Shell Programming and Scripting

Need your help in appending header(file1 contains header ) to my file2. I am using KSH AIX OS.
I know how to do with taking temporary files.

Code:

cat file1  >temp
 cat file2 >>temp
  mv temp  file2

Is there way to append directly to a file in ksh.

I don't find Sed -i option on my unix flavor.

You can use awk, cat, ed, ex, sed (with or without -i), or lots of other methods. All of them are going to use a temp file to prepend data into an existing file. Some of them will make the temp file obvious; others will use the temp file under the covers.

Can you please share me the method without using temp files. The problem I had is my data files are in GB's (20GB). My process takes more time to move 20GB of data into tmp file instead what I taught is adding a single line to 20GB data is much faster.

As I said before, there is no way to add data to the start of a file without copying the data at least once. If the file you're modifying has more than one link and you don't want to break the links or the temp file is on a different filesystem than the file you're modifying, you'll have to copy the data twice.

Even if you have more than 20B of memory you can allocate to a program to edit your file, you still have to read the entire 20GB into memory and write the entire 20+GB of data back into your file.

Of course you could create a new filesystem type that allows you to add data to either end of a file without moving existing data and create a new system call to write data into a file at negative offsets. (But, before you ask, I'll warn you that I'm not going to volunteer to design either of those for you for free in a forum like this!)

Is that "Inserting Header to another file" an exercise on its own or is it done in preparation of another processing step? If the latter, can't you "add the header" in that step? e.g. awk '...' file1 file2 or cat file1 file2

https://www.unix.com/answers-to-frequ...-original.html seems to be relevant here

Now that you know sed -i would create a "invisible" temp file too and your sed version does not support the -i option, you might want to try following Perl equivalent:

From perlfaq5 - perldoc.perl.org :

Code:

You can even add a line to the beginning of a file, since the current line prints at the end of the loop:

    perl -pi -e 'print "Put before first line\n" if $. == 1' inFile.txt

How about our good ole ex utility...

Code:

ex -sc '0r file1 | x' file2

---------- Post updated at 12:01 PM ---------- Previous update was at 11:57 AM ----------

AFAIK ed and ex would use an internal buffer instead of a temporary file...