updates only

Shell Programming and Scripting
1

Hi,
I have a file called Data-today.Txt that is updated every 5 minutes.

# cat '/root/Desktop/window/'`date +%b%Y`'/Data-'`date +%d%m%y`'.Txt' > /root/temp.txt

I want to read it every hour and findout the changes and process only those lines added since the last check.
I tried diff but did not get what I want.

At 9:56 A. M. the file looked:
This is line one
This is line two

At 10:00 A. M. I processed these two lines.

At 10:05 A. M. the original file will look like:
This is line one
This is line two
This is line three

at 11:00 A. M. I want to process only the newly added line i.e.
This is line three

Any help will be appreciated.

Regards,
Shantanu Oak

2

Can the file change anywhere? Or can lines only be added to it? If lines can only be added to it, just keep track of the last line number:

wc -l <filename> >/root/lastcheck-line.dat

Then a while later, do:

read L </root/lastcheck-line.dat
awk "NR==$L,0" <filename>  >/root/temp.txt

Once you're done, you can print the length again. You can do it altogether this way:

L=1; test -s /root/lastcheck-line.dat && read L </root/lastcheck-line.dat
awk "NR==$L,0 { print } END { print NR >'/root/lastcheck-line.dat' }" <filename>  >/root/temp.txt