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lib/CWB/CQP.pm  view on Meta::CPAN

=head1 DESCRIPTION

A B<CWB::CQP> object represents an instance of the corpus query processor CQP
running as a background process.  By calling suitable methods on this object,
arbitrary CQP commands can be executed and their output can be captured.   
The C<STDERR> stream of the CQP process is monitored for error messages,
which can automatically trigger an error handler.

Every B<CWB::CQP> object has its own CQP background process and communication is
fully asynchronous.  This enables scripts to perform other actions while a long
CQP command is executing, or to run multiple CQP instances in parallel.

=cut

use warnings;
use strict;

use sigtrap qw(die PIPE);       # catch write errors to background CQP process
## $SIG{'CHLD'} = 'IGNORE'; # it would be nice to reap child processes automatically, but this seems to mess up closing pipes

lib/CWB/CQP.pm  view on Meta::CPAN

    push @{$self->{'error_message'}}, split /\n/, $stderr_buffer;  # append output on stderr to error message
    $self->error(@{$self->{'error_message'}});                     # may call error handler and abort, or print message and continue
  }
  return $lines;
}

=item I<$cqp>->B<run>(I<$cmd>);

Start a single CQP command I<$cmd> in the background.  This method returns immediately.
Command output can then be read with the B<getline>, B<getlines> and B<getrow> methods.
If asynchronous communication is desired, use B<ready> to check whether output is available.

It is an error to B<run> a new command before the output of the previous command has completely
been processed.

=cut

sub run {
  croak 'USAGE:  $cqp->run($cmd]);'
    unless @_ == 2;
  my $self = shift;

t/31_cqp_dickens.t.dont_run  view on Meta::CPAN

  if ($r1->[0] != $r2->[0] or 
      $r1->[1] != $r2->[1] or 
      $r1->[2] != $r2->[2] or 
      $r2->[3] != -1) {
    print "\n!! returned row #".($i+1)." [@$r2] differs from undumped table [@$r1]\n";
    exit 1;
  }
}
print "ok\n";

# step 22: test asynchronous execution
print " - testing asynchronous command execution ... ";
$dickens_found = 0;
$CQP->run("show corpora");
while (defined($_ = $CQP->getline)) {
  $dickens_found = 1 if /^DICKENS$/
}
if (not $dickens_found) {
  print "\n!! corpus DICKENS not found in output of 'show corpora'\n";
  exit 1;
}
print "ok\n";