Asp Forum - ENV['COLUMNS']

pedro mg

2/10/2007 8:48:00 AM

Hi,

in irb I can have access to ENV['COLUMNS'] for the # of columns in the
shell, and works fine.
But inside a script (ruby script.rb), I can't have access to that hash
key and value.
I've done a:

puts ENV.to_a

and i can not see both COLUMNS and LINES
What would be the problem ?
--
pedro mg

7 Answers

Brian Candler

2/10/2007 1:38:00 PM

On Sat, Feb 10, 2007 at 08:25:09PM +0900, pedro mg wrote:
> in irb I can have access to ENV['COLUMNS'] for the # of columns in the
> shell, and works fine.
> But inside a script (ruby script.rb), I can't have access to that hash
> key and value.
> I've done a:
>
> puts ENV.to_a
>
> and i can not see both COLUMNS and LINES
> What would be the problem ?

Nothing to do with ruby...

brian@mappit:~$ echo $COLUMNS
80
brian@mappit:~$ printenv | grep COLUMNS
brian@mappit:~$

This is a shell-internal variable, and not exported by default to processes
launched from the shell. But it can be if you wish:

brian@mappit:~$ export COLUMNS
brian@mappit:~$ printenv | grep 80
COLUMNS=80
brian@mappit:~$

Brian.

Brian Candler

2/10/2007 2:57:00 PM

On Sat, Feb 10, 2007 at 10:56:35PM +0900, Lloyd Zusman wrote:
> > This is a shell-internal variable, and not exported by default to processes
> > launched from the shell. But it can be if you wish:
>
> Well, if that were the case, the variable wouldn't be visible within
> irb, either. Since it is, then it must be an exported environment
> variable and not just shell internal.

Well, on my system:

brian@mappit:~$ irb1.8
irb(main):001:0> ENV.size
=> 39
irb(main):002:0> exit
brian@mappit:~$ ruby1.8 -e 'puts ENV.size'
37
brian@mappit:~$ printenv | wc -l
37
brian@mappit:~$

So my guess is that irb is setting these variables itself, or calling some
library which does so (readline perhaps?)

> I think that the problem has to do with how script.rb is being invoked.
> Is it started from something other than a terminal session? ... perhaps
> via a cron job or a startup daemon? If so, then LINES and COLUMNS would
> not normally be set, since those environment variables are usually
> initialized and exported only within an interactive shell.

I thought of that, but all the examples shown above and in my previous reply
were typed into a terminal session.

Regards,

Brian.

akbarhome

2/10/2007 3:10:00 PM

On Feb 10, 3:48 pm, pedro mg <_nospam_s...@tquadrado.com> wrote:
> Hi,
>
> in irb I can have access to ENV['COLUMNS'] for the # of columns in the
> shell, and works fine.
> But inside a script (ruby script.rb), I can't have access to that hash
> key and value.
> I've done a:
>

Because when you play with irb, it is clear that you use terminal/
console so ENV['COLUMNS'] does matter. But when you execute ruby
script, it is not clear whether this ruby script need terminal so
ENV['COLUMNS'] does not matter.

pedro mg

2/10/2007 8:49:00 PM

akbarhome wrote:
> On Feb 10, 3:48 pm, pedro mg <_nospam_s...@tquadrado.com> wrote:
>> in irb I can have access to ENV['COLUMNS'] for the # of columns in the
>> shell, and works fine.
>> But inside a script (ruby script.rb), I can't have access to that hash
>> key and value.
>> I've done a:
>
> Because when you play with irb, it is clear that you use terminal/
> console so ENV['COLUMNS'] does matter. But when you execute ruby
> script, it is not clear whether this ruby script need terminal so
> ENV['COLUMNS'] does not matter.

sorry but that seems not to be a satisfactory explanation.
Just because it is not clear whether the ruby script needs terminal,
that features is cutted out ?

In this case, i need to know the # of terminal window columns for my
terminal client app. So, it matters.
Is there any way to get it ?

--
pedro mg
ruby 1.8.4 (2005-12-24) [i486-linux]
ubuntu linux edgy-eft 2.6.17-10-386 #2

pedro mg

2/11/2007 12:21:00 AM

> akbarhome wrote:
>> Because when you play with irb, it is clear that you use terminal/
>> console so ENV['COLUMNS'] does matter. But when you execute ruby
>> script, it is not clear whether this ruby script need terminal so
>> ENV['COLUMNS'] does not matter.

akbarhome, unless what you mean is: that info is not available because
you need to call another lib ;) Is that what you meant ?

--
pedro mg

pedro mg

2/11/2007 12:31:00 AM

Brian Candler wrote:
>> I think that the problem has to do with how script.rb is being invoked.
>> Is it started from something other than a terminal session? ... perhaps
>> via a cron job or a startup daemon? If so, then LINES and COLUMNS would
>> not normally be set, since those environment variables are usually
>> initialized and exported only within an interactive shell.
>
> I thought of that, but all the examples shown above and in my previous reply
> were typed into a terminal session.

yes Brian, me too. I'm running the script in a terminal shell.

--
pedro mg
ruby 1.8.4 (2005-12-24) [i486-linux]
ubuntu linux edgy-eft 2.6.17-10-386 #2

Ryan Davis

2/11/2007 10:51:00 AM

On Feb 10, 2007, at 3:25 AM, pedro mg wrote:

> Hi,
>
> in irb I can have access to ENV['COLUMNS'] for the # of columns in
> the shell, and works fine.
> But inside a script (ruby script.rb), I can't have access to that
> hash key and value.
> I've done a:
>
> puts ENV.to_a
>
> and i can not see both COLUMNS and LINES
> What would be the problem ?

COLUMNS isn't exported. You shouldn't be able to see it within your
irb session without exporting it or doing something else special.

% echo $COLUMNS
80
% ruby -e 'p ENV.keys.grep(/COL/)'
[]
% irb
>> p ENV.keys.grep(/COL/)
[]
=> nil
>> ^d

% export COLUMNS
% ruby -e 'p ENV.keys.grep(/COL/)'
["COLUMNS"]
% irb
>> p ENV.keys.grep(/COL/)
["COLUMNS"]
=> nil
>> ^d

I suggest you use stty instead.

% ruby -e 'p `stty size`.scan(/\d+/).map { |s| s.to_i }'
[24, 80]

comp.lang.ruby

ENV['COLUMNS']

pedro mg

Brian Candler

Brian Candler

akbarhome

pedro mg

pedro mg

pedro mg

Ryan Davis

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