On 2008-09-13, Tim Chase <[EMAIL PROTECTED]> wrote:
> Not sure what's going on here and hoping for some insight:
>
> [EMAIL PROTECTED]:~$ echo $COLUMNS
> 129
> [EMAIL PROTECTED]:~$ python2.5
> Python 2.5.2 (r252:60911, May 28 2008, 08:35:32)
> [GCC 4.2.4 (Debian 4.2.4-1)] on linux2
> Type "help", "copyright", "credits" or "license" for more
> information.
> >>> import os
> >>> os.environ.get('COLUMNS')
> >>> 'COLUMNS' in os.environ
> False
>
> I can coerce it by using
>
> [EMAIL PROTECTED]:~$ COLUMNS=$COLUMNS python2.5
> Python 2.5.2 (r252:60911, May 28 2008, 08:35:32)
> [GCC 4.2.4 (Debian 4.2.4-1)] on linux2
> Type "help", "copyright", "credits" or "license" for more
> information.
> >>> import os
> >>> 'COLUMNS' in os.environ
> True
>
> However, this seems hokey to me.
>
> FWIW, this is in Bash on Debian.
In bash (and other descendants of the Bourne shell), there are
two types of environment variables: 1) local variables that are
not passed on to child processes and 2) exported variables that
_are_ passed on to children.
By default, when a variable is created it is local and will not
be inherited by sub-processes.
> What's the best way to read what seems to be a
> pseudo-environment variable?
You can't. You need to export the variable in the parent shell
before it exec's the child:
$ echo $COLUMNS
80
$ python -c "import os; print os.environ['COLUMNS']"
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/usr/lib/python2.5/UserDict.py", line 22, in __getitem__
raise KeyError(key)
KeyError: 'COLUMNS'
$ export COLUMNS
$ python -c "import os; print os.environ['COLUMNS']"
80
Now, on to the question you're about to ask:
Q: How do I find out how big my terminal is from a Python
program?
A: You use the TIOCGWINSZ ioctl call on the terminal's file
descriptor:
>>> import sys,fcntl,termios,struct
>>> data = fcntl.ioctl(sys.stdout.fileno(), termios.TIOCGWINSZ, '1234')
>>> struct.unpack('hh',data)
(24, 80)
There's a more detailed explanation here (including an
explanation of what the third parameter to ioctl() does, and
how you detect changes in the window size):
http://mail.python.org/pipermail/python-list/2006-February/365710.html
There's also chance that you'd be better off just using ncurses or
newt for screen management, but that's another post.
--
Grant
--
http://mail.python.org/mailman/listinfo/python-list
