why have csh as well as tcsh?

[Tim Daneliuk]

On 12/26/18 8:21 AM, iam at sdf.org wrote:
> what's the reason to have two options for shells
> during the installation when the manual manages
> to the same for both?
> _______________________________________________


csh was the default/standard shell in BSD historically.  Some years
ago, tcsh was created as an extension to csh to add things like
command line completion.  (The man page has much to say about these.)

Rather than ship two binaries, FreeBSD (and many other systems)
ship tcsh with a second link to it called 'csh' for backward compatibility
so that existing scripts that refer to csh will still work.

It may also be the case (I don't know, I have not tested this) that
the binary behaves differently if it is started as csh rather than
tcsh to act more like "old" csh.  Like I said, I've not actually checked
this.

Incidentally, many Linux distros do the same thing with bash and sh.
IIRC bash *does* "downshift" to only old behaviors when started sh.

HTH,

----------------------------------------------------------------------------Tim Daneliuk     tundra at tundraware.comPGP Key:         http://www.tundraware.com/PGP/