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Connect to a Postgres Database and Run a Query From a Bash Script

Published: 2019-06-07 • Last updated: 2021-05-03

Table of Contents

Prerequisites

  • psql (PostgreSQL) version 9.0.x or higher is installed and on your PATH. See install steps for Mac
  • 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="localhost"
export POSTGRES_PORT="5432"
export POSTGRES_DATABASE="some_database"
export POSTGRES_USERNAME="some_user"
export POSTGRES_PASSWORD="some_password"

A script.sh file:

#!/usr/bin/env bash

# Load database connection info
source .env

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

# If psql is not available, then exit
if ! command -v psql > /dev/null; then
  echo "This script requires psql to be installed and on your PATH ..."
  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

Make it executable:

$ chmod 755 script.sh

Print results to stdout:

$ ./script.sh
foo
bar

Write results to file:

$ ./script.sh > 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