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# 1  
Old 10-12-2016
Help understanding the script
Could someone please help me in understanding the code below:
Code:
#!/usr/bin/ksh
Month=`date|cut -c5-7`                         
Day=`date|cut -c9-10`                          
Year=`date|cut -c27-28`
Rom2Jul() { case $Month in Feb) Day=$(( $Day+31 ));;
                           Mar) Day=$(( $Day+59 ));;
                           Apr) Day=$(( $Day+90 ));;
                           May) Day=$(( $Day+120 ));;
                           Jun) Day=$(( $Day+151 ));;
                           Jul) Day=$(( $Day+181 ));;
                           Aug) Day=$(( $Day+212 ));;
                           Sep) Day=$(( $Day+243 ));;
                           Oct) Day=$(( $Day+273 ));;
                           Nov) Day=$(( $Day+304 ));;
                           Dec) Day=$(( $Day+334 ));; esac }
Rom2Jul

Current=$(( $Year*365+$Day-2 ))

PrevHostname=''
PrevBackup=0
while read input                               
do Month=${input:0:3}
   Day=${input:4:2}
   Hostname=${input:13:12}
   Rom2Jul
   if [[ ${input:9:1} = ':' ]] then Year=`date|cut -c27-28`; else Year=${input:10:2}; fi
   Backup=$(( $Year*365+$Day ))
   if [[ $PrevHostname = '' ]] then PrevHostname=$Hostname; PrevBackup=$Backup
      else if [[ $PrevHostname != $Hostname ]] then echo $PrevBackup $PrevHostname 
                                                    PrevHostname=$Hostname; PrevBackup=$Backup
              else if (( $Backup > $PrevBackup )) then PrevBackup=$Backup; fi; fi; fi; done 
echo $PrevBackup $PrevHostname

---------- Post updated at 04:54 PM ---------- Previous update was at 04:35 PM ----------

I am specifically trying to understand the
Code:
PrevHostname=''
PrevBackup=0
while read input                               
do Month=${input:0:3}
   Day=${input:4:2}
   Hostname=${input:13:12}

# 2  
Old 10-12-2016
Run the script by setting xtrace and verbose:-
Code:
#!/usr/bin/ksh -xv

If you have any questions even after going over the output, post it here.
# 3  
Old 10-12-2016
Hi,

Code:
Month=${input:0:3}

In value of input variable selects characters starting from 0 to 3.
Suppose input=Hello then Month variable will have Hel as a value .

Please try yoda suggested and LinkHere
Last edited by rbatte1; 10-13-2016 at 07:01 AM.. Reason: Converted CODE tags to ICODE tags
This User Gave Thanks to greet_sed For This Post:
rbatte1
# 4  
Old 10-12-2016
Also, you could replace the first 17 lines of that script with:

Code:
Current=$(( $(date +%y*365+%j) ))

This User Gave Thanks to Chubler_XL For This Post:
rbatte1
# 5  
Old 10-13-2016
That's a strange script, and it is difficult to read/understand. Try e.g. serious indentation, and the proposals given above. For your special question, see here:
Code:
PrevHostname=''                 # preset variable to empty
PrevBackup=0                    # preset variable to 0
while read input                # read variable "input" from stdin
                                # input contents:   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                # input char count:  01234567890123456789012345 
                                # result in variables:
do Month=${input:0:3}           # ABC
   Day=${input:4:2}             # DE
   Hostname=${input:13:12}      # NOPQRSTUVWX

This User Gave Thanks to RudiC For This Post:
Chubler_XL
# 6  
Old 10-13-2016
There is another Rom2Jul under the while loop

Should I just delete it, if I use Current=$(( $(date +%y*365+%j) ))

---------- Post updated at 12:19 PM ---------- Previous update was at 12:08 PM ----------

If I change the code to include
Code:
Current=$(( $(date +%y*365+%j) ))

I am getting "stale" message for even those which are not 3 days old. Any help/advise will be appreciated.

Thanks
Last edited by rbatte1; 10-14-2016 at 08:07 AM.. Reason: Changed some CODE tags to ICODE tags
# 7  
Old 10-13-2016
The backup backup Julian date calculation is quite simple if you have GNU date available on your system.

GNU date would allow us to convert date strings in this manor:

Code:
$ date -d "Oct 7 2016"
Fri, Oct 07, 2016 12:00:00 AM

Your calculation would then simply be:

Code:
PrevHostname=''
PrevBackup=0
while read input
do
  if [[ ${input:9:1} = ':' ]] then
     DateStr="${input:0:3} ${input:4:2}"
  else
     DateStr="${input:0:3} ${input:4:2} 20${input:10:2}"
  fi
  Backup=$(( $(date -d "$DateStr" +%y*365+%j) ))
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