p4 环境变量的优先级

Perforce settings such as port, user, and workspace names using the following methods, listed in order of precedence:
1.
On the command line, using flags
2.
In a config file, if P4CONFIG is set
3.
User environment variables (on UNIX or Windows)
4.
System environment variables (on Windows, system-wide environment variables are not necessarily the same thing as user environment variables)
5.
On Windows or OS X, in the user registry or settings (set by issuing the p4 set command)
6.
On Windows or OS X, in the system registry or system settings (set by issuing the p4 set -s command)

http://www.perforce.com/perforce/doc.current/manuals/p4guide/02_config.html