说明
diff命令可以逐行比较纯文本文件的内容，并输出文件的差异
格式
diff [option] [file1] [file2]
常用参数说明
- -y：以并列的方式显示文件的异同之处
- -c：使用上下文的输出方式
- -W：在使用-y参数时，指定显示宽度
- -u：使用统一的格式输出
示例
1、默认情况下
[root@localhost ~]# cat diff1.txt
i
am
is
xiaohai
today
[root@localhost ~]# cat diff2.txt
hello
world
is
xiaohai
very
good
[root@localhost ~]# diff diff1.txt diff2.txt
1,2c1,2 #第一个文件的1到2行改变成第二个文件的1,2行
< i
< am
---
> hello
> world
5c5,6 #第一个文件的第五号改成第二个文件的5到6行
< today
---
> very
> good
diff默认情况下有三种提示：
a：增加
c：改变
d：删除
5c5,6或者1,2c1,2：字母前面是文件1的行号，字母后面是文件2的行号。其中<开头的是文件1，>开头的属于文件2
2、并排显示差异
[root@localhost ~]# diff -y diff1.txt diff2.txt
i | hello
am | world
is is
xiaohai xiaohai
today | very
> good
#如果上面对比宽度较大，那么可以是-W来控制
[root@localhost ~]# diff -y -W 30 diff1.txt diff2.txt
i | hello
am | world
is is
xiaohai xiaohai
today | very
> good
3、上下文输出
[root@localhost ~]# diff -c diff1.txt diff2.txt
*** diff1.txt 2018-06-04 11:56:25.159021083 -0400
--- diff2.txt 2018-06-04 11:55:56.554022518 -0400
***************
*** 1,5 ****
! i
! am
is
xiaohai
! today
--- 1,6 ----
! hello
! world
is
xiaohai
! very
! good
命令结果说明如下：
-：表示文件2比文件1少的行数
+：表示文件2比文件1多的行数
!：表示文件2与文件1不同行数
4、统一格式输出
[root@localhost ~]# diff -u diff1.txt diff2.txt
--- diff1.txt 2018-06-04 11:56:25.159021083 -0400
+++ diff2.txt 2018-06-04 11:55:56.554022518 -0400
@@ -1,5 +1,6 @@
-i
-am
+hello
+world
is
xiaohai
-today
+very
+good
5、还可以比较目录
[root@localhost ~]# diff /etc/rc3.d/ /etc/rc6.d/
Only in /etc/rc6.d/: K36mysqld
Only in /etc/rc6.d/: K79iprdump
Only in /etc/rc6.d/: K80iprinit
Only in /etc/rc6.d/: K80iprupdate
Only in /etc/rc6.d/: K90network
Only in /etc/rc3.d/: S10network
Only in /etc/rc3.d/: S20iprinit
Only in /etc/rc3.d/: S20iprupdate
Only in /etc/rc3.d/: S21iprdump
Only in /etc/rc3.d/: S64mysqld
6、修改下diff2.txt文件，删除前两行，然后执行上面的命令
[root@localhost ~]# diff -y diff1.txt diff2.txt
i <
am <
is is
xiaohai xiaohai
today | very
> good
[root@localhost ~]# diff -c diff1.txt diff2.txt
*** diff1.txt 2018-06-04 11:56:25.159021083 -0400
--- diff2.txt 2018-06-04 12:07:10.105988728 -0400
***************
*** 1,5 ****
- i
- am
is
xiaohai
! today
--- 1,4 ----
is
xiaohai
! very
! good
[root@localhost ~]# diff -u diff1.txt diff2.txt
--- diff1.txt 2018-06-04 11:56:25.159021083 -0400
+++ diff2.txt 2018-06-04 12:07:10.105988728 -0400
@@ -1,5 +1,4 @@
-i
-am
is
xiaohai
-today
+very
+good