[Ilugc] .a-tip-a-day (patch - apply diffs and act as inverse of diff)
- From: steve@xxxxxxxxxxxx (steve)
- Date: Wed Sep 30 10:39:16 2009
Hi,
Just a couple of points worth mentioning ...
On 09/30/2009 05:24 AM, Girish Venkatachalam wrote:
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:
[...snip...]
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
To do this (in fact in general, it is always be a good idea) to use the
"--dry-run" switch. According to the man page:
--dry-run
Print the results of applying the patches without actually changing
any files.
Another userful switch is the -b or -B switches - Make backup file of the files
being patched. See the man page for more info.
o patch always needs the '<' operator. Without that patch
will never do its job
Umm. That is incorrect. patch reads from stdin. So, you can also send the
output
of a pipe to patch. For instance in the days before git, the quick way to
update
your kernel sources if you already had an old version of the sources was to get
only the patchset and apply them. Something like ...
$ cd /usr/src/patches
$ wget -O-
ftp://www.kernel.org/<url>/patch-<version>.bz2 | bunzip2 - | patch
-p1
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?
...so, you can also send multiple patchfiles to patch ...
$ cat somefile[1234].diff | patch -p1
...and patch will do the right thing !
cheers,
- steve
--
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