Re: Set debug output width in REPL

[Mark H Weaver <mhw@netris.org>]

ludo@gnu.org (Ludovic Courtès) writes:
>> [...] If one wanted to have a port automatically
>> query its terminal for the width, one could either (IIRC) catch the SIGWINCH
>> signalor could call a getenv/tget function before printing a pretty-print or
>> truncated-print.
>
> How about having a per-REPL setting that’s automatically set to the
> terminal’s width by default?
>
> What’s the exact call to get the width?

There's an ioctl (TIOCGWINSZ) that queries the kernel's idea of the
terminal size.  See the autoconf macro AC_HEADER_TIOCGWINSZ and the
gnulib modules winsz-ioctl and winsz-termios.  Search for TIOCGWINSZ and
SIGWINCH in various packages (e.g. openssh and ncurses) to see how they
do it.  This is the rough idea:

AC_CHECK_HEADERS([termios.h])
AC_HEADER_TIOCGWINSZ


#if HAVE_TERMIOS_H
# include <termios.h>
#endif

#if GWINSZ_IN_SYS_IOCTL
# include <sys/ioctl.h>
#endif

#ifdef TIOCGWINSZ
  struct winsize ws;
  if (ioctl(term_file_descriptor, TIOCGWINSZ, &ws) < 0)
    ERROR;
  terminal_width = ws.ws_col;
#endif

Ideally this code would be called not only during initialization, but
also in response to the SIGWINCH signal.

    Best,
     Mark