[PATCH/RFC] bash.1: "shopt -s checkwinsize" has no effect in non-interactive shells

[Jonathan Nieder]

Explain that COLUMNS and LINES are not set automatically in
non-interactive shells, and recommend direct use of the tput utility
from ncurses as a replacement.

Fixes: http://bugs.debian.org/628638
Reported-by: Leslie A Rhorer <lrhorer@satx.rr.com>
Helped-by: Leslie A Rhorer <lrhorer@satx.rr.com>
---
Hi Chet et al,

Here's a quick documentation patch, based on the report mentioned
above.  Thoughts of all kinds welcome.

 doc/bash.1 |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/doc/bash.1 b/doc/bash.1
index 1890b3c..4df0986 100644
--- a/doc/bash.1
+++ b/doc/bash.1
@@ -1802,7 +1802,10 @@ being closed.
 .TP
 .B COLUMNS
 Used by the \fBselect\fP builtin command to determine the terminal width
-when printing selection lists.  Automatically set upon receipt of a SIGWINCH.
+when printing selection lists.  Automatically set in interactive shells
+upon receipt of a SIGWINCH.
+To obtain the width of the terminal in a non-interactive shell,
+use \fBCOLUMNS\fP=$(tput cols).
 .TP
 .B COMPREPLY
 An array variable from which \fBbash\fP reads the possible completions
@@ -2021,9 +2024,12 @@ This variable determines the locale category used for 
number formatting.
 .TP
 .B LINES
 Used by the \fBselect\fP builtin command to determine the column length
-for printing selection lists.  Automatically set upon receipt of a
+for printing selection lists.  Automatically set in interactive shells
+upon receipt of a
 .SM
 .BR SIGWINCH .
+To obtain the width of the terminal in a non-interactive shell,
+use \fBLINES\fP=$(tput lines).
 .TP
 .B MAIL
 If this parameter is set to a file name and the
@@ -8732,8 +8738,8 @@ above).  The shell always
 postpones exiting if any jobs are stopped.
 .TP 8
 .B checkwinsize
-If set, \fBbash\fP checks the window size after each command
-and, if necessary, updates the values of
+If set and the shell is interactive, \fBbash\fP checks the window size
+after each command and, if necessary, updates the values of
 .SM
 .B LINES
 and
-- 
1.7.5.3