From 33d44db8f48fc024999b4697e8778ed716a1d9ae Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ungol.org>
Date: Mon, 30 Mar 2020 11:59:37 -0400
Subject: use predictably resettable getopt()

---
 Makefile   |  4 +--
 builtins.c |  4 +--
 getopt.c   | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 sh.h       |  2 ++
 4 files changed, 88 insertions(+), 5 deletions(-)
 create mode 100644 getopt.c

diff --git a/Makefile b/Makefile
index 12f6a23..15f5688 100644
--- a/Makefile
+++ b/Makefile
@@ -12,14 +12,14 @@ SOURCES=alias.c bg.c builtins.c cd.c command.c false.c fc.c fg.c getopts.c \
 	ulimit.c umask.c wait.c \
 	dot.c eval.c exec.c exit.c export.c readonly.c shift.c times.c trap.c \
 	unset.c \
-	interactive.c parse.c init.c
+	interactive.c parse.c init.c getopt.c
 HEADERS=sh.h
 OBJECTS=alias.o bg.o builtins.o cd.o command.o false.o fc.o fg.o getopts.o \
 	hash.o jobs.o kill.o newgrp.o pwd.o read.o set.o main.o true.o type.o \
 	ulimit.o umask.o wait.o \
 	dot.o eval.o exec.o exit.o export.o readonly.o shift.o times.o trap.o \
 	unset.o \
-	interactive.o parse.o init.o \
+	interactive.o parse.o init.o getopt.o \
 	sh.tab.o sh.yy.o
 BUILTINS=alias bg cd command false fc fg getopts jobs kill newgrp pwd read \
 	true ulimit umask unalias wait
diff --git a/builtins.c b/builtins.c
index b98d16e..da39beb 100644
--- a/builtins.c
+++ b/builtins.c
@@ -143,9 +143,7 @@ int sh_builtin(int argc, char *argv[])
 		}
 	}
 
-	optind = 1;
-	opterr = 1;
-	optarg = NULL;
+	optind = 0;
 
 	return m(argc, argv);
 }
diff --git a/getopt.c b/getopt.c
new file mode 100644
index 0000000..5f6baaa
--- /dev/null
+++ b/getopt.c
@@ -0,0 +1,83 @@
+#include <sys/types.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int sh_getopt(int argc, char * const argv[], const char *optstring)
+{
+	static int optchar = 0;
+	char *option = NULL;
+
+	if (optind == 0) {
+		optind = 1;
+		optchar = 0;
+	}
+
+	if (argv[optind] == NULL) {
+		return -1;
+	}
+
+	if (argv[optind][0] != '-') {
+		return -1;
+	}
+
+	if (!strcmp(argv[optind], "-")) {
+		return -1;
+	}
+
+	if (!strcmp(argv[optind], "--")) {
+		optind++;
+		optchar = 0;
+		return -1;
+	}
+
+	if (optchar == 0 && argv[optind][optchar] != '-') {
+		return -1;
+	}
+
+	optchar++;
+
+	if (argv[optind][optchar] == '\0') {
+		optind++;
+		optchar = 0;
+		return getopt(argc, argv, optstring);
+	}
+
+	option = strchr(optstring, argv[optind][optchar]);
+
+	if (!option) {
+		optopt = argv[optind][optchar];
+		if (opterr != 0 && optstring[0] != ':') {
+			fprintf(stderr, "%s: invalid option -%c\n", argv[0],
+			optopt);
+		}
+		return '?';
+	}
+
+	if (option[1] != ':') {
+		return *option;
+	}
+
+	if (argv[optind][optchar + 1] == '\0') {
+		optarg = argv[++optind];
+	} else {
+		optarg = argv[optind] + optchar + 1;
+	}
+
+	optind++;
+	if (optarg == NULL) {
+		optopt = *option;
+		if (opterr != 0 && optstring[0] != ':') {
+			fprintf(stderr, "%s: missing argument to option -%c\n",
+			argv[0], optopt);
+		}
+		return optstring[0] == ':' ? ':' : '?';
+	}
+
+	optchar = 0;
+	return *option;
+}
+
+/*
+POSIX(2)
+*/
diff --git a/sh.h b/sh.h
index 477226d..3479baa 100644
--- a/sh.h
+++ b/sh.h
@@ -70,4 +70,6 @@ void sh_trap(int trapno);
 
 int yyparse(void);
 
+#define getopt sh_getopt
+
 #endif
-- 
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