[X-Unix] Hiding apps from the command line

[Eugene Lee]

On Fri, Mar 26, 2004 at 05:04:34PM +0000, Stroller wrote:
: 
: On Mar 26, 2004, at 12:15 pm, Eugene Lee wrote:
: >
: >: #! /bin/sh
: >
: >No spaces here, it should be "#!/bin/sh" (without the quotes).
: 
: It's probably more elegant to use #!/bin/bash at the beginning of your 
: scripts, as we don't actually have a Bourne shell on our Macs.

True, but not everyone has /bin/bash.  Some have /usr/local/bin/bash.
/bin/sh is guaranteed to be more portable.

: In 
: additional to its superset of commands `bash` does, I believe, behave 
: slightly differently from traditional `sh`; if invoked as `sh` Bash 
: _should_ behave as `sh`, however I am not aware that this has been 
: demonstrated. [1]

Actually, the binary does behave differently according to the man page:

	...
       --norc Do  not  read  and  execute  the  personal  initialization file
              ~/.bashrc if the shell is interactive.  This  option  is on  by
              default if the shell is invoked as sh.
	...
       If  bash  is  invoked  with  the name sh, it tries to mimic the startup
       behavior of historical versions of sh as  closely  as  possible,  while
       conforming  to the POSIX standard as well.  When invoked as an interac-
       tive login shell, or a non-interactive shell with the  --login  option,
       it  first  attempts  to read and execute commands from /etc/profile and
       ~/.profile, in that order.  The  --noprofile  option  may  be  used  to
       inhibit  this  behavior.  When invoked as an interactive shell with the
       name sh, bash looks for the variable ENV, expands its value  if  it  is
       defined,  and uses the expanded value as the name of a file to read and
       execute.  Since a shell invoked as sh does not attempt to read and exe-
       cute  commands from any other startup files, the --rcfile option has no
       effect.  A non-interactive shell invoked with  the  name  sh  does  not
       attempt  to  read  any  other  startup files.  When invoked as sh, bash
       enters posix mode after the startup files are read.
	...
       Bash attempts to determine when it is being run  by  the  remote  shell
       daemon,  usually  rshd.  If bash determines it is being run by rshd, it
       reads and executes commands from ~/.bashrc, if that file exists and  is
       readable.  It will not do this if invoked as sh.  The --norc option may
       be used to inhibit this behavior, and the --rcfile option may  be  used
       to  force  another  file to be read, but rshd does not generally invoke
       the shell with those options or allow them to be specified.

However, the differences are slight at best and are not worth arguments
that are better reserved for more interesting topics.


-- 
Eugene Lee
http://www.coxar.pwp.blueyonder.co.uk/