UNIX for Dummies Questions & Answers

200901
200902
.
.
.
till 
201311

FILENAME=whatever.txt
DATESTR=$(date +%Y%m)
grep $DATESTR "$FILENAME" > /dev/null || echo $DATESTR >> "$FILENAME"

{ cat file; date +%Y%m; } | uniq

#!/bin/bash
#
# --genDate.sh
#
# -- script will take a start and end date in format
# -- yyyymm and generate a list beginning with the
# -- starting date until the end date
#

# prompt for the start and end dates
read -p "Enter start date in yyyy/mm format: " startDate
read -p "  Enter end date in yyyy/mm format: " endDate

# set counter
counter=1

# set newdate var
newDate=0

# reformat the start date to mm/dd/yyyy format
# to make the date command happy
newStartDate=$(echo $startDate | awk 'BEGIN{FIELDWIDTHS="4 2"}{print $2"/01/"$1}')

# generate date list
echo
echo "Generating date list from $startDate to $endDate:"
echo
sleep 1
echo "$startDate"
while [ $newDate != $endDate ]
do
    newDate=$(date --date="$newStartDate + $counter month" +%Y%m)
    echo "$newDate"
    ((counter=$counter+1))
done
echo

# done
exit 0

./genDate.sh
Enter start date in yyyy/mm format: 200901
  Enter end date in yyyy/mm format: 201001

Generating date list from 200901 to 201001:

200901
200902
200903
200904
200905
200906
200907
200908
200909
200910
200911
200912
201001

date: illegal option -- -
Usage: date [-u] [+Field Descriptors]
date.sh[14]: test: argument expected