1、目录管理
【ls、cd、pwd、mkdir、rmdir、tree】
tree：list contents of directories in a tree-like format.
2、文件管理
【touch、stat、file、rm、cp、mv、nano、install】
stat - display file or file system status.
install - copy files and set attributes
-d 可以创建目录
3、时间管理
【date、clock、hwclock、cal】
4、查看文件
【cat、tac、head、tail、more、less、file、du】
file - determine file type.
du - estimate file space usage.
5、文本处理
【cut、join、uniq、sort、sed、awk、wc、tr】
cut - remove sections from each line of files.
join - join lines of two files on a common field.
uniq - report or omit repeated lines.
sort - sort lines of text files.
sed - stream editor for filtering and transforming text.
gawk - pattern scanning and processing language.
wc - print the number of newlines, words, and bytes in files.
tr - translate or delete characters.
