sccash/README.md

# sccash - Simple C Cash

A lightweight, fast CLI currency converter written in C for USD, JPY, and EUR conversions.

## Features

- **Dual Mode Operation**: Command-line arguments for scripting, interactive prompts for manual use
- **Table Formatted Output**: Clean, readable conversion results
- **Lightweight**: No external dependencies, standard C library only
- **Fast**: Compiles to a small, efficient binary
- **Error Handling**: Clear error messages for invalid inputs

## Exchange Rates (as of March 26, 2026)

- **1 USD** = 159.67 JPY
- **1 USD** = 0.866 EUR  
- **1 EUR** = 184.20 JPY

*Note: These rates are hardcoded and may not reflect current market rates.*

## Compilation

```bash
gcc -o sccash sccash.c -Wall -O2
```

Or for a static binary:
```bash
gcc -o sccash sccash.c -Wall -O2 -static
```

## Installation

### Option 1: Local Installation
```bash
# Compile first
gcc -o sccash sccash.c -Wall -O2

# Copy to local bin directory
mkdir -p ~/bin
cp sccash ~/bin/

# Add to PATH if not already
export PATH="$HOME/bin:$PATH"
```

### Option 2: System-wide Installation
```bash
# Compile first
gcc -o sccash sccash.c -Wall -O2

# Install to system path (requires sudo)
sudo cp sccash /usr/local/bin/

# Verify installation
sccash --help
```

## Usage

### CLI Mode

Pass three arguments: `amount`, `from_currency`, and `to_currency`.

```bash
./sccash <amount> <from> <to>
```

**Examples:**

```bash
# Convert 100 USD to JPY
./sccash 100 USD JPY

# Convert 50 EUR to USD
./sccash 50 EUR USD

# Convert 1000 JPY to EUR
./sccash 1000 JPY EUR
```

### Interactive Mode

Run without arguments for interactive prompts:

```bash
./sccash
```

Example session:
```
=== sccash - Simple C Cash ===

Available currencies: USD, JPY, EUR

Enter amount: 100
Convert from (USD/JPY/EUR): USD
Convert to (USD/JPY/EUR): JPY

+--------+---------------+--------+----------------+
|  FROM  |    AMOUNT     |   TO   |  CONVERTED     |
+--------+---------------+--------+----------------+
| USD    |        100.00 | JPY    |       15967.00 |
+--------+---------------+--------+----------------+

Show all conversions? (y/n): y

+--------+---------------+--------+----------------+
|  FROM  |    AMOUNT     |   TO   |  CONVERTED     |
+--------+---------------+--------+----------------+
| USD    |        100.00 | JPY    |       15967.00 |
| USD    |        100.00 | EUR    |          86.60 |
+--------+---------------+--------+----------------+

Exchange Rates (as of March 26, 2026):
  1 USD = 159.67 JPY
  1 USD = 0.866 EUR
  1 EUR = 184.20 JPY
```

## Sample Output

```bash
$ ./sccash 250 USD EUR

+--------+---------------+--------+----------------+
|  FROM  |    AMOUNT     |   TO   |  CONVERTED     |
+--------+---------------+--------+----------------+
| USD    |        250.00 | EUR    |         216.50 |
+--------+---------------+--------+----------------+
```

## Error Handling

```bash
$ ./sccash 100 GBP USD
Error: Invalid source currency 'GBP'
Available: USD, JPY, EUR

$ ./sccash
=== sccash - Simple C Cash ===

Available currencies: USD, JPY, EUR

Enter amount: invalid
Error: Invalid amount
```

## Architecture

sccash uses USD as the base currency for all conversions:

1. Convert source amount to USD
2. Convert USD amount to target currency

This approach minimizes rounding errors and keeps the code simple and maintainable.

## Currencies Supported

- **USD** - United States Dollar
- **JPY** - Japanese Yen
- **EUR** - Euro

Currency codes are case-insensitive (usd, USD, Usd all work).

## Technical Details

- **Lines of Code**: ~200
- **Dependencies**: Standard C library only (stdio.h, stdlib.h, string.h, ctype.h)
- **Memory Usage**: Minimal - uses only the stack
- **Output Format**: Fixed-width table with 2 decimal precision

## Building for Different Platforms

### Linux
```bash
gcc -o sccash sccash.c -Wall -O2
```

### macOS
```bash
clang -o sccash sccash.c -Wall -O2
```

### Windows (MinGW)
```bash
gcc -o sccash.exe sccash.c -Wall -O2
```

## License

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

## Contributing

This is a simple, focused tool. Contributions should maintain the design goals:
- Keep it lightweight
- No external dependencies
- Simple, readable code
- Clear error messages

## Author

Created with simplicity and performance in mind.

---

**Note**: Currency values fluctuate constantly. The exchange rates in this tool are fixed as of March 26, 2026. For real-time rates, consider using a service with API integration.