Re: [9front] Re: /bin/"" use of rc -c instead of eval

[Romano <me+unobe@fallglow.com>]

On Fri Jul  5 16:52:25 -0700 2024, ality@pbrane.org wrote:
> Romano <me+unobe@fallglow.com> once said:
> > I use " and "" to review previous commands and execute them, and
> > I was puzzled when a previous 'cd' command didn't work. I
> > suspected it might be perhaps to 'cd' being a built-in, and
> > looking at the source code for "" my suspicion was confirmed. The
> > last line that executes the command is: rc -c $"_x
> >
> > Any reason why this isn't using eval instead so that rc built-ins
> > work (eval $"_x)
> 
> Did you try it? What happened?
> 
> Hint: what you seem to want is not
> 
> 	"" cd.*foo
> 
> but
> 	. <{" cd.*foo}
> 

Thanks, Anthony, even eval won't work for what I want. I had lazily
just tested:
  rc -c 'cd /sys/src'
against:
  eval 'cd /sys/src'

The above eval works if run directly, but not when within a shell
script like "", so I'd have to think of some other way. 

One way that looks promising is defining "" as a function with
the source of "" and changing 'rc -c' to 'eval':

cpu% whatis ""
fn "" {
	PROMPT='[^ 	]*(%|;)+[ 	]+'
	_x=`{
		" $*|tail -1
	}
	if(~ $#_x 0){
		>[1=2]echo no such command found
		exit notfound
	}
	>[1=2]echo '	' $_x
	_x=`{
		echo -n 'eval '''; echo $_x|sed 's/^'^$PROMPT^'//; s/''/''''/g; s/$/''/'
	}
	eval $"_x
}
cpu% pwd
/
cpu% "" cd /sys
	 cpu% cd /sys/src
cpu% pwd
/sys/src
cpu%