Re: $cd /bin

["Jerry Feldman-2" <user=4@nabble.blu.org>]

On Mon, 3 Dec 2007 17:45:10 -0600 
Brian Medley <[hidden email]> wrote: 

> On Mon, Dec 03, 2007 at 03:52:14PM -0500, Matthew Gillen wrote: 
> 
> > Brian Medley wrote: 
> > > On Sun, Dec 02, 2007 at 08:07:14AM -0500, Jerry Feldman wrote: 
> > > 
> > > Understood, but I don't see the rational of the script to begin 
> > > with.  The script is "cd" it is part of the OS, but doesn't seem 
> > > like it would ever do anything.  Also, these files share the 
> > > hardlinked file: 
> > > 
> > > $ ls -lFai cd 
> > > 52922 -r-xr-xr-x   15 root  wheel  147 Aug 19  2006 cd* 
> > > $ s find / -inum 52922 
> > > /usr/bin/alias 
> > > /usr/bin/bg 
> > > /usr/bin/cd 
> > > /usr/bin/command 
> > > /usr/bin/fc 
> > > /usr/bin/fg 
> > > /usr/bin/getopts 
> > > /usr/bin/hash 
> > > /usr/bin/jobs 
> > > /usr/bin/read 
> > > /usr/bin/type 
> > > /usr/bin/ulimit 
> > > /usr/bin/umask 
> > > /usr/bin/unalias 
> > > /usr/bin/wait 
> > 
> > That means it's using the old unix trick of having one binary that changes 
> > behavior based on how it was invoked (ie for different values of argv[0]). 
> > The script part is to strip argv[0] down to something that the binary "knows" 
> > (ie the /usr/bin/ part is something you don't want hard-coded into the binary). 
> 
> However, the script doesn't appear to do anything: 
> 
> sh-2.05b$ alias a 
> sh: alias: a: not found 
> sh-2.05b$ alias b 
> sh: alias: b: not found 
> sh-2.05b$ /usr/bin/alias a='echo a' 
> sh-2.05b$ alias b='echo b' 
> sh-2.05b$ a 
> sh: a: command not found 
> sh-2.05b$ b 
> b 
> sh-2.05b$ cat /usr/bin/alias 
> #!/bin/sh 
> # $FreeBSD: src/usr.bin/alias/generic.sh,v 1.1 2002/07/16 22:16:03 wollman Exp $ 
> # This file is in the public domain. 
> ${0##*/} ${1+"$@"} 
> sh-2.05b$