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。
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 deleted This is a line that will be changed This is a line that will be unchanged
after.txt
This is a line that has been changed This is a line that will be unchanged This is a line that has been added
- 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 changed 3a3 > This is a line that has been added
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
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。
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
- 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
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
是被删除的行
+This is a line that has been changed
是增加的行
This is a line that will be unchanged
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
diff的统一格式比较与输出是按顺序进行的。
- patch命令的应用:
diff before.txt after.txt > mypatch.txt
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
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
- 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 new echo "This is one. It's unchanged." | tee old/one new/one echo "This is two. It will change." > old/two echo "This is two. It changed."> new/two echo "This is three. It's new" > new/three
创建修补文件
diff -Nur old/ new/ > mypatch.diff
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 new diff -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:
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.
打补丁到old目录,新建old/three以及更改old/two
patch --dir old < mypatch.diff ls -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
- 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
用gui工具gvimdiff来显示两个文件
gvimdiff after.txt before.txt
新建文件orig.c
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”);
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”);
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
diff3 me.c orig.c you.c
#输出:
====1
1:3c
printf("This was changed by me. \n");
2:3c
3:3c
printf("This will be changed by me. \n");
====3
1:7c
2:7c
printf("This will be changed by you.\n");
3:7c
printf("This was changed by you.\n");
注:
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.
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.
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.
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.
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 }
参考来源：