View file File name : remove-shell Content :#!/bin/sh -e if test $# -eq 0 then echo usage: $0 shellname '[shellname ...]' 1>&2 exit 1 fi file=/etc/shells # I want this to be GUARANTEED to be on the same filesystem as $file tmpfile=${file}.tmp otmpfile=${file}.tmp2 set -o noclobber trap "rm -f $tmpfile $otmpfile" EXIT if ! cat $file > $tmpfile then cat 1>&2 <<EOF Either another instance of $0 is running, or it was previously interrupted. Please examine ${tmpfile} to see if it should be moved onto ${file}. EOF exit 1 fi # this is supposed to be reliable, not pretty for i do REALDIR="$(dirname $(realpath -m $i))/$(basename $i)" for j in "$i" "$REALDIR" do grep -v "^${j}$" $tmpfile > $otmpfile || true mv $otmpfile $tmpfile done done chmod --reference=$file $tmpfile chown --reference=$file $tmpfile mv $tmpfile $file trap "" EXIT exit 0