diff --git a/libc/stdlib/setenv.c b/libc/stdlib/setenv.c
new file mode 100644
index 0000000..856db5e
--- /dev/null
+++ b/libc/stdlib/setenv.c
@@ -0,0 +1,105 @@
+/*	$OpenBSD: setenv.c,v 1.9 2005/08/08 08:05:37 espie Exp $ */
+/*
+ * Copyright (c) 1987 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+char *__findenv(const char *name, int *offset);
+
+extern char **environ;
+
+/*
+ * setenv --
+ *	Set the value of the environmental variable "name" to be
+ *	"value".  If rewrite is set, replace any current value.
+ */
+int
+setenv(const char *name, const char *value, int rewrite)
+{
+	static char **lastenv;			/* last value of environ */
+	char *C;
+	int l_value, offset;
+
+	if (*value == '=')			/* no `=' in value */
+		++value;
+	l_value = strlen(value);
+	if ((C = __findenv(name, &offset))) {	/* find if already exists */
+		if (!rewrite)
+			return (0);
+		if ((int)strlen(C) >= l_value) {	/* old larger; copy over */
+			while ((*C++ = *value++))
+				;
+			return (0);
+		}
+	} else {					/* create new slot */
+		size_t cnt;
+		char **P;
+
+		for (P = environ; *P != NULL; P++)
+			;
+		cnt = P - environ;
+        P = (char **)realloc(lastenv, sizeof(char *) * (cnt + 2));
+		if (!P)
+			return (-1);
+		if (lastenv != environ)
+			memcpy(P, environ, cnt * sizeof(char *));
+		lastenv = environ = P;
+		offset = cnt;
+		environ[cnt + 1] = NULL;
+	}
+	for (C = (char *)name; *C && *C != '='; ++C)
+		;				/* no `=' in name */
+	if (!(environ[offset] =			/* name + `=' + value */
+	    malloc((size_t)((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".
+ */
+int
+unsetenv(const char *name)
+{
+	char **P;
+	int offset;
+
+	while (__findenv(name, &offset))	/* if set multiple times */
+		for (P = &environ[offset];; ++P)
+			if (!(*P = *(P + 1)))
+				break;
+
+        return 0;
+}