Shell Programming and Scripting

Try...

Code:

awk '{a[NR]=$0}END{a[0]=h;for(i=0;i<=NR;i++)print a[i]>FILENAME}' h="HeaderText" ExtractDataFile.txt

Use nawk or /usr/xpg4/bin/awk on Solaris.

Unfortunately, any solution is going to use a temp file, either explicitly or behind the scenes.

You might as well go with:

Code:

(
echo WHATEVER HEADER INFO YOU NEED
cat original_file
) > temp_file

mv temp_file original_file

What I typically like to do though in situations like these is create an associated
file_name.info file which contains all the header and other useful information like
create-dt, created-by-user, number-of-records, number-of-bytes and check-sums.

This also works for using ftp when a polling program is trying to figure out when a
large file is finished being created so it can snatch it up right away. Instead of
polling for the size to stop growing, it just waits til the info file is created.

The solution which Ygor provided works!!

I would like to understand how it works though

thanx anyways

In fact one of the other methods i would think works is something like this
1) Create a file that has vi commands

CommandsOfVi.script

Code:

vi cmd to goto line 1
vi cmd to insert 'Header Text'
vi cmd to save and quit a file

2) Open a file using vi and non-interactive mode by using the above commands file as input

Code:

vi ExtractDataFile.txt < CommandsOfVi.script

I had done something a few years back, but don't remember the syntax etc. so just put it in a very simplified manner here - this approach, I believe, wont use a temp file