Linux - Howto create patch

First, how to create patch file?
Patch file is a readable file that created by diff with -c (context output format). It doesn’t matter and if you wanna know more, man diff. To patch the entire folder of source codes(as usually people do)I do as bellow:

Assume Original source code at folder Tb01, and latest source code at folder Tb02. And there have multiple sub directories at Tb01 and Tb02 too.

diff -crB Tb01 Tb02 > Tb02.patch

-c context, -r recursive (multiple levels dir), -B is to ignore Blank Lines.
I put -B because blank lines is really useless for patching, sometimes I need to manually read the patch file to track the changes, without -B is really headache.

How to patch?
First of all, please do a dry-run before really patch it. Bare in mind, patch will be working very specifically. Let say the version 3 Tb03.patch is use to patch from Tb02, if you apply patch on Tb01, sometimes it will corrupt your source code. So, to make sure it works, do a dry run. Dry-run means a fake-test, do it at the directory of the source code targeted to patch.

Doing dry-run like this:

patch --dry-run -p1 -i Tb02.patch

The success output looks like this:

patching file TbApi.cpp
patching file TbApi.h
patching file TbCard.cpp
...

The failure ouptut looks like this:

patching file TbCard.cpp
Hunk #2 FAILED at 585.
1 out of 2 hunks FAILED -- saving rejects to file TbCard.cpp.rej
patching file TbCard.h
Hunk #1 FAILED at 57.
Hunk #2 FAILED at 77.
Hunk #3 succeeded at 83 with fuzz 1 (offset -21 lines).
....

At last, if the dry-run is giving good result, do this and enjoy the compilation.

patch -p1 -i Tb02.patch

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Useful example, thanks. There are two things I would add - first, before running patch, cd into the new directory (the one to be patched). That’s how the command knows which tree to modify.

diff -crB Tb01 Tb02 > Tb02.patch
cp -r Tb01 Tb03
cd Tb03
patch –dry-run -p1 -i ../Tb02.patch

Second, if there were files in Tb02 that did not exist in Tb01 and you want them included in the patch, give diff the -N option:

diff -crBN Tb01 Tb02 > Tb02.patch

Lastly, I’d note that diff and patch really only work with text files. It can’t deal with jpegs, pdfs, or other binary objects. This can be a bit of a pain for web and GUI developers.


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Tested:
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diff -Naur file1 file2 > diff.patch

patch -p0 < diff.patch