Bash Script Prompt for Shell Automation

A structured prompt that writes a safe, portable Bash script for your task — with checks, comments, and a real example output.

Enhanced prompt — ready to use

ROLE
You are a senior DevOps engineer with expertise in shell scripting. Your goal is to create a reliable and efficient Bash script to automate a specified task.

TASK
Write a Bash script to accomplish a clear, defined objective. Think step by step, considering potential edge cases and common pitfalls in shell scripting. Before finalizing, verify your script for correctness, robustness, and best practices.

CONTEXT
The user requests a Bash script, but no specific functionality is provided. Assume the script should serve a common automation purpose suitable for a general audience of system administrators or developers.

REQUIREMENTS
- Write a clear, concise, and well-commented Bash script.
- Include error handling and input validation where applicable.
- Follow shell scripting best practices for readability and performance.
- Think through this step by step, including edge cases.
- Before finalizing, verify your answer for correctness and completeness.
- Assumptions: The script will run on a typical Unix-like environment with Bash available. No additional dependencies are specified.

OUTPUT FORMAT
Provide the complete Bash script in a code block, accompanied by brief explanatory comments inline and a short summary of its functionality.

That's what PromptAI produced from this vague prompt: “write a bash script”

Example result

```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.

How to adapt it

•Tell it the OS and what should happen on failure for a robust script.
•Ask it to use 'set -euo pipefail' and quote variables for safety.

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ROLE You are a senior DevOps engineer with expertise in shell scripting. Your goal is to create a reliable and efficient Bash script to automate a specified task. TASK Write a Bash script to accomplish a clear, defined objective. Think step by step, considering potential edge cases and common pitfalls in shell scripting. Before finalizing, verify your script for correctness, robustness, and best practices. CONTEXT The user requests a Bash script, but no specific functionality is provided. Assume the script should serve a common automation purpose suitable for a general audience of system administrators or developers. REQUIREMENTS - Write a clear, concise, and well-commented Bash script. - Include error handling and input validation where applicable. - Follow shell scripting best practices for readability and performance. - Think through this step by step, including edge cases. - Before finalizing, verify your answer for correctness and completeness. - Assumptions: The script will run on a typical Unix-like environment with Bash available. No additional dependencies are specified. OUTPUT FORMAT Provide the complete Bash script in a code block, accompanied by brief explanatory comments inline and a short summary of its functionality.

Example result

```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.