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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/libpq-status.html

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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>33.2. Connection Status Functions</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="libpq-connect.html" title="33.1. Database Connection Control Functions" /><link rel="next" href="libpq-exec.html" title="33.3. Command Execution Functions" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">33.2. Connection Status Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="libpq-connect.html" title="33.1. Database Connection Control Functions">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="libpq.html" title="Chapter 33. libpq - C Library">Up</a></td><th width="60%" align="center">Chapter 33. <span xmlns="http://www.w3.org/1999/xhtml" class="application">libpq</span> - C Library</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="libpq-exec.html" title="33.3. Command Execution Functions">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="LIBPQ-STATUS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">33.2. Connection Status Functions</h2></div></div></div><p>

  3.    These functions can be used to interrogate the status

  4.    of an existing database connection object.

  5.   </p><div class="tip"><h3 class="title">Tip</h3><p>

  6.     <a id="id-1.7.3.9.3.1.1" class="indexterm"></a>

  7.     <a id="id-1.7.3.9.3.1.2" class="indexterm"></a>

  8.     <span class="application">libpq</span> application programmers should be careful to

  9.     maintain the <code class="structname">PGconn</code> abstraction.  Use the accessor

  10.     functions described below to get at the contents of <code class="structname">PGconn</code>.

  11.     Reference to internal <code class="structname">PGconn</code> fields using

  12.     <code class="filename">libpq-int.h</code> is not recommended because they are subject to change

  13.     in the future.

  14.    </p></div><p>

  15.    The following functions return parameter values established at connection.

  16.    These values are fixed for the life of the connection.  If a multi-host

  17.    connection string is used, the values of <code class="function">PQhost</code>,

  18.    <code class="function">PQport</code>, and <code class="function">PQpass</code> can change if a new connection

  19.    is established using the same <code class="structname">PGconn</code> object.  Other values

  20.    are fixed for the lifetime of the <code class="structname">PGconn</code> object.

  21. 

  22.    </p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQDB"><span class="term">

  23.       <code class="function">PQdb</code>

  24.       <a id="id-1.7.3.9.4.6.1.1.2" class="indexterm"></a>

  25.      </span></dt><dd><p>

  26.        Returns the database name of the connection.

  27. </p><pre class="synopsis">

  28. char *PQdb(const PGconn *conn);

  29. </pre><p>

  30.       </p></dd><dt id="LIBPQ-PQUSER"><span class="term">

  31.       <code class="function">PQuser</code>

  32.       <a id="id-1.7.3.9.4.6.2.1.2" class="indexterm"></a>

  33.      </span></dt><dd><p>

  34.        Returns the user name of the connection.

  35. </p><pre class="synopsis">

  36. char *PQuser(const PGconn *conn);

  37. </pre><p>

  38.       </p></dd><dt id="LIBPQ-PQPASS"><span class="term">

  39.       <code class="function">PQpass</code>

  40.       <a id="id-1.7.3.9.4.6.3.1.2" class="indexterm"></a>

  41.      </span></dt><dd><p>

  42.        Returns the password of the connection.

  43. </p><pre class="synopsis">

  44. char *PQpass(const PGconn *conn);

  45. </pre><p>

  46.       </p><p>

  47.        <code class="function">PQpass</code> will return either the password specified

  48.        in the connection parameters, or if there was none and the password

  49.        was obtained from the <a class="link" href="libpq-pgpass.html" title="33.15. The Password File">password

  50.        file</a>, it will return that.  In the latter case,

  51.        if multiple hosts were specified in the connection parameters, it is

  52.        not possible to rely on the result of <code class="function">PQpass</code> until

  53.        the connection is established.  The status of the connection can be

  54.        checked using the function <code class="function">PQstatus</code>.

