Adding who, chroot, env and split.

Thanks "Galos, David" <galosd83@students.rowan.edu>!

env.c

@@ -0,0 +1,44 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include "util.h"
+
+extern char **environ;
+
+static void usage(void);
+
+int
+main(int argc, char **argv)
+{
+	ARGBEGIN {
+	case 'i':
+		clearenv();
+		break;
+	case 'u':
+		unsetenv(EARGF(usage()));
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	for(; *argv && strchr(*argv, '='); argv++)
+		putenv(*argv);
+
+	if(*argv) {
+		execvp(*argv, argv);
+		enprintf(127-(errno!=EEXIST), "env: '%s':", *argv);
+	}
+
+	while(environ && *environ)
+		printf("%s\n", *environ++);	
+
+	return 0;
+}
+
+void
+usage(void)
+{
+	eprintf("usage: env [-i] [-u name]... [name=value]... [cmd [arg...]]\n");
+}