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From: dsp@ptsfa.UUCP
Newsgroups: comp.unix.questions
Subject: Re: Korn Shell
Message-ID: <2201@ptsfa.UUCP>
Date: Mon, 16-Mar-87 21:00:43 EST
Article-I.D.: ptsfa.2201
Posted: Mon Mar 16 21:00:43 1987
Date-Received: Wed, 18-Mar-87 01:24:57 EST
References: <580@csun.UUCP> <5680@brl-smoke.ARPA>
Reply-To: dsp@ptsfa.UUCP (David St.Pierre)
Organization: Pacific * Bell, San Ramon, CA
Lines: 229
Keywords: Korn shell ksh aliases parameters

In article <5680@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>In article <580@csun.UUCP> aeusesef@csun.UUCP (Sean Eric Fagan) writes:
>>I tried making a
>>function called cd, but it didn't work, and an alias called cd did work, but
>>I was unable to pass parameters into it.  Any one have any suggestions?
>
>I don't have much experience with ksh, but I have plenty with the
>SVR2 shell, which ksh is supposed to be almost entirely upward-
>compatible with.  Indeed, the SVR2 shell provided no way to
>redefine builtins.  We have fixed that in our version, with no
>apparent ill effects, and use the feature heavily (especially for
>"cd").  Along the way we added V8's "builtin" and "whatis" builtins.

Here's part of my ENV file for ksh. I've honestly forgotten
some of this. Order is important because the built-in is used
in the function _cd and then the alias is applied later.

Also a function to implement the V8 "whatis" - I guess it does
because that's what the comment tells me :-) (I didn't write it)
I have no idea what the "builtin" builtin does.

And popd, pushd, dirs, probably thanks to someone on the net a few
years ago.
---------

_cd	() { cd $1 > /dev/null; PS1="$PWD !> " ; }

alias	cd=_cd
alias	dirs='. $HOME/.functions;dirs'
alias	popd='. $HOME/.functions;popd'
alias	pushd='. $HOME/.functions;pushd'

# whatis --- ksh function to implement the V8 whatis builtin
function whatis
{
	'typeset' i_ foo_	# local variables
	'typeset' -i var
	for i_ in $*
	do
		var=0
		if 'set' | grep "^${i_}=" > /dev/null
		then
			'set' | grep "^${i_}="
			var=1
		fi
		foo_="`'whence' -v ${i_}`"

		case "$foo_" in
		*built-in*)	'print' - builtin ${i_}
				;;
		*function*)	'typeset' -f ${i_}
				;;
		*exported*)	'print' - "alias -x '${i_}=${foo_##*alias for }"
				;;
		*tracked*)	'print' - "alias -t '${i_}=${foo_##*alias for }'"
				;;
		*alias*)	'print' - "alias '${i_}=${foo_##*alias for }'"
				;;
		*not\ found)	if ((! var))
				then
					'print' - "$foo_"
				fi
				;;
		*)		'print' - "${foo_##*is }"
				;;
		esac
	done
	return 0
}

unalias pushd popd dirs swapdir

#
#	The directory stack grows upward from 0.  This is different from
#	the csh version where the top of the stack is always 0.
#	However, the direction of our stack is secretly reversed
#	when necessary to preserve the illusion of a stack with top
#	at 0.  The idea is to make this program appear identical
#	to its counterpart in csh.
#
#	invariant: dirstack[top] == $PWD
#
#	From the csh man page...
#
#     dirs
#          Prints the directory stack; the top of the stack is at
#          the left, the first directory in the stack being the
#          current directory.
#
#     popd
#     popd +n
#          Pops the directory stack, returning to the new top
#          directory.  With a argument `+n' discards the nth entry
#          in the stack.  The elements of the directory stack are
#          numbered from 0 starting at the top.
#
#     pushd
#     pushd name
#     pushd +n
#          With no arguments, pushd exchanges the top two elements
#          of the directory stack.  Given a name argument, pushd
#          changes to the new directory (ala cd) and pushes the
#          old current working directory (as in csw) onto the
#          directory stack.  With a numeric argument, rotates the
#          nth argument of the directory stack around to be the
#          top element and changes to it.  The members of the
#          directory stack are numbered from the top starting at
#          0.
#
let top=0
dirstack[top]=$PWD

pushd ()
{
	dirstack[top]=$PWD	# kludge to force . to top of stack
	case $# in
	0)
		if (( top > 0 )) ; then
			let n=top-1
			swapdir $n $top
		else
			echo No other directory.
		fi
		;;
	1)
		case $1 in
		+[1-9]*)
			n=$1
			n=${n#+}
			if (( n > top )) ; then
				echo Directory stack not that deep.
				break
			else
				let n=top-n	# "reverse" the stack
				swapdir $n $top
			fi
			unset n
			;;
		*)
			if  cd $1 ; then
				((top=top+1))
				dirstack[top]=$PWD
				dirs
			fi
			;;
		esac
		;;
	*)
		echo Too many arguments.
		;;
	esac
}

popd ()
{
	dirstack[top]=$PWD	# kludge to force . to top of stack
	case $# in
	0)
		case $top in
		0)
			echo Directory stack empty.
			;;
		*)
			unset dirstack[top]
			let top=top-1
			cd ${dirstack[top]}
			dirs
			;;
		esac
		;;
	1)
		case $1 in
		+[1-9]*)
			n=$1
			n=${n#+}
			if (( n > top )) ; then
				echo Directory stack not that deep.
				unset n
				break
			else
				let n=top-n	# "reverse" the stack, and
				# shift the stack down one for all entries >= n
				while (( n < top ))
				do
					let m=n+1
					dirstack[n]=${dirstack[m]}
					let n=n+1
				done
				unset dirstack[top] m n
				let top=top-1
				dirs
			fi
			;;
		*)
			echo Bad directory.
			;;
		esac
 		;;
	*)
		echo Too many arguments.
		;;
	esac
}

dirs ()
{
	dirstack[top]=$PWD	# kludge to force . to top of stack
	let n=top
	while (( n >= 0 ))
	do
		echo "${dirstack[n]} "\\c
		let n=n-1
	done
	echo ""
	unset n
}

swapdir ()
{
	t=${dirstack[$1]}
	dirstack[$1]=${dirstack[$2]}
	dirstack[$2]=$t
	cd ${dirstack[top]}
	dirs
	unset t
}
-- 
David St. Pierre    415/823-6800  {ihnp4,lll-crg,ames,qantel,pyramid}!ptsfa!dsp
It looks like it's going to go on ad infinitum for a while.