  55.       </p></dd><dt id="LIBPQ-PQHOST"><span class="term">

  56.       <code class="function">PQhost</code>

  57.       <a id="id-1.7.3.9.4.6.4.1.2" class="indexterm"></a>

  58.      </span></dt><dd><p>

  59.        Returns the server host name of the active connection.

  60.        This can be a host name, an IP address, or a directory path if the

  61.        connection is via Unix socket.  (The path case can be distinguished

  62.        because it will always be an absolute path, beginning

  63.        with <code class="literal">/</code>.)

  64. </p><pre class="synopsis">

  65. char *PQhost(const PGconn *conn);

  66. </pre><p>

  67.       </p><p>

  68.        If the connection parameters specified both <code class="literal">host</code> and

  69.        <code class="literal">hostaddr</code>, then <code class="function">PQhost</code> will

  70.        return the <code class="literal">host</code> information.  If only

  71.        <code class="literal">hostaddr</code> was specified, then that is returned.

  72.        If multiple hosts were specified in the connection parameters,

  73.        <code class="function">PQhost</code> returns the host actually connected to.

  74.       </p><p>

  75.        <code class="function">PQhost</code> returns <code class="symbol">NULL</code> if the

  76.        <em class="parameter"><code>conn</code></em> argument is <code class="symbol">NULL</code>.

  77.        Otherwise, if there is an error producing the host information (perhaps

  78.        if the connection has not been fully established or there was an

  79.        error), it returns an empty string.

  80.       </p><p>

  81.        If multiple hosts were specified in the connection parameters, it is

  82.        not possible to rely on the result of <code class="function">PQhost</code> until

  83.        the connection is established.  The status of the connection can be

  84.        checked using the function <code class="function">PQstatus</code>.

  85.       </p></dd><dt id="LIBPQ-PQHOSTADDR"><span class="term">

  86.       <code class="function">PQhostaddr</code>

  87.       <a id="id-1.7.3.9.4.6.5.1.2" class="indexterm"></a>

  88.      </span></dt><dd><p>

  89.        Returns the server IP address of the active connection.

  90.        This can be the address that a host name resolved to,

  91.        or an IP address provided through the <code class="literal">hostaddr</code>

  92.        parameter.

  93. </p><pre class="synopsis">

  94. char *PQhostaddr(const PGconn *conn);

  95. </pre><p>

  96.       </p><p>

  97.        <code class="function">PQhostaddr</code> returns <code class="symbol">NULL</code> if the

  98.        <em class="parameter"><code>conn</code></em> argument is <code class="symbol">NULL</code>.

  99.        Otherwise, if there is an error producing the host information

  100.        (perhaps if the connection has not been fully established or

  101.        there was an error), it returns an empty string.

  102.       </p></dd><dt id="LIBPQ-PQPORT"><span class="term">

  103.       <code class="function">PQport</code>

  104.       <a id="id-1.7.3.9.4.6.6.1.2" class="indexterm"></a>

  105.      </span></dt><dd><p>

  106.        Returns the port of the active connection.

  107. 

  108. </p><pre class="synopsis">

  109. char *PQport(const PGconn *conn);

  110. </pre><p>

  111.       </p><p>

  112.        If multiple ports were specified in the connection parameters,

  113.        <code class="function">PQport</code> returns the port actually connected to.

  114.       </p><p>

  115.        <code class="function">PQport</code> returns <code class="symbol">NULL</code> if the

  116.        <em class="parameter"><code>conn</code></em> argument is <code class="symbol">NULL</code>.

  117.        Otherwise, if there is an error producing the port information (perhaps

  118.        if the connection has not been fully established or there was an

  119.        error), it returns an empty string.

  120.       </p><p>

  121.        If multiple ports were specified in the connection parameters, it is

  122.        not possible to rely on the result of <code class="function">PQport</code> until

  123.        the connection is established.  The status of the connection can be

  124.        checked using the function <code class="function">PQstatus</code>.

  125.       </p></dd><dt id="LIBPQ-PQTTY"><span class="term">

  126.       <code class="function">PQtty</code>

  127.       <a id="id-1.7.3.9.4.6.7.1.2" class="indexterm"></a>

  128.      </span></dt><dd><p>

  129.        Returns the debug <acronym class="acronym">TTY</acronym> of the connection.

  130.        (This is obsolete, since the server no longer pays attention

  131.        to the <acronym class="acronym">TTY</acronym> setting, but the function remains

  132.        for backward compatibility.)

