.TH "PQgetf" 3 2011 "libpqtypes" "libpqtypes Manual"
.SH NAME
PQgetf \- Gets one or more values from a PGresult in a scanf fashion.
.SH SYNOPSIS
.LP
\fB#include <libpqtypes.h>
.br
.sp
int PQgetf(const PGresult *\fIres\fP, int \fItup_num\fP,
.br
           const char *\fIformat\fP, ...);
.br
int PQgetvf(const PGresult *\fIres\fP, int \fItup_num\fP,
.br
           const char *\fIformat\fP, va_list ap);
\fP
.SH DESCRIPTION
.LP
The \fIPQgetf\fP() and \fIPQgetvf\fP() functions get one or more field
values from a PGresult using a scanf style interface.  The \fItup_num\fP
argument indicates which tuple to read values from; values can
only be read from one tuple at a time.

The \fIformat\fP argument is a data type specifier string
indicating the values to retrieve, like %int4 or #timestamp.  Any
number of fields, in any order, can be retrieved in a single call.
Each data type specifier has a cooresponding \fBfield_num, type-args, [...]\fP
contained within the function\'s variable argument list.  The
\fBfield_num\fP either indicates tuple field number or tuple field
name, depending on whether the data type in \fIformat\fP used a \'%\'
or \'#\' specifer mark (\`man \fIpqt-specs(3)\fP\').  The \fBtype-args\fP can be one or more
arguments required by the specific data type: for example, "%int4"
would require a pointer to a PGint4.  All built-in PostgreSQL data
types require a single pointer value.
.SH RETURN VALUE
.LP
On success, a non-zero value is returned.  On error, zero is
returned and \fIPQgeterror(3)\fP will contain an error message.

If the retrieval of any field fails, the get operation is aborted and
function will fail.  Eventhough some fields may have succeeded prior to
the failure, their values should not be trusted.  Instead, make
another \fIPQgetf\fP() call.  Getting an array or a composite can lead
to memory leaks when getf fails.  This is because these types allocate
a PGresult object that must be cleared.  To avoid leaks, it is recommended
to perform cleanup even if getf fails, retrieve arrays and composites by
themselves or make them the last field in a getf call.
.SH EXAMPLES
.LP
.SS Using PQgetf on a PGresult
The example uses the libpq PQexec function to execute a query and then uses
\fIPQgetf\fP() to retrieve field values.  It is important to note that
libpqtypes execution functions, like \fIPQparamExec(3)\fP, do not need to
generate the PGresult provided to \fIPQgetf\fP().
.RS
.nf
.LP
\fBint success;
PGint4 i4;
PGtext text;
PGbytea bytea;
PGpoint pt;
PGresult *res = PQexec(conn, "SELECT i,t,b,p FROM tbl");

/* Get some field values from the result (order doesn\'t matter) */
success = PQgetf(res,
	0,            /* get field values from tuple 0 */
	"%int4 #text %bytea %point",
	              /* type format specifiers (get text by name \'#\') */
	0,   &i4,     /* get an int4 from field num 0 */
	"t", &text,   /* get a text from field name "t" */
	2,   &bytea,  /* get a bytea from field num 2 */
	3,   &pt);    /* get a point from field num 3 */

/* Output an error message using PQgeterror(3). */
if(!success)
	fprintf(stderr, "*ERROR: %s\\n", PQgeterror());

/* Output the values, do this before PQclear() */
else
	printf("int4=%d, text=%s, bytea=%d bytes, point=(%f,%f)\\n",
		i4, text, bytea.len, pt.x, pt.y);

PQclear(res);
\fP
.fi
.RE
.SH AUTHOR
.LP
A contribution of eSilo, LLC. for the PostgreSQL Database Management System.
Written by Andrew Chernow and Merlin Moncure.
.SH REPORTING BUGS
.LP
Report bugs to <libpqtypes@esilo.com>.
.SH COPYRIGHT
.LP
Copyright (c) 2011 eSilo, LLC. All rights reserved.
.br
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or  FITNESS
FOR A PARTICULAR PURPOSE.
.SH SEE ALSO
.LP
\fIpqt-specs(3)\fP, \fIPQgeterror(3)\fP