This is part of The Pile, a partial archive of some open source mailing lists and newsgroups.
To: "J. J. Horner" <jhorner@2jnetworks.com>
From: Brian Reichert <reichert@numachi.com>
Subject: Re: Running a shell command inside a cgi/perl
script
Date: Fri, 30 Nov 2001 16:23:41 -0500
Just to toot my own horn, I'd like to mention that I wrote the
System2 module, with an eye toward running commands, and getting
isolated STDOUT/STDERR as well as exit values. Well, it makes me
happy.
On Fri, Nov 30, 2001 at 03:45:23PM -0500, J. J. Horner wrote:
> * Kairam, Raj (KairamR@coned.com) [011130 15:10]:
> > In my perl script I have a line like this.
> > system( "'/usr/bin/lp -dhp4si /tmp/plotreq.txt' > /tmp/plotid.txt");
You've got these quotes wrong: you're executing a command (via Bourne
shell) called '/usr/bin/lp -dhp4si /tmp/plotreq.txt', which I expect
doesn't exist on your system. :)
> > I have tried this also and did not work.
> > @lplist = ("/usr/bin/lp", "-dhp4si /tmp/plotreq.txt");
> > system(@lplist);
Here, you're passing an argument to 'lp'; the filename it's looking
for is '-dhp4si /tmp/plotreq.txt'. Again, I doubt that exists on
your system. :)
> >
> > hp4si is the destination printer.
> > /tmp/plotreq.txt is small text file to be sent to the printer.
> > /tmp/plotid.txt is the output of lp command ( just one line to indicate job
> > id )to be saved.
> > If I run the command /usr/bin/lp -dhp4si /tmp/plotreq.txt > /tmp/plotid.txt
> > it is fine as a command line.
Here, your shell is breaking out the commands/arguments on whitespace,
which is what you were hoping for.
You'd want something like (modulo shell metacharacters, etc.):
system qw('/usr/bin/lp -dhp4si /tmp/plotreq.txt > /tmp/plotid.txt');
But this doesn't get you STDERR, if there was any sortr of problem.
So, I do this:
use System2;
my @args = qw('/usr/bin/lp -dhp4si /tmp/plotreq.txt');
my ($out, $err) = system2(@args);
You could now check $? for whether or not your invocation to lp failed:
my ($exit_value, $signal_num, $dumped_core) = &System2::exit_status($?);
warn "lp choked!: $err" if $exit_value;
And, depending on the success/failure you have all of the output
of lp in STDOUT or STDERR, as appropriate.
> > This is the context.
> > sub search {
> > some code
> > ....
> > open(REQFILE, ">/tmp/plotreq.txt") || die "sorry, could not open
> > /tmp/plotreq.txt";
You should use $! to print _why_ this failed.
> > some more code to generate content for plotreq.txt
> > ......
> > close(REQFILE);
> > .... This is where I tried the above to send the file to the printer.
> > }
Note that you aren't making use of unique filenames. This is a
CGI program; you could hypothetically have multiple instances of
this code running at once.
===
To: "Kairam, Raj" <KairamR@coned.com>, <modperl@apache.org>
From: "Rodney Broom" <mod_perl@rbroom.com>
Subject: Re: Running a shell command inside a cgi/perl
script
Date: Fri, 30 Nov 2001 13:56:05 -0700
From: Kairam, Raj <KairamR@coned.com>
> system( "'/usr/bin/lp -dhp4si /tmp/plotreq.txt' > /tmp/plotid.txt");
> If I run the command /usr/bin/lp -dhp4si /tmp/plotreq.txt > /tmp/plotid.txt
> it is fine as a command line.
I may be missing something, but it looks to me like you are running a different command from system() than what you are doing on the command line. That is, system() apears to be getting this:
'/usr/bin/lp -dhp4si /tmp/plotreq.txt' > /tmp/plotid.txt
And the shell apears to be getting this:
/usr/bin/lp -dhp4si /tmp/plotreq.txt > /tmp/plotid.txt
When I need error checking, I'll often use open() instead of system().
===