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From: df@nud.UUCP
Newsgroups: net.sources,comp.unix.questions,comp.unix.wizards
Subject: Korn Shell LRU Directory History
Message-ID: <337@nud.UUCP>
Date: Thu, 26-Mar-87 00:25:33 EST
Article-I.D.: nud.337
Posted: Thu Mar 26 00:25:33 1987
Date-Received: Sat, 28-Mar-87 08:36:41 EST
Reply-To: df@nud.UUCP (Dale Farnsworth, NO7K)
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 188
Keywords: Korn shell ksh aliases directory history
Xref: utgpu net.sources:6409 comp.unix.questions:1519 comp.unix.wizards:1555

With the recent discussion on Korn Shell aliases for cd, I thought I'd
post my own cd alias.  It maintains a directory history in least
recently used (LRU) order.  You can print the directory history
and cd to a recent directory via number or pattern matching.
I much prefer it to pushd/popd since the history occurs automatically
through the cd command.
Optionally, all your shells can share the same directory via a history
file, though there is a slight performance hit for this particular feature.

Here is an example of its use.
==============================================================
	$ pwd
	/usr/df
	$ cd /
	$ cd /bin
	$ cd /usr/bin
	$ cd -l			# "cd -l" lists directory history
	  3 /usr/df
	  2 /
	  1 /bin
	  0 /usr/bin
	$ cd -3			# "cd -3" cd's to third most recent directory
	/usr/df
	$ cd -l
	  3 /
	  2 /bin
	  1 /usr/bin
	  0 /usr/df
	$ cd -bin		# "cd -foo" cd's to most recent directory name
	/usr/bin		# 		containing the string "foo"
	$ cd -l
	  3 /
	  2 /bin
	  1 /usr/df
	  0 /usr/bin
	$ 
==============================================================

From $HOME/.profile:
==============================================================
export CDHISTFILE CDHIST PWD
CDHIST=$HOME
# CDHISTFILE=$HOME/.cdhistory	# set this for directory history file.
CDHISTFILE=
ENV=$HOME/.kshrc
==============================================================

From $HOME/.kshrc (Korn shell ENV file):
==============================================================
alias set_prompt="PS1='$ '"	# of course, my real prompt is different.
alias cd='. $HOME/.functions; _cd'
alias md='. $HOME/.functions; md'
==============================================================

From $HOME/.functions (Where my function definitions reside):
==============================================================
alias cd=_cd
function _cd
{
	typeset -i cdlen i
	typeset t

	if [ $# -eq 0 ]
	then
		set -- $HOME
	fi

	if [ "$CDHISTFILE" -a -r "$CDHISTFILE" ] # if directory history exists
	then
		typeset CDHIST
		i=-1
		while read -r t			# read directory history file
		do
			CDHIST[i=i+1]=$t
		done <$CDHISTFILE
	fi

	if [ "${CDHIST[0]}" != "$PWD" -a "$PWD" != "" ]
	then
		_cdins				# insert $PWD into cd history
	fi

	cdlen=${#CDHIST[*]}			# number of elements in history

	case "$@" in
	-)					# cd to new dir
		if [ "$OLDPWD" = "" ] && ((cdlen>1))
		then
			print ${CDHIST[1]}
			'cd' ${CDHIST[1]}
		else
			'cd' $@
		fi
		;;
	-l)					# print directory list
		typeset -R3 num
		((i=cdlen))
		while (((i=i-1)>=0))
		do
			num=$i
			print "$num ${CDHIST[i]}"
		done
		return
		;;
	-[0-9]|-[0-9][0-9])			# cd to dir in list
		if (((i=${1#-})<cdlen))
		then
			print ${CDHIST[i]}
			'cd' ${CDHIST[i]}
		else
			'cd' $@
		fi
		;;
	-*)					# cd to matched dir in list
		t=${1#-}
		i=1
		while ((i<cdlen))
		do
			case ${CDHIST[i]} in
			*$t*)
				print ${CDHIST[i]}
				'cd' ${CDHIST[i]}
				break
				;;
			esac
			((i=i+1))
		done
		if ((i>=cdlen))
		then
			'cd' $@
		fi
		;;
	*)					# cd to new dir
		'cd' $@
		;;
	esac

	_cdins					# insert $PWD into cd history

	if [ "$CDHISTFILE" ]
	then
		cdlen=${#CDHIST[*]}		# number of elements in history

		i=0
		while ((i<cdlen))
		do
			print -r ${CDHIST[i]}	# update directory history
			((i=i+1))
		done >$CDHISTFILE
	fi
	set_prompt
}

function _cdins					# insert $PWD into cd history
{						# meant to be called only by _cd
	typeset -i i

	((i=0))
	while ((i<${#CDHIST[*]}))		# see if dir is already in list
	do
		if [ "${CDHIST[$i]}" = "$PWD" ]
		then
			break
		fi
		((i=i+1))
	done

	if ((i>22))				# limit max size of list
	then
		i=22
	fi

	while (((i=i-1)>=0))			# bump old dirs in list
	do
		CDHIST[i+1]=${CDHIST[i]}
	done

	CDHIST[0]=$PWD				# insert new directory in list
}
==============================================================

Cd is a sizable alias, but actually executes quite quickly.
I hope it is useful to someone else; I've been using it for several months.

-Dale

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