Updating a single line in a text file

[scottykid1827]

Hello, everyone. I'm somewhat new to linux and I'm having a problem trying to automatically update a text file. Maybe someone here can help me out.

I have a text file called namelist.wps. In this file there is a line that reads:

start_date = '2010-12-26_12:00:00', '2010-12-26_12:00:00',

I have to automatically update the year, month, and day of month. I set values for the year, month, and day of month using the following code in a c-shell script:

set y1 = `date +%Y`
set m1 = `date +%m`
set d1 = `date +%d`

After I do this, how do I update year, month, and day of month, without changing any of the other lines in the namelist.wps file?

[scottykid1827]

I think sed could be used to do this but I don't know how.

[scottykid1827]

Ok. This is the code for the script I am trying to use:

#!/bin/csh

set y1 = `date +%Y`
set m1 = `date +%m`
set d1 = `date +%d`

set date1 = ${y1}-${m1}-${d1}_12:00:00

cat namelist.wps | sed 's/^.*start_date.*$/ start_date = '$date1', '$date1',/' >newnamelist.wps

exit 0

The out put in the newnamelist.wps file is :

 start_date = 2010-12-31_12:00:00, 2010-12-31_12:00:00,

The Problem is that I need single quotes around the dates so it reads as follows:

 start_date = '2010-12-31_12:00:00', '2010-12-31_12:00:00',

Someone please help.