how to manage dates in shell

Question

emphasized textI have a file containing 14000 dates . I wrote a script to find the last 5 days ,

26/03/2002:11:52:25
27/03/2002:11:52:25
29/03/2002:11:30:41
30/03/2002:11:30:41
26/03/2002:11:30:41
02/04/2002:11:30:41
03/04/2002:11:30:41
04/04/2002:11:30:41
05/04/2002:11:52:25
06/04/2002:11:52:25

suppose this is the file , now I have date 02/04/2002:11:30:41 as an out put . I want to put the dates from 02/04/2002 till the end of the file in another file .

start-date = 02/04/2002 (this is my start date) 
while [start-date lt end-date] do (while start date is less than end date )
start-date++ ( add one day to start day so if its 2/4/2002 it will become 3/4/2002)
echo $start-date|tee -a file1  (put it in a file)

Answer 1

There are some ways to do this: grep, sed, awk, ...

You can get the line number of matching pattern by one of the following:

• grep -n pattern -m 1 input | cut -d: -f1
• awk '/pattern/{ print NR }' input | head -1

and print from that line to the end of the file:

• $ sed -n "$(awk '/02\/04\/2002:11:30:41/ { print NR }' input | head -1),$ p" input

or:

• $ awk 'NR >= line_number' line_number=$(grep -n 02/04/2002:11:30:41 -m 1 input | cut -d: -f1) input

You also can use grep -A (--after-context) or tail, ...