语法：
BusyBox v1.22.1 (2015-11-10 11:07:12 ) multi-call binary.
Usage: ls [-1AaCxdLHRFplinsehrSXvctu] [-w WIDTH] [FILE]...
List directory contents
-1 One column output 按列显示。显示成一竖列。
-a Include entries which start with . 包括隐藏目录一起显示出来。
-A Like -a, but exclude . and .. 显示的隐藏目录不含. 和 ..
-C List by columns
-x List by lines
-d List directory entries instead of contents
-L Follow symlinks 不显示链接自己，而是链接的目标。
-m fill width with a comma separated list of entries 如何显示在一行里，则逗号分隔。
-H Follow symlinks on command line
-R Recurse 显示目标目录和其所有子目录。
-p Append / to dir entries
-F Append indicator (one of */=@|) to entries
-l Long listing format 长格式，又叫详细格式。每个文件显示一行。
-i List inode numbers 会在文件前多显示一个它的inode值。
-n List numeric UIDs and GIDs instead of names 显示UID和GID的值而不是名字。
-s List allocated blocks
-e List full date and time
-h List sizes in human readable format (1K 243M 2G)
-r Sort in reverse order
-S Sort by size
-X Sort by extension
-v Sort by version
-c With -l: sort by ctime
-t With -l: sort by mtime
-u With -l: sort by atime
-w N Assume the terminal is N columns wide
--color[={always,never,auto}] Control coloring