Re: bin/45430: ash uses argv[0] as $0 for scripts without #!

[David Laight <david%l8s.co.uk@localhost>]

The following reply was made to PR bin/45430; it has been noted by GNATS.

From: David Laight <david%l8s.co.uk@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: bin/45430: ash uses argv[0] as $0 for scripts without #!
Date: Wed, 5 Oct 2011 19:47:57 +0100

 On Wed, Oct 05, 2011 at 01:40:01PM +0000, spbnick%gmail.com@localhost wrote:
 > >Number:         45430
 > >Category:       bin
 > >Synopsis:       ash uses argv[0] as $0 for scripts without #!
 ...
 > ash shell uses argv[0] as $0 in scripts lacking shebang line, located
 > during $PATH lookup, while using full file path for the scripts with
 > shebang line.
 
 This isn't a bug!
 For a normal program binary argv[0] is whatever the user typed, this
 also applies to non #! scripts executed by the shell.
 
 The execution of #! scripts is done by the kernel which has to
 pass the interpreter the full pathname of the script file.
 
 For suid #! scripts the kernel will pass the name of an open fd
 (as /dev/fd/n) as argv[0] to be absolutely sure the correct file
 is opened (no symlink dances).
 
 This has the 'odd' side effect that you normally need 'rx' permissions
 to run a #! script - unless it is suid and you aren't the owner, in
 which case 'x' is enough.
 
        David
 
 -- 
 David Laight: david%l8s.co.uk@localhost