Connect to a Postgresql database and run a query from a Bash script

Published: 2019-06-07 • Last updated: 2019-09-12

# Prerequisites

psql (PostgreSQL) 9.0.x or higher is installed and on your PATH
The following files are in the same directory

# Files

A query.sql file:

-- this file must end in a new line
SELECT 'foo'
WHERE 1 = 1
UNION ALL
SELECT 'bar'
WHERE 2 = 2;

An .env file:

export POSTGRES_HOST="some-host.com"
export POSTGRES_PORT="5432"
export POSTGRES_DATABASE="some_database"
export POSTGRES_USERNAME="some_user"
export POSTGRES_PASSWORD="some_password"

A script.bash file:

#!/bin/bash

# Load database connection info
source .env 

# Read query into a variable
sql="$(cat query.sql)"

# If psql is not installed, then exit
if ! command -v psql > /dev/null; then 
  echo "PostgreSQL is required..."
  exit 1 
fi 

# Connect to the database, run the query, then disconnect
PGPASSWORD="$POSTGRES_PASSWORD" psql -t -A \
-h "$POSTGRES_HOST" \
-p "$POSTGRES_PORT" \
-d "$POSTGRES_DATABASE" \
-U "$POSTGRES_USERNAME" \
-c "$sql"

Usage:

$ ./script.bash
foo
bar

$ ./script.bash > results.txt

Notes:

There isn’t an option to pass the password, so that’s why the PGPASSWORD environment variable is set
The -t option turns off printing of column names and result row count footers
The -A option switches to unaligned output mode