bin/45006: nvi gives nonsense error when TERM environment variable unset

[fair%netbsd.org@localhost]

>Number:         45006
>Category:       bin
>Synopsis:       nvi gives nonsense error when TERM environment variable unset
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue May 31 03:00:00 +0000 2011
>Originator:     Erik E. Fair
>Release:        NetBSD 5.1_STABLE
>Organization:
International Organization of Internet Clock Watchers
>Environment:
        
        
System: NetBSD digital.clock.org 5.1_STABLE NetBSD 5.1_STABLE (FLAPJACK2) #2: 
Wed May 18 13:17:14 PDT 2011 
root%digital.clock.org@localhost:/var/obj/sys/arch/sparc64/compile/FLAPJACK2 
sparc64
Architecture: sparc64
Machine: sparc64
>Description:
        When nvi is started as "vi" and the TERM environment variable is unset,
        nvi gives a nonsense error and exits with a non-zero status. This is a
        regression from original "vi" which would revert to "ex" line editing 
mode
        under these circumstances.

        This is particularly annoying when attempting to use vipw(8) in single
        user mode of a freshly booted NetBSD system (when TERM is unlikely to
        be set), and is likely to be confusing to less experienced system
        administrators. It certainly violates the principle of least 
astonishment.

>How-To-Repeat:
        /bin/csh
        % unsetenv TERM
        % vi
        ex/vi: Error: unknown: Invalid argument
        % 

>Fix:
        

>Unformatted: