common-names.sh

#!/bin/bash
#
# Print common lines between all given files
#

# exit on any error
set -e

# exit if no files given
USAGE="Usage: $0 file1 [file2 [file3...]]"
if [ "$#" == "0" ]; then
    echo "$USAGE"
    exit 2
fi

# create temporary directory
tmpdir=$(mktemp -d) || exit 1

# remove temporary directory on exit
trap "rm -rf -- '$tmpdir'" EXIT

# initial copy
result="$tmpdir/result"
cp <(sort -u "$1") "$result"
shift

# while there are files left
while (( "$#" )); do
    # extract common lines two files at a time
    comm -12 "$result" <(sort -u "$1") >"$tmpdir/tmp"
    mv "$tmpdir/tmp" "$result"
    shift
done

# output result
cat "$result"

# cleanup
rm -rf -- "$tmpdir"
trap - EXIT
exit