head :output the first part of files :輸出文件首部
head選項:
-c ,--bytes=[-]k :print the first K bytes of each file; with the leading ‘-’,print all but the last K bytes of each file : 打印文件前k個字符,必須有k值,-k表示打印文件至倒數第k個字符位置,第k個字符會被打印出來。
-n ,--lines=[-]K :print the first K lines instead of the first 10; with the leading ‘-’, print all but the last K lines of each file :不加k也行,默認打印10行,-k用法同-c中的-k相同。