Shell Programming and Scripting

      TOPOFFILE=$(

                                TOPOFFILEHA=$(head -10 data.txt | egrep "^$SystemDateM" | head -1 | awk '{print $1" "$2" "$3}')

                                        PAMONTH=$(case $SystemDateM in
                                        Jan) echo "12" ;; Feb) echo $(( 2 - 1 )) ;; Mar) echo $(( 3 - 1 )) ;; Apr) echo $(( 4 - 1 )) ;; May) echo $(( 5 - 1 )) ;; Jun) echo $(( 6 - 1 )) ;;
                                        Jul) echo $(( 7 - 1 )) ;; Aug) echo $(( 8 - 1 )) ;; Sep) echo $(( 9 - 1 )) ;; Oct) echo $(( 10 - 1 )) ;; Nov) echo $(( 11 - 1 )) ;; Dec) echo $(( 12 - 1 )) ;; esac
                                        })

                                        PAMONTHREV=$(case $PAMONTH in
                                        1) echo "Jan" ;; 2) echo "Feb" ;; 3) echo "Mar" ;; 4) echo "Apr" ;; 5) echo "May" ;; 6) echo "Jun" ;;
                                        7) echo "Jul" ;; 8) echo "Aug" ;; 9) echo "Sep" ;; 10) echo "Oct" ;; 11) echo "Nov" ;; 12) echo "Dec" ;; esac
                                        })

                                if [ -z "${TOPOFFILEHA}" ] ; then

                                        PAMONTHREVA=$(case $PAMONTHREV in
                                        Jan) echo "12" ;; Feb) echo $(( 2 - 1 )) ;; Mar) echo $(( 3 - 1 )) ;; Apr) echo $(( 4 - 1 )) ;; May) echo $(( 5 - 1 )) ;; Jun) echo $(( 6 - 1 )) ;;
                                        Jul) echo $(( 7 - 1 )) ;; Aug) echo $(( 8 - 1 )) ;; Sep) echo $(( 9 - 1 )) ;; Oct) echo $(( 10 - 1 )) ;; Nov) echo $(( 11 - 1 )) ;; Dec) echo $(( 12 - 1 )) ;; esac
                                        })

                                        PAMONTHREV=$(case $PAMONTHREVA in
                                        1) echo "Jan" ;; 2) echo "Feb" ;; 3) echo "Mar" ;; 4) echo "Apr" ;; 5) echo "May" ;; 6) echo "Jun" ;;
                                        7) echo "Jul" ;; 8) echo "Aug" ;; 9) echo "Sep" ;; 10) echo "Oct" ;; 11) echo "Nov" ;; 12) echo "Dec" ;; esac
                                        })

                                        TOPOFFILEH=$(egrep "^${PAMONTHREV}" < data.txt | tail -1 | $AWK '{print $1" "$2" "$3}')

                                        echo "${TOPOFFILEH}"
                                fi


                                )

Jun  9 01:40:55 sss nagios: Auto-save of retention data completed successfully.
Jun  9 01:52:53 sss rsyslogd: -- MARK --
Jun  9 02:07:53 sss rsyslogd: -- MARK --
Jun  9 02:22:53 sss rsyslogd: -- MARK --

function f_prevmon
{
typeset mon[1]="Jan"                      # list of months names
typeset mon[2]="Feb"
typeset mon[3]="Mar"
typeset mon[4]="Apr"
typeset mon[5]="May"
typeset mon[6]="Jun"
typeset mon[7]="Jul"
typeset mon[8]="Aug"
typeset mon[9]="Sep"
typeset mon[10]="Oct"
typeset mon[11]="Nov"
typeset mon[12]="Dec"

typeset -i idx=1                           # array index
typeset -L3 -l monbuf=""                   # convert to lowercase, truncate to 3 chars
typeset -L3 -l in="$1"                     # same with first passed parameter

while [ $idx -le 12 ] ; do
     monbuf="${mon[$idx]}"
     if [ "$in" = "$monbuf" ] ; then       # if month is found
          (( idx -= 1 ))                   # get previous one, rotate on 0
          if (( idx == 0 )) ; then
               idx=12
          fi
          print - "${mon[$idx]}"           # to stdout
          return $idx                      # and return
     fi
     (( idx += 1 ))
done
                                           # we get here only if $1 matched nothing
return 255                                 # so return an error
}

#!/bin/ksh

FPATH=$FPATH:/path/to/f_prevmon


typeset month="Apr"          # some arbitrary starting date
typeset start="$month"         # we need this to avoid infinite loops

while [ ! -e /path/to/myfile.${month}.ext ] ; do
     month=$(f_prevmon $month)
     if [ $? -eq 255 ] ; then
          print - "f_prevmon encountered an unintelligible months name"
          exit 255
     fi
     if [ "$month" = "$start" ] ; then
          print - "we tried all months, but did not find anything. Aborting now."
          exit 255
     fi
done

print - "the file you looked for is: /path/to/myfile.${month}.ext"

exit 0