Yesterday we saw diff in somewhat detail.
http://ae.iitm.ac.in/pipermail/ilugc/2009-September/051658.html
Today we are going to see the most important tool that every hacker should know:
PATCH(1) PATCH(1)
NAME
patch - apply a diff file to an original
SYNOPSIS
patch [options] [originalfile [patchfile]]
but usually just
patch -pnum <patchfile
There ya go. patch applies a diff from the original file to get a modified file.
This is what you do when you send your genius invention to your mother stream
upstream. IOW you need to send a bunch of patch files or even have them in one
single patch file(also known as patch set) to the author/maintainer of
the project.
But applying patch can be painful.
Here is an example.
$ cat file.txt
Slow day. Practice crawling.
You are farsighted, a good planner, an ardent lover, and a faithful friend.
You will lose your present job and have to become a door to door mayonnaise
salesman.
Don't Worry, Be Happy.
-- Meher Baba
Q: Why should you always serve a Southern Carolina football man
soup in a plate?
A: 'Cause if you give him a bowl, he'll throw it away.
$ cat file-new.txt
You are farsighted, a good planner, an ardent lover, and a faithful friend.
You will lose your present job and have to become a door to door mayonnaise
salesman.
-- Meher Baba
Q: Why should you always serve a Southern Carolina football man
soup in a plate?
A: 'Cause if you give him a bowl, he'll throw it away.
Don't Worry, Be Happy.
You will be winged by an anti-aircraft battery.
You will reach the highest possible point in your business or profession.
Slow day. Practice crawling.
$ diff -u file.txt file-new.txt
--- file.txt 2009-09-30 05:14:00.000000000 +0530
+++ file-new.txt 2009-09-30 05:14:31.000000000 +0530
@@ -1,9 +1,13 @@
-Slow day. Practice crawling.
You are farsighted, a good planner, an ardent lover, and a faithful friend.
You will lose your present job and have to become a door to door mayonnaise
salesman.
-Don't Worry, Be Happy.
-- Meher Baba
Q: Why should you always serve a Southern Carolina football man
soup in a plate?
A: 'Cause if you give him a bowl, he'll throw it away.
+Don't Worry, Be Happy.
+
+You will be winged by an anti-aircraft battery.
+
+You will reach the highest possible point in your business or profession.
+Slow day. Practice crawling.
Now the idea is to create file-new.txt from a guy who has file.txt.
How do you do it?
$ cp file.txt /tmp
$ diff -u file.txt file-new.txt > patch.txt
$ cd /tmp
$ patch -p0 < patch.txt
Now look at file.txt.
It has the same contents as file-new.txt
$ diff /tmp/file.txt ~/file-new.txt
Both files are same.
Now why I say patch is complicated.
Try patch again on top of patched file.
$ patch -p0 </home/girish/patch.txt
patching file file.txt
Reversed (or previously applied) patch detected! Assume -R? [n]
What a question and how confusing?
You should ask Larry Wall, the author of perl and this patch utility
why his brain works
in such a complicated fashion.
Anyway remember these things with patch.
o patch needs a p0 or p1 argument, typically it is only one
of these two - try to find out
when to use what switch
o patch always needs the '<' operator. Without that patch
will never do its job
Once again it shows Larry's complex thought process. Isn't it obvious
that I will only give
a patchfile as argument to patch? Why should I redirect? Anyway I have
nothing personal
against the fellow.
After all I love Perl.
Anyway patch files can contain a lot of gunk both at the top and
bottom. You can apply a patch
from a saved e-mail or in the middle of a document and it will still work.
-Girish
--
Gayatri Hitech
web: http://gayatri-hitech.com
SpamCheetah Spam filter:
http://spam-cheetah.com
