Shell Programming and Scripting

I couldn't explain this program through algorithm.
Please tell me the meaning of this programme. The coding is in below.

initialize_variables()
{
# initialise the variables
export R_HOME=`echo $HOME`
export RELEASE_HOME =$R_HOME/RELEASE
export RELEASE_LOG_DIR=$RELEASE_HOME/log

export REPORTS_HOME = $R_HOME/reports_home
export REPORTS_HOME_LOG = $REPORTS_HOME/log
export REPORTS_HOME_TMP = $REPORTS_HOME/tmp
export REPORTS_HOME_REPORT = $REPORTS_HOME/report
export R_3.4.4=$R_HOME/R3.4.4
export LOG_FILE=$R_3.4.4/tmp/r.log
export R_3.4.4_LOG=$R_3.4.4/log
export CLASSES_DIR=$R_3.4.4/jars/ETicket
export CLASSPATH=$CLASSES_DIR:$CLASSES_DIR/ETicket:$CLASSES_DIR/ETicket/ETicketClient.jar
}


on_exit()
{
if [ $1 -ne 0 ]
then
echo "Encountered some problems in processing" >>$LOG_FILE
raise ticket

echo "Raising Ticket for log file processing i.e. delete and moving the log files " >>$LOG_FILE
cd $CLASSES_DIR/ETicket
java ETicket.ETicketClient -i TICKET -n "debpr_p_p_cleanup_rlogs" -j p -r 3 -t "server logs" -f f -d "Error in deleting the server logs" >>$LOG_FILE
cd -
echo "Done" >>$LOG_FILE
cd $cur_dir

else
echo "Sucessfully completed the job" >> $LOG_FILE
fi

exit $1
}


#================================================================================
# Main code starts here
#================================================================================

#initialising variables
initialize_variables



if [ -d $RELEASE_LOG_DIR ]
then
cd $RELEASE_LOG_DIR
echo $RELEASE_LOG_DIR >> $LOG_FILE
find . \( -name '*.log*' -type f \) -mtime +30 -exec rm -f {} \;
fi

if [ $? -ne 0 ]
then
echo "Error occured in deleting files from log directory" >> $LOG_FILE
on_exit 1
else
echo "Successfully deleted files from log directory" >> $LOG_FILE
on_exit 0
fi


if [ -d $REPORTS_HOME_LOG ]
then
cd $REPORTS_HOME_LOG
echo $REPORTS_HOME_LOG >> $LOG_FILE
find . \( -name '*.log' -type f \) -mtime +30 -exec rm -f {} \;
fi
if [ $? -ne 0 ]
then
echo "Error occured in deleting files from log directory" >> $LOG_FILE
on_exit 1
else
echo "Successfully deleted files from log directory" >> $LOG_FILE
on_exit 0
fi



if [ -d $REPORTS_HOME_TMP ]
then
cd $REPORTS_HOME_TMP
echo $REPORTS_HOME_TMP >> $LOG_FILE
find . \( -name '*.txt' -type f \) -mtime +60 -exec rm -f {} \;
fi

if [ $? -ne 0 ]
then
echo "Error occured in deleting files from log directory" >> $LOG_FILE
on_exit 1
else
echo "Successfully deleted files from log directory" >> $LOG_FILE
on_exit 0
fi


if [ -d $REPORTS_HOME_REPORT ]
then
cd $REPORTS_HOME_REPORT
echo $REPORTS_HOME_REPORT >> $LOG_FILE
find . \( -name '*.xls' -type f \) -mtime +60 -exec rm -f {} \;
fi

if [ $? -ne 0 ]
then
echo "Error occured in deleting files from log directory" >> $LOG_FILE
on_exit 1
else
echo "Successfully deleted files from log directory" >> $LOG_FILE
on_exit 0
fi


if [ -d $R_3.4.4_LOG ]
then
cd $R_3.4.4_LOG
echo $R_3.4.4_LOG >> $LOG_FILE
find . \( -name '*.log' -type f \) -mtime +15 -exec rm -f {} \;
fi
if [ $? -ne 0 ]
then
echo "Error occured in deleting files from log directory" >> $LOG_FILE
on_exit 1

else
echo "Successfully deleted files from log directory" >> $LOG_FILE
on_exit 1

fi