  133. 

  134. </p><pre class="synopsis">

  135. char *PQtty(const PGconn *conn);

  136. </pre><p>

  137.       </p></dd><dt id="LIBPQ-PQOPTIONS"><span class="term">

  138.       <code class="function">PQoptions</code>

  139.       <a id="id-1.7.3.9.4.6.8.1.2" class="indexterm"></a>

  140.      </span></dt><dd><p>

  141.        Returns the command-line options passed in the connection request.

  142. </p><pre class="synopsis">

  143. char *PQoptions(const PGconn *conn);

  144. </pre><p>

  145.       </p></dd></dl></div><p>

  146.   </p><p>

  147.    The following functions return status data that can change as operations

  148.    are executed on the <code class="structname">PGconn</code> object.

  149. 

  150.    </p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQSTATUS"><span class="term">

  151.       <code class="function">PQstatus</code>

  152.       <a id="id-1.7.3.9.5.2.1.1.2" class="indexterm"></a>

  153.      </span></dt><dd><p>

  154.        Returns the status of the connection.

  155. </p><pre class="synopsis">

  156. ConnStatusType PQstatus(const PGconn *conn);

  157. </pre><p>

  158.       </p><p>

  159.        The status can be one of a number of values.  However, only two of

  160.        these are seen outside of an asynchronous connection procedure:

  161.        <code class="literal">CONNECTION_OK</code> and

  162.        <code class="literal">CONNECTION_BAD</code>. A good connection to the database

  163.        has the status <code class="literal">CONNECTION_OK</code>.  A failed

  164.        connection attempt is signaled by status

  165.        <code class="literal">CONNECTION_BAD</code>.  Ordinarily, an OK status will

  166.        remain so until <code class="function">PQfinish</code>, but a communications

  167.        failure might result in the status changing to

  168.        <code class="literal">CONNECTION_BAD</code> prematurely.  In that case the

  169.        application could try to recover by calling

  170.        <code class="function">PQreset</code>.

  171.       </p><p>

  172.        See the entry for <code class="function">PQconnectStartParams</code>, <code class="function">PQconnectStart</code>

  173.        and <code class="function">PQconnectPoll</code> with regards to other status codes that

  174.        might be returned.

  175.       </p></dd><dt id="LIBPQ-PQTRANSACTIONSTATUS"><span class="term">

  176.       <code class="function">PQtransactionStatus</code>

  177.       <a id="id-1.7.3.9.5.2.2.1.2" class="indexterm"></a>

  178.      </span></dt><dd><p>

  179.        Returns the current in-transaction status of the server.

  180. 

  181. </p><pre class="synopsis">

  182. PGTransactionStatusType PQtransactionStatus(const PGconn *conn);

  183. </pre><p>

  184. 

  185.        The status can be <code class="literal">PQTRANS_IDLE</code> (currently idle),

  186.        <code class="literal">PQTRANS_ACTIVE</code> (a command is in progress),

  187.        <code class="literal">PQTRANS_INTRANS</code> (idle, in a valid transaction block),

  188.        or <code class="literal">PQTRANS_INERROR</code> (idle, in a failed transaction block).

  189.        <code class="literal">PQTRANS_UNKNOWN</code> is reported if the connection is bad.

  190.        <code class="literal">PQTRANS_ACTIVE</code> is reported only when a query

  191.        has been sent to the server and not yet completed.

  192.       </p></dd><dt id="LIBPQ-PQPARAMETERSTATUS"><span class="term">

  193.       <code class="function">PQparameterStatus</code>

  194.       <a id="id-1.7.3.9.5.2.3.1.2" class="indexterm"></a>

  195.      </span></dt><dd><p>

  196.        Looks up a current parameter setting of the server.

  197. 

