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- #!/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 ${file}.
- EOF
- exit 1
- fi
-
- # this is supposed to be reliable, not pretty
- for i
- do
- grep -v "^${i}$" $tmpfile > $otmpfile || true
- mv $otmpfile $tmpfile
- done
-
- chmod --reference=$file $tmpfile
- chown --reference=$file $tmpfile
-
- mv $tmpfile $file
-
- trap "" EXIT
- exit 0
-