Conversion of units of temperature

temperature_units_conv.c

/* Conversion of units of temperature */
/* 
 * Copyright (c) 2014 Abderraouf Adjal
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/* to compile: gcc -std=c99 -O2 main.c -o tuc */


#include <stdio.h>
#include <string.h>	/* strcmp() */
#include <sysexits.h>	/* EX_OK, EX_USAGE, EX_DATAERR */
#include <stdlib.h>	/* atof() */


int is_valid_celsius_temperature(float c);
int is_valid_kelvin_temperature(float k);
int is_valid_fahrenheit_temperature(float f);

float celsius_to_fahrenheit(float c);
float celsius_to_kelvin(float c);

float fahrenheit_to_celsius(float f);
float fahrenheit_to_kelvin(float f);

float kelvin_to_celsius(float k);
float kelvin_to_fahrenheit(float k);


int main(int argc, char **argv)
{
	float temperature;
	
	if (argc != 4)
	{
		if (argc != 1)
		{
			fprintf(stderr, "Invalid command line usage.\n");
		}
		fprintf(stderr, "Usage: %s IN_UNIT OUT_UNIT VALUE\n", argv[0]);
		return EX_USAGE;
	}
	
	temperature = (float)atof(argv[3]);
	
	if (!strcmp(argv[1], "c") || !strcmp(argv[1], "C"))
	{ /* from celsius */
		if (is_valid_celsius_temperature(temperature))
		{
			if (!strcmp(argv[2], "c") || !strcmp(argv[2], "C"))
			{
				printf("%.2f\n", temperature);
			}
			else if (!strcmp(argv[2], "k") || !strcmp(argv[2], "K"))
			{
				printf("%.2f\n", celsius_to_kelvin(temperature));
			}
			else if (!strcmp(argv[2], "f") || !strcmp(argv[2], "F"))
			{
				printf("%.2f\n", celsius_to_fahrenheit(temperature));
			}
			else
			{ /* Invalid cmd usage */
				fprintf(stderr, "Invalid command line usage.\nUsage: %s IN_UNIT OUT_UNIT VALUE\n", argv[0]);
				return EX_USAGE;
			}
		}
		else
		{
			fprintf(stderr, "Invalid temperature.\n");
			return EX_DATAERR;
		}
	}
	else if (!strcmp(argv[1], "k") || !strcmp(argv[1], "K"))
	{ /* from kelvin */
		if (is_valid_kelvin_temperature(temperature))
		{
			if (!strcmp(argv[2], "k") || !strcmp(argv[2], "K"))
			{
				printf("%.2f\n", temperature);
			}
			else if (!strcmp(argv[2], "c") || !strcmp(argv[2], "C"))
			{
				printf("%.2f\n", kelvin_to_celsius(temperature));
			}
			else if (!strcmp(argv[2], "f") || !strcmp(argv[2], "F"))
			{
				printf("%.2f\n", kelvin_to_fahrenheit(temperature));
			}
			else
			{ /* Invalid cmd usage */
				fprintf(stderr, "Invalid command line usage.\nUsage: %s IN_UNIT OUT_UNIT VALUE\n", argv[0]);
				return EX_USAGE;
			}
		}
		else
		{
			fprintf(stderr, "Invalid temperature.\n");
			return EX_DATAERR;
		}
	}
	else if (!strcmp(argv[1], "f") || !strcmp(argv[1], "F"))
	{ /* from fahrenheit */
		if (is_valid_fahrenheit_temperature(temperature))
		{
			if (!strcmp(argv[2], "f") || !strcmp(argv[2], "F"))
			{
				printf("%.2f\n", temperature);
			}
			else if (!strcmp(argv[2], "c") || !strcmp(argv[2], "C"))
			{
				printf("%.2f\n", fahrenheit_to_celsius(temperature));
			}
			else if (!strcmp(argv[2], "k") || !strcmp(argv[2], "K"))
			{
				printf("%.2f\n", fahrenheit_to_kelvin(temperature));
			}
			else
			{ /* Invalid cmd usage */
				fprintf(stderr, "Invalid command line usage.\nUsage: %s IN_UNIT OUT_UNIT VALUE\n", argv[0]);
				return EX_USAGE;
			}
		}
		else
		{
			fprintf(stderr, "Invalid temperature.\n");
			return EX_DATAERR;
		}
	}
	else
	{ /* Invalid cmd usage */
		fprintf(stderr, "Invalid command line usage.\nUsage: %s IN_UNIT OUT_UNIT VALUE\n", argv[0]);
		return EX_USAGE;
	}
	
	return EX_OK;
}


/**
 * return 0 if the temperature is invalid;
 * return 1 if the temperature is valid;
 */
 
int is_valid_celsius_temperature(float c)
{
	return ((c < (- 273.15) || c > 49727.0) ? 0 : 1);
}

int is_valid_kelvin_temperature(float k)
{
	return ((k < 0.0 || k > 50000.0) ? 0 : 1);
}

int is_valid_fahrenheit_temperature(float f)
{
	return ((f < (- 459.67) || f > 89541.0) ? 0 : 1);
}


float celsius_to_fahrenheit(float c)
{
	return (c * (9.0/5.0) + 32.0);
}

float celsius_to_kelvin(float c)
{
	return (c + 273.15);
}


float fahrenheit_to_celsius(float f)
{
	return ((f - 32.0) * (5.0/9.0));
}

float fahrenheit_to_kelvin(float f)
{
	return ((f + 459.67) * (5.0/9.0));
}


float kelvin_to_celsius(float k)
{
	return (k - 273.15);
}

float kelvin_to_fahrenheit(float k)
{
	return (k * (9.0/5.0) - 459.67);
}