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<!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>33.10. 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 V1.79.1" /><link rel="prev" href="libpq-copy.html" title="33.9. Functions Associated with the COPY Command" /><link rel="next" href="libpq-misc.html" title="33.11. Miscellaneous Functions" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">33.10. Control Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="libpq-copy.html" title="33.9. Functions Associated with the COPY Command">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 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="libpq-misc.html" title="33.11. 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">33.10. 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 <a class="xref" href="libpq-control.html#LIBPQ-PQCLIENTENCODING"><code class="function">PQclientEncoding</code></a>.
</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
<a class="xref" href="libpq-status.html#LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a> and <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTERRORMESSAGE"><code class="function">PQresultErrorMessage</code></a>.
</p><pre class="synopsis">
typedef enum
{
PQERRORS_TERSE,
PQERRORS_DEFAULT,
PQERRORS_VERBOSE,
PQERRORS_SQLSTATE
} PGVerbosity;
PGVerbosity PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity);
</pre><p>
<a class="xref" href="libpq-control.html#LIBPQ-PQSETERRORVERBOSITY"><code class="function">PQsetErrorVerbosity</code></a> 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 <em class="firstterm">DEFAULT</em> 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. The <em class="firstterm">SQLSTATE</em>
mode includes only the error severity and the <code class="symbol">SQLSTATE</code>
error code, if one is available (if not, the output is like
<em class="firstterm">TERSE</em> mode).
</p><p>
Changing the verbosity setting does not affect the messages available
from already-existing <code class="structname">PGresult</code> objects, only
subsequently-created ones.
(But see <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTVERBOSEERRORMESSAGE"><code class="function">PQresultVerboseErrorMessage</code></a> 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 <a class="xref" href="libpq-status.html#LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a>
and <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTERRORMESSAGE"><code class="function">PQresultErrorMessage</code></a>.
</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>
<a class="xref" href="libpq-control.html#LIBPQ-PQSETERRORCONTEXTVISIBILITY"><code class="function">PQsetErrorContextVisibility</code></a> 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.
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 in error
messages, not in notices and warnings.
(However, if the verbosity setting is <em class="firstterm">TERSE</em>
or <em class="firstterm">SQLSTATE</em>, <code class="literal">CONTEXT</code> fields
are omitted regardless of the context display mode.)
</p><p>
Changing this mode does not
affect the messages available from
already-existing <code class="structname">PGresult</code> objects, only
subsequently-created ones.
(But see <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTVERBOSEERRORMESSAGE"><code class="function">PQresultVerboseErrorMessage</code></a> 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 <a class="xref" href="libpq-control.html#LIBPQ-PQTRACE"><code class="function">PQtrace</code></a>.
</p><pre class="synopsis">
void PQuntrace(PGconn *conn);
</pre><p>
</p></dd></dl></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="libpq-copy.html" title="33.9. Functions Associated with the COPY Command">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="libpq.html" title="Chapter 33. libpq — C Library">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="libpq-misc.html" title="33.11. Miscellaneous Functions">Next</a></td></tr><tr><td width="40%" align="left" valign="top">33.9. Functions Associated with the <code xmlns="http://www.w3.org/1999/xhtml" class="command">COPY</code> Command </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 33.11. Miscellaneous Functions</td></tr></table></div></body></html>
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