console-tools/resize.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * resize - set terminal width and height.
   4  *
   5  * Copyright 2006 Bernhard Reutner-Fischer
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9 //config:config RESIZE
  10 //config:       bool "resize (1.2 kb)"
  11 //config:       default y
  12 //config:       help
  13 //config:       This program is used to (re)set the width and height of your current
  14 //config:       terminal.
  15 //config:
  16 //config:config FEATURE_RESIZE_PRINT
  17 //config:       bool "Print environment variables"
  18 //config:       default y
  19 //config:       depends on RESIZE
  20 //config:       help
  21 //config:       Prints the newly set size (number of columns and rows) of
  22 //config:       the terminal.
  23 //config:       E.g.:
  24 //config:       COLUMNS=80;LINES=44;export COLUMNS LINES;
  25
  26 //applet:IF_RESIZE(APPLET_NOEXEC(resize, resize, BB_DIR_USR_BIN, BB_SUID_DROP, resize))
  27 /* bb_common_bufsiz1 usage here is safe wrt NOEXEC: not expecting it to be zeroed. */
  28
  29 //kbuild:lib-$(CONFIG_RESIZE) += resize.o
  30
  31 //usage:#define resize_trivial_usage
  32 //usage:       ""
  33 //usage:#define resize_full_usage "\n\n"
  34 //usage:       "Resize the screen"
  35
  36 #include "libbb.h"
  37 #include "common_bufsiz.h"
  38
  39 #define ESC "\033"
  40
  41 #define old_termios_p ((struct termios*)bb_common_bufsiz1)
  42 #define INIT_G() do { setup_common_bufsiz(); } while (0)
  43
  44 static void
  45 onintr(int sig UNUSED_PARAM)
  46 {
  47         tcsetattr(STDERR_FILENO, TCSANOW, old_termios_p);
  48         _exit_FAILURE();
  49 }
  50
  51 int resize_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  52 int resize_main(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
  53 {
  54         struct termios new;
  55         struct winsize w = { 0, 0, 0, 0 };
  56         int ret;
  57
  58         INIT_G();
  59
  60         /* We use _stderr_ in order to make resize usable
  61          * in shell backticks (those redirect stdout away from tty).
  62          * NB: other versions of resize open "/dev/tty"
  63          * and operate on it - should we do the same?
  64          */
  65
  66         tcgetattr(STDERR_FILENO, old_termios_p); /* fiddle echo */
  67 //TODO: die if the above fails?
  68         memcpy(&new, old_termios_p, sizeof(new));
  69         new.c_cflag |= (CLOCAL | CREAD);
  70         new.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
  71         bb_signals(0
  72                 + (1 << SIGINT)
  73                 + (1 << SIGQUIT)
  74                 + (1 << SIGTERM)
  75                 + (1 << SIGALRM)
  76                 , onintr);
  77         /* Users report:
  78          *      The resize command messes up the terminal.
  79          *      In my case it looks like it is hanging and
  80          *      I need to press ctrl-c to get a prompt.
  81          *      Actually the program does not hang but just
  82          *      the terminal is messed up.
  83          * Replaced TCSANOW with TCSAFLUSH:
  84          * "the change occurs after all output written to fd
  85          * has been transmitted, and all input that has been
  86          * received but not read will be discarded before
  87          * the change is made.
  88          */
  89         tcsetattr(STDERR_FILENO, TCSAFLUSH, &new);
  90
  91         /* save_cursor_pos 7
  92          * scroll_whole_screen [r
  93          * put_cursor_waaaay_off [$x;$yH
  94          * get_cursor_pos [6n
  95          * restore_cursor_pos 8
  96          */
  97         fprintf(stderr, ESC"7" ESC"[r" ESC"[999;999H" ESC"[6n");
  98         alarm(3); /* Just in case terminal won't answer */
  99 //BUG: death by signal won't restore termios
 100         scanf(ESC"[%hu;%huR", &w.ws_row, &w.ws_col);
 101         fprintf(stderr, ESC"8");
 102
 103         /* BTW, other versions of resize recalculate w.ws_xpixel, ws.ws_ypixel
 104          * by calculating character cell HxW from old values
 105          * (gotten via TIOCGWINSZ) and recomputing *pixel values */
 106         ret = ioctl(STDERR_FILENO, TIOCSWINSZ, &w);
 107
 108         tcsetattr(STDERR_FILENO, TCSANOW, old_termios_p);
 109
 110         if (ENABLE_FEATURE_RESIZE_PRINT)
 111                 printf("COLUMNS=%d;LINES=%d;export COLUMNS LINES;\n",
 112                         w.ws_col, w.ws_row);
 113
 114         return ret;
 115 }