#!/bin/bash

ARGS=2  # Two args to script expected.
E_BADARGS=65
E_UNREADABLE=66

if [ $# -ne "$ARGS" ]
then
  echo "Usage: `basename $0` file1 file2"
  exit $E_BADARGS
fi

if [[ ! -r "$1" || ! -r "$2" ]]
then
  echo "Both files to be compared must exist and be readable."
  exit $E_UNREADABLE
fi

cmp $1 $2 &> /dev/null  # /dev/null buries the output of the "cmp" command.
#   cmp -s $1 $2  has same result ("-s" silent flag to "cmp")
#   Thank you  Anders Gustavsson for pointing this out.
#
# Also works with 'diff', i.e.,   diff $1 $2 &> /dev/null

if [ $? -eq 0 ]         # Test exit status of "cmp" command.
then
  echo "File \"$1\" is identical to file \"$2\"."
else  
  echo "File \"$1\" differs from file \"$2\"."
fi

exit 0