EasyArgs

A simple, single-header argument parser for C that eliminates boilerplate and code duplication.

Features

• Single header file: Just include easyargs.h and you're good to go
• Zero duplication: Define your arguments once to get struct fields, parsing, and help generation automatically
• Type-safe: Supports all common C types with built-in parsing
• Flexible: Handle required arguments, optional arguments with defaults, and boolean flags
• Automatic help generation: Professional-looking usage and help text generated from your definitions

Quick Start

Check out ./examples to see some use cases!

1. Define your arguments

// Define required positional arguments
#define REQUIRED_ARGS \
    REQUIRED_STRING_ARG(input_file, "input", "Input file path") \
    REQUIRED_STRING_ARG(output_file, "output", "Output file path")

// Define optional arguments with defaults
#define OPTIONAL_ARGS \
    OPTIONAL_UINT_ARG(threads, 1, "-t", "threads", "Number of threads to use")

// Define boolean flags
#define BOOLEAN_ARGS \
    BOOLEAN_ARG(help, "-h", "Show help")

2. Include EasyArgs

#include "easyargs.h"

3. Use it in your main function

int main(int argc, char* argv[]) {
    // Initialize with the default values specified above
    args_t args = make_default_args();

    // Parse arguments
    if (!parse_args(argc, argv, &args) || args.help) {
        print_help(argv[0]);
        return 1;
    }

    // Use your arguments
    printf("Processing %s -> %s\n", args.input_file, args.output_file);
    printf("Using %u threads\n", args.threads);

    return 0;
}

4. Compile and Run

gcc file_processor.c -o file_processor
./file_processor input.txt output.txt -t 4

Argument Types

Required Arguments

Required arguments are positional and must be provided in order:

#define REQUIRED_ARGS \
    REQUIRED_STRING_ARG(name, "label", "description") \
    REQUIRED_SIZE_ARG(count, "count", "Number of items") \
    REQUIRED_DOUBLE_ARG(threshold, "threshold", "Processing threshold")

Supported types:

• REQUIRED_STRING_ARG - char*
• REQUIRED_CHAR_ARG - char
• REQUIRED_INT_ARG - int
• REQUIRED_UINT_ARG - unsigned int
• REQUIRED_LONG_ARG - long
• REQUIRED_ULONG_ARG - unsigned long
• REQUIRED_LONG_LONG_ARG - long long
• REQUIRED_ULONG_LONG_ARG - unsigned long long
• REQUIRED_SIZE_ARG - size_t
• REQUIRED_FLOAT_ARG - float
• REQUIRED_DOUBLE_ARG - double

Optional Arguments

Optional arguments have flags and default values:

#define OPTIONAL_ARGS \
    OPTIONAL_INT_ARG(verbose, 0, "-v", "level", "Verbosity level") \
    OPTIONAL_STRING_ARG(config, "config.ini", "--config", "file", "Configuration file") \
    OPTIONAL_DOUBLE_ARG(factor, 1.5, "-f", "factor", "Scaling factor", 2)

Note: OPTIONAL_FLOAT_ARG and OPTIONAL_DOUBLE_ARG take an additional precision parameter for displaying defaults in help text.

Supported types: Same as required arguments, but with OPTIONAL_ prefix.

Boolean Arguments

Boolean flags toggle between true and false if present or missing, respectively:

#define BOOLEAN_ARGS \
    BOOLEAN_ARG(verbose, "-v", "Enable verbose output") \
    BOOLEAN_ARG(quiet, "-q", "Suppress all output") \
    BOOLEAN_ARG(force, "--force", "Force overwrite existing files")

Advanced Usage

Custom Parsing

For basic types, parsing is handled automatically. For required arguments that need custom parsing, you can specify a parser function:

#define REQUIRED_ARG(type, name, label, description, parser)

Error Handling

parse_args() returns 0 if parsing fails (e.g., not enough required arguments). Always check the return value:

if (!parse_args(argc, argv, &args)) {
    fprintf(stderr, "Error parsing arguments\n");
    print_help(argv[0]);
    return 1;
}

Installation

1. Download easyargs.h
2. Place it in your project directory or include path
3. Include it in your source files: #include "easyargs.h"

No compilation or linking required — it's header-only!