diff --git a/libc/stdlib/strtoul.c b/libc/stdlib/strtoul.c
new file mode 100644
index 0000000..61dbb6f
--- /dev/null
+++ b/libc/stdlib/strtoul.c
@@ -0,0 +1,102 @@
+/*	$OpenBSD: strtoul.c,v 1.7 2005/08/08 08:05:37 espie Exp $ */
+/*
+ * Copyright (c) 1990 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 <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+
+/*
+ * Convert a string to an unsigned long integer.
+ *
+ * Ignores `locale' stuff.  Assumes that the upper and lower case
+ * alphabets and digits are each contiguous.
+ */
+unsigned long
+strtoul(const char *nptr, char **endptr, int base)
+{
+	const char *s;
+	unsigned long acc, cutoff;
+	int c;
+	int neg, any, cutlim;
+
+	/*
+	 * See strtol for comments as to the logic used.
+	 */
+	s = nptr;
+	do {
+		c = (unsigned char) *s++;
+	} while (isspace(c));
+	if (c == '-') {
+		neg = 1;
+		c = *s++;
+	} else {
+		neg = 0;
+		if (c == '+')
+			c = *s++;
+	}
+	if ((base == 0 || base == 16) &&
+	    c == '0' && (*s == 'x' || *s == 'X')) {
+		c = s[1];
+		s += 2;
+		base = 16;
+	}
+	if (base == 0)
+		base = c == '0' ? 8 : 10;
+
+	cutoff = ULONG_MAX / (unsigned long)base;
+	cutlim = ULONG_MAX % (unsigned long)base;
+	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
+		if (isdigit(c))
+			c -= '0';
+		else if (isalpha(c))
+			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
+		else
+			break;
+		if (c >= base)
+			break;
+		if (any < 0)
+			continue;
+		if (acc > cutoff || (acc == cutoff && c > cutlim)) {
+			any = -1;
+			acc = ULONG_MAX;
+			errno = ERANGE;
+		} else {
+			any = 1;
+			acc *= (unsigned long)base;
+			acc += c;
+		}
+	}
+	if (neg && any > 0)
+		acc = -acc;
+	if (endptr != 0)
+		*endptr = (char *) (any ? s - 1 : nptr);
+	return (acc);
+}