expectperl-discuss

[Expectperl-discuss] Occasional Pty problems with Expect on FreeBSD. Please help me!

[Dave S. <kin...@ya...>]

Hi!

I really need some help, and am so glad that I've
finally found this discussion group!

I am using Perl and Expect to manage a simple test
infrastructure at my company. Every so often a cron
job fires off a Perl script. That script then executes
other Perl scripts, which monitor tests via Expect.
Most of those scripts start out by calling
Expect->spawn("ssh"), to ssh to another machine and
run/monitor their specific test.

Occasionally though, Expect's spawn routine dies with
one of two errors, both of which come from the Pty.pm
module. I can't figure out what they mean or how to
fix them though, which is driving me batty!

1) "Cannot open a pty".
   This comes from a failure of the pty_allocate
function, in the "new" subroutine of Pty.pm. My Pty.pm
is version 1.02. I cannot find the "pty_allocate"
subroutine in any .pm or .pl file on my system, so I
don't know why it is failing sometimes.

2) "Error: could not connect pty as controlling
terminal!"
   I see this one more often. It is also in Pty.pm, in
the make_slave_controlling_terminal subroutine.
According to the code, it comes from a failure to open
/dev/tty.

Can anyone help me? Expect is about the only tool I
can use for my testing infrastructure (that I know
about at least). But these occasional failures make my
infrastructure itself unreliable. I could really use
some assistance.

Thanks so much,
Dave

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Re: [Expectperl-discuss] Occasional Pty problems with Expect on FreeBSD. Please help me!

[Roland G. <RGi...@cp...>]

> 1) "Cannot open a pty".
>    This comes from a failure of the pty_allocate
> function, in the "new" subroutine of Pty.pm. My Pty.pm
> is version 1.02. I cannot find the "pty_allocate"
> subroutine in any .pm or .pl file on my system, so I
> don't know why it is failing sometimes.

Looks like you ran out of ptys on your system. This can happen if you 
have a lot of simultanious connections to spawned commands (or a lot of 
windows open). You didn't say what OS you are running on, you may want 
to look into /dev to see how pty* there are. Or into /dev/ptmx/. Go ask 
a local guru.

BTW, the pty_allocate() is written in C and in an .XS module...


> 2) "Error: could not connect pty as controlling
> terminal!"

This may be related to 1) and also is very system-dependent. Maybe an 
OS-upgrade is in order?

Oh, and I think somebody already pointed out the SSH module? Be sure to 
read the entry in the Expect FAQ about automating ssh. You should NOT be 
using Expect purely to enter passwords for login, there are better 
mechanisms for that...

Hope this helps,

Roland
--
RGi...@cp...

Re: [Expectperl-discuss] Occasional Pty problems with Expect on FreeBSD. Please help me!

[Dave S. <kin...@ya...>]

I am running FreeBSD. I've also used the MAKEDEV
command to make as many ptys on my machine as it can
support, which is supposedly 256. I know that I am not
using that many though.

I am not using Expect purely for interaction with the
ssh login prompt. I also need it to send commands to
programs that run within the ssh shell, and to read
back the output of those commands. If you know of
another way to do this (besides the already mentioned
Net::SSH), I'd be grateful for the info.

Thanks,
Dave

--- Roland Giersig <RGi...@cp...> wrote:
> > 1) "Cannot open a pty".
> >    This comes from a failure of the pty_allocate
> > function, in the "new" subroutine of Pty.pm. My
> Pty.pm
> > is version 1.02. I cannot find the "pty_allocate"
> > subroutine in any .pm or .pl file on my system, so
> I
> > don't know why it is failing sometimes.
> 
> Looks like you ran out of ptys on your system. This
> can happen if you 
> have a lot of simultanious connections to spawned
> commands (or a lot of 
> windows open). You didn't say what OS you are
> running on, you may want 
> to look into /dev to see how pty* there are. Or into
> /dev/ptmx/. Go ask 
> a local guru.
> 
> BTW, the pty_allocate() is written in C and in an
> .XS module...
> 
> 
> > 2) "Error: could not connect pty as controlling
> > terminal!"
> 
> This may be related to 1) and also is very
> system-dependent. Maybe an 
> OS-upgrade is in order?
> 
> Oh, and I think somebody already pointed out the SSH
> module? Be sure to 
> read the entry in the Expect FAQ about automating
> ssh. You should NOT be 
> using Expect purely to enter passwords for login,
> there are better 
> mechanisms for that...
> 
> Hope this helps,
> 
> Roland
> --
> RGi...@cp...
> 
> 
> 
>
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