#!/bin/bash# file-integrity.sh: Checking whether files in a given directory#                    have been tampered with.E_DIR_NOMATCH=70E_BAD_DBFILE=71dbfile=File_record.md5# Filename for storing records (database file).set_up_database (){  echo ""$directory"" > "$dbfile"  # Write directory name to first line of file.  md5sum "$directory"/* >> "$dbfile"  # Append md5 checksums and filenames.}check_database (){  local n=0  local filename  local checksum  # ------------------------------------------- #  #  This file check should be unnecessary,  #+ but better safe than sorry.  if [ ! -r "$dbfile" ]  then    echo "Unable to read checksum database file!"    exit $E_BAD_DBFILE  fi  # ------------------------------------------- #  while read record[n]  do    directory_checked="${record[0]}"    if [ "$directory_checked" != "$directory" ]    then      echo "Directories do not match up!"      # Tried to use file for a different directory.      exit $E_DIR_NOMATCH    fi    if [ "$n" -gt 0 ]   # Not directory name.    then      filename[n]=$( echo ${record[$n]} | awk '{ print $2 }' )      #  md5sum writes records backwards,      #+ checksum first, then filename.      checksum[n]=$( md5sum "${filename[n]}" )      if [ "${record[n]}" = "${checksum[n]}" ]      then        echo "${filename[n]} unchanged."      elif [ "`basename ${filename[n]}`" != "$dbfile" ]             #  Skip over checksum database file,             #+ as it will change with each invocation of script.	     #  ---	     #  This unfortunately means that when running	     #+ this script on $PWD, tampering with the	     #+ checksum database file will not be detected.	     #  Exercise: Fix this.	then          echo "${filename[n]} : CHECKSUM ERROR!"        # File has been changed since last checked.      fi      fi    let "n+=1"  done <"$dbfile"       # Read from checksum database file. }  # =================================================== ## main ()if [ -z  "$1" ]then  directory="$PWD"      #  If not specified,else                    #+ use current working directory.  directory="$1"fi  clear                   # Clear screen.echo " Running file integrity check on $directory"echo# ------------------------------------------------------------------ #  if [ ! -r "$dbfile" ] # Need to create database file?  then    echo "Setting up database file, \""$directory"/"$dbfile"\"."; echo    set_up_database  fi  # ------------------------------------------------------------------ #check_database          # Do the actual work.echo #  You may wish to redirect the stdout of this script to a file,#+ especially if the directory checked has many files in it.exit 0#  For a much more thorough file integrity check,#+ consider the "Tripwire" package,#+ http://sourceforge.net/projects/tripwire/.