  198. </p><pre class="synopsis">

  199. const char *PQparameterStatus(const PGconn *conn, const char *paramName);

  200. </pre><p>

  201. 

  202.        Certain parameter values are reported by the server automatically at

  203.        connection startup or whenever their values change.

  204.        <code class="function">PQparameterStatus</code> can be used to interrogate these settings.

  205.        It returns the current value of a parameter if known, or <code class="symbol">NULL</code>

  206.        if the parameter is not known.

  207.       </p><p>

  208.        Parameters reported as of the current release include

  209.        <code class="varname">server_version</code>,

  210.        <code class="varname">server_encoding</code>,

  211.        <code class="varname">client_encoding</code>,

  212.        <code class="varname">application_name</code>,

  213.        <code class="varname">is_superuser</code>,

  214.        <code class="varname">session_authorization</code>,

  215.        <code class="varname">DateStyle</code>,

  216.        <code class="varname">IntervalStyle</code>,

  217.        <code class="varname">TimeZone</code>,

  218.        <code class="varname">integer_datetimes</code>, and

  219.        <code class="varname">standard_conforming_strings</code>.

  220.        (<code class="varname">server_encoding</code>, <code class="varname">TimeZone</code>, and

  221.        <code class="varname">integer_datetimes</code> were not reported by releases before 8.0;

  222.        <code class="varname">standard_conforming_strings</code> was not reported by releases

  223.        before 8.1;

  224.        <code class="varname">IntervalStyle</code> was not reported by releases before 8.4;

  225.        <code class="varname">application_name</code> was not reported by releases before 9.0.)

  226.        Note that

  227.        <code class="varname">server_version</code>,

  228.        <code class="varname">server_encoding</code> and

  229.        <code class="varname">integer_datetimes</code>

  230.        cannot change after startup.

  231.       </p><p>

  232.        Pre-3.0-protocol servers do not report parameter settings, but

  233.        <span class="application">libpq</span> includes logic to obtain values for

  234.        <code class="varname">server_version</code> and <code class="varname">client_encoding</code> anyway.

  235.        Applications are encouraged to use <code class="function">PQparameterStatus</code>

  236.        rather than <span class="foreignphrase"><em class="foreignphrase">ad hoc</em></span> code to determine these values.

  237.        (Beware however that on a pre-3.0 connection, changing

  238.        <code class="varname">client_encoding</code> via <code class="command">SET</code> after connection

  239.        startup will not be reflected by <code class="function">PQparameterStatus</code>.)

  240.        For <code class="varname">server_version</code>, see also

  241.        <code class="function">PQserverVersion</code>, which returns the information in a

  242.        numeric form that is much easier to compare against.

  243.       </p><p>

  244.        If no value for <code class="varname">standard_conforming_strings</code> is reported,

  245.        applications can assume it is <code class="literal">off</code>, that is, backslashes

  246.        are treated as escapes in string literals.  Also, the presence of

  247.        this parameter can be taken as an indication that the escape string

  248.        syntax (<code class="literal">E'...'</code>) is accepted.

  249.       </p><p>

  250.        Although the returned pointer is declared <code class="literal">const</code>, it in fact

  251.        points to mutable storage associated with the <code class="literal">PGconn</code> structure.

  252.        It is unwise to assume the pointer will remain valid across queries.

  253.       </p></dd><dt id="LIBPQ-PQPROTOCOLVERSION"><span class="term">

  254.       <code class="function">PQprotocolVersion</code>

  255.       <a id="id-1.7.3.9.5.2.4.1.2" class="indexterm"></a>

  256.      </span></dt><dd><p>

  257.        Interrogates the frontend/backend protocol being used.

  258. </p><pre class="synopsis">

  259. int PQprotocolVersion(const PGconn *conn);

  260. </pre><p>

  261.        Applications might wish to use this function to determine whether certain

  262.        features are supported.  Currently, the possible values are 2 (2.0

  263.        protocol), 3 (3.0 protocol), or zero (connection bad).  The

  264.        protocol version will

  265.        not change after connection startup is complete, but it could

  266.        theoretically change during a connection reset.  The 3.0 protocol

  267.        will normally be used when communicating with

  268.        <span class="productname">PostgreSQL</span> 7.4 or later servers; pre-7.4 servers

  269.        support only protocol 2.0.  (Protocol 1.0 is obsolete and not

  270.        supported by <span class="application">libpq</span>.)

