[TUHS] Shell control through external commands

[Nemo]

On 10 September 2016 at 05:41, Joerg Schilling <schily at schily.net> wrote:
> Michael Kjörling <michael at kjorling.se> wrote:
>
>> On 10 Sep 2016 09:45 +0200, from dnied at tiscali.it (Dario Niedermann):
>> > Il 15/07/2016 alle 14:27, Norman Wilson ha scritto:
>> >> lu$ cat /bin/cd
>> >> #!/bin/sh
>> >> builtin cd "$@"
>> >> lu$
>> >
>> > But doesn't this change the current dir only in the child shell?
>> > Which then exits right after the second line, parent shell's $PWD
>> > unaffected. I really don't see how this script is useful.
>>
>> It does appear rather useless. Curiously, Debian (checked on Wheezy =
>> bash 4.2+dfsg-0.1+deb7u3 and Jessie = bash 4.3-11+b1) seems to not
>> supply anything like that, so it would appear to be some kind of
>> Fedora-ism rather than a part of anything upstream; that, or the
>> Debian folks are actually paying attention to what they ship onto
>> users' systems.
>
> POSIX requires some commands to be callable via exec().

Solaris 10 has the following amusing implementation (/usr/bin/cd):

#!/bin/ksh -p
#
#ident  "@(#)alias.sh   1.2     00/02/15 SMI"
#
# Copyright (c) 1995 by Sun Microsystems, Inc.
#
cmd=`basename $0`
$cmd "$@"

N.