[Qemu-devel] [PATCH v3] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code

[Qemu-devel] [PATCH v3] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code

[Daniel P. Berrangé]

From: "Daniel P. Berrange" <berrange@redhat.com>

qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
done and thus getchar() will never return the EOF constant. Instead we have to
query the TTY attributes to determine the configured EOF character (usually
Ctrl-D / 0x4), and then explicitly check for that value. This fixes the
regression that prevented Ctrl-D from triggering an exit of qemu-io that has
existed since readline was first added in

  commit 0cf17e181798063c3824c8200ba46f25f54faa1a
  Author: Stefan Hajnoczi <stefanha@redhat.com>
  Date:   Thu Nov 14 11:54:17 2013 +0100

    qemu-io: use readline.c

It also ensures that a newline is printed when exiting, to complete the
line output by the "qemu-io> " prompt.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---

Changed in v3:

 - print newline when exiting

 qemu-io.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/qemu-io.c b/qemu-io.c
index f554ab614b..2c00ea068e 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -11,6 +11,9 @@
 #include "qemu/osdep.h"
 #include <getopt.h>
 #include <libgen.h>
+#ifndef _WIN32
+#include <termios.h>
+#endif
 
 #include "qapi/error.h"
 #include "qemu-io.h"
@@ -42,6 +45,26 @@ static bool imageOpts;
 
 static ReadLineState *readline_state;
 
+static int ttyEOF;
+
+static int get_eof_char(void)
+{
+#ifdef _WIN32
+    return 0x4; /* Ctrl-D */
+#else
+    struct termios tty;
+    if (tcgetattr(STDIN_FILENO, &tty) != 0) {
+        if (errno == ENOTTY) {
+            return 0x0; /* just expect read() == 0 */
+        } else {
+            return 0x4; /* Ctrl-D */
+        }
+    }
+
+    return tty.c_cc[VEOF];
+#endif
+}
+
 static int close_f(BlockBackend *blk, int argc, char **argv)
 {
     blk_unref(qemuio_blk);
@@ -323,7 +346,8 @@ static char *fetchline_readline(void)
     readline_start(readline_state, get_prompt(), 0, readline_func, &line);
     while (!line) {
         int ch = getchar();
-        if (ch == EOF) {
+        if (ttyEOF != 0x0 && ch == ttyEOF) {
+            printf("\n");
             break;
         }
         readline_handle_byte(readline_state, ch);
@@ -593,6 +617,7 @@ int main(int argc, char **argv)
     qemuio_add_command(&close_cmd);
 
     if (isatty(STDIN_FILENO)) {
+        ttyEOF = get_eof_char();
         readline_state = readline_init(readline_printf_func,
                                        readline_flush_func,
                                        NULL,
-- 
2.14.3

Re: [Qemu-devel] [PATCH v3] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code

[Kevin Wolf]

Am 12.02.2018 um 19:48 hat Daniel P. Berrangé geschrieben:
> From: "Daniel P. Berrange" <berrange@redhat.com>
> 
> qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> done and thus getchar() will never return the EOF constant. Instead we have to
> query the TTY attributes to determine the configured EOF character (usually
> Ctrl-D / 0x4), and then explicitly check for that value. This fixes the
> regression that prevented Ctrl-D from triggering an exit of qemu-io that has
> existed since readline was first added in
> 
>   commit 0cf17e181798063c3824c8200ba46f25f54faa1a
>   Author: Stefan Hajnoczi <stefanha@redhat.com>
>   Date:   Thu Nov 14 11:54:17 2013 +0100
> 
>     qemu-io: use readline.c
> 
> It also ensures that a newline is printed when exiting, to complete the
> line output by the "qemu-io> " prompt.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

Thanks, applied to the block branch.

Kevin

Re: [Qemu-devel] [PATCH v3] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code

[Eric Blake]

On 02/12/2018 12:48 PM, Daniel P. Berrangé wrote:
> From: "Daniel P. Berrange" <berrange@redhat.com>
> 
> qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> done and thus getchar() will never return the EOF constant. Instead we have to
> query the TTY attributes to determine the configured EOF character (usually
> Ctrl-D / 0x4), and then explicitly check for that value. This fixes the
> regression that prevented Ctrl-D from triggering an exit of qemu-io that has
> existed since readline was first added in
> 
>    commit 0cf17e181798063c3824c8200ba46f25f54faa1a
>    Author: Stefan Hajnoczi <stefanha@redhat.com>
>    Date:   Thu Nov 14 11:54:17 2013 +0100
> 
>      qemu-io: use readline.c
> 
> It also ensures that a newline is printed when exiting, to complete the
> line output by the "qemu-io> " prompt.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org