/***************************************************************************
 * env.c:	Environment variable functions.
 *
 * Part of...
 *
 *	FREE:	Display free space on your disk volumes.
 *		Author:  Daniel Jay Barrett, barrett@cs.jhu.edu.
 *
 * This program is Freely Distributable.  Make all the copies you want
 * and give them away.  Use this code in any way you like.
***************************************************************************/

#include "free.h"

/* Return the value of ENV: environment variable "variableName", if it
 * exists. */

char *GetEnv(char *variableName)
{
	char envVar[ENV_NAME_LENGTH];
	BPTR fileHandle;

	sprintf(envVar, "ENV:%s", variableName);
	if ((fileHandle = Open(envVar, MODE_OLDFILE)) == 0)
		return(NULL);
	else
		return(TheEnvValue(fileHandle));
}


/* Given a fileHandle on an environment variable, read the "file" and
 * find the value of the variable.
 * As far as I can tell, the value may have some garbage (control)
 * characters after it.  I make sure to put a null ('\0') in place of
 * the first such control character (if any).
 *
 * If the value is too large (>= BUFSIZ-1), then we can't handle it.
 * Return NULL.
 * Otherwise, terminate the value with a null and return a pointer to
 * it.  We use a static array for this. */
	
char *TheEnvValue(BPTR fileHandle)
{
	static char envString[BUFSIZ];
	int numChars;

	numChars = 0;

	if (Read(fileHandle, envString, (long)sizeof(envString)) > 0)
	{
		envString[BUFSIZ-1] = '\0';	/* Terminate for safety. */
		while (envString[numChars] >= ' ')
			numChars++;
		if (numChars < sizeof(envString)-1)
			envString[numChars] = '\0';
		else
			numChars = 0;
	}
	Close(fileHandle);
	return(numChars ? envString : NULL);
}