PostgreSQL 8.4.2 Documentation
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# 30.13. Environment Variables

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` behaves the same as host connection parameter.

- `PGHOSTADDR` behaves the same as hostaddr connection parameter. This can be set instead of or in addition to `PGHOST` to avoid DNS lookup overhead.

- `PGPORT` behaves the same as port connection parameter.

- `PGDATABASE` behaves the same as dbname connection parameter.

- `PGUSER` behaves the same as user connection parameter. database.

- `PGPASSWORD` behaves the same as password connection parameter. 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 30.14).

- `PGPASSFILE` specifies the name of the password file to use for lookups. If not set, it defaults to `~/.pgpass` (see Section 30.14).

- `PGSERVICE` behaves the same as service connection parameter.

- `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` behaves the same as options connection parameter.

- `PGSSLMODE` behaves the same as sslmode connection parameter.

- `PGREQUIRESSL` behaves the same as requiressl connection parameter.

- `PGSSLCERT` behaves the same as sslcert connection parameter.

- `PGSSLKEY` behaves the same as sslkey connection parameter.

- `PGSSLROOTCERT` behaves the same as sslrootcert connection parameter.

- `PGSSLCRL` behaves the same as sslcrl connection parameter.

- `PGKRBSRVNAME` behaves the same as krbsrvname connection parameter.

- `PGGSSLIB` behaves the same as gsslib connection parameter.

- `PGCONNECT_TIMEOUT` behaves the same as connect_timeout connection parameter.

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.)

- `PGDATESTYLE` sets the default style of date/time representation. (Equivalent to `SET datestyle TO ...`.)

- `PGTZ` sets the default time zone. (Equivalent to `SET timezone TO ...`.)

- `PGCLIENTENCODING` sets the default client character set encoding. (Equivalent to `SET client_encoding TO ...`.)

- `PGGEQO` sets the default mode for the genetic query optimizer. (Equivalent to `SET geqo TO ...`.)

Refer to the SQL command SET for information on correct values for these environment variables.

The following environment variables determine internal behavior of libpq; they override compiled-in defaults.

- `PGSYSCONFDIR` sets the directory containing the `pg_service.conf` file.

- `PGLOCALEDIR` sets the directory containing the `locale` files for message internationalization.

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