The following environment variables can be used to select default
connection parameter values, which will be used by
PQconnectdb, PQsetdbLogin and
PQsetdb if no value is directly specified by the calling
code. These are useful to avoid hard-coding database connection
information into simple client applications, for example.
PGHOST sets the database server name.
If this begins with a slash, it specifies Unix-domain communication
rather than TCP/IP communication; the value is then the name of the
directory in which the socket file is stored (in a default installation
setup this would be /tmp).
PGHOSTADDR specifies the numeric IP address of the database
server. This can be set instead of or in addition to PGHOST
to avoid DNS lookup overhead. See the documentation of
these parameters, under PQconnectdb above, for details
on their interaction.
When neither PGHOST nor PGHOSTADDR is set,
the default behavior is to connect using a local Unix-domain socket; or on
machines without Unix-domain sockets, libpq will
attempt to connect to localhost.
PGPORT sets the TCP port number or Unix-domain socket
file extension for communicating with the
PostgreSQL server.
PGDATABASE sets the
PostgreSQL database name.
PGUSER sets the user name used to connect to the
database.
PGPASSWORD sets the password used if the server
demands password authentication. Use of this environment variable
is not recommended for security reasons (some operating systems
allow non-root users to see process environment variables via
ps); instead consider using the
~/.pgpass file (see Section 30.13).
PGPASSFILE specifies the name of the password file to
use for lookups. If not set, it defaults to ~/.pgpass
(see Section 30.13).
PGSERVICE
sets the service name to be looked up in
pg_service.conf. This offers a shorthand way
of setting all the parameters.
PGREALM sets the Kerberos realm to use with
PostgreSQL, if it is different from the
local realm. If PGREALM is set,
libpq applications will attempt
authentication with servers for this realm and use separate ticket
files to avoid conflicts with local ticket files. This
environment variable is only used if Kerberos authentication is
selected by the server.
PGOPTIONS sets additional run-time options for the
PostgreSQL server.
PGSSLMODE determines whether and with what priority
an SSL connection will be negotiated with the server.
There are four modes: disable will attempt only an
unencrypted SSL connection; allow will
negotiate, trying first a non-SSL connection, then if
that fails, trying an SSL connection; prefer
(the default) will negotiate, trying first an SSL
connection, then if that fails, trying a regular non-SSL
connection; require will try only an SSL
connection. If PostgreSQL is compiled without SSL
support, using option require will cause an error, while
options allow and prefer will be accepted
but libpq will not in fact attempt an SSL
connection.
PGREQUIRESSL sets whether or not the connection must
be made over SSL. If set to "1",
libpq will refuse to connect if the server does not
accept an SSL connection (equivalent to
sslmode prefer). This option is deprecated
in favor of the sslmode setting, and is only available
if PostgreSQL is compiled with SSL support.
PGSSLKEY specifies the hardware token that stores the
secret key for the client certificate. The value of this variable
should consist of a colon-separated engine name (engines are
OpenSSL loadable modules) and an engine-specific key
identifier. If this is not set, the secret key must be kept in a
file.
PGKRBSRVNAME sets the Kerberos service name to use
when authenticating with Kerberos 5 or GSSAPI.
PGGSSLIB sets the GSS library to use for GSSAPI
authentication.
PGCONNECT_TIMEOUT sets the maximum number of seconds
that libpq will wait when attempting to
connect to the PostgreSQL server. If
unset or set to zero, libpq will wait
indefinitely. It is not recommended to set the timeout to less than
2 seconds.
The following environment variables can be used to specify default
behavior for each PostgreSQL session. (See
also the ALTER USER
and ALTER DATABASE
commands for ways to set default behavior on a per-user or per-database
basis.)
