Because Plan 9 supplies commands with the same name as but different
behavior than many basic Unix system commands
rm), it is not recommended to run with the Plan 9 bin directory
ahead of the system directories.
9 is a shell script that sets up a Plan 9 environment and runs
cmd . It sets
$PLAN9 if necessary
$PLAN9/bin to the beginning of
$PATH before running
If run with no arguments,
9 does not do anything, so it can be invoked from
sh-style shells using
9 in order to make the current shell start running in the Plan 9 environment.
9.rc is the same as
9 but written for use by the shell
u.rc are the inverse of
9.rc: they move
$PLAN9/bin to the end of the path.