Best way of finding terminal width/height?

[Joel Hedlund]

> You just call the failed read() or write() again.  Unless
> there's some way that the read/write partially succeeded and
> you don't have any way to know how many bytes were
> read/written, If that's the case then Python's "file" object
> read and write would appear to be broken by design.

Wow... I tried to set up an example that would fail, and it didn't. It seems the test only fails if I use the keyboard to cram stuff into stdin, and not if stdin is a regular pipe. 

Could this perhaps be some kind of misbehavior on behalf of my terminal emulator (GNOME Terminal 2.12.0 in Ubuntulinux 5.10)?

Example follows:

<winch.py>

import signal, os, sys
from terminal_info import get_terminal_size

terminal_size = get_terminal_size()

_bTerminalSizeChanged = False

def report_terminal_size_change(signum, frame):
    global _bTerminalSizeChanged
    _bTerminalSizeChanged = True

def update_terminal_size():
    global _bTerminalSizeChanged, terminal_size
    terminal_size = get_terminal_size()
    _bTerminalSizeChanged = False
    
signal.signal(signal.SIGWINCH, report_terminal_size_change)

# Retry IO operations until successful.
io_successful = False
while not io_successful:
    try:
        s = sys.stdin.read()
        io_successful = True
    except IOError:
        pass

io_successful = False
while not io_successful:
    try:
        sys.stdout.write(s)
        io_successful = True
    except IOError:
        pass

</winch.py>

Then run the prog and pipe a large chunk of text into stdin, and redirect stdout to a file:

$ cat /a/large/text/file | python winch.py > copy.of.the.large.file

Now, what happens for me is exactly what I wanted. I can resize the window as much as I like, and a diff 

$ diff /a/large/text/file copy.of.the.large.file

comes up empty. A perfectly good copy.

However, if I do this instead (try to use keyboard to push stuff into stdin):

$ python winch.py > copy.of.the.large.file

I expect python not to return until I press Ctrl-D on my keyboard, but it does return as soon as I enter more than one line of text and then resize the window (one unterminated line is ok). 

Example text to type in:
moo moo
cow cow

As soon as I have typed in something that includes a newline charater through the keyboard and try to resize the terminal, sys.stdin.read() will return whatever I put in no far and no exception raised.

Weird. Could it in fact my terminal that's screwing things up for me?

/Joel