head

语法

head [options] files

同样也是过滤命令，默认打印每个文档首10行内容。

参数

• -c | --bytes=[-]NUM 显示前NUM个字节的内容。后面如添加了计数单位将会相应改变。-NUM表示出去末尾的个数字节。

• -n | --lines=[-]NUM 显示前NUM行。默认值为10。

• -q | --quiet | --silent 不打印头部显示的文件名。

• -v | --verbose 打印头部显示的文件名。

• -z | --zero-terminated 将所有换行符看做为NUL，不作为新行。

• --help 显示帮助文档。

• --version 显示版本信息。

Example

• head test

  默认显示文档前10行内容。

  root@3ff83ffc7119:/# head test
  line1
  line2
  line3
  This is line4
  This is line5
  This is line6
  This is line7
  
  line1 copy
  line2 copy
  

• head -n 5 test

  指定显示行数为开头5行。

  root@3ff83ffc7119:/# head -n 5 test
  line1
  line2
  line3
  This is line4
  This is line5
  

• head -c 5 test

  显示指定字节数，单位计量表示b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, T, P, E, Z, Y后续亦如此规律。

  root@3ff83ffc7119:/# head -c 5 test
  line1root@3ff83ffc7119:/#
  root@3ff83ffc7119:/# head -c 6 test
  line1 root@3ff83ffc7119:/# head -c 6k test
  line1
  line2
  line3
  This is line4
  This is line5
  This is line6
  This is line7
  
  line1 copy
  line2 copy
  line3 copy
  This is line4 copy
  This is line5 copy
  This is line6 copy
  This is line7 copy
  

• head -v test

  显示更多的显示信息，==> test <== 这里表示文件名

  root@3ff83ffc7119:/# head -v -n 5 test
  ==> test <==
  line1
  line2
  line3
  This is line4
  This is line5
  root@3ff83ffc7119:/# head -v test
  ==> test <==
  line1
  line2
  line3
  This is line4
  This is line5
  This is line6
  This is line7
  
  line1 copy
  line2 copy
  

• head -z test

  不计算换行。

  root@3ff83ffc7119:/# head -z test
  line1
  line2
  line3
  This is line4
  This is line5
  This is line6
  This is line7
  
  line1 copy
  line2 copy
  line3 copy
  This is line4 copy
  This is line5 copy
  This is line6 copy
  This is line7 copy
  

• head --version

  显示当前版本

  root@3ff83ffc7119:/# head --version
  head (GNU coreutils) 8.28
  Copyright (C) 2017 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.
  
  Written by David MacKenzie and Jim Meyering.