<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!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>34.10. Control 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 Vsnapshot" /><link rel="prev" href="libpq-copy.html" title="34.9. Functions Associated with the COPY Command" /><link rel="next" href="libpq-misc.html" title="34.11. Miscellaneous 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">34.10. Control Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="libpq-copy.html" title="34.9. Functions Associated with the COPY Command">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="libpq.html" title="Chapter 34. libpq - C Library">Up</a></td><th width="60%" align="center">Chapter 34. <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 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="libpq-misc.html" title="34.11. Miscellaneous Functions">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="LIBPQ-CONTROL"><div class="titlepage"><div><div><h2 class="title" style="clear: both">34.10. Control Functions</h2></div></div></div><p>
These functions control miscellaneous details of <span class="application">libpq</span>'s
behavior.
</p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQCLIENTENCODING"><span class="term">
<code class="function">PQclientEncoding</code>
<a id="id-1.7.3.17.3.1.1.2" class="indexterm"></a>
</span></dt><dd><p>
Returns the client encoding.
</p><pre class="synopsis">
int PQclientEncoding(const PGconn *<em class="replaceable"><code>conn</code></em>);
</pre><p>
Note that it returns the encoding ID, not a symbolic string
such as <code class="literal">EUC_JP</code>. If unsuccessful, it returns -1.
To convert an encoding ID to an encoding name, you
can use:
</p><pre class="synopsis">
char *pg_encoding_to_char(int <em class="replaceable"><code>encoding_id</code></em>);
</pre><p>
</p></dd><dt id="LIBPQ-PQSETCLIENTENCODING"><span class="term">
<code class="function">PQsetClientEncoding</code>
<a id="id-1.7.3.17.3.2.1.2" class="indexterm"></a>
</span></dt><dd><p>
Sets the client encoding.
</p><pre class="synopsis">
int PQsetClientEncoding(PGconn *<em class="replaceable"><code>conn</code></em>, const char *<em class="replaceable"><code>encoding</code></em>);
</pre><p>
<em class="replaceable"><code>conn</code></em> is a connection to the server,
and <em class="replaceable"><code>encoding</code></em> is the encoding you want to
use. If the function successfully sets the encoding, it returns 0,
otherwise -1. The current encoding for this connection can be
determined by using <code class="function">PQclientEncoding</code>.
</p></dd><dt id="LIBPQ-PQSETERRORVERBOSITY"><span class="term">
<code class="function">PQsetErrorVerbosity</code>
<a id="id-1.7.3.17.3.3.1.2" class="indexterm"></a>
</span></dt><dd><p>
Determines the verbosity of messages returned by
<code class="function">PQerrorMessage</code> and <code class="function">PQresultErrorMessage</code>.
</p><pre class="synopsis">
typedef enum
{
PQERRORS_TERSE,
PQERRORS_DEFAULT,
PQERRORS_VERBOSE
} PGVerbosity;
PGVerbosity PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity);
</pre><p>
<code class="function">PQsetErrorVerbosity</code> sets the verbosity mode, returning
the connection's previous setting. In <em class="firstterm">TERSE</em> mode,
returned messages include severity, primary text, and position only;
this will normally fit on a single line. The default mode produces
messages that include the above plus any detail, hint, or context
fields (these might span multiple lines). The <em class="firstterm">VERBOSE</em>
mode includes all available fields. Changing the verbosity does not
affect the messages available from already-existing
<code class="structname">PGresult</code> objects, only subsequently-created ones.
(But see <code class="function">PQresultVerboseErrorMessage</code> if you
want to print a previous error with a different verbosity.)
</p></dd><dt id="LIBPQ-PQSETERRORCONTEXTVISIBILITY"><span class="term">
<code class="function">PQsetErrorContextVisibility</code>
<a id="id-1.7.3.17.3.4.1.2" class="indexterm"></a>
</span></dt><dd><p>
Determines the handling of <code class="literal">CONTEXT</code> fields in messages
returned by <code class="function">PQerrorMessage</code>
and <code class="function">PQresultErrorMessage</code>.
</p><pre class="synopsis">
typedef enum
{
PQSHOW_CONTEXT_NEVER,
PQSHOW_CONTEXT_ERRORS,
PQSHOW_CONTEXT_ALWAYS
} PGContextVisibility;
PGContextVisibility PQsetErrorContextVisibility(PGconn *conn, PGContextVisibility show_context);
</pre><p>
<code class="function">PQsetErrorContextVisibility</code> sets the context display mode,
returning the connection's previous setting. This mode controls
whether the <code class="literal">CONTEXT</code> field is included in messages
(unless the verbosity setting is <em class="firstterm">TERSE</em>, in which
case <code class="literal">CONTEXT</code> is never shown). The <em class="firstterm">NEVER</em> mode
never includes <code class="literal">CONTEXT</code>, while <em class="firstterm">ALWAYS</em> always
includes it if available. In <em class="firstterm">ERRORS</em> mode (the
default), <code class="literal">CONTEXT</code> fields are included only for error
messages, not for notices and warnings. Changing this mode does not
affect the messages available from
already-existing <code class="structname">PGresult</code> objects, only
subsequently-created ones.
(But see <code class="function">PQresultVerboseErrorMessage</code> if you
want to print a previous error with a different display mode.)
</p></dd><dt id="LIBPQ-PQTRACE"><span class="term">
<code class="function">PQtrace</code>
<a id="id-1.7.3.17.3.5.1.2" class="indexterm"></a>
</span></dt><dd><p>
Enables tracing of the client/server communication to a debugging file stream.
</p><pre class="synopsis">
void PQtrace(PGconn *conn, FILE *stream);
</pre><p>
</p><div class="note"><h3 class="title">Note</h3><p>
On Windows, if the <span class="application">libpq</span> library and an application are
compiled with different flags, this function call will crash the
application because the internal representation of the <code class="literal">FILE</code>
pointers differ. Specifically, multithreaded/single-threaded,
release/debug, and static/dynamic flags should be the same for the
library and all applications using that library.
</p></div></dd><dt id="LIBPQ-PQUNTRACE"><span class="term">
<code class="function">PQuntrace</code>
<a id="id-1.7.3.17.3.6.1.2" class="indexterm"></a>
</span></dt><dd><p>
Disables tracing started by <code class="function">PQtrace</code>.
</p><pre class="synopsis">
void PQuntrace(PGconn *conn);
</pre><p>
</p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="libpq-copy.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="libpq.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="libpq-misc.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">34.9. Functions Associated with the <code class="command">COPY</code> Command </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 34.11. Miscellaneous Functions</td></tr></table></div></body></html>
