Very Computer

by **John Lesl** » Wed, 03 Nov 2004 21:17:39

I am looking for the most efficient way in a script to add the
contents of a 4 line file to the top of another much larger file. It
would be good to avoid the I-O of doing a cat of the large file to the
end of the small file.

Any ideas?

by **Stachu 'Dozzie' K** » Wed, 03 Nov 2004 21:32:54

Quote:> I am looking for the most efficient way in a script to add the
> contents of a 4 line file to the top of another much larger file. It
> would be good to avoid the I-O of doing a cat of the large file to the
> end of the small file.

> Any ideas?

I think any way to put the small file in the beginning the big one will
end up with writting the big one after small one, so cat is IMO as good
way to do it as any other. If you want to avoid such operation try to
change something before creating that big file.

--
Stanislaw Klekot

by **Walt** » Fri, 05 Nov 2004 03:27:55

> > I am looking for the most efficient way in a script to add the
> > contents of a 4 line file to the top of another much larger file. It
> > would be good to avoid the I-O of doing a cat of the large file to the
> > end of the small file.

> > Any ideas?

> I think any way to put the small file in the beginning the big one will
> end up with writting the big one after small one, so cat is IMO as good
> way to do it as any other. If you want to avoid such operation try to
> change something before creating that big file.

**
Awk or sed might be able to do that, but I do not know how.
The quickest might be to:

$ mv big scratch
$ mv small big
$ cat scratch >> big

Walt R.
**

by **rakesh shar** » Fri, 05 Nov 2004 18:15:22

> > > I am looking for the most efficient way in a script to add the
> > > contents of a 4 line file to the top of another much larger file. It
> > > would be good to avoid the I-O of doing a cat of the large file to the
> > > end of the small file.

> > > Any ideas?

man dd

Quote:> **
> Awk or sed might be able to do that, but I do not know how.

sed -e '
1r small_file
1N
' Large_file

note: in case your large file contains just 1 line then the above
won't work. In fact, 'sed' cannot accomplish this :-(.

We can then do it in a 2-pass way as:

sed -e '
1{
r add
$n
N

Quote:}

' Large_file | \
sed -e '
1{h;d;}
${p;g;}
'

by **Michael Pao** » Mon, 08 Nov 2004 12:50:37

> I am looking for the most efficient way in a script to add the
> contents of a 4 line file to the top of another much larger file. It
> would be good to avoid the I-O of doing a cat of the large file to the
> end of the small file.

> Any ideas?

$ echo '0r small_file

Quote:> w
> q' | ed big_file

(the "> " is PS2 prompt, not literally entered)

This, however, doesn't necessarily avoid the I/O.

Very Computer

add file to top of another file

add file to top of another file

add file to top of another file

add file to top of another file

add file to top of another file

add file to top of another file