caeser-cipher

Usage

./caesar-cipher [-E|-e|-D|-d] [message_or_input_file] [-o output_file] [-k key]

This program encrypts or decrypts text using the Caesar cipher. You can specify options via command-line flags or be prompted for missing values.

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Command-Line Options

Flag	Argument	Description
-E	[message]	Encrypt mode. If followed by text, encrypts it directly.
-D	[message]	Decrypt mode. If followed by text, decrypts it directly.
-e	[input_file]	Encrypt mode. If followed by a file path, encrypts the file’s contents.
-d	[input_file]	Decrypt mode. If followed by a file path, decrypts the file’s contents.
-o	output_file	Specifies an output file to save the result.
-k	key (integer)	Specifies the shift key (between 1-25) for the cipher.

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Examples

Encrypting a message directly:

./caesar-cipher -E "hello world" -k 3

Encrypts "hello world" with shift 3, outputs to stdout.

Decrypting from a file and saving output:

./caesar-cipher -d input.txt -k 5 -o decrypted.txt

Reads input.txt, decrypts using key 5, and writes to decrypted.txt.

Encrypting interactively (prompt for missing values):

./caesar-cipher -e -o encrypted.txt

Prompts for the input file and shift key.

Incorrect Usage (Missing Key Argument):

./caesar-cipher -E "hello" -k

The program will detect the missing key and prompt for it.

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Behavior

• If a required flag (-k or input text) is missing, the user will be prompted.
• -E and -D (uppercase) can take a message directly.
• -e and -d (lowercase) can take a file path.
• -o and -k must be followed by an argument.

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Building

Prerequisites

Make sure you have the following installed:

• CMake (version 3.10 or higher)
• A C++ compiler (GCC, Clang, MSVC, etc.)

Build Instructions

1. Configure and Generate Build Files

Run the following command from the project root:

cmake -S . -B build

2. Compile the Project

Build the project with:

cmake --build build

This will generate the executable caesar-cipher inside the build/ directory.

3. Running the Program

Once compiled, you can run the program like this:

./build/caesar-cipher [options]