Initial Spring 2016 commit.

userland/lib/libc/unix/execvp.c

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2013
+ *	The President and Fellows of Harvard College.
+ *
+ * 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 UNIVERSITY 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 UNIVERSITY 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+
+/*
+ * POSIX C function: exec a program on the search path. Tries
+ * execv() repeatedly until one of the choices works.
+ */
+int
+execvp(const char *prog, char *const *args)
+{
+	const char *searchpath, *s, *t;
+	char progpath[PATH_MAX];
+	size_t len;
+
+	if (strchr(prog, '/') != NULL) {
+		execv(prog, args);
+		return -1;
+	}
+
+	searchpath = getenv("PATH");
+	if (searchpath == NULL) {
+		errno = ENOENT;
+		return -1;
+	}
+
+	for (s = searchpath; s != NULL; s = t) {
+		t = strchr(s, ':');
+		if (t != NULL) {
+			len = t - s;
+			/* advance past the colon */
+			t++;
+		}
+		else {
+			len = strlen(s);
+		}
+		if (len == 0) {
+			continue;
+		}
+		if (len >= sizeof(progpath)) {
+			continue;
+		}
+		memcpy(progpath, s, len);
+		snprintf(progpath + len, sizeof(progpath) - len, "/%s", prog);
+		execv(progpath, args);
+		switch (errno) {
+		    case ENOENT:
+		    case ENOTDIR:
+		    case ENOEXEC:
+			/* routine errors, try next dir */
+			break;
+		    default:
+			/* oops, let's fail */
+			return -1;
+		}
+	}
+	errno = ENOENT;
+	return -1;
+}