some basic PostgreSQL orchestration from Bash

I had to designed some scripts for migration, upgrade and rebuild PostgreSQL. Some fragments can be useful for others:

Prolog:

#!/bin/bash

# Installation prefix
prefix=/usr/local/pgsql

PGCTL="$prefix/bin/pg_ctl"
PGUSER=postgres

if [ ! -n "$PGDATA" ]; then
  PGDATA="$prefix/data"
fi

Ensure a stop of PostgreSQL, continue when server is down:

echo "shutdown server"
su - $PGUSER -c "$PGCTL status -D $PGDATA" 
if [ $? != 1 ]; then
  su - $PGUSER -c "$PGCTL stop -D  $PGDATA -m fast"
  if [ $? != 1 -a $? != 0 ]; then
    su - $PGUSER  -c "$PGCTL status -D  $PGDATA"
    while [ $? != 1 -a $? != 3 ]; do
      echo "PostgreSQL still running.."
      sleep 1
      su - $PGUSER -c "$PGCTL status -D  $PGDATA"
    done
  fi
fi

Start server and continue when server is ready to accept connection:

echo "start server"
/etc/init.d/pgsql start
$prefix/bin/pg_isready
while [ $? != 0 ]; do
  sleep 1;
  $prefix/bin/pg_isready
done