Various environments and weird less behaviour

Question

I am playing with I/O redirection and have problem with less behaving differently in two environments. Both environments are Solaris-based and are of the same version.

I am executing program in two environments like this:

env 1:

script </dev/pts/1 >&/dev/pts/1 (/dev/pts/1 is my SSH session terminal)

env 2:

script </dev/console >&/dev/console (/dev/console is Solaris main console)

Script looks like this:

#!/bin/bash

exec 4>>/tmp/script.log
export PS4='[\D{%FT%TZ}] $(tty): ${BASH_SOURCE}:${LINENO}:    ${FUNCNAME[0]:+${FUNCNAME[0]}(): }'
export BASH_XTRACEFD=4
set -o xtrace

export TERM=xterm-color

file=/path/to/big/file
less -MQEX ${file}
read

In env 1 everything works correctly, I am able to control less and scroll up/down, quit etc. In env 2, the less only displays first part of file and quits without being able to scroll up/down or manipulate within the file. env 2 is a script, which is run from SMF manifest. The things I have tried:

1. playing around with various bash options (interactive vs non-interactive), but it doesn't have any influence on this. In both environments I have the following bash options ($-) set "hxB".

2. setting different TERM types didn't affect less behaviour. I have tried "xterm", "vt100" and "vt220".

I am not sure what else should I try or where to look. How should I proceed with the debugging of less behavior? Any hints are appreciated.

Answer 1

If that is really a Solaris console, it is not compatible with xterm (or anything related to a VT100). VT100s use an escape sequence for scrolling which does interesting things with the Sun hardware.

Referring to the manual page for wscons, anything that is marked with "SUN" in the name in parenthesis is pretty much guaranteed to be a point of incompatibility. Like the VT100 scrolling controls, these are escape sequences not part of "ANSI X3.64" (long ago withdrawn, replaced by ECMA-48). The source of your problem is this one:

ESC[#r Set Scrolling (SUNSCRL)

Takes one parameter, n (default 0). Sets to n an internal register which determines how many lines the screen scrolls up when a line-feed function is performed with the cursor on the bottom line. A parameter of 2 or 3 introduces a small amount of jump when a scroll occurs. A parameter of 34 clears the screen rather than scrolling. The initial setting is 1 on reset.

A parameter of zero initiates wrap mode instead of scrolling. If a linefeed occurs on the bottom line during wrap mode, the cursor goes to the same character position in the top line of the screen. When a line feed occurs, the line that the cursor moves to is cleared and no scrolling occurs. ESC [ 1 r exits back to scroll mode.

For more information, see the description of the Line-feed (CTRL-J) control function above.

A VT100-style CSR (change scrolling region) takes two parameters, which are the starting and ending rows of the scrolling region.