diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/less-177/ttyin.c

   1 /*
   2  * Routines dealing with getting input from the keyboard (i.e. from the user).
   3  */
   4
   5 #include "less.h"
   6 #if __MSDOS__
   7 #include <io.h>
   8 #include <stdio.h>
   9 #include <fcntl.h>
  10 #include <signal.h>
  11 #endif
  12
  13 static int tty;
  14
  15 /*
  16  * Open keyboard for input.
  17  */
  18         public void
  19 open_getchr()
  20 {
  21 #if __MDDOS__
  22         /*
  23          * Open a new handle to CON: in binary mode
  24          * for unbuffered keyboard read.
  25          */
  26         tty = open("CON", O_RDONLY|O_BINARY);
  27 #else
  28         /*
  29          * Try /dev/tty.
  30          * If that doesn't work, use file descriptor 2,
  31          * which in Unix is usually attached to the screen,
  32          * but also usually lets you read from the keyboard.
  33          */
  34         tty = open("/dev/tty", 0);
  35         if (tty < 0)
  36                 tty = 2;
  37 #endif
  38 }
  39
  40 /*
  41  * Get a character from the keyboard.
  42  */
  43         public int
  44 getchr()
  45 {
  46         char c;
  47         int result;
  48
  49         do
  50         {
  51                 result = iread(tty, &c, sizeof(char));
  52                 if (result == READ_INTR)
  53                         return (READ_INTR);
  54                 if (result < 0)
  55                 {
  56                         /*
  57                          * Don't call error() here,
  58                          * because error calls getchr!
  59                          */
  60                         quit(1);
  61                 }
  62 #if __MSDOS__
  63                 /*
  64                  * In raw read, we don't see ^C so look here for it.
  65                  */
  66                 if (c == '\003')
  67                         raise(SIGINT);
  68 #endif
  69                 /*
  70                  * Various parts of the program cannot handle
  71                  * an input character of '\0'.
  72                  * If a '\0' was actually typed, convert it to '\200' here.
  73                  */
  74                 if (c == '\0')
  75                         c = '\200';
  76         } while (result != 1);
  77
  78         return (c);
  79 }