BUG #5978: Running postgress in a shell script fails

The following bug has been logged online:

Bug reference: 5978
Logged by: Paul Deschamps
Email address: pdescham49(at)gmail(dot)com
PostgreSQL version: 8.4.6
Operating system: Ubuntu 10.4
Description: Running postgress in a shell script fails
Details:

When running postgres in a shell using the -c option it looks as though it
parses the contents of the --command as command line arguments.

---BEGIN SCRIPT---
#!/bin/bash
psql --version
PCOMMAND='psql postgres -c"SELECT tablename FROM PG_TABLES limit 1;"'

echo "PGSQL - Execution from a shell script test"
echo
echo "Running Command:"${PCOMMAND}

echo "TEST 1 "
OUTPUT1=$(${PCOMMAND})
echo $OUTPUT1
echo
echo "TEST 2"
OUTPUT2=`$PCOMMAND`
echo $OUTPUT2
echo
echo "TEST 3"
OUTPUT3=`exec $PCOMMAND`
echo $OUTPUT3
echo
echo "TEST 4"
$PCOMMAND

echo "TEST 5"
psql postgres -c"SELECT tablename FROM PG_TABLES limit 1;"
---END SCRIPT---

---BEGIN OUTPUT---
[postgres(at)host03 scripts]$ ./test.sh
psql (PostgreSQL) 8.4.6
PGSQL - Execution from a shell script test

Running Command:psql postgres -c"SELECT tablename FROM PG_TABLES limit 1;"
TEST 1
psql: warning: extra command-line argument "FROM" ignored
psql: warning: extra command-line argument "PG_TABLES" ignored
psql: warning: extra command-line argument "limit" ignored
psql: warning: extra command-line argument "1;"" ignored
psql: FATAL: role "tablename" does not exist

TEST 2
psql: warning: extra command-line argument "FROM" ignored
psql: warning: extra command-line argument "PG_TABLES" ignored
psql: warning: extra command-line argument "limit" ignored
psql: warning: extra command-line argument "1;"" ignored
psql: FATAL: role "tablename" does not exist

TEST 3
psql: warning: extra command-line argument "FROM" ignored
psql: warning: extra command-line argument "PG_TABLES" ignored
psql: warning: extra command-line argument "limit" ignored
psql: warning: extra command-line argument "1;"" ignored
psql: FATAL: role "tablename" does not exist

TEST 4
psql: warning: extra command-line argument "FROM" ignored
psql: warning: extra command-line argument "PG_TABLES" ignored
psql: warning: extra command-line argument "limit" ignored
psql: warning: extra command-line argument "1;"" ignored
psql: FATAL: role "tablename" does not exist
TEST 5
tablename
-----------
pg_type
(1 row)

---END OUTPUT---