  271.       </p></dd><dt id="LIBPQ-PQSERVERVERSION"><span class="term">

  272.       <code class="function">PQserverVersion</code>

  273.       <a id="id-1.7.3.9.5.2.5.1.2" class="indexterm"></a>

  274.      </span></dt><dd><p>

  275.        Returns an integer representing the server version.

  276. </p><pre class="synopsis">

  277. int PQserverVersion(const PGconn *conn);

  278. </pre><p>

  279.       </p><p>

  280.        Applications might use this function to determine the version of the

  281.        database server they are connected to.  The result is formed by

  282.        multiplying the server's major version number by 10000 and adding

  283.        the minor version number.  For example, version 10.1 will be

  284.        returned as 100001, and version 11.0 will be returned as 110000.

  285.        Zero is returned if the connection is bad.

  286.       </p><p>

  287.        Prior to major version 10, <span class="productname">PostgreSQL</span> used

  288.        three-part version numbers in which the first two parts together

  289.        represented the major version.  For those

  290.        versions, <code class="function">PQserverVersion</code> uses two digits for each

  291.        part; for example version 9.1.5 will be returned as 90105, and

  292.        version 9.2.0 will be returned as 90200.

  293.       </p><p>

  294.        Therefore, for purposes of determining feature compatibility,

  295.        applications should divide the result of <code class="function">PQserverVersion</code>

  296.        by 100 not 10000 to determine a logical major version number.

  297.        In all release series, only the last two digits differ between

  298.        minor releases (bug-fix releases).

  299.       </p></dd><dt id="LIBPQ-PQERRORMESSAGE"><span class="term">

  300.       <code class="function">PQerrorMessage</code>

  301.       <a id="id-1.7.3.9.5.2.6.1.2" class="indexterm"></a>

  302.      </span></dt><dd><p>

  303.        <a id="id-1.7.3.9.5.2.6.2.1.1" class="indexterm"></a> Returns the error message

  304.        most recently generated by an operation on the connection.

  305. 

  306. </p><pre class="synopsis">

  307. char *PQerrorMessage(const PGconn *conn);

  308. </pre><p>

  309. 

  310.       </p><p>

  311.        Nearly all <span class="application">libpq</span> functions will set a message for

  312.        <code class="function">PQerrorMessage</code> if they fail.  Note that by

  313.        <span class="application">libpq</span> convention, a nonempty

  314.        <code class="function">PQerrorMessage</code> result can consist of multiple lines,

  315.        and will include a trailing newline. The caller should not free

  316.        the result directly. It will be freed when the associated

  317.        <code class="structname">PGconn</code> handle is passed to

  318.        <code class="function">PQfinish</code>.  The result string should not be

  319.        expected to remain the same across operations on the

  320.        <code class="literal">PGconn</code> structure.

  321.       </p></dd><dt id="LIBPQ-PQSOCKET"><span class="term"><code class="function">PQsocket</code><a id="id-1.7.3.9.5.2.7.1.2" class="indexterm"></a></span></dt><dd><p>

  322.        Obtains the file descriptor number of the connection socket to

  323.        the server.  A valid descriptor will be greater than or equal

  324.        to 0; a result of -1 indicates that no server connection is

  325.        currently open.  (This will not change during normal operation,

  326.        but could change during connection setup or reset.)

  327. 

  328. </p><pre class="synopsis">

  329. int PQsocket(const PGconn *conn);

  330. </pre><p>

  331. 

