diff命令的使用

摘要：本文详细介绍了diff命令的基本用法
作者：zieckey （zieckey＠yahoo.com.cn）
    All Rights Reserved！
有这样两个文件：
程序清单1 ：hello.c
#include
int main(void)
{
    char msg[] = "Hello world!";
    puts(msg);
    printf("Welcome to use diff commond./n");
    return 0;   
}
程序清单2：hello_diff.c
#include
#include
int main(void)
{
    char msg[] = "Hello world,fome hello_diff.c";
    puts(msg);
    printf("hello_diff.c says,'Here you are,using diff.'/n");
    return 0;   
}
我们使用diff命令来查看这两个文件的不同之处，有一下几种方便的方法：
1、普通格式输出：
[root@localhost diff]# diff hello.c hello_diff.c
1a2
> #include
5c6
<       char msg[] = "Hello world!";
---
>       char msg[] = "Hello world,fome hello_diff.c";
8c9
<       printf("Welcome to use diff commond./n");
---
>       printf("hello_diff.c says,'Here you are,using diff.'/n");
[root@localhost diff]#
上面的“1a2”表示后面的一个文件"hello_diff.c"比前面的一个文件"hello.c"多了一行
"5c6"表示第一个文件的第5行与第二个文件的第6行有区别
2、并排格式输出
[root@localhost diff]# diff hello.c hello_diff.c -y -W 130
#include                                               #include
                                                              > #include
int main(void)                                                  int main(void)
{                                                               {
        char msg[] = "Hello world!";                          |         char msg[] = "Hello world,fome hello_diff.c";
        puts(msg);                                                      puts(msg);
        printf("Welcome to use diff commond./n");             |         printf("hello_diff.c says,'Here you are,using diff.'/
        return 0;                                                       return 0;
}                                                               }
[root@localhost diff]#
这种并排格式的对比一目了然，可以快速找到不同的地方。
-W选择可以指定输出列的宽度，这里指定输出列宽为130
3、上下文输出格式
[root@localhost diff]# diff hello.c hello_diff.c -c
*** hello.c     2007-09-25 17:54:51.000000000 +0800
--- hello_diff.c        2007-09-25 17:56:00.000000000 +0800
***************
*** 1,11 ****
  #include
  int main(void)
  {
!       char msg[] = "Hello world!";
        puts(msg);
!       printf("Welcome to use diff commond./n");
        return 0;
  }
--- 1,12 ----
  #include
+ #include
  int main(void)
  {
!       char msg[] = "Hello world,fome hello_diff.c";
        puts(msg);
!       printf("hello_diff.c says,'Here you are,using diff.'/n");
        return 0;
  }
[root@localhost diff]#
这种方式在开头两行作了比较文件的说明，这里有三中特殊字符：
＋        比较的文件的后者比前着多一行
－        比较的文件的后者比前着少一行       
！        比较的文件两者有差别的行
4、统一输出格式
[root@localhost diff]# diff hello.c hello_diff.c -u
--- hello.c     2007-09-25 17:54:51.000000000 +0800
+++ hello_diff.c        2007-09-25 17:56:00.000000000 +0800
@@ -1,11 +1,12 @@
#include
+#include
int main(void)
{
-       char msg[] = "Hello world!";
+       char msg[] = "Hello world,fome hello_diff.c";
        puts(msg);
-       printf("Welcome to use diff commond./n");
+       printf("hello_diff.c says,'Here you are,using diff.'/n");
        return 0;
}
[root@localhost diff]#
正如看到的那样，统一格式的输出更加紧凑，所以更易于理解，更易于修改。
5、其他
假如你想查看两个文件是否不同又不想显示差异之处的话，可以加上－q选项：
[root@localhost diff]# diff hello.c hello_diff.c -q
Files hello.c and hello_diff.c differ
[root@localhost diff]# 另外你还可以提供一些匹配规则来忽略某中差别，可以用 -I regexp
[root@localhost diff]# diff hello.c hello_diff.c -c -I include
*** hello.c     2007-09-25 17:54:51.000000000 +0800
--- hello_diff.c        2007-09-25 17:56:00.000000000 +0800
***************
*** 2,11 ****
  int main(void)
  {
!       char msg[] = "Hello world!";
        puts(msg);
!       printf("Welcome to use diff commond./n");
        return 0;
  }
--- 3,12 ----
  int main(void)
  {
!       char msg[] = "Hello world,fome hello_diff.c";
        puts(msg);
!       printf("hello_diff.c says,'Here you are,using diff.'/n");
        return 0;
  }
[root@localhost diff]#
这里通过“ -I include”选项来忽略带有“ include”字样的行