On Jan 6, 2010, at 6:31 PM, Kevin Grittner wrote:
> As far as I've been able to determine so far, to call psql in a
> relatively portable way would require something like this:
>
> http://perldoc.perl.org/perlfork.html
Here's an example using IPC::Open3:
#!/usr/local/bin/perl -w
use strict; use warnings;
use IPC::Open3; use Symbol 'gensym'; use constant EOC => "__DONE__\n";
my ($in1, $out1, $err1) = (gensym, gensym, gensym); my ($in2, $out2, $err2) = (gensym, gensym, gensym);
my $pid1 = open3 $in1, $out1, $err1, 'bash'; my $pid2 = open3 $in2, $out2, $err2, 'bash';
print $in1 "cd ~/dev/postgresql\n"; print $in1 "ls doc\n"; print $in1 "echo ", EOC; while ((my $line =
<$out1>)){ last if $line eq EOC; print "LS: $line"; }
print "#### Finished file listing\n\n";
print $in2 "cd ~/dev/postgresql\n"; print $in2 "head -4 README\n"; print $in2 "echo ", EOC; while (defined( my
$line= <$out2> )) { last if $line eq EOC; print "HEAD: $line"; }
print "#### Finished reading README\n\n";
print $in1 "exit\n"; print $in2 "exit\n"; waitpid $pid2, 0;
print "#### All done!\n";
With that, I get:
LS: KNOWN_BUGS LS: MISSING_FEATURES LS: Makefile LS: README.mb.big5 LS: README.mb.jp LS: TODO
LS: bug.template LS: src #### Finished file listing
HEAD: PostgreSQL Database Management System HEAD: ===================================== HEAD: HEAD:
Thisdirectory contains the source code distribution of the PostgreSQL #### Finished reading README
#### All done!
I could easily write a very simple module to abstract all that stuff for you, then you could just do something like:
my $psql1 = Shell::Pipe->new(qw(psql -U postgres)); my $psql2 = Shell::Pipe->new(qw(psql -U postgres));
$psql1->print('SELECT * from pg_class'); while (my $line = $psql1->readln) { print "Output: $line\n" }
$psql1->close;
All I'd need is some more reliable way than "echo "DONE__\n" to be able to tell when a particular command has finished
outputting.
Thoughts?
Best,
David
