Add Month to a Variable Date in Shell Script

Add month to a variable date in shell script

You seem to be looking for:

date -d "20170601+1 month" +%Y-%m-%d

When using multiple -d flags in the same command, date seems to only use the last one.

And of course, feel free to replace 20170601 by $VAR containing any date.

Adding months using shell script

Well,

date -d "1-$(echo "ABC,XYZ,123,Sep-2018" | awk -F ","  '{ print $4 }')+3 months" "+%b-%Y"

(Careful, that code continues past the edge of the box.)

Shows you how to get it working. Just replace the echo with a shell variable as you loop through the dates.

Basically, you use awk to grab just the date portion, add a 1- to the front to turn it into a real date then use the date command to do the math and then tell it to give you just the month abbreviation and year.

The line above gives just the date portion. The first part can be found using:

stub=`echo "ABC,XYZ,123,Dec-2018" | awk -F ","  '{ printf("%s,%s,%s,",$1,$2,$3) }'`

How to increment a date in a Bash script

Use the date command's ability to add days to existing dates.

The following:

DATE=2013-05-25

for i in {0..8}
do
   NEXT_DATE=$(date +%m-%d-%Y -d "$DATE + $i day")
   echo "$NEXT_DATE"
done

produces:

05-25-2013
05-26-2013
05-27-2013
05-28-2013
05-29-2013
05-30-2013
05-31-2013
06-01-2013
06-02-2013

Note, this works well in your case but other date formats such as yyyymmdd may need to include "UTC" in the date string (e.g., date -ud "20130515 UTC + 1 day").

How to set a variable to current date and date-1 in linux?

You can try:

#!/bin/bash
d=$(date +%Y-%m-%d)
echo "$d"

EDIT: Changed y to Y for 4 digit date as per QuantumFool's comment.

How to subtract or add date from a variable?

With GNU date it can be done quite easily with its -d switch.

x=20170402
date -d "$x -1 days" "+%Y%m%d"
20170401

and for 2 days

date -d "$x - 2 days" "+%Y%m%d"
20170331

Using awk to add one month to a date

Awk has limited support for date calculation, so here is a bash only solution relying on the date command:

IFS='$';
while read n t; do 
  printf '%s$"%s"\n' "$n" "$(date -d "${t//\"/} +1 month" '+%F %T')"
done <file

The input field separator is set to $ to get the time into $t variable.

The double quote of the date field are removed using bash parameter expansion ${t//\"/}.

This allows to pass the +1 month key word to date.

Then the printf prints back to the original format of the input file.

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