From 26bb34cf036027dfa22dfae8d8fc2f6bfd6acb75 Mon Sep 17 00:00:00 2001
From: Byron Rakitzis <byron@archone.tamu.edu>
Date: Wed, 27 May 1992 00:00:01 +0100
Subject: release: rc-1.4

---
 execve.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 execve.c

(limited to 'execve.c')

diff --git a/execve.c b/execve.c
new file mode 100644
index 0000000..b21b30c
--- /dev/null
+++ b/execve.c
@@ -0,0 +1,61 @@
+/* execve.c: an execve() for geriatric unices without #! */
+
+/*
+   NOTE: this file depends on a hack in footobar.c which places two free spots before
+   av[][] so that execve does not have to call malloc.
+*/
+
+#include <errno.h>
+#include "rc.h"
+
+#define giveupif(x) { if (x) goto fail; }
+
+extern int my_execve(const char *path, const char **av, const char **ev) {
+	int fd, len, fst, snd, end;
+	bool noarg;
+	char pb[256]; /* arbitrary but generous limit */
+	execve(path, av, ev);
+	if (errno != ENOEXEC)
+		return -1;
+	fd = rc_open(path, rFrom);
+	giveupif(fd < 0);
+	len = read(fd, pb, sizeof pb);
+	close(fd);
+	/* reject scripts which don't begin with #! */
+	giveupif(len <= 0 || pb[0] != '#' || pb[1] != '!');
+	for (fst = 2; fst < len && (pb[fst] == ' ' || pb[fst] == '\t'); fst++)
+		; /* skip leading whitespace */
+	giveupif(fst == len);
+	for (snd = fst; snd < len && pb[snd] != ' ' && pb[snd] != '\t' && pb[snd] != '\n'; snd++)
+		; /* skip first arg */
+	giveupif(snd == len);
+	noarg = (pb[snd] == '\n');
+	pb[snd++] = '\0'; /* null terminate the first arg */
+	if (!noarg) {
+		while (snd < len && (pb[snd] == ' ' || pb[snd] == '\t'))
+			snd++; /* skip whitespace to second arg */
+		giveupif(snd == len);
+		noarg = (pb[snd] == '\n'); /* could have trailing whitespace after only one arg */
+		if (!noarg) {
+			for (end = snd; end < len && pb[end] != ' ' && pb[end] != '\t' && pb[end] != '\n'; end++)
+				; /* skip to the end of the second arg */
+			giveupif(end == len);
+			if (pb[end] == '\n') {
+				pb[end] = '\0'; /* null terminate the first arg */
+			} else {		/* else check for a spurious third arg */
+				pb[end++] = '\0';
+				while (end < len && (pb[end] == ' ' || pb[end] == '\t'))
+					end++;
+				giveupif(end == len || pb[end] != '\n');
+			}
+		}
+	}
+	*av = path;
+	if (!noarg)
+		*--av = pb + snd;
+	*--av = pb + fst;
+	execve(*av, av, ev);
+	return -1;
+fail:	errno = ENOEXEC;
+	return -1;
+}
-- 
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