I want to write a for loop that starts from a date (received as string) and cycles through all dates for a set number of days. I solved the problem in the end but I don't understand why another attempt fails the way it does and I'm hoping for an explanation.
This the end solution:
a=3
start_date="2017-09-01"
for ((i=0;i<$a;i++));
do
cur_date=`date -d $start_date" -"$i" days"`
echo $cur_date
done
Resulting in:
Fri Sep 1 00:00:00 CEST 2017
Sat Sep 2 00:00:00 CEST 2017
Sun Sep 3 00:00:00 CEST 2017
Which is ok, however this:
for i in {0..$a}
do
cur_date=`date -d $start_date" "$i" days"`
echo $cur_date
done
Results in:
date: invalid date ‘2017-09-01 {0..3} days’
While this:
for i in {0..3}
do
cur_date=`date -d $start_date" "$i" days"`
echo $cur_date
done
Returns the correct sequence So, the question is, why using a variable that has the same value instead of the just value breaks the code?
Thanks
