Hi,

Fairly new to unix scripting, hoping to get some help.

using AIX v5

Basically I have 3 files 1). Header record 2). many detail record 3). Trailer record

My desired result is 1 file which contains Heaeder, Detail, Trailer


Currenty I am using a series of:
cat detail >> header
rm detail
cat trailer >> header
rm trailer
mv header detail

Now the problem with this approach is that my detail file quite often is in excess of 5gb, so the time is takes to do the cat seems like a waste of time to me. I would really like to be able to concatenate the header to the beginning of the detail and only "move" the one record.

Any ideas would be appreciated.

Thanks,

I assume some program is creating the "detail" file .. how much control over that program do you have? If you could go into it and tell it to stick your header information at the top of the file before it runs through the loop or whatever piece of code creates the 5gb detail file, that might be best...

We do have control over the program creating the files, but the header and trailer are created based upon the sum of the detail records so not possible to hold off writing all the details.

Chad.

I assume that before doing the following you already have the header, trailer and detail files

in that case

cat header detail trailer > newfile

I hope I havent much misunderstood the question

Won't that still copy the 5gb file ? I see how it is much more econimical as far as commands go though...


Thanks,

To edit any file in any way you will have to read it directly or indirectly
so any command/script/method will take atleast the time required to open the file and save it bak
so what you need to really worry is that you do minimum possible operations on the huge file

but you cannot avoid the time for

1. open
2. read

on the file to have it changed

penguin,

Thanks, that confirms my fear. However, I will try doing it in the one command and see how it works.

Thanks for your time and help.