auto import from //depot/cupcake/@135843
diff --git a/sh/arith.y b/sh/arith.y
new file mode 100644
index 0000000..d51ed38
--- /dev/null
+++ b/sh/arith.y
@@ -0,0 +1,199 @@
+%{
+/* $NetBSD: arith.y,v 1.17 2003/09/17 17:33:36 jmmv Exp $ */
+
+/*-
+ * Copyright (c) 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[] = "@(#)arith.y 8.3 (Berkeley) 5/4/95";
+#else
+__RCSID("$NetBSD: arith.y,v 1.17 2003/09/17 17:33:36 jmmv Exp $");
+#endif
+#endif /* not lint */
+
+#include <stdlib.h>
+#include "expand.h"
+#include "shell.h"
+#include "error.h"
+#include "output.h"
+#include "memalloc.h"
+
+const char *arith_buf, *arith_startbuf;
+
+void yyerror(const char *);
+#ifdef TESTARITH
+int main(int , char *[]);
+int error(char *);
+#endif
+
+%}
+%token ARITH_NUM ARITH_LPAREN ARITH_RPAREN
+
+%left ARITH_OR
+%left ARITH_AND
+%left ARITH_BOR
+%left ARITH_BXOR
+%left ARITH_BAND
+%left ARITH_EQ ARITH_NE
+%left ARITH_LT ARITH_GT ARITH_GE ARITH_LE
+%left ARITH_LSHIFT ARITH_RSHIFT
+%left ARITH_ADD ARITH_SUB
+%left ARITH_MUL ARITH_DIV ARITH_REM
+%left ARITH_UNARYMINUS ARITH_UNARYPLUS ARITH_NOT ARITH_BNOT
+%%
+
+exp: expr {
+ return ($1);
+ }
+ ;
+
+
+expr: ARITH_LPAREN expr ARITH_RPAREN { $$ = $2; }
+ | expr ARITH_OR expr { $$ = $1 ? $1 : $3 ? $3 : 0; }
+ | expr ARITH_AND expr { $$ = $1 ? ( $3 ? $3 : 0 ) : 0; }
+ | expr ARITH_BOR expr { $$ = $1 | $3; }
+ | expr ARITH_BXOR expr { $$ = $1 ^ $3; }
+ | expr ARITH_BAND expr { $$ = $1 & $3; }
+ | expr ARITH_EQ expr { $$ = $1 == $3; }
+ | expr ARITH_GT expr { $$ = $1 > $3; }
+ | expr ARITH_GE expr { $$ = $1 >= $3; }
+ | expr ARITH_LT expr { $$ = $1 < $3; }
+ | expr ARITH_LE expr { $$ = $1 <= $3; }
+ | expr ARITH_NE expr { $$ = $1 != $3; }
+ | expr ARITH_LSHIFT expr { $$ = $1 << $3; }
+ | expr ARITH_RSHIFT expr { $$ = $1 >> $3; }
+ | expr ARITH_ADD expr { $$ = $1 + $3; }
+ | expr ARITH_SUB expr { $$ = $1 - $3; }
+ | expr ARITH_MUL expr { $$ = $1 * $3; }
+ | expr ARITH_DIV expr {
+ if ($3 == 0)
+ yyerror("division by zero");
+ $$ = $1 / $3;
+ }
+ | expr ARITH_REM expr {
+ if ($3 == 0)
+ yyerror("division by zero");
+ $$ = $1 % $3;
+ }
+ | ARITH_NOT expr { $$ = !($2); }
+ | ARITH_BNOT expr { $$ = ~($2); }
+ | ARITH_SUB expr %prec ARITH_UNARYMINUS { $$ = -($2); }
+ | ARITH_ADD expr %prec ARITH_UNARYPLUS { $$ = $2; }
+ | ARITH_NUM
+ ;
+%%
+int
+arith(s)
+ const char *s;
+{
+ long result;
+
+ arith_buf = arith_startbuf = s;
+
+ INTOFF;
+ result = yyparse();
+ arith_lex_reset(); /* reprime lex */
+ INTON;
+
+ return (result);
+}
+
+
+/*
+ * The exp(1) builtin.
+ */
+int
+expcmd(argc, argv)
+ int argc;
+ char **argv;
+{
+ const char *p;
+ char *concat;
+ char **ap;
+ long i;
+
+ if (argc > 1) {
+ p = argv[1];
+ if (argc > 2) {
+ /*
+ * concatenate arguments
+ */
+ STARTSTACKSTR(concat);
+ ap = argv + 2;
+ for (;;) {
+ while (*p)
+ STPUTC(*p++, concat);
+ if ((p = *ap++) == NULL)
+ break;
+ STPUTC(' ', concat);
+ }
+ STPUTC('\0', concat);
+ p = grabstackstr(concat);
+ }
+ } else
+ p = "";
+
+ i = arith(p);
+
+ out1fmt("%ld\n", i);
+ return (! i);
+}
+
+/*************************/
+#ifdef TEST_ARITH
+#include <stdio.h>
+main(argc, argv)
+ char *argv[];
+{
+ printf("%d\n", exp(argv[1]));
+}
+error(s)
+ char *s;
+{
+ fprintf(stderr, "exp: %s\n", s);
+ exit(1);
+}
+#endif
+
+void
+yyerror(s)
+ const char *s;
+{
+
+// yyerrok;
+ yyclearin;
+ arith_lex_reset(); /* reprime lex */
+ error("arithmetic expression: %s: \"%s\"", s, arith_startbuf);
+ /* NOTREACHED */
+}