67 lines
1.9 KiB
Bash
67 lines
1.9 KiB
Bash
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#!/bin/sh
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bye()
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{
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echo $1
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exit 1
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}
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TOPDIR=$1
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LNSRC=$2
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LNDEST=$3
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LINKCMD=$4
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## Check command line
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[ $# -lt 4 ] && bye "Usage: $0 <Top Directory> <Link Source> <Link Destination> <Link command>"
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## Check for existence of link source file
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[ -n "$LNSRC" ] || bye "Internal error (LNSRC definition)"
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## Check for existence of link destination file
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[ -n "$LNDEST" ] || bye "Internal error (LNDEST definition)"
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if diff -s $TOPDIR/$LNDEST $LNSRC >/dev/null 2>&1
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then
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echo " =====> $LNSRC and $TOPDIR/$LNDEST are in sync"
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else
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echo " =====> resetting $TOPDIR/$LNDEST to point to $LNSRC"
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## At this point, we must create a link at the link destination
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## which points back to our link source. This requires us to
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## build a path FROM the destination back to the source
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#1) Get the source directory as an absolute path
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SRCDIR=`pwd`/`dirname $LNSRC`
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#2) Get the destination directory as an absolute path (TOPDIR is
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## a relative path from the current directory).
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cd $TOPDIR
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ROOTDIR=`pwd`
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DESTDIR=`dirname "$ROOTDIR"/"$LNDEST"`
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#3) Build a ../../ chain from the destination directory to the
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## current directory (ROOTDIR), which will become the prefix to
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## the path
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T=`dirname $LNDEST`
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while [ "$T" != "." ]
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do
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T=`dirname $T`;PFX=../"$PFX"
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done
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#4) strip the absolute path prefix of SRCDIR leading to the current
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## directory, so we are left with the relative path from the current
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## directory to the link source directory. Prefix that with PFX.
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LINK="$PFX"`echo $SRCDIR $ROOTDIR | awk '{ print substr($1,length($2)+2,512) }'`/`basename $LNDEST`
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#5) Create the links by changing to the destination directory,
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## removing any old versions of the link and creating a new one
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[ -d `dirname $LNDEST` ] || mkdir -p `dirname $LNDEST`
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cd `dirname $LNDEST`
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rm -f `basename $LNDEST`
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$LINKCMD $LINK `basename $LNDEST`
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fi
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exit 0
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