head命令
作用：显示文件的头部内容，默认显示前面１０行
格式：
head [option] [file]
-n <行数>
-c <字节>
ghostwu@dev:~/linux/more$ head ghostwu.txt
this is ghostwu how are you file thank you
file thank you
file thank you
file thank you
ghostwu@dev:~/linux/more$ head - ghostwu.txt
this is ghostwu ghostwu@dev:~/linux/more$ cat ghostwu.txt | head -
this is ghostwu how are you
ghostwu@dev:~/linux/more$ head -c ghostwu.txt
this is ghghostwu@dev:~/linux/more$ cat -n ghostwu.txt | head
this is ghostwu how are you file thank you
file thank you
file thank you
file thank you
ghostwu@dev:~/linux/more$