How to create a patch using diff

Use

Patch file maily used for distributing your software as source code is an excellent idea because it allows a people easily understand how you have implemented things and how you used feature.And also allows people to check and mainly to reuse the source code.

Syntax :


patch - apply a diff file to an original


Synopsis:

       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum <patchfile

patch : Solves  probably only a small percentage of source code has changed between each release.

It was written by Larry Wall, who also written the Perl programming language.

The patch allows you to distribute just the difference between two version

for example this version1 named as file1.c

This is file1
line 2
line 3
there is no line 4, this is line 5
line 6
and then version2 named as file2.c

 for example this version1 named as file2.c

This is file2
line 2
line 3
line 4
line 5
line 6
a new line 8

create a difference listing with diff command

$diff file1.c file2.c > diffs

The diff file contains

1c1
< This is file1
---
> This is file2
4c4,5
< there is no line 4, this is line 5
---
> line 4
> line 5
5a7
> a new line 8
you can update your file using patch as follws

$patch file1.c diffs


The patch command has now changed file1.c to be same as file2.c

to unpatch

$Patch -R file1.c diffs

Now the file1.c contains it's original

That's all you need to get started with diff and patch. For more information use:

man diff
man patch

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