Linux diff与patch的使用
用了这么久linux，发现还有这么精妙的功能没有使用到，都不好意思跟人说我会linux了。
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首先提供两个测试使用的简单文本文件
before.txt
This is a line to be deletedThis is a line that will be changedThis is a line that will be unchanged
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?after.txt
This is a line that has been changedThis is a line that will be unchangedThis is a line that has been added
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diff的传统格式输出diff before.txt after.txt 1,2c1< This is a line to be deleted< This is a line that will be changed---> This is a line that has been changed3a3> This is a line that has been added
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?说明：
1,2c1是指替换第1个文件的第1,2行到第2个文件的第2行,这里的1,2是指第1个文件的第1,2行,c是替换的意思,最后的1是第2个文件的第1行。
<号是指第1个文件更改或删除的行。
—号是分割两个文件。
>号是第2个文件中增加或删除的行。
3a3是指将第2个文件的第3行插入到第一个文件的第3行。也就是说第1个文件的:
< This is a line to be deleted< This is a line that will be changed
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?被替换成第2个文件的:
> This is a line that has been changed
由于第1个文件的第3行和第2个文件的第2行一致,所以不做修改。
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由于第2个文件的第3行是第1个文件所不具有的,所以在第1个文件的最后一行增加:
> This is a line that has been added
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diff的统一格式输出diff -u before.txt after.txt | tee mypatch.diff--- before.txt 2009-06-20 05:21:49.000000000 +0800+++ after.txt 2009-06-20 04:03:16.000000000 +0800@@ -1,3 +1,3 @@-This is a line to be deleted-This is a line that will be changed+This is a line that has been changed This is a line that will be unchanged+This is a line that has been added
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?说明：
diff -u选项是统一格式输出.
— before.txt 2009-06-20 05:21:49.000000000 +0800
— before.txt是指旧文件
+++ after.txt 2009-06-20 04:03:16.000000000 +0800
+++ after.txt是指新文件.
@@ -1,3 +1,3 @@
@@ -1,3是指第1个文件一共有3行,+1,3 @@是指第2个文件一共有3行.
-This is a line to be deleted-This is a line that will be changed
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?是被删除的行
+This is a line that has been changed
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?是增加的行
This is a line that will be unchanged
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?没有-号和+号是指该行不变,因为after.txt和before.txt都有这行.
+This is a line that has been added
?是增加的行
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diff的统一格式比较与输出是按顺序进行的。
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patch命令的应用:diff before.txt after.txt > mypatch.txt
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?用patch修补before.txt文件,使before.txt和after.txt一致.
cat mypatch.txt | patch before.txt patching file before.txt
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?比较两个文件，现在是一致的了
cmp before.txt after.txt
?用patch命令恢复before.txtpatch -R before.txt < mypatch.txt
patching file before.txt
?注:-R标记告诉patch在反向上应用区别或者撤销patch.
再比较两个文件,现在不一致了.
cmp before.txt after.txt before.txt after.txt differ: byte 17, line 1
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diff命令在目录中的应用?
新建old和new目录,old目录包含了初始内容,new目录包含文件的最新版本
mkdir old newecho "This is one. It's unchanged." | tee old/one new/oneecho "This is two. It will change." > old/twoecho "This is two. It changed."> new/twoecho "This is three. It's new" > new/three
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?创建修补文件
diff -Nur old/ new/ > mypatch.diff
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注:-r选项按照文件目录递归创建修补文件；-u还是统一模式；-N是指当diff遇到一个只存在于两个树中的一个树中的文件时,默认情况下跳过文件并且打印一个警告到stderr。这个行为可以通过-N选项来更改,这也导致了diff认为丢失的文件实际上是存在的,但它是空的.采用这种方式,一个修补文件可以包括已经创建的文件.然后应用修补程序创建新的文件.
more mypatch.diff # 输出:diff -Nur old/three new/three--- old/three 1970-01-01 08:00:00.000000000 +0800+++ new/three 2009-06-20 06:55:34.000000000 +0800@@ -0,0 +1 @@+This is three. It's newdiff -Nur old/two new/two--- old/two 2009-06-20 06:55:08.000000000 +0800+++ new/two 2009-06-20 06:55:21.000000000 +0800@@ -1 +1 @@-This is two. It will change.+This is two. It changed.
?注释:
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diff -Nur old/three new/three是指下面比较old/three new/three两个文件。因为没有old/three文件,所以在old/three中增加+This is three。 It’s new diff -Nur old/two new/two是指下面比较old/two new/two两个文件。因为old/two与new/two的第3行不一致,所以删除This is two. It will change.增加This is two. It changed.
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打补丁到old目录,新建old/three以及更改old/two
patch --dir old < mypatch.diffls -l old/# 输出:one three two
?恢复old目录的内容,包括删除old/three,以及恢复old/two文件patch --dir old -R < mypatch.diff
patch --dir old -R < mypatch.diff# 输出:ls -l old/one two
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?检查和合并更改用vim突出显示单个字符的更改来表示区别
vim -d after.txt before.txt
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?用gui工具gvimdiff来显示两个文件
gvimdiff after.txt before.txt
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?新建文件orig.c
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void foo(void){ printf("This will be changed by me. \n"); printf("This will be unchanged,\n"); printf("This will be changed by you.\n");}?复制文件orig.c到me.c,更改第4行为printf(”This was changed by me. \n”);
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void foo(void){ printf("This was changed by me. \n"); printf("This will be unchanged,\n"); printf("This will be changed by you.\n");}?
?复制文件orig.c到you.c,更改第7行为printf(”This was changed by you.\n”);
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void foo(void){ printf("This will be changed by me. \n"); printf("This will be unchanged,\n"); printf("This was changed by you.\n");}?
?版本工具如cvs,subversion使用GNU合并工具称为diff3
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diff3 me.c orig.c you.c #输出:====11:3c printf("This was changed by me. \n");2:3c3:3c printf("This will be changed by me. \n");====31:7c2:7c printf("This will be changed by you.\n");3:7c printf("This was changed by you.\n");?注:
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在没有参数的情况下,diff3产生的输出说明了那行更改.
====1和====3指明造成同原始文件不同的是哪一个修改文件.
编号方式基于参数序列.
也就是第1个文件和第3个文件与原文件不同.
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1:3c printf("This was changed by me. \n");3:3c printf("This will be changed by me. \n");?1:3c表示第1个文件的第3行与3:3c表示的第3个文件的第3行不同.
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为什么不显示与原文件的比较呢。因为第3个文件的第3行与源文件(第2个文件)相同.所以与哪个文件比较无所谓了.
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2:7c printf("This will be changed by you.\n");3:7c printf("This was changed by you.\n");?
?2:7c表示第2个文件的第7行与3:7c表示的第3个文件的第7行不同.
diff3会试图为我们进行合并.合并是在源文件的基础上,依据两个新文件进行修改。源文件是第二个文件,第一个文件和第三个文件可以互换，但他们必须有共同的祖先，就是第二个文件.
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diff3 -m me.c orig.c you.c |cat -n#输出: 1 void foo(void) 2 { 3 printf("This was changed by me. \n"); 4 5 printf("This will be unchanged,\n"); 6 7 printf("This was changed by you.\n"); 8 }?
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参考来源：
http://gooss.org/linux-diff-and-patch-depth-analysis-of/
1 楼 shiq_stone 2011-10-21 这个东西更有意思