help-显现指令的运用信息
许多可执行程序都支撑–help选项，–help选项描绘了指令支撑的语法和选项。例如：
[me@linuxbox ~]$ mkdir –help
Usage: mkdir [OPTION] DIRECTORY…
Create the DIRECTORY(ies)， if they do not already exist.
-Z, –context=CONTEXT (SELinux) set security context to CONTEXT
Mandatory arguments to long options are mandatory for short options too.
-m, –mode=MODE set file mode (as in chmod)， not a=rwx – umask
-p, –parents no error if existing, make parent directories as
needed
-v, –verbose print a message for each created directory
–help display this help and exit
–version output version information and exit
Report bugs to
一些程序不支撑–help选项，可是咱们仍是要试试。这通常会发生一条过错音讯，该过错音讯也能提醒相同的指令运用信息。
