Open /proc/pid/fd/[0-2] in non-blocking mode just in case we might

block in open.

src/ttyname.c

@@ -165,7 +165,7 @@ get_process_ttyname(void)
 	ppid = getppid();
 	for (i = STDIN_FILENO; i < STDERR_FILENO && tty == NULL; i++) {
 	    snprintf(path, sizeof(path), "/proc/%d/fd/%d", (int)ppid, i);
-	    fd = open(path, O_RDONLY|O_NOCTTY, 0);
+	    fd = open(path, O_RDONLY|O_NOCTTY|O_NONBLOCK, 0);
 	    if (fd != -1) {
 		tty = ttyname(fd);
 		close(fd);