Postgres cannot see my PGDATA environment variable - postgresql

Question

Can anyone explain this:
~$ echo $PGDATA
/Library/PostgreSQL/9.2/data
~$ cd /Library/PostgreSQL/9.2/
/Library/PostgreSQL/9.2$ sudo su postgres
bash-3.2$ echo $PGDATA
<blank line>
bash-3.2$ pg_ctl start
pg_ctl: no database directory specified and environment variable PGDATA unset
Try "pg_ctl --help" for more information.
bash-3.2$ export PGDATA="/Library/PostgreSQL/9.2/data"
bash-3.2$ pg_ctl start
server starting
bash-3.2$
The following is in my ~/.bashrc file:
export PGDATA="/Library/PostgreSQL/9.2/data"
I'm not mis-spelling the path in PGDATA:
~$ echo $PGDATA
/Library/PostgreSQL/9.2/data
export PGDATA="/Library/PostgreSQL/9.2/data"

Answer 1

sudo can't be assumed to keep the environment variables of its caller.
See its manpage for the details with your specific OS.
As far as I know, environment variables are attached to a shell, and as far as I can tell I'm in the same shell.
This works for me:
~$ cd /Library/PostgreSQL/9.2/
/Library/PostgreSQL/9.2$ sudo -E su postgres
...
-E The -E (preserve environment) option will override the
env_reset option in sudoers(5)). It is only available when
either the matching command has the SETENV tag or the
setenv option is set in sudoers(5).
I only understand the following:
The -E (preserve environment) option
Next comment:
When I su to postgres I do su - postgres. Notice the hyphen.
Here is what my man pages say about the hyphen:
-l Simulate a full login. The environment is discarded except for
HOME, SHELL, PATH, TERM, and USER. HOME and SHELL are modified
as above. USER is set to the target login. PATH is set to
``/bin:/usr/bin''. TERM is imported from your current environ-
ment. The invoked shell is the target login's, and su will
change directory to the target login's home directory.
- (no letter) The same as -l.
I don't see how that will preserve the PGDATA environment variable, and this is what happened when I tried the hyphen:
/Library/PostgreSQL/9.2$ sudo su - postgres
Password:
7studs-computer:~ postgres$ ls
bin pgAdmin3.app
data pg_env.sh
doc scripts
include share
installer stackbuilder.app
lib uninstall-postgresql.app
7studs-computer:~ postgres$ pg_ctl start
-bash: pg_ctl: command not found
7studs-computer:~ postgres$ ls
bin pgAdmin3.app
data pg_env.sh
doc scripts
include share
installer stackbuilder.app
lib uninstall-postgresql.app
7studs-computer:~ postgres$ cd bin
7studs-computer:bin postgres$ ls
clusterdb pg_config pgbench
createdb pg_controldata pltcl_delmod
createlang pg_ctl pltcl_listmod
createuser pg_dump pltcl_loadmod
dropdb pg_dumpall postgres
droplang pg_receivexlog postmaster
dropuser pg_resetxlog psql
ecpg pg_restore reindexdb
initdb pg_standby vacuumdb
oid2name pg_test_fsync vacuumlo
pg_archivecleanup pg_test_timing
pg_basebackup pg_upgrade
7studs-computer:bin postgres$ ./pg_ctl start
pg_ctl: no database directory specified and environment variable PGDATA unset
Try "pg_ctl --help" for more information.
7studs-computer:bin postgres$
So the hyphen doesn't work for me (OSX 10.6.8).