Linux 补丁生成与使用

我们在升级Linux 内核的时候，难免会接触到补丁的知识。下面对如何生成补丁和如何打补丁作讲解。

生成补丁：

制作 hello.c 和 hello_new.c 两个文件如如下所示。

➜  diff ls
hello.c  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World");
}
➜  diff cat hello_new.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}

使用 diff  -uN 命令 进行生成patch 

➜  diff diff -uN hello_new.c hello.c > hi.patch
➜  diff cat hi.patch 
--- hello_new.c    2018-07-17 16:58:23.679704122 +0800
+++ hello.c    2018-07-17 16:57:59.190677641 +0800
@@ -1,6 +1,5 @@
 #include "stdio.h"
 int main(int argc ,char **argv)
 {
-    printf("Hello World\n");
-    return 0;
+    printf("Hello World");
 }

至此，patch 已经创建完毕。

 之后，我们进行使用 patch 命令 对 hello.c 文件进行打补丁。

➜  diff patch -p0 <hi.patch 
patching file hello.c
Reversed (or previously applied) patch detected!  Assume -R? [n] y
➜  diff cat hello.c
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}
➜  diff ls
hello.c  hello.c.orig  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c.orig 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World");
}
➜  diff cat hello.c
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}
➜  diff 

可见，补丁已经成功应用，并且生成了 .orig 源文件。 --backup-if-mismatch  选项，可以不进行生成orig 文件。

➜  diff patch -p0 --no-backup-if-mismatch < hi.patch 
patching file hello.c
Reversed (or previously applied) patch detected!  Assume -R? [n] y
➜  diff ls
hello.c  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}

diff 和 patch 命令介绍：

1、diff

－－－－－－－－－－－－－－－－－－－－

NAME

       diff - find differences between two files

SYNOPSIS

       diff [options] from-file to-file

－－－－－－－－－－－－－－－－－－－－

简单的说，diff的功能就是用来比较两个文件的不同，然后记录下来，也就是所谓的diff补丁。语法格式：diff 【选项】 源文件（夹） 目的文件（夹），就是要给源文件（夹）打个补丁，使之变成目的文件（夹），术语也就是“升级”。下面介绍三个最为常用选项：

-r 是一个递归选项，设置了这个选项，diff会将两个不同版本源代码目录中的所有对应文件全部都进行一次比较，包括子目录文件。

-N 选项确保补丁文件将正确地处理已经创建或删除文件的情况。

-u 选项以统一格式创建补丁文件，这种格式比缺省格式更紧凑些。

2、patch

－－－－－－－－－－－－－－－－－－

NAME

       patch - apply a diff file to an original

SYNOPSIS

       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum <patchfile>

－－－－－－－－－－－－－－－－－－

简单的说，patch就是利用diff制作的补丁来实现源文件（夹）和目的文件（夹）的转换。这样说就意味着你可以有源文件（夹）――>目的文件（夹），也可以目的文件（夹）――>源文件（夹）。下面介绍几个最常用选项：

-pnum or --strip=num Strip the smallest prefix containing num leading slashes from each file name found in the patch file. A sequence of one or more adjacent slashes is counted as a single slash. This controls how file names found in the patch file are treated, in case you keep your files in a different directory than the person who sent out the patch. For example, supposing the file name in the patch file was

/u/howard/src/blurfl/blurfl.c

setting -p0 gives the entire file name unmodified, -p1 gives

u/howard/src/blurfl/blurfl.c

without the leading slash, -p4 gives

blurfl/blurfl.c

and not specifying -p at all just gives you blurfl.c. Whatever you end up with is looked for either in the current directory, or the directory specified by the -d option.

具体的使用说明，可以使用 man diff 和 man patch 命令来进行查看。

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