[Amit Bansal]

This is simple bash script which I have created to get difference between 2 dates. Please feel free to comment on improving it further

 

#!/bin/bash
##usage sh diff_days.sh date1 date2
##date format MMDDYYYY
usage () {
echo "usage:sh diff_days.sh date1 date2"
echo "date format MMDDYYYY"
exit 1
}
get_days() {
l_date=$1
l_mnth=`echo $l_date|cut -c1-2`;
l_dt=`echo $l_date|cut -c3-4`;
l_year=`echo $l_date|cut -c5-8`;
l_days=0;
t_days=0;
#Month array
month[1]="31";
month[3]="31";
month[4]="30";
month[5]="31";
month[6]="30";
month[7]="31";
month[8]="31";
month[9]="30";
month[10]="31";
month[11]="30";
month[12]="31";
#To check leap year
 if [ $[$l_year % 400] -eq 0 -o \( $[$l_year % 4] -eq 0 -a $[$l_year % 100] -ne 0 \) ] ; then
 month[2]="29";
 else
 month[2]="28";
 fi

for ((i=1;i<$l_mnth;i++))
do
l_days=`expr $l_days + ${month[$i]}`;
done
t_days=`expr $l_dt + $l_days`
echo $t_days
}
verify_date() {
local l_date=$1
retcode=0
if [ ${#l_date} -ne 8 ]; then
retcode=1
fi
l_mnth=`echo $l_date|cut -c1-2`;
l_dt=`echo $l_date|cut -c3-4`;
l_year=`echo $l_date|cut -c5-8`;
if [ $l_mnth -lt 1 -o $l_mnth -gt 12 ]; then
retcode=1
fi
echo $retcode
}

l_date1=$1
l_date2=$2
check=`verify_date $l_date1`;
[[ $check -eq 1 ]] && usage;
check=`verify_date $l_date2`;
[[ $check -eq 1 ]] && usage;
get_year1=`echo $l_date1|cut -c5-8`
get_year2=`echo $l_date2|cut -c5-8`
get_day_of_yr1=`get_days $l_date1`;
get_day_of_yr2=`get_days $l_date2`;
diff_days=`expr \( $get_year1 - $get_year2 \) \* 365 + $get_day_of_yr1 - $get_day_of_yr2 `;
echo $diff_days

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