ExtremeXOS pager does not work correctly in gnome-terminal, because gnome-terminal ignores the CSI CUB control sequence used by ExtremeXOS

[Erik Auerswald]

The pager of the ExtremeXOS switch operating system's CLI uses the (not strictly correct) control sequence "CSI60;D" to delete the pager prompt before displaying the next line of output. The correct control sequence would be "CSI60D" (without a semicolon), but basically all other terminal emulators accept both forms (tested with screen, xterm, rxvt, PuTTY (on Windows), Mac OS X terminal).

This affects working with Extreme Networks switches using the default terminal application in Ubuntu. Windows (PuTTY) and Mac OS X (terminal application) users do not experience a similar problem.

A simple test to check the control sequence is:

printf 'CSI CUB with semicolon is not\x1b[4;D accepted\n'

In gnome-terminal this prints: "CSI CUB with semicolon is not accepted"
In screen, xterm, and rxvt this prints: "CSI CUB with semicolon is accepted"

Changing the above command to not contain a semicolon works on gnome-terminal as well:

printf 'CSI CUB without semicolon is not\x1b[4D accepted\n'

In gnome-terminal, screen, xterm, and rxvt this prints "CSI CUB without semicolon is accepted"

Thus gnome-terminal breaks backwards-compatibility by a too-pedantic interpretation of VT100 control sequences. As a result it is less convenient to use Ubuntu when working with products of Extreme Networks than using Windows or Mac OS X.

If some one wants to verify this with ExtremeXOS, the EXOS VM available on GitHub (https://github.com/extremenetworks/Virtual_EXOS) can be used.

Info about my system:

$ lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04

$ apt-cache policy gnome-terminal
gnome-terminal:
  Installed: 3.6.2-0ubuntu1
  Candidate: 3.6.2-0ubuntu1
  Version table:
 *** 3.6.2-0ubuntu1 0
        500 http://ftp.uni-kl.de/pub/linux/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

This happened on Ubuntu 12.04 LTS as well.

[Egmont Koblinger (egmont-gmail)]

Upstream bugreport: https://bugzilla.gnome.org/show_bug.cgi?id=748144