Hi,

I am using Bash shell to create some data and these data would be piped out to a file, let say output.txt.

This output.txt I would like to add some extra header information such as comments, descriptions and general information on the text.

I would like to know how could I maintain this type of information. I did try out using append to a file. In other word,I created a file with initial description and comments on it. Then, these data I would append (using << output.txt).

However, one limitation of this is that the data would be keep adding on top of the file each time repeated command are executed. Anyone have idea to solve this?

Besides, another problem is by having this header, I would like to further extract the data from the output.txt without the description and comments. I tried using head and tail but it doesnt work automatically. In other words, let say description and comment I have as first 5 lines of the output.txt. Currently I extract out these data using cat output.txt|..<all the operation>. But I could not help but extracting the first 5 lines as well.

Please advise. Appreciate alot.


Thanks.

-Jason