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PQputf(3)                      libpqtypes Manual                     PQputf(3)

NAME
       PQputf, PQputvf - Packs a set of parameters in a PGparam for use with a
       parameterized query.

SYNOPSIS
       #include <libpqtypes.h>

       int PQputf(PGparam *param, const char *format, ...);
       int PQputvf(PGparam *param, char *stmtBuf, size_t stmtBufLen,
                   const char *format, va_list ap);

DESCRIPTION
       The PQputf() and PQputvf() functions put one or more query parameters
       into a PGparam using a printf style interface.  Any number of
       parameters can be put at the same time.

       The format argument is a data type specifier string indicating the
       parameters being put, such as "%int4 %polygon".  format cannot be NULL
       or an empty string.  The variable argument list must match the format,
       either "..." or ap.  The number of arguments required for each data
       type is dependant on the data type itself; built-in PostgreSQL types
       always require a single argument.

       The PQputvf() function can construct a parameterized command string
       from format, as long as stmtBuf and stmtBufLen have been provided.  If
       the construction of stmtBuf is not desired, set it to NULL and set
       stmtBufLen to 0.  When a constructed statement is desired, the contents
       of format will be copied to stmtBuf and all data type specifiers, like
       "%int4", will be replaced with $1, $2, etc...  syntax.  The result is a
       parameterized statement in synch with param and ready to be executed.
       For instance: if spec is "SELECT %int4 + %int4", the resulting stmtBuf
       would be "SELECT $1 + $2".

RETURN VALUE
       On success, a non-zero value is returned.  On error, zero is returned
       and PQgeterror(3) will contain an error message.

       If any put operation fails, the param is reverted back to the number of
       parameters it had prior to the function call; partial puts are not
       allowed.

EXAMPLES
   Using PQputf
       The example uses PQputf() to put a couple parameters into a PGparam.

              PGtext text = "foobar";
              PGint8 i8 = PQT_INT64CONST(1099511627776);
              PGparam *param = PQparamCreate(conn);

              if(!PQputf(param, "%text %int8", text, i8))
                   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

              PQparamClear(param);

   Using PQputvf
       The example creates an application function named execf.  execf is a
       wrapper to PQputvf(), as well as PQparamExec(3).  It is similar to
       PQexecf().  The only difference is that the PQexecf implementation uses
       a smaller stack buffer and allocates heap memory when needed.

              PGresult *
              execf(PGconn *conn, const char *format, ...)
              {
                   va_list ap;
                   char stmt[32768];
                   PGparam *param;
                   PGresult *res = NULL;

                   /* create the temporary PGparam */
                   if(!(param = PQparamCreate(conn)))
                        return NULL; /* PQseterror already called */

                   /* put the params, create the stmt and exec it */
                   va_start(ap, format);
                   if(PQputvf(param, stmt, sizeof(stmt), format, ap))
                        res = PQparamExec(conn, param, stmt, 1); // resfmt is binary
                   va_end(ap);

                   /* param must be cleared */
                   PQparamClear(param);
                   return res;
              }

              /* Example: execf will put 2 ints and execute "SELECT $1 * $2" */
              PGresult *res = execf(conn, "SELECT %int4 * %int4", 100, 67);
              if(!res)
                   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

AUTHOR
       A contribution of eSilo, LLC. for the PostgreSQL Database Management
       System.  Written by Andrew Chernow and Merlin Moncure.

REPORTING BUGS
       Report bugs to <libpqtypes@esilo.com>.

COPYRIGHT
       Copyright (c) 2011 eSilo, LLC. All rights reserved.
       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or  FITNESS FOR A PARTICULAR
       PURPOSE.

SEE ALSO
       pqt-specs(3), PQparamCreate(3), PQgeterror(3), PQseterror(3)

libpqtypes                           2011                            PQputf(3)