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Full Discussion: Help understanding the script
Top Forums Shell Programming and Scripting Help understanding the script Post 302983522 by hasn318 on Wednesday 12th of October 2016 04:54:14 PM
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}

 

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LEARN ABOUT REDHAT

ddate

DDATE(1)						     Emperor Norton Utilities							  DDATE(1)

NAME

       ddate - converts Gregorian dates to Discordian dates

SYNOPSIS

       ddate [+format] [date]

DESCRIPTION

       ddate prints the date in Discordian date format.

       If called with no arguments, ddate will get the current system date, convert this to the Discordian date format and print this on the stan-
       dard output. Alternatively, a Gregorian date may be specified on the command line, in the form of a numerical day, month and year.

       If a format string is specified, the Discordian date will be printed in a format specified by the string. This mechanism works similarly to
       the format string mechanism of date(1), only almost completely differently. The fields are:

       %A     Full name of the day of the week (i.e., Sweetmorn)

       %a     Abbreviated name of the day of the week (i.e., SM)

       %B     Full name of the season (i.e., Chaos)

       %b     Abbreviated name of the season (i.e., Chs)

       %d     Ordinal number of day in season (i.e., 23)

       %e     Cardinal number of day in season (i.e., 23rd)

       %H     Name of current Holyday, if any

       %N     Magic code to prevent rest of format from being printed unless today is a Holyday.

       %n     Newline

       %t     Tab

       %X     Number of days remaining until X-Day. (Not valid if the SubGenius options are not compiled in.)

       %{

       %}     Used to enclose the part of the string which is to be replaced with the words "St. Tib's Day" if the current day is St. Tib's Day.

       %.     Try it and see.

EXAMPLES

       % ddate
       Sweetmorn, Bureaucracy 42, 3161 YOLD

       % ddate +'Today is %{%A, the %e of %B%}, %Y. %N%nCelebrate %H'
       Today is Sweetmorn, the 42nd of Bureaucracy, 3161.

       % ddate +"It's %{%A, the %e of %B%}, %Y. %N%nCelebrate %H" 26 9 1995
       It's Prickle-Prickle, the 50th of Bureaucracy, 3161.
       Celebrate Bureflux

       % ddate +'Today's %{%A, the %e of %B%}, %Y. %N%nCelebrate %H' 29 2 1996
       Today's St. Tib's Day, 3162.

BUGS

       ddate(1)  will  produce	undefined  behaviour if asked to produce the date for St. Tib's day and its format string does not contain the St.
       Tib's Day delimiters %{ and %}.

NOTE

       After `X-Day' passed without incident, the Church of the SubGenius declared that it had got the year upside down -  X-Day  is  actually	in
       8661 AD rather than 1998 AD.  Thus, the True X-Day is Cfn 40, 9827.

AUTHOR

       Original program by Druel the Chaotic aka Jeremy Johnson (mpython@gnu.ai.mit.edu)
       Major rewrite by Lee H:. O:. Smith, KYTP, aka Andrew Bulhak (acb@dev.null.org)
       Five tons of flax.

DISTRIBUTION POLICY

       Public domain. All rites reversed.

SEE ALSO

       date(1),
       http://www.subgenius.com/
       Malaclypse the Younger, Principia Discordia, Or How I Found Goddess And What I Did To Her When I Found Her

								59 Bureaucracy 3161							  DDATE(1)
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