linux 命令之head

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head用来显示文件的开头至标注输出中，默认head命令打印其相应文件的开头10行

命令格式： head [参数] [文件名]

参数：

-q 隐藏文件名

-v 显示文件名

-c 显示文件字节数

-n 显示文件行数

测试文本文件：

a.txt

内容如下

root:x:0:0:root:/root:/bin/bashdaemon:x:1:1:daemon:/usr/sbin:/bin/shbin:x:2:2:bin:/bin:/bin/shsys:x:3:3:sys:/dev:/bin/shsync:x:4:65534:sync:/bin:/bin/syncgames:x:5:60:games:/usr/games:/bin/shman:x:6:12:man:/var/cache/man:/bin/shlp:x:7:7:lp:/var/spool/lpd:/bin/shmail:x:8:8:mail:/var/mail:/bin/shnews:x:9:9:news:/var/spool/news:/bin/shuucp:x:10:10:uucp:/var/spool/uucp:/bin/shproxy:x:13:13:proxy:/bin:/bin/shwww-data:x:33:33:www-data:/var/www:/bin/shbackup:x:34:34:backup:/var/backups:/bin/shlist:x:38:38:Mailing List Manager:/var/list:/bin/shirc:x:39:39:ircd:/var/run/ircd:/bin/shgnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/shnobody:x:65534:65534:nobody:/nonexistent:/bin/shlibuuid:x:100:101::/var/lib/libuuid:/bin/shsyslog:x:101:103::/home/syslog:/bin/falsemessagebus:x:102:105::/var/run/dbus:/bin/falsecolord:x:103:108:colord colour management daemon,,,:/var/lib/colord:/bin/falselightdm:x:104:111:Light Display Manager:/var/lib/lightdm:/bin/falsewhoopsie:x:105:114::/nonexistent:/bin/falseavahi-autoipd:x:106:117:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/falseavahi:x:107:118:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/falseusbmux:x:108:46:usbmux daemon,,,:/home/usbmux:/bin/falsekernoops:x:109:65534:Kernel Oops Tracking Daemon,,,:/:/bin/falsepulse:x:110:119:PulseAudio daemon,,,:/var/run/pulse:/bin/falsertkit:x:111:122:RealtimeKit,,,:/proc:/bin/falsespeech-dispatcher:x:112:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/shhplip:x:113:7:HPLIP system user,,,:/var/run/hplip:/bin/falsesaned:x:114:123::/home/saned:/bin/falsegino:x:1000:1000:gino,,,:/home/gino:/bin/bash

例子：

# head -v a.txt

结果如下：（显示文件名，以及文件开头10行）

==> a.txt <==root:x:0:0:root:/root:/bin/bashdaemon:x:1:1:daemon:/usr/sbin:/bin/shbin:x:2:2:bin:/bin:/bin/shsys:x:3:3:sys:/dev:/bin/shsync:x:4:65534:sync:/bin:/bin/syncgames:x:5:60:games:/usr/games:/bin/shman:x:6:12:man:/var/cache/man:/bin/shlp:x:7:7:lp:/var/spool/lpd:/bin/shmail:x:8:8:mail:/var/mail:/bin/shnews:x:9:9:news:/var/spool/news:/bin/sh

# head -c 20 a.txt

显示结果如下：（开头20个字符）

root:x:0:0:root:/roo

# head -n 3 a.txt

显示结果如下：（开头到第三行）

root:x:0:0:root:/root:/bin/bashdaemon:x:1:1:daemon:/usr/sbin:/bin/shbin:x:2:2:bin:/bin:/bin/sh

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