[root@NetAdmin ~]# su --help
用法:su [选项]... [-] [用户 [参数]...]
Change the effective user id and group id to that of USER.
-, -l, --login make the shell a login shell
-c, --command=COMMAND pass a single COMMAND to the shell with -c
--session-command=COMMAND pass a single COMMAND to the shell with -c
and do not create a new session
-f, --fast pass -f to the shell (for csh or tcsh)
-m, --preserve-environment do not reset environment variables
-p same as -m
-s, --shell=SHELL run SHELL if /etc/shells allows it
--help 显示此帮助信息并退出
--version 输出版本信息并退出
单独的 - 代表 -l。如果未给出[用户],则假定为 root。