www.nico.schottelius.org/software/cinit/browse_source/cinit-0.3pre16/bin/cinit-conf.svc.dependency.add

#!/bin/sh
# 
# 2008      Nico Schottelius (nico-cinit-conf at schottelius.org)
# 
# This file is part of cinit-conf.
#
# cinit-conf is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# cinit-conf is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with cinit-conf. If not, see <http://www.gnu.org/licenses/>.
#
# cinit: create dependency: service a needs or wants service b
#

set -x

# initialise cinit-conf framework
hier="${0%/*}"; set -e; . "${hier}/cinit-conf.read-conf"

if [ $# -ne 3 ]; then
   echo "`basename $0`: service_A [wants|needs] service_B"
   echo ""
   echo "   Service A needs or wants Service B."
   echo "   You must specify whether to use wants or needs."
   echo ""
   exit 23
fi

SVC_A="$1"
DEP="$2"
SVC_B="$3"

# adding 'wishes' for x-mas and requires for 'the mass' and 'tv'
case "${DEP}" in
   wishes|wants) DEP="$C_WANTS" ;;
   needs|requires) DEP="$C_NEEDS" ;;
   *) echo "Use \"want\" or \"need\" as type of dependency."
esac

# First of all create absolute paths
# if SVC_X beginning matches R_CINIT_DIR it is absolute
# else it is relative to R_CINIT_DIR
echo "${SVC_A}" | grep "^${R_SVC_DIR}" >/dev/null || SVC_A="${R_SVC_DIR}/${SVC_A}"
echo "${SVC_B}" | grep "^${R_SVC_DIR}" >/dev/null || SVC_B="${R_SVC_DIR}/${SVC_B}"

SVC_A_ABS=$(cd "${SVC_A}" && pwd -P)
SVC_B_ABS=$(cd "${SVC_B}" && pwd -P)

SVC_A_REL="${SVC_A_ABS##*/}"
SVC_B_REL="${SVC_B_ABS##*/}"

set +e
match=""
count="0"
svc_stripped="$(echo $SVC_A_ABS | sed -e 's;/$;;' -e 's;/[^/]*$;;')"
while [ "$svc_stripped" ]; do
   match="$(echo ${SVC_B_ABS} | grep "^${svc_stripped}")"
   count=$(($count+1))
   if [ "$match" ]; then
      relpath=""
      while [ "$count" -gt 0 ]; do
         source="../${source}"
         count=$(($count-1))
      done
      source="${source}${SVC_B_REL}"

      break
   fi
   svc_stripped="$(echo $svc_stripped | sed -e 's;/$;;' -e 's;/[^/]*$;;')"
done

# nothing in common? link absolute
if [ ! "$match" ]; then
   source="${SVC_B_ABS}"
fi

# Then find out the level of subdirs, excluding destdir!
# FIXME: could someone PLEASE simplify that?
#SLASHES=$(echo $SVC_A | sed -e 's,/$,,' -e 's,[^/],,g' -e 's,/,../,g' -e 's,^,../../,')

# find common anchor and link after that:
# /destdir/etc/cinit/svc/svca/b/
# /destdir/etc/cinit/svc/svca/c/
# results in ../c/
# Thus: 
# while unmatched
# remove /* (one level, shortest match)
# 


# 1. remove destdir, if present 2. remove everything but the slashes 3. replace them with ../
# 
SLASHES=$(echo $SVC_A | sed -e "s;^$DESTDIR;;" -e 's,/$,,' -e 's,[^/],,g' -e 's,/,../,g' -e 's,^,../../,')
DEST_NAME=$(echo $SVC_A | sed -e 's,/$,,' -e 's,/,-,g')

SOURCE="${SLASHES}${SVC_B}"
DEP_DIR="${SVC_A}/${DEP}"

if [ ! -d "$DEP_DIR" ]; then
   echo "$DEP_DIR does not exist, creating..."
   mkdir "$DEP_DIR"
   if [ $? -ne 0 ]; then
      echo "Error occured due to creating directory. Exiting."
      exit 1
   fi
fi

DEST="${DEP_DIR}/${DEST_NAME}"

echo -n "Linking ${source} to ${DEST} ... "
ln -sf "${source}" "${DEST}"
echo "finished."