linux su and su -l

[zxc@vp5 ~]$ echo $PATH
/opt/Avaya/VoicePortal/Support/VP-Tools/:/opt/Avaya/VoicePortal/MPP/bin:/usr/kerberos/bin:/opt/Avaya/InstallAgent/bin:/usr/local/bin:/bin:/usr/bin:/home/zxc/bin
[zxc@vp5 ~]$ su

Password:

[root@vp5 zxc]# echo $PATH

/opt/Avaya/VoicePortal/Support/VP-Tools/:/usr/kerberos/sbin:/opt/Avaya/VoicePortal/Support/VP-Tools/:/opt/Avaya/VoicePortal/MPP/bin:/usr/kerberos/bin:/opt/Avaya/InstallAgent/bin:/usr/local/bin:/bin:/usr/bin:/home/zxc/bin

[zxc@vp5 ~]$ su -

Password:

[root@vp5 ~]# echo $PATH

/opt/Avaya/VoicePortal/Support/VP-Tools/:/opt/Avaya/VoicePortal/MPP/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/opt/Avaya/InstallAgent/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

[root@vp5 ~]#

 

[root@vp5 ~]# su --help
Usage: su [OPTION]... [-] [USER [ARG]...]
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 display this help and exit
--version output version information and exit

A mere - implies -l. If USER not given, assume root.