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See \u003ca class=\"xref\" href=\"/docs/18/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS\" title=\"32.1.1.3. Specifying Multiple Hosts\"\u003eSection 32.1.1.3\u003c/a\u003e for details.\u003c/p\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","manual_path":"libpq-connect.html#LIBPQ-CONNECT-HOST","precedence_evidence":["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.","Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . 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If a host name looks like an absolute path name, it specifies Unix-domain communication rather than TCP/IP communication; the value is the name of the directory in which the socket file is stored. (On Unix, an absolute path name begins with a slash. On Windows, paths starting with drive letters are also recognized.) If the host name starts with @ , it is taken as a Unix-domain socket in the abstract namespace (currently supported on Linux and Windows). The default behavior when host is not specified, or is empty, is to connect to a Unix-domain socket in /tmp (or whatever socket directory was specified when PostgreSQL was built). On Windows, the default is to connect to localhost .","BodyHTML":"\u003cdiv\u003e\u003cdl\u003e\u003cdt id=\"LIBPQ-CONNECT-HOST\"\u003e\u003cspan\u003e\u003ccode\u003ehost\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eName of host to connect to. If a host name looks like an absolute path name, it specifies Unix-domain communication rather than TCP/IP communication; the value is the name of the directory in which the socket file is stored. (On Unix, an absolute path name begins with a slash. On Windows, paths starting with drive letters are also recognized.) If the host name starts with \u003ccode\u003e@\u003c/code\u003e, it is taken as a Unix-domain socket in the abstract namespace (currently supported on Linux and Windows). The default behavior when \u003ccode\u003ehost\u003c/code\u003e is not specified, or is empty, is to connect to a Unix-domain socket in \u003ccode\u003e/tmp\u003c/code\u003e (or whatever socket directory was specified when \u003cspan\u003ePostgreSQL\u003c/span\u003e was built). On Windows, the default is to connect to \u003ccode\u003elocalhost\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eA comma-separated list of host names is also accepted, in which case each host name in the list is tried in order; an empty item in the list selects the default behavior as explained above. See \u003ca href=\"/docs/18/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS\" rel=\"nofollow\"\u003eSection 32.1.1.3\u003c/a\u003e for details.\u003c/p\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","SourceRevision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","ContentHash":"431818e831271d4a48a6af65b1fec8aabfae8d6e60f90a6126a79358a6d51d45","Payload":{"description":["Name of host to connect to. If a host name looks like an absolute path name, it specifies Unix-domain communication rather than TCP/IP communication; the value is the name of the directory in which the socket file is stored. (On Unix, an absolute path name begins with a slash. On Windows, paths starting with drive letters are also recognized.) If the host name starts with @ , it is taken as a Unix-domain socket in the abstract namespace (currently supported on Linux and Windows). The default behavior when host is not specified, or is empty, is to connect to a Unix-domain socket in /tmp (or whatever socket directory was specified when PostgreSQL was built). On Windows, the default is to connect to localhost ."],"manual_html":"\u003cdiv\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt id=\"LIBPQ-CONNECT-HOST\"\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003ehost\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eName of host to connect to. If a host name looks like an absolute path name, it specifies Unix-domain communication rather than TCP/IP communication; the value is the name of the directory in which the socket file is stored. (On Unix, an absolute path name begins with a slash. On Windows, paths starting with drive letters are also recognized.) If the host name starts with \u003ccode class=\"literal\"\u003e@\u003c/code\u003e, it is taken as a Unix-domain socket in the abstract namespace (currently supported on Linux and Windows). The default behavior when \u003ccode class=\"literal\"\u003ehost\u003c/code\u003e is not specified, or is empty, is to connect to a Unix-domain socket in \u003ccode class=\"filename\"\u003e/tmp\u003c/code\u003e (or whatever socket directory was specified when \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e was built). On Windows, the default is to connect to \u003ccode class=\"literal\"\u003elocalhost\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003eA comma-separated list of host names is also accepted, in which case each host name in the list is tried in order; an empty item in the list selects the default behavior as explained above. See \u003ca class=\"xref\" href=\"/docs/18/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS\" title=\"32.1.1.3. Specifying Multiple Hosts\"\u003eSection 32.1.1.3\u003c/a\u003e for details.\u003c/p\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","related":[{"label":"Connection service file","url":"/docs/18/libpq-pgservice.html"},{"label":"Password file","url":"/docs/18/libpq-pgpass.html"},{"label":"All libpq environment variables","url":"/docs/18/libpq-envars.html"}],"sections":[{"paragraphs":["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.","Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .","Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."],"title":"Default resolution and service-file precedence"},{"paragraphs":["PGHOST behaves the same as the host connection parameter."],"title":"Environment variable evidence"}],"tables":[{"columns":[{"key":"name","label":"Variable"},{"key":"description","label":"Documented behavior"}],"key":"environment","rows":[{"description":"PGHOST behaves the same as the host connection parameter.","name":{"text":"PGHOST","url":"/docs/18/libpq-envars.html"}}],"title":"Environment fallback"}]}},"RequestedLocale":"zh-Hans","Fallback":true,"Versions":["10","11","12","13","14","15","16","17","18","19","20"],"Locales":["en"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}