How to print dates between two dates in the format% Y% m% d in a shell script?

Question

I have two arguments as input: startdate=20160512and enddate=20160514.

I want to be able to generate days between these two dates in my bash script, not including the start date, but including enddate:

20160513 20160514 I am using a Linux machine. How to do it? Thank you

Answer 1

Using the GNU Date:

$ d=; n=0; until [ "$d" = "$enddate" ]; do ((n++)); d=$(date -d "$startdate + $n days" +%Y%m%d); echo $d; done
20160513
20160514

Or, a few lines:

startdate=20160512
enddate=20160514
d=
n=0
until [ "$d" = "$enddate" ]
do  
    ((n++))
    d=$(date -d "$startdate + $n days" +%Y%m%d)
    echo $d
done

How it works

• d=; n=0

  Initialize variables.

• until [ "$d" = "$enddate" ]; do

  Run a loop that ends on enddate.

• ((n++))

  Increase the day counter.

• d=$(date -d "$startdate + $n days" +%Y%m%d)

  Calculate the date ndays after startdate.

• echo $d

  Display date.

• done

  End of cycle signal.

Answer 2

OSX, , , enddate, .

startdate=20160512
enddate=20160514

loop_date=$startdate

let j=0
while [ "$loop_date" -ne "$enddate" ]; do
        loop_date=`date   -j -v+${j}d  -f "%Y%m%d" "$startdate" +"%Y%m%d"`
        echo $loop_date
        let j=j+1
done

Answer 3

Another option is to use dateseqfrom dateutils( http://www.fresse.org/dateutils/#dateseq ). -ichanges the input format, and -fchanges the output format.

$ dateseq -i%Y%m%d -f%Y%m%d 20160512 20160514
20160512
20160513
20160514
$ dateseq 2016-05-12 2016-05-14
2016-05-12
2016-05-13
2016-05-14