commands/screendump/screendump.c

   1 /*      screendump 1.2 - dump the contents of the console
   2  *                                                      Author: Kees J. Bot
   3  *                                                              16 Dec 1994
   4  */
   5 #define nil 0
   6 #include <sys/types.h>
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <errno.h>
  10 #include <fcntl.h>
  11 #include <string.h>
  12 #include <termios.h>
  13 #include <sys/ioctl.h>
  14
  15 #define BIOS_CRTBASE    0x00463L        /* BIOS parameters: CRT base. */
  16 #define CRTBASE_MONO    0x03B4          /* Value of CRT base for mono mode. */
  17
  18 #define MONO_BASE       0xB0000L        /* Screen memory in monochrome mode. */
  19 #define COLOR_BASE      0xB8000L        /* ... colour mode. */
  20
  21 #define DEF_COLS        80              /* Default screen geometry. */
  22 #define DEF_ROWS        25
  23
  24 #define MAX_COLS        132             /* Maximum screen geometry. */
  25 #define MAX_ROWS        60
  26
  27 char MEMORY[] =         "/dev/mem";     /* Memory device to read screen. */
  28 int mfd;                                /* Open memory device. */
  29
  30 void tell(const char *message)
  31 {
  32         write(2, message, strlen(message));
  33 }
  34
  35 void fatal(const char *label)
  36 {
  37         const char *err= strerror(errno);
  38
  39         tell("screendump: ");
  40         tell(label);
  41         tell(": ");
  42         tell(err);
  43         tell("\n");
  44         exit(1);
  45 }
  46
  47 long video_base(void)
  48 /* Is it monochrome or colour? */
  49 {
  50         static unsigned short bios_crtbase;
  51
  52         if (lseek(mfd, (off_t) BIOS_CRTBASE, SEEK_SET) == -1) fatal(MEMORY);
  53         switch (read(mfd, &bios_crtbase, sizeof(bios_crtbase))) {
  54         case -1:
  55                 fatal(MEMORY);
  56         default:
  57                 tell("screendump: can't obtain BIOS parameter: short read\n");
  58                 exit(1);
  59         case sizeof(bios_crtbase):
  60                 /* Fine */;
  61         }
  62
  63         return bios_crtbase == CRTBASE_MONO ? MONO_BASE : COLOR_BASE;
  64 }
  65
  66 int main(void)
  67 {
  68         static unsigned char screen[MAX_COLS * MAX_ROWS * 2];
  69         unsigned char *ps;
  70         long base;
  71         int lfd;
  72         int row;
  73         int nrows, ncols;
  74         struct winsize winsize;
  75
  76         /* Open the memory device. */
  77         if ((mfd= open(MEMORY, O_RDONLY)) < 0) fatal(MEMORY);
  78
  79         base= video_base();
  80
  81         /* Read screen memory. */
  82         if (lseek(mfd, base, SEEK_SET) == -1) fatal(MEMORY);
  83
  84         switch (read(mfd, screen, sizeof(screen))) {
  85         case -1:
  86                 fatal(MEMORY);
  87         default:
  88                 tell("screendump: can't obtain screen dump: short read\n");
  89                 exit(1);
  90         case sizeof(screen):
  91                 /* Fine */;
  92         }
  93
  94         /* Try to obtain the screen geometry from /dev/log. */
  95         ncols= DEF_COLS;
  96         nrows= DEF_ROWS;
  97         if ((lfd= open("/dev/log", O_WRONLY)) != -1
  98                 && ioctl(lfd, TIOCGWINSZ, &winsize) == 0
  99         ) {
 100                 if (40 <= winsize.ws_col && winsize.ws_col <= MAX_COLS) {
 101                         ncols= winsize.ws_col;
 102                 }
 103                 if (25 <= winsize.ws_row && winsize.ws_row <= MAX_COLS) {
 104                         nrows= winsize.ws_row;
 105                 }
 106         }
 107         if (lfd != -1) close(lfd);
 108
 109         /* Print the contents of the screen line by line.  Omit trailing
 110          * blanks.  Note that screen memory consists of pairs of characters
 111          * and attribute bytes.
 112          */
 113         ps= screen;
 114         for (row= 0; row < nrows; row++) {
 115                 char line[MAX_COLS + 1];
 116                 char *pl= line;
 117                 int column;
 118                 int blanks= 0;
 119
 120                 for (column= 0; column < ncols; column++) {
 121                         if (*ps <= ' ') {
 122                                 /* Skip trailing junk. */
 123                                 blanks++;
 124                         } else {
 125                                 /* Reinsert blanks and add a character. */
 126                                 while (blanks > 0) { *pl++= ' '; blanks--; }
 127                                 *pl++= *ps;
 128                         }
 129                         /* Skip character and attribute byte. */
 130                         ps+= 2;
 131                 }
 132                 *pl++= '\n';
 133                 if (write(1, line, pl - line) < 0) fatal("stdout");
 134         }
 135         exit(0);
 136 }