  332.       </p></dd><dt id="LIBPQ-PQBACKENDPID"><span class="term"><code class="function">PQbackendPID</code><a id="id-1.7.3.9.5.2.8.1.2" class="indexterm"></a></span></dt><dd><p>

  333.        Returns the process <acronym class="acronym">ID</acronym> (PID)<a id="id-1.7.3.9.5.2.8.2.1.2" class="indexterm"></a>

  334.        of the backend process handling this connection.

  335. 

  336. </p><pre class="synopsis">

  337. int PQbackendPID(const PGconn *conn);

  338. </pre><p>

  339.       </p><p>

  340.        The backend <acronym class="acronym">PID</acronym> is useful for debugging

  341.        purposes and for comparison to <code class="command">NOTIFY</code>

  342.        messages (which include the <acronym class="acronym">PID</acronym> of the

  343.        notifying backend process).  Note that the

  344.        <acronym class="acronym">PID</acronym> belongs to a process executing on the

  345.        database server host, not the local host!

  346.       </p></dd><dt id="LIBPQ-PQCONNECTIONNEEDSPASSWORD"><span class="term"><code class="function">PQconnectionNeedsPassword</code><a id="id-1.7.3.9.5.2.9.1.2" class="indexterm"></a></span></dt><dd><p>

  347.        Returns true (1) if the connection authentication method

  348.        required a password, but none was available.

  349.        Returns false (0) if not.

  350. 

  351. </p><pre class="synopsis">

  352. int PQconnectionNeedsPassword(const PGconn *conn);

  353. </pre><p>

  354.       </p><p>

  355.        This function can be applied after a failed connection attempt

  356.        to decide whether to prompt the user for a password.

  357.       </p></dd><dt id="LIBPQ-PQCONNECTIONUSEDPASSWORD"><span class="term"><code class="function">PQconnectionUsedPassword</code><a id="id-1.7.3.9.5.2.10.1.2" class="indexterm"></a></span></dt><dd><p>

  358.        Returns true (1) if the connection authentication method

  359.        used a password. Returns false (0) if not.

  360. 

  361. </p><pre class="synopsis">

  362. int PQconnectionUsedPassword(const PGconn *conn);

  363. </pre><p>

  364.       </p><p>

  365.        This function can be applied after either a failed or successful

  366.        connection attempt to detect whether the server demanded a password.

  367.       </p></dd></dl></div><p>

  368.   </p><p>

  369.     The following functions return information related to SSL. This information

  370.     usually doesn't change after a connection is established.

  371. 

  372.     </p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQSSLINUSE"><span class="term"><code class="function">PQsslInUse</code><a id="id-1.7.3.9.6.1.1.1.2" class="indexterm"></a></span></dt><dd><p>

  373.         Returns true (1) if the connection uses SSL, false (0) if not.

  374. 

  375. </p><pre class="synopsis">

  376. int PQsslInUse(const PGconn *conn);

  377. </pre><p>

  378.       </p></dd><dt id="LIBPQ-PQSSLATTRIBUTE"><span class="term"><code class="function">PQsslAttribute</code><a id="id-1.7.3.9.6.1.2.1.2" class="indexterm"></a></span></dt><dd><p>

  379.         Returns SSL-related information about the connection.

  380. 

  381. </p><pre class="synopsis">

  382. const char *PQsslAttribute(const PGconn *conn, const char *attribute_name);

  383. </pre><p>

  384.       </p><p>

  385.        The list of available attributes varies depending on the SSL library

  386.        being used, and the type of connection. If an attribute is not

  387.        available, returns NULL.

  388.       </p><p>

  389.        The following attributes are commonly available:

  390.        </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">library</code></span></dt><dd><p>

  391.             Name of the SSL implementation in use. (Currently, only

  392.             <code class="literal">"OpenSSL"</code> is implemented)

  393.            </p></dd><dt><span class="term"><code class="literal">protocol</code></span></dt><dd><p>

  394.              SSL/TLS version in use. Common values

  395.              are <code class="literal">"TLSv1"</code>, <code class="literal">"TLSv1.1"</code>

  396.              and <code class="literal">"TLSv1.2"</code>, but an implementation may

  397.              return other strings if some other protocol is used.

