Re: [doc] LINES/COLUMNS auto-update in non-interactive shells contradicts manual

Chet Ramey <[email protected]> Mon, 11 May 2026 11:37:42 -0400

Newsgroups	gmane.comp.shells.bash.bugs
Organization	ITS, Case Western Reserve University
Message-ID	<[email protected]>

On 5/10/26 5:13 AM, Ilya Tsoy via Bug reports for the GNU Bourne Again 
SHell wrote:

> Bash Version: 5.1
> Patch Level: 16
> Release Status: release

This is very old. I understand that it's not your decision.

> 
> Description:
> The bash(1) manual states that LINES and COLUMNS are "automatically set
> ... in an interactive shell upon receipt of a SIGWINCH". 

The bash-5.3 man page says:

"Automatically set if the
  checkwinsize option is enabled or in an interactive  shell  upon
  receipt of a SIGWINCH."

And the description of checkwinsize describes the behavior and says it's
enabled by default.

> This silently breaks scripts that use LINES or COLUMNS as user variables

Using LINES or COLUMNS for some different purpose is unwise: Unix programs
have used these variables with the same semantics bash applies to them for
literally decades.

POSIX warns against using these and other common variables:

"It is unwise to conflict with certain variables that are frequently
exported by widely used command interpreters and applications:"

and LINES and COLUMNS are in that list, among many others.

https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap08.html#tag_08_03

> Fix:
> A documentation patch clarifying that LINES/COLUMNS may be updated in
> any shell where checkwinsize is enabled and a TTY is available,

Even the bash-5.1 man page says this.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    [email protected]    http://tiswww.cwru.edu/~chet/

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