[TUHS] Shell control through external commands

Norman Wilson norman at oclsc.org
Fri Jul 15 22:27:18 AEST 2016


  The existence of cd as a real command is a bit silly (Ubuntu doesn't
  seem to bother with it), but it is technically required by the standard.


Just for the record, Fedora 21 supplies /bin/cd, as part
of package bash-4.3.42-1.  Interestingly, it is a shell

lu$ cat /bin/cd
builtin cd "$@"

As has been said here, it's hard to see the functional point.

Others have remarked on the continued life of /bin/true and
/bin/false.  There are some who use those as shells in /etc/passwd
for logins that should never actually be allowed to do anything
directly.  I have no strong personal feeling about that, I'm just

And to be fair (as has also already been displayed here), the
copyright notice inserted in the once-empty /bin/true was hundreds
of bytes long, not thousands.  Let us call out silliness, but let
us not make it out as any sillier than it actually is.

Norman Wilson
Toronto ON
UNIX old fart and amateur pedant

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