shell_builtin_read: set cc[VMIN] to 1; lineedit: don't clear c_cc[VINTR]

First change fixes "read -n NUM". Apparently poll() won't report
data availability if cc[VMIN] > 1 until there are at least cc[VMIN] bytes.

function                                             old     new   delta
read_line_input                                     3885    3877      -8
shell_builtin_read                                  1097    1087     -10
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-18)             Total: -18 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/shell/shell_common.c b/shell/shell_common.c
index bbc22ed34..51c92d60e 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -138,7 +138,13 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
                 old_tty = tty;
                 if (nchars) {
                         tty.c_lflag &= ~ICANON;
-                        tty.c_cc[VMIN] = nchars < 256 ? nchars : 255;
+                        // Setting it to more than 1 breaks poll():
+                        // it blocks even if there's data. !??
+                        //tty.c_cc[VMIN] = nchars < 256 ? nchars : 255;
+                        /* reads would block only if < 1 char is available */
+                        tty.c_cc[VMIN] = 1;
+                        /* no timeout (reads block forever) */
+                        tty.c_cc[VTIME] = 0;
                 }
                 if (read_flags & BUILTIN_READ_SILENT) {
                         tty.c_lflag &= ~(ECHO | ECHOK | ECHONL);