less: fall back to using fd #1 for keyboard reading. Closes 9231

function old new delta less_main 2535 2540 +5 Signed-off-by: Denys Vlasenko <[email protected]>
mirror · Sep 13, 2016 · 3c0e579 · 3c0e579
1 parent 20a3262
commit 3c0e579
Showing 1 changed file with 12 additions and 4 deletions.
diff --git a/miscutils/less.c b/miscutils/less.c
@@ -1797,9 +1797,10 @@ int less_main(int argc, char **argv)
  /* Some versions of less can survive w/o controlling tty,
  * try to do the same. This also allows to specify an alternative
  * tty via "less 1<>TTY".
- * We don't try to use STDOUT_FILENO directly,
+ *
+ * We prefer not to use STDOUT_FILENO directly,
  * since we want to set this fd to non-blocking mode,
- * and not bother with restoring it on exit.
+ * and not interfere with other processes which share stdout with us.
  */
  tty_name = xmalloc_ttyname(STDOUT_FILENO);
  if (tty_name) {
@@ -1811,8 +1812,15 @@ int less_main(int argc, char **argv)
  /* Try controlling tty */
  try_ctty:
  tty_fd = open(CURRENT_TTY, O_RDONLY);
- if (tty_fd < 0)
- return bb_cat(argv);
+ if (tty_fd < 0) {
+ /*
+ * If all else fails, less 481 uses stdout. Mimic that.
+ * Testcase where usually both ttyname(STDOUT_FILENO)
+ * and open(CURRENT_TTY) fail:
+ * su -s /bin/sh -c 'busybox less FILE' - nobody
+ */
+ tty_fd = STDOUT_FILENO;
+ }
  }
  ndelay_on(tty_fd);
  kbd_fd = tty_fd; /* save in a global */