libpq/

#include <stdio.h>
#include <stdlib.h>
#include <libpq-fe.h>

// (c) Aleksander Alekseev 2016 | http://remontka.com/

#define UNUSED(x) (void)(x)

static const char * user_phone_arr [ ] [ 2 ] = {
{ «user111» , «phone111» } ,
{ «user222» , «phone222» } ,
{ «user333» , «phone333» } ,
{ NULL , NULL }
} ;

static PGconn * conn = NULL ;
static PGresult * res = NULL ;

static void
terminate ( int code )
{
if ( code != 0 )
fprintf ( stderr , «%s n » , PQerrorMessage ( conn ) ) ;

if ( res != NULL )
PQclear ( res ) ;

if ( conn != NULL )
PQfinish ( conn ) ;

exit ( code ) ;
}

static void
clearRes ( )
{
PQclear ( res ) ;
res = NULL ;
}

static void
processNotice ( void * arg , const char * message )
{
UNUSED ( arg ) ;
UNUSED ( message ) ;

// do nothing
}

int
main ( )
{
int libpq_ver = PQlibVersion ( ) ;
printf ( «Version of libpq: %d n » , libpq_ver ) ;

conn = PQconnectdb ( «user=eax password= host=127.0.0.1 dbname=eax» ) ;
if ( PQstatus ( conn ) != CONNECTION_OK )
terminate ( 1 ) ;

// Don’t output notices like:
// NOTICE:  relation «phonebook» already exists, skipping
// see http://stackoverflow.com/a/12504406/1565238
PQsetNoticeProcessor ( conn , processNotice , NULL ) ;

int server_ver = PQserverVersion ( conn ) ;
char * user = PQuser ( conn ) ;
char * db_name = PQdb ( conn ) ;

printf ( «Server version: %d n » , server_ver ) ;
printf ( «User: %s n » , user ) ;
printf ( «Database name: %s n » , db_name ) ;

// same for insert, update, delete, begin, commit …
res = PQexec ( conn , «CREATE TABLE IF NOT EXISTS phonebook »
«(id SERIAL PRIMARY KEY, name VARCHAR(64), »
«phone VARCHAR(64), last_changed TIMESTAMP)» ) ;
if ( PQresultStatus ( res ) != PGRES_COMMAND_OK )
terminate ( 1 ) ;
clearRes ( ) ;

res = PQexec ( conn , «DELETE FROM phonebook» ) ;
if ( PQresultStatus ( res ) != PGRES_COMMAND_OK )
terminate ( 1 ) ;
clearRes ( ) ;

const char * query =
«INSERT INTO phonebook (name, phone, last_changed) »
» VALUES ($1, $2, now());» ;
const char * params [ 2 ] ;

for ( int i = 0 ; ; i ++ )
{
const char * user = user_phone_arr [ i ] [ 0 ] ;
const char * phone = user_phone_arr [ i ] [ 1 ] ;
if ( user == NULL || phone == NULL )
break ;

params [ 0 ] = user ;
params [ 1 ] = phone ;

res = PQexecParams ( conn , query , 2 , NULL , params ,
NULL , NULL , 0 ) ;
if ( PQresultStatus ( res ) != PGRES_COMMAND_OK )
terminate ( 1 ) ;
clearRes ( ) ;
}

res = PQexec ( conn , «SELECT id, name, phone, last_changed »
«FROM phonebook» ) ;
if ( PQresultStatus ( res ) != PGRES_TUPLES_OK )
terminate ( 1 ) ;

int ncols = PQnfields ( res ) ;
printf ( «There are %d columns:» , ncols ) ;
for ( int i = 0 ; i < ncols ; i ++ )
{
char * name = PQfname ( res , i ) ;
printf ( » %s» , name ) ;
}
printf ( » n » ) ;

int nrows = PQntuples ( res ) ;
for ( int i = 0 ; i < nrows ; i ++ )
{
char * id = PQgetvalue ( res , i , 0 ) ;
char * name = PQgetvalue ( res , i , 1 ) ;
char * phone = PQgetvalue ( res , i , 2 ) ;
char * last_changed = PQgetvalue ( res , i , 3 ) ;
printf ( «Id: %s, Name: %s, Phone: %s, Last changed: %s n » ,
id , name , phone , last_changed ) ;
}

printf ( «Total: %d rows n » , nrows ) ;

clearRes ( ) ;
terminate ( 0 ) ;
return 0 ;
}