void getmemPointer()
{
    fprintf(stderr,"ShmemIndex  ShmemIndex is %ld \n", ShmemIndex);
    return;
}

/*
 * Main entry point for bgwriter process
 *
 * This is invoked from AuxiliaryProcessMain, which has already created the
 * basic execution environment, but not enabled signals yet.
 */
void
BackgroundWriterMain(void)
{
        //added by gaojian
        fprintf(stderr,"BackgroundWriterMain........");
        getmemPointer();
…

}

/*
 * Main entry point for walwriter process
 *
 * This is invoked from AuxiliaryProcessMain, which has already created the
 * basic execution environment, but not enabled signals yet.
 */
void
WalWriterMain(void)
{
        //added by gaojian
        fprintf(stderr,"WalWriterMain...........");
        getmemPointer();
......
}

[postgres@localhost bin]$ ./postgres -D /usr/local/pgsql/data
LOG:  database system was shut down at 2012-11-06 16:59:15 CST
BackgroundWriterMain........ShmemIndex  ShmemIndex is 128175904 
WalWriterMain...........ShmemIndex  ShmemIndex is 128175904 
LOG:  autovacuum launcher started
LOG:  database system is ready to accept connections