Initial Contribution
diff --git a/sh/mystring.c b/sh/mystring.c
new file mode 100644
index 0000000..aecf83e
--- /dev/null
+++ b/sh/mystring.c
@@ -0,0 +1,133 @@
+/* $NetBSD: mystring.c,v 1.16 2003/08/07 09:05:35 agc Exp $ */
+
+/*-
+ * Copyright (c) 1991, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Kenneth Almquist.
+ *
+ * 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 <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)mystring.c 8.2 (Berkeley) 5/4/95";
+#else
+__RCSID("$NetBSD: mystring.c,v 1.16 2003/08/07 09:05:35 agc Exp $");
+#endif
+#endif /* not lint */
+
+/*
+ * String functions.
+ *
+ * equal(s1, s2) Return true if strings are equal.
+ * scopy(from, to) Copy a string.
+ * scopyn(from, to, n) Like scopy, but checks for overflow.
+ * number(s) Convert a string of digits to an integer.
+ * is_number(s) Return true if s is a string of digits.
+ */
+
+#include <stdlib.h>
+#include "shell.h"
+#include "syntax.h"
+#include "error.h"
+#include "mystring.h"
+
+
+char nullstr[1]; /* zero length string */
+
+/*
+ * equal - #defined in mystring.h
+ */
+
+/*
+ * scopy - #defined in mystring.h
+ */
+
+
+/*
+ * scopyn - copy a string from "from" to "to", truncating the string
+ * if necessary. "To" is always nul terminated, even if
+ * truncation is performed. "Size" is the size of "to".
+ */
+
+void
+scopyn(const char *from, char *to, int size)
+{
+
+ while (--size > 0) {
+ if ((*to++ = *from++) == '\0')
+ return;
+ }
+ *to = '\0';
+}
+
+
+/*
+ * prefix -- see if pfx is a prefix of string.
+ */
+
+int
+prefix(const char *pfx, const char *string)
+{
+ while (*pfx) {
+ if (*pfx++ != *string++)
+ return 0;
+ }
+ return 1;
+}
+
+
+/*
+ * Convert a string of digits to an integer, printing an error message on
+ * failure.
+ */
+
+int
+number(const char *s)
+{
+
+ if (! is_number(s))
+ error("Illegal number: %s", s);
+ return atoi(s);
+}
+
+
+
+/*
+ * Check for a valid number. This should be elsewhere.
+ */
+
+int
+is_number(const char *p)
+{
+ do {
+ if (! is_digit(*p))
+ return 0;
+ } while (*++p != '\0');
+ return 1;
+}