CLI output pager

Buffers output from CLI commands as it arrives and allows the terminal to
view this buffer one page at a time.

- View of the buffer is moved with space/enter/up/down/page-up/page-down/
  home/end.
- At the end of the CLI command if less than one page of output was
  generated then the pager is not engaged.
- 'q' to quit the pager, or scroll off the bottom.
- Pager prompt displays the current view aperture line numbers and total
  number of lines buffered.
- Can be disabled at runtime with "no-cli-pager" in the unix configuration.
- The number of lines that will be stored in the buffer is limited to
  prevent excessive memory use; this limit is configurable with
  "cli-pager-buffer-limit" in the unix configuration.
- Both these options can also be set in the console with "set terminal
  pager [on|off] [limit <lines>]".

Limitations:
- Does not yet implement a search function.
- Whilst the terminal size is detected and tracked, changing the terminal
  size when the pager is being used will not cause a redraw of the page.
- Lines that wrap the right most column are not yet handled gracefully.

Change-Id: I69548c1464eff79c53e122668f25758266daf1c2
Signed-off-by: Chris Luke <chrisy@flirble.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/vlib/vlib/unix/unix.h b/vlib/vlib/unix/unix.h
index 20aec675ee0..2922b4e2a68 100644
--- a/vlib/vlib/unix/unix.h
+++ b/vlib/vlib/unix/unix.h
@@ -113,6 +113,12 @@ typedef struct {
   /* Suppress the welcome banner at CLI session start */
   int cli_no_banner;
 
+  /* Maximum pager buffer size */
+  u32 cli_pager_buffer_limit;
+
+  /* Suppress the pager */
+  int cli_no_pager;
+
   /* Store the original state of stdin when it's a tty */
   struct termios tio_stdin;
   int tio_isset;