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<chapter id="libpq">

If this begins with a slash, 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. The

default is to connect to a Unix-domain socket in

<filename>/tmp</filename>.<indexterm><primary>Unix domain

socket</></>

default behavior when <literal>host</literal> is not specified

is to connect to a Unix-domain

socket<indexterm><primary>Unix domain socket</></> in

<filename>/tmp</filename> (or whatever socket directory was specified

when <productname>PostgreSQL</> was built). On machines without

Unix-domain sockets, the default is to connect to <literal>localhost</>.

</para>

</listitem>

</varlistentry>

<para>

Without either a host name or host address,

<application>libpq</application> will connect using a

local Unix domain socket.

local Unix-domain socket; or on machines without Unix-domain

sockets, it will attempt to connect to <literal>localhost</>.

</para>

</listitem>

</varlistentry>

these parameters, under <function>PQconnectdb</function> above, for details

on their interaction.

</para>

<para>

When neither <envar>PGHOST</envar> nor <envar>PGHOSTADDR</envar> is set,

the default behavior is to connect using a local Unix-domain socket; or on

machines without Unix-domain sockets, <application>libpq</application> will

attempt to connect to <literal>localhost</>.

</para>

</listitem>

<listitem>

<para>

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PostgreSQL documentation

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<term><option>--port <replaceable class="parameter">port</replaceable></></term>

<listitem>

<para>

Specifies the TCP port or the local Unixdomain

Specifies the TCP port or the local Unix-domain

socket file extension on which the server is listening for

connections. Defaults to the value of the <envar>PGPORT</envar>

environment variable or, if not set, to the port specified at

<option>-d</option>, <option>-h</option>, <option>-p</option>, and

<option>-U</option> respectively. If an argument is found that does

not belong to any option it will be interpreted as the database name

(or the user name, if the database name is also given). Not all

these options are required, defaults do apply. If you omit the host

name, <application>psql</> will connect via a Unix domain socket

to a server on the local host, or via TCP/IP to <literal>localhost</> on machines

that don't have Unix domain sockets. The default port number is compile-time determined.

(or the user name, if the database name is already given). Not all

these options are required; there are useful defaults. If you omit the host

name, <application>psql</> will connect via a Unix-domain socket

to a server on the local host, or via TCP/IP to <literal>localhost</> on

machines that don't have Unix-domain sockets. The default port number is

determined at compile time.

Since the database server uses the same default, you will not have

to specify the port in most cases. The default user name is your

Unix user name, as is the default database name. Note that you can't

just connect to any database under any user name. Your database

administrator should have informed you about your access rights. To

save you some typing you can also set the environment variables

administrator should have informed you about your access rights.

</para>

<para>

When the defaults aren't quite right, you can save yourself

some typing by setting the environment variables

<envar>PGDATABASE</envar>, <envar>PGHOST</envar>,

<envar>PGPORT</envar> and <envar>PGUSER</envar> to appropriate

<envar>PGPORT</envar> and/or <envar>PGUSER</envar> to appropriate

values.

</para>

pset.getPassword= false;

options.host="localhost";

parse_psql_options(argc,argv,&options);

if (!pset.popt.topt.fieldSep)

charportstr[128];

structaddrinfo*addrs=NULL;

structaddrinfohint;

constchar*node=NULL;

constchar*node;

intret;

if (!conn)

node=conn->pghost;

hint.ai_family=AF_UNSPEC;

}

{

node=NULL;

hint.ai_family=AF_UNIX;

UNIXSOCK_PATH(portstr,portnum,conn->pgunixsocket);

}

node="localhost";

hint.ai_family=AF_UNSPEC;

}

ret=getaddrinfo_all(node,portstr,&hint,&addrs);