  398.            </p></dd><dt><span class="term"><code class="literal">key_bits</code></span></dt><dd><p>

  399.             Number of key bits used by the encryption algorithm.

  400.            </p></dd><dt><span class="term"><code class="literal">cipher</code></span></dt><dd><p>

  401.             A short name of the ciphersuite used, e.g.

  402.             <code class="literal">"DHE-RSA-DES-CBC3-SHA"</code>. The names are specific

  403.             to each SSL implementation.

  404.            </p></dd><dt><span class="term"><code class="literal">compression</code></span></dt><dd><p>

  405.             If SSL compression is in use, returns the name of the compression

  406.             algorithm, or "on" if compression is used but the algorithm is

  407.             not known. If compression is not in use, returns "off".

  408.            </p></dd></dl></div><p>

  409.       </p></dd><dt id="LIBPQ-PQSSLATTRIBUTENAMES"><span class="term"><code class="function">PQsslAttributeNames</code><a id="id-1.7.3.9.6.1.3.1.2" class="indexterm"></a></span></dt><dd><p>

  410.        Return an array of SSL attribute names available. The array is terminated by a NULL pointer.

  411. </p><pre class="synopsis">

  412. const char * const * PQsslAttributeNames(const PGconn *conn);

  413. </pre><p>

  414.       </p></dd><dt id="LIBPQ-PQSSLSTRUCT"><span class="term"><code class="function">PQsslStruct</code><a id="id-1.7.3.9.6.1.4.1.2" class="indexterm"></a></span></dt><dd><p>

  415.        Return a pointer to an SSL-implementation-specific object describing

  416.        the connection.

  417. </p><pre class="synopsis">

  418. void *PQsslStruct(const PGconn *conn, const char *struct_name);

  419. </pre><p>

  420.       </p><p>

  421.        The struct(s) available depend on the SSL implementation in use.

  422.        For OpenSSL, there is one struct, available under the name "OpenSSL",

  423.        and it returns a pointer to the OpenSSL <code class="literal">SSL</code> struct.

  424.        To use this function, code along the following lines could be used:

  425. </p><pre class="programlisting">

  426. #include &lt;libpq-fe.h&gt;

  427. #include &lt;openssl/ssl.h&gt;

  428. 

  429. ...

  430. 

  431.     SSL *ssl;

  432. 

  433.     dbconn = PQconnectdb(...);

  434.     ...

  435. 

  436.     ssl = PQsslStruct(dbconn, "OpenSSL");

  437.     if (ssl)

  438.     {

  439.         /* use OpenSSL functions to access ssl */

  440.     }

  441. </pre><p>

  442.       </p><p>

  443.        This structure can be used to verify encryption levels, check server

  444.        certificates, and more. Refer to the <span class="productname">OpenSSL</span>

  445.        documentation for information about this structure.

  446.       </p></dd><dt id="LIBPQ-PQGETSSL"><span class="term"><code class="function">PQgetssl</code><a id="id-1.7.3.9.6.1.5.1.2" class="indexterm"></a></span></dt><dd><p>

  447.        <a id="id-1.7.3.9.6.1.5.2.1.1" class="indexterm"></a>

  448.        Returns the SSL structure used in the connection, or null

  449.        if SSL is not in use.

  450. 

  451. </p><pre class="synopsis">

  452. void *PQgetssl(const PGconn *conn);

  453. </pre><p>

  454.       </p><p>

  455.        This function is equivalent to <code class="literal">PQsslStruct(conn, "OpenSSL")</code>. It should

  456.        not be used in new applications, because the returned struct is

  457.        specific to OpenSSL and will not be available if another SSL

  458.        implementation is used. To check if a connection uses SSL, call

  459.        <code class="function">PQsslInUse</code> instead, and for more details about the

  460.        connection, use <code class="function">PQsslAttribute</code>.

  461.       </p></dd></dl></div><p>

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