Clem Cole <clemc at ccc.com> wrote:

> A few years later, I did switch to typing to the csh when I got to UCB, but
> that was not until after the MIT job control stuff had been spliced into
> the BSD kernel (Horton & Kleckner were probably the ones that convinced me
> to learn it).  With job control I became a fan, but never warmed up to the
> programming syntax.   I picked up the mantra that I still consider wise --
> "type to Joy and program to Bourne."   This is comfortable for the ROMS in
> the muscles of my fingers, but my scripts are portable.

Job control of course was an important improvement. I took the idea and 
implemented in my bsh in 1985.

Now looking back, it is interesting, that there are just four shells that 
implement support for vfork():

-	csh - the first

-	bsh since 1985

-	ksh vfork() probably since 1984, jobcontrol apparently since 1982.

-	bosh (my recent Bourne Shell) since 2014

But on a decent OS, vfork() helps a lot to speed up the shell.

On Solaris, fork() is copy-on-write based but still 3x slower than vfork().

Jörg

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