Calculate the number of days between 2 dates - bash script

Shell Programming and Scripting
1

I wrote the day calculator also in bash. I would like to now, that is it good so?

#!/bin/bash

datum1=`date -d "1991/1/1" "+%s"`
datum2=`date "+%s"`

diff=$(($datum2-$datum1))

days=$(($diff/(60*60*24)))

echo $days

Thanks in advance for your help!

2

Looks alright. What is it that you want to know exactly?

3

It doesn't need bash specifically, by the way.

What it does need is a modern version of GNU date, so if you take this script to a Solaris or AIX or other such system it won't work.

4 
 
#/bin/ksh
 
# date format: yyyy-mm-dd
 
DATE1="2002-04-30"
DATE2="2006-12-02"
 
typeset -L4 y1 y2
typeset -Z -R2 mm dd
 
y1=$DATE1
y2=$DATE2
fy=$y1
my=$DATE1
my=${my#*-}
my=${my%-*}
 
c=0
d2=0
while [[ $y1 -le $y2 ]]
do
for mm in 1 2 3 4 5 6 7 8 9 10 11 12
do
[[ $y1 -eq $fy ]] && [[ $mm -lt $my ]] && continue
cal $mm $y1 | while read line
do
line=${line%%[a-zA-Z]*}
[[ -n ${line:-""} ]] && {
for dd in $line
do
(( c = c + 1 ))
[[ "$y1-$mm-$dd" = "$DATE1" ]] && { d1=$c ; }
[[ "$y1-$mm-$dd" = "$DATE2" ]] && { d2=$c ; break ; }
done
}
[[ ${d2:-0} -gt 0 ]] && break
done
[[ ${d2:-0} -gt 0 ]] && break
done
(( y1 = y1 + 1 ))
done
(( days = d2 - d1 ))
echo $days