PostgreSQL backup script

backup_db.sh

#!/bin/bash

## README
#
# Automatic PostgreSQL backup script
# Version:        v1.0.5
# Author:         Emzi0767
# Usage:
#  ./backup_db.sh <database> <username> <password> <max_count>
#
# Use with cron. This script will automatically backup your
# PostgreSQL database, compress the backup

NAME="Automatic PostgreSQL backup script"
VERSION="v1.0.5"
AUTHOR="Emzi0767"
USAGE="./backup_db.sh <database> <username> <password> <max_count>"

do_backup() {
    echo "Beginning database backup..."

    #############################
    # Backup initialisation logic
    #############################

    targetdir="/home/emzi0767/dat/db_backups/$1"

    # Check if the directory doesn't exist, and if it doesn't, create it
    if [ ! -d "$targetdir" ]
    then
        echo "Target directory ($targetdir) doesn't exist, creating"
        mkdir "$targetdir"
    fi

    # Enter the target directory
    cd "$targetdir"

    #############################
    # Postgres backup logic
    #############################

    # Format the filename
    filename="$1_$(date +%s).sql"

    echo "Database: $1"
    echo "Username: $2"
    echo "Target:   $filename"

    # Dump the database
    PGPASSWORD="$3" pg_dump -U "$2" -d "$1" > "$filename"
    echo "Postgres dump completed, compressing"

    # Compress the backup
    xz -z9e "$filename"
    echo "Completed"

    #############################
    # Backup trimming logic
    #############################

    # Find the oldest backups and count them
    files=$(ls -1t | grep '\.sql\.xz$' | tail -n +$(($4 + 1)))
    filecount=$(echo -n "$files" | wc -l)
    filecount=$(($filecount + 1))

    echo "Trimming backups to $4 latest"
    echo "Will remove $filecount files"

    # Remove the oldest backups
    for i in $files
    do
        rm $i
        echo "Removed $i"
    done

    echo "Backups trimmed"
}

print_usage() {
    echo "$NAME $VERSION by $AUTHOR"
    echo "Usage:"
    echo "  $USAGE"
}

if [ "$1" == "--help" ] || [ "$1" == "-h" ]
then
    print_usage
elif [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ] || [ -z "$4" ]
then
    print_usage
else
    do_backup "$1" "$2" "$3" "$4"
fi