每天一个Linux命令（15）tail命令

tail命令用于输入文件中的尾部内容。tail命令默认在屏幕上显示指定文件的末尾10行。

如果给定的文件不止一个，则在显示的每个文件前面加一个文件名标题。

    (1)用法:

用法:   tail [必要参数] [选择参数]   [文件]

如果没有指定文件或者文件名为“-”，则读取标准输入。

    (2)功能:

功能:  输出文件的末尾部分

    (3)选项参数:

1) -n <k行数>                                     显示文件末尾k行内容

2) -c <k字节数>                                  显示文件末尾k个字节数

3) -f 　　　　　　　　　　　　　　　　　 循环读取 　　　　　　　　　　　　　　

4) -q 　　　　　　　　　　　　　　　　　不显示处理信息

5) -v 　　　　　　　　　　　　　　　　　显示详细的处理信息

    (4)实例:

1)[root@localhost Documents]# tail -n 5 ./tail_text          查看文件后5行的内容

[root@localhost Documents]# cat tail_text
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
[root@localhost Documents]# tail -n  ./tail_text
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

　　  等价于tail -5  text_tail  查看后5行的内容

[root@localhost Documents]# tail - tail_text
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

2)[root@localhost Documents]# tail -n +5 tail_text             从第5行开始显示

[root@localhost Documents]# tail -n + tail_text
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

3)[root@localhost Documents]# head -n -5 tail_text与[root@localhost Documents]# tail -n -5 tail_text

[root@localhost Documents]# head -n  tail_text　　　　　　　　　　//显示文件前5行的内容
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
[root@localhost Documents]# head -n - tail_text　　　　　　　　　　//除了文件后五行全部显示
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!                                          //head命令的-n参数，当后面的整数为正为负是有区别的
[root@localhost Documents]# tail -n  tail_text                 //tail命令的-n参数，当后面的整数为正为负是一样的
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
[root@localhost Documents]# tail -n - tail_text               //都是显示末尾的整数的绝对值行
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

4)[root@localhost Documents]# tail -c 30 tail_text                     显示末尾的字节数

[root@localhost Documents]# tail -c  tail_text
n line!
>  the twelve line!
[root@localhost Documents]# tail -c - tail_text
n line!
>  the twelve line!
[root@localhost Documents]# head -c  tail_text
>  the first line!
>  the [root@localhost Documents]# head -c - tail_text
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleve[root@localhost Documents]# 

5)[root@localhost Documents]# tail -f tail_text               循环读取内容输出到标准输出

[root@localhost Documents]# tail -f tail_text                             //默认是后10行
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
^C
[root@localhost Documents]# tail -f -n  tail_text                     //也可以自己指定
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
^Z
[]+  已停止               tail -f -n  tail_text
[root@localhost Documents]# tail -f -n  tail_text
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

当然，也可以把信息输入到文件中:

[root@localhost Documents]# tail -f tail_text>tempory
^Z
[]+  已停止               tail -f tail_text > tempory
[root@localhost Documents]# cat tempory
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!

6)[root@localhost Documents]# tail -n +5 tail_text与[root@localhost Documents]# tail -n 5 tail_text

[root@localhost Documents]# tail -n + tail_text
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
[root@localhost Documents]# tail -n  tail_text
>  the eighth line!
>  the nineth line!
>  the tenth line!
>  the eleven line!
>  the twelve line!
[root@localhost Documents]# head -n + tail_text
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
[root@localhost Documents]# head -n  tail_text
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!

7)[root@localhost Documents]# tail -n +10 tail_text |head -n -2

[root@localhost Documents]# tail -n + tail_text       //从第10行显示到尾部
>  the tenth line!
>  the eleven line!
>  the twelve line!
[root@localhost Documents]# head -n - tail_text       //除了末尾两行之外前面的都显示
>  the first line!
>  the second line!
>  the third line!
>  the forth line!
>  the fifth line!
>  the sixth line!
> o7 the seventh line!
>  the eighth line!
>  the nineth line!
>  the tenth line!
[root@localhost Documents]# tail -n + tail_text |head -n -2   //综合起来，用管道命令就是后一个命令处理前面的结果，因此达到只显示第10行的效果
>  the tenth line!
[root@localhost Documents]#