Bash Script Prompt for Shell Automation

```bash #!/bin/bash # # backup_dir.sh - Incremental backup script for a specified directory # # This script creates a timestamped compressed backup of a given source directory, # storing it in a specified backup directory. The script performs input validation, # checks for potential errors, and avoids common pitfalls. # # Usage: ./backup_dir.sh /path/to/source /path/to/backup # set -euo pipefail # Strict mode for safety # Function to print usage instructions usage() { echo "Usage: $0 SOURCE_DIRECTORY BACKUP_DIRECTORY" echo "Creates a compressed backup of SOURCE_DIRECTORY inside BACKUP_DIRECTORY." exit 1 } # Function to print errors to stderr error() { echo "Error: $1" >&2 exit 1 } # Validate arguments if [[ $# -ne 2 ]]; then usage fi SOURCE_DIR=$1 BACKUP_DIR=$2 # Resolve absolute paths for clarity and safety SOURCE_DIR=$(readlink -f -- "$SOURCE_DIR") || error "Failed to resolve source directory path." BACKUP_DIR=$(readlink -f -- "$BACKUP_DIR") || error "Failed to resolve backup directory path." # Check that source directory exists and is a directory if [[ ! -d "$SOURCE_DIR" ]]; then error "Source directory '$SOURCE_DIR' does not exist or is not a directory." fi # Check that backup directory exists; if not, attempt to create it if [[ ! -d "$BACKUP_DIR" ]]; then echo "Backup directory '$BACKUP_DIR' does not exist. Attempting to create it..." if ! mkdir -p -- "$BACKUP_DIR"; then error "Failed to create backup directory '$BACKUP_DIR'. Check permissions." fi fi # Check write permission on backup directory if [[ ! -w "$BACKUP_DIR" ]]; then error "No write permission on backup directory '$BACKUP_DIR'." fi # Generate a timestamped backup filename TIMESTAMP=$(date +%Y%m%d_%H%M%S) SRC_BASENAME=$(basename -- "$SOURCE_DIR") BACKUP_FILE="${BACKUP_DIR}/${SRC_BASENAME}_backup_${TIMESTAMP}.tar.gz" # Inform user about the backup operation echo "Backing up '$SOURCE_DIR' to '$BACKUP_FILE' ..." # Create the compressed tar archive if tar -czf "$BACKUP_FILE" -C "$(dirname "$SOURCE_DIR")" "$SRC_BASENAME"; then echo "Backup successful." else error "Backup failed during archive creation." fi # Optional: Verify the archive integrity (basic test) if tar -tzf "$BACKUP_FILE" &> /dev/null; then echo "Backup archive verified successfully." else error "Backup archive verification failed." fi exit 0 ``` --- ### Summary This Bash script automates the task of backing up a directory by creating a compressed (tar.gz) archive with a timestamped filename. It accepts two positional arguments: the source directory to back up and the target backup directory. The script validates arguments, ensures directories exist (creating the backup directory if needed), checks permissions, and handles errors gracefully. It also verifies the integrity of the created backup archive before completing. This makes it a safe and reliable tool for sysadmins and developers to perform incremental backups quickly and consistently.