head 与 tail 就像它的名字一样的浅显易懂，它是用来显示开头或结尾某个数量的文字区块，head 用来显示档案的开头至标准输出中，而 tail 想当然尔就是看档案的结尾。

命令

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bobo@ubuntu:~/test$ head --help
Usage: head [OPTION]... [FILE]...
Print the first 10 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=[-]NUM       print the first NUM bytes of each file;
                             with the leading '-', print all but the last
                             NUM bytes of each file
  -n, --lines=[-]NUM       print the first NUM lines instead of the first 10;
                             with the leading '-', print all but the last
                             NUM lines of each file
  -q, --quiet, --silent    never print headers giving file names
  -v, --verbose            always print headers giving file names
  -z, --zero-terminated    line delimiter is NUL, not newline
      --help     display this help and exit
      --version  output version information and exit

NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/head>
or available locally via: info '(coreutils) head invocation'

命令功能

head 用来显示档案的开头至标准输出中，默认head命令打印其相应文件的开头10行。

使用实例：

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bobo@ubuntu:~/test$ cat test1.txt
this is line 1
this is line 2
this is line 3
this is line 4
this is line 5
this is line 6
this is line 7
this is line 8
bobo@ubuntu:~/test$

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bobo@ubuntu:~/test$ cat test2.txt
hello
world
this is test2
bobo@ubuntu:~/test$

显示文件的前n行

通过-n控制要输出的行数，默认输出前10行

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bobo@ubuntu:~/test$ head -n 3 test1.txt
this is line 1
this is line 2
this is line 3
bobo@ubuntu:~/test$

当行数前添加-时，输出除了最后 n 行外的其他内容

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bobo@ubuntu:~/test$ head -n -3 test1.txt
this is line 1
this is line 2
this is line 3
this is line 4
this is line 5
bobo@ubuntu:~/test$

-c 参数使用相同，只是显示的是前多少个字符，而不是多少行而已

显示文件名

打开多个文件时，默认会输出文件名

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bobo@ubuntu:~/test$ head test1.txt test2.txt
==> test1.txt <==
this is line 1
this is line 2
this is line 3
this is line 4
this is line 5
this is line 6
this is line 7
this is line 8

==> test2.txt <==
hello
world
this is test2
bobo@ubuntu:~/test$

使用-q 会不输出文件名

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bobo@ubuntu:~/test$ head -q test1.txt test2.txt
this is line 1
this is line 2
this is line 3
this is line 4
this is line 5
this is line 6
this is line 7
this is line 8
hello
world
this is test2
bobo@ubuntu:~/test$

单个文件时，默认也不会输出文件名，但是可以用 -v 设置始终显示文件名

参考文献