每天一个Linux命令（14）head命令

head命令用于显示文件的开头的内容。在默认情况下，head命令显示文件的头10行内容。
    如果指定了多于一个文件，在每一段输出前会给出文件名作为文件头。

如果不指定文件，或者文件为"-"，则从标准输入读取数据。

    (1)用法:

用法: head [选项]... [文件]...

    (2)功能:

将每个指定文件的头10 行显示到标准输出。

    (3)选项参数:

1)-q 　　　　　　　　　　　　隐藏文件名

2)-v 　　　　　　　　　　　　显示文件名

3)-c<字节> 　　　　　　　　 显示字节数

4)-n<行数> 　　　　　　　　 显示的行数

    (4)实例:

1)[root@localhost Documents]# head head_text      　　　　　　默认显示文件的前10行

[root@localhost Documents]# ll
总用量
-rw-r--r--.  root root  5月    : head_text
-rw-r--r--.  root root   5月    : less1
-rw-r--r--.  root root   5月    : less2
[root@localhost Documents]# head head_text
I am studing orders of Linux!
I am trying to write as many as lines of text!

No matter how low you consider yourself,
there is always someone looking behind you,
hoping that they were that high!

Something you want keep all the time,always you will lose!

2)[root@localhost Documents]# head -5 head_text  与    [root@localhost Documents]# head -n 5 head_text         　　  相同的功能：自定义显示文件前5行

[root@localhost Documents]# head - head_text
I am studing orders of Linux!
I am trying to write as many as lines of text!

No matter how low you consider yourself,
[root@localhost Documents]# head -n  head_text
I am studing orders of Linux!
I am trying to write as many as lines of text!

No matter how low you consider yourself,

3)[root@localhost Documents]# head -c 20 head_text     　　　　　　指定自定义显示前20个字节的内容

[root@localhost Documents]# head -c  head_text
I am studing orders [root@localhost Documents]#
[root@localhost Documents]# head -c  head_text
I am studing orders of Linux!
I am trying to write as many a

4)[root@localhost Documents]# head -c -50 head_text     　　　　　 指定除末尾的50个字节外全部显示

[root@localhost Documents]# head -c - head_text
I am studing orders of Linux!
I am trying to write as many as lines of text!

No matter how low you consider yourself,
there is always someone looking behind you,
hoping that they were that high!

Something you want keep all the time,always you will lose!

Never forget to say "thanks"!

Hppay today,also,prepared for happiness in the future!

Don't aim your success if you want it,just do what you love and believe and finally you will success!

Maybe you can be laze man like a pig,but you can't feel free as it!

I am a college school student!
I am planning to live and work in hangzhou or guangzhou!
I am from[root@localhost Documents]# 

5)I am from[root@localhost Documents]# head -n -10 head_text            　　　　　　　　除最后10行外全部显示

I am from[root@localhost Documents]# head -n - head_text
I am studing orders of Linux!
I am trying to write as many as lines of text!

No matter how low you consider yourself,
there is always someone looking behind you,
hoping that they were that high!

Something you want keep all the time,always you will lose!

Never forget to say "thanks"!

[root@localhost Documents]# 

6)[root@localhost Documents]# head -v less1 less2                             　　　　　　　　显示多个文件，并且在显示前打印出每个文件的文件名

[root@localhost Documents]# head -v  less1 less2
==> less1 <==
Lost means Get!

No losing No getting!

End!

==> less2 <==
If you want keep,you always lose!

Certainly It is!
End!

-v参数是默认的，即是不加也会如此:

[root@localhost Documents]# head less1 less2
==> less1 <==
Lost means Get!

No losing No getting!

End!

==> less2 <==
If you want keep,you always lose!

Certainly It is!
End!

7)[root@localhost Documents]# head -q -n 3 less1 less2 head_text              -q参数用来指定显示多个文件，不加文件名。同时也可以用-n 10指定只显示前3行

[root@localhost Documents]# head -q -n  less1 less2 head_text
Lost means Get!

No losing No getting!
If you want keep,you always lose!

Certainly It is!
I am studing orders of Linux!
I am trying to write as many as lines of text!

[root@localhost Documents]# 

8)[root@localhost Documents]# head --help

[root@localhost Documents]# head --help
用法：head [选项]... [文件]...
Print the first  lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -c, --bytes=[-]K         print the first K bytes of each file;
                             with the leading '-', print all but the last
                             K bytes of each file
  -n, --lines=[-]K         print the first K lines instead of the first ;
                             with the leading '-', print all but the last
                             K lines of each file
  -q, --quiet, --silent    不显示包含给定文件名的文件头
  -v, --verbose        总是显示包含给定文件名的文件头
      --help        显示此帮助信息并退出
      --version        显示版本信息并退出

K 后面可以跟乘号:
b , kB , K , MB *, M *,
GB **, G **, 对于T, P, E, Z, Y 同样适用。

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
请向<http://translationproject.org/team/zh_CN.html> 报告head 的翻译错误
要获取完整文档，请运行：info coreutils 'head invocation'

9)[root@localhost Documents]# head --version

[root@localhost Documents]# head --version
head (GNU coreutils) 8.22
Copyright (C)  Free Software Foundation, Inc.
许可证：GPLv3+：GNU 通用公共许可证第3 版或更新版本<http://gnu.org/licenses/gpl.html>。
本软件是自由软件：您可以自由修改和重新发布它。
在法律范围内没有其他保证。

由David MacKenzie 和Jim Meyering 编写。