Make improvements

- Introduce path module to redbean
- Fix glitch with linenoise printing extra line on eof
- Introduce closefrom() and close_range() system calls
- Make file descriptor closing more secure in pledge.com

libc/calls/closefrom.c

@@ -0,0 +1,60 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/errno.h"
+#include "libc/limits.h"
+#include "libc/sysv/errfuns.h"
+
+/**
+ * Closes extra file descriptors, e.g.
+ *
+ *     // close all non-stdio file descriptors
+ *     if (closefrom(3) == -1) {
+ *       for (int i = 3; i < 256; ++i) {
+ *         close(i);
+ *       }
+ *     }
+ *
+ * @return 0 on success, or -1 w/ errno
+ * @error ENOSYS if not Linux 5.9+ / FreeBSD / OpenBSD
+ * @error EBADF on OpenBSD if `first` is greater than highest fd
+ * @error EINVAL if flags are bad or first is greater than last
+ * @error EMFILE if a weird race condition happens on Linux
+ * @error EINTR possibly on OpenBSD
+ * @error ENOMEM on Linux maybe
+ * @note supported on Linux 5.9+, FreeBSD 8+, and OpenBSD
+ */
+int closefrom(int first) {
+  int rc, err;
+  if (first >= 0) {
+    err = errno;
+    if ((rc = sys_close_range(first, -1, 0)) == -1) {
+      if (errno == ENOSYS) {
+        errno = err;
+        rc = sys_closefrom(first);
+      }
+    }
+  } else {
+    rc = ebadf();
+  }
+  STRACE("closefrom(%d) → %d% m", first, rc);
+  return rc;
+}