to avoid. (Please feel free to correct
me
> > on anything of the above.)
> >
> > What I tried to archive now can be summarized in this little script:
> >
> > my $stdout = IO::File->new('stdout', 'w');
> > my $stderr = IO::File->new('stderr', 'w');
> >
> > my $pid = fork();
> > die("Could not fork, stopping") if(not defined $pid);
> >
> > if(0 == $pid) {
> > *STDOUT = $stdout;
> > *STDERR = $stderr;
> > system("df", "-h");
> > my $rc = $?;
> > $stdout->flush(););
> > exit($rc << 127););
> > } else {
> > print "Parent.\n";;
> > wait();
> > print "RC=$?\n";
> > }
> >
> > $stdout->close();
> > $stderr->close();
> >
> >
> > That does not, however, work as expected. I do get STDERR's output (if
I,
> > for example, change the command in system() to something that does not
> > work, e. g. system("df", "garbage", "-FOO"); the error is to be found
in
> > the stderr file), but not the output on STDOUT -- that is printed out
on
> > screen just as usual.
> >
> > What am I missing here? How can I do a fork, re-open STDOUT/STDERR to
write
> > to an instance of IO::Handle, and get the return code?
> >
> > Thanks for any hints.
> >
> > -- Eric
> >
> >
> > --
> > To unsubscribe, e-mail: beginners-unsubscr...@perl.org
> > For additional commands, e-mail: beginners-h...@perl.org
> > http://learn.perl.org/
> >
> >
> >
>
> You need [IPC::Open3][1]. It allows you to run a command and capture
> the STDOUT, STDERR, and (via the [$?][2] variable). Here is an
> example:
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> use IPC::Open3;
>
> #the program gets run by itself with an argument
> if (@ARGV) {
> print "this went to STDOUT\n";
> print STDERR "this went to STDERR\n";
> exit 55;
> }
>
> my $err = 1; #err handle must be true or it gets combined into out
> my $pid = open3 my $in, my $out, $err, $^X, $0, 1
> or die "could not run '$^X $0 1': $!";
>
> waitpid $pid, 0; #wait for program to finish;
> my $return_code = $? >> 8;
> my $stdout = join "", <$out>;
> my $stderr = join "", <$err>;
>
> print "I saw $return_code as the return code\n",
> "and [$stdout] on STDOUT and [$stderr] on STDERR.\n";
>
>
> [1] : http://perldoc.perl.org/IPC/Open3.html
> [2] : http://perldoc.perl.org/perlvar.html#$?
>
> --
> Chas. Owens
> wonkden.net
> The most important skill a programmer can have is the ability to read.
>
> --
> To unsubscribe, e-mail: beginners-unsubscr...@perl.org
> For additional commands, e-mail: beginners-h...@perl.org
> http://learn.perl.org/
>
>
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