#! /bin/sh
#
# check_files listfile m3dir sysdir
#
# The listfile must contain a list of filenames, one per line.  It is read,
# and all leading instances of m3dir are replaced with sysdir.  If all
# the resulting files exist and are readable, then sysdir is echoed to
# the standard output.  Otherwise, nothing is echoed.  In any event, the
# exit status is successful.

if [ $# -ne 3 ]; then
    echo "Usage: $0 listfile m3dir sysdir" >&2
    exit 1
fi

listfile=$1
m3dir=$2
sysdir=$3

result=${sysdir}
for i in $(sed "s,^${m3dir},${sysdir}," ${listfile}); do
    if [ ! -r $i ]; then
	result=
	break
    fi
done

echo ${result}
exit 0