setenv.c

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/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid1[] = "@(#)setenv.c	5.3 (Berkeley) 5/16/90";
static char sccsid2[] = "@(#)getenv.c	5.6 (Berkeley) 5/16/90";
#endif /* LIBC_SCCS and not lint */

#if defined(SOLARIS)
/* for bcopy() and bzero() */
#include "bstring.h"
#endif

/*
 * setenv --
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
setenv(name, value, rewrite)
	register char *name, *value;
	int rewrite;
{
	extern char **environ, *malloc();
	static int alloced;			/* if allocated space before */
	register char *C;
	int l_value, offset;
	static char *_findenv();

	if (*value == '=')			/* no `=' in value */
		++value;
	l_value = strlen(value);
	if ((C = _findenv(name, &offset))) {	/* find if already exists */
		if (!rewrite)
			return(0);
		if (strlen(C) >= l_value) {	/* old larger; copy over */
			while (*C++ = *value++);
			return(0);
		}
	}
	else {					/* create new slot */
		register int	cnt;
		register char	**P;

		for (P = environ, cnt = 0; *P; ++P, ++cnt);
		if (alloced) {			/* just increase size */
			environ = (char **)realloc((char *)environ,
			    (sizeof(char *) * (cnt + 2)));
			if (!environ)
				return(-1);
		}
		else {				/* get new space */
			alloced = 1;		/* copy old entries into it */
			P = (char **)malloc((sizeof(char *) *
			    (cnt + 2)));
			if (!P)
				return(-1);
			bcopy(environ, P, cnt * sizeof(char *));
			environ = P;
		}
		environ[cnt + 1] = 0;
		offset = cnt;
	}
	for (C = name; *C && *C != '='; ++C);	/* no `=' in name */
	if (!(environ[offset] =			/* name + `=' + value */
	    malloc(((int)(C - name) + l_value + 2))))
		return(-1);
	for (C = environ[offset]; (*C = *name++) && *C != '='; ++C);
	for (*C++ = '='; *C++ = *value++;);
	return(0);
}

/*
 * unsetenv(name) --
 *	Delete environmental variable "name".
 */
void
unsetenv(name)
	char	*name;
{
	extern char **environ;
	register char **P;
	int offset;
	static char *_findenv();

	while (_findenv(name, &offset))		/* if set multiple times */
		for (P = &environ[offset];; ++P)
			if (!(*P = *(P + 1)))
				break;
}

/*
 * getenv --
 *	Returns ptr to value associated with name, if any, else NULL.
 */
char *
getenv(name)
	char *name;
{
	int offset;
	static char *_findenv();

	return(_findenv(name, &offset));
}

/*
 * _findenv --
 *	Returns pointer to value associated with name, if any, else NULL.
 *	Sets offset to be the offset of the name/value combination in the
 *	environmental array, for use by setenv(3) and unsetenv(3).
 *	Explicitly removes '=' in argument name.
 */
static char *
_findenv(name, offset)
	register char *name;
	int *offset;
{
	extern char **environ;
	register int len;
	register char **P, *C;

	for (C = name, len = 0; *C && *C != '='; ++C, ++len);
	for (P = environ; *P; ++P)
		if (!strncmp(*P, name, len))
			if (*(C = *P + len) == '=') {
				*offset = P - environ;
				return(++C);
			}
	return(0);
}