Send by e-mail new entries in the Bash history of all users.

mail-history.sh

#!/bin/bash
#
# Send by e-mail new entries in the Bash history of all users.
#
# usage: mail-history <email> <subject>
#

TMPFILE=`tempfile 2>/dev/null` || TMPFILE=`mktemp` || exit 1
declare -i CHANGES
CHANGES=0
TO=$1
SUBJECT=$2

function append_history {
  USERNAME=$1
  HOMEDIR=$2
  SEP="################################################"
  if [ -r $HOMEDIR/.bash_history ] ; then
    if [ -r $HOMEDIR/.bash_history.mailed ] ; then
      diff $HOMEDIR/.bash_history.mailed $HOMEDIR/.bash_history > /dev/null || {
        ( echo && echo $SEP && echo "new commands in bash history of $USERNAME: " && echo ) >> $TMPFILE
        ( diff $HOMEDIR/.bash_history.mailed $HOMEDIR/.bash_history | grep -e '^>' | sed -e 's/> //' ) >> $TMPFILE
        CHANGES=$CHANGES+1
      }
    else
      ( echo && echo $SEP && echo "new commands in bash history of $USERNAME: " && echo && cat $HOMEDIR/.bash_history ) >> $TMPFILE
      CHANGES=$CHANGES+1
    fi
    cp $HOMEDIR/.bash_history $HOMEDIR/.bash_history.mailed
  fi
}

( last -a && echo ) >> $TMPFILE

append_history root /root

for user in `ls /home` ; do
  append_history $user /home/$user
done

if [ "x$CHANGES" != "x0" ] ; then
  cat $TMPFILE | mail -s "$SUBJECT" $TO
fi

rm $TMPFILE