util-linux/more.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini more implementation for busybox
   4  *
   5  * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
   6  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   7  *
   8  * Latest version blended together by Erik Andersen <andersen@codepoet.org>,
   9  * based on the original more implementation by Bruce, and code from the
  10  * Debian boot-floppies team.
  11  *
  12  * Termios corrects by Vladimir Oleynik <dzo@simtreas.ru>
  13  *
  14  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  15  */
  16
  17 #include "libbb.h"
  18
  19 /* Support for FEATURE_USE_TERMIOS */
  20
  21 struct globals {
  22         int cin_fileno;
  23         struct termios initial_settings;
  24         struct termios new_settings;
  25 } FIX_ALIASING;
  26 #define G (*(struct globals*)bb_common_bufsiz1)
  27 #define INIT_G() ((void)0)
  28 #define initial_settings (G.initial_settings)
  29 #define new_settings     (G.new_settings    )
  30 #define cin_fileno       (G.cin_fileno      )
  31
  32 #define setTermSettings(fd, argp) \
  33 do { \
  34         if (ENABLE_FEATURE_USE_TERMIOS) \
  35                 tcsetattr(fd, TCSANOW, argp); \
  36 } while (0)
  37 #define getTermSettings(fd, argp) tcgetattr(fd, argp)
  38
  39 static void gotsig(int sig UNUSED_PARAM)
  40 {
  41         /* bb_putchar_stderr doesn't use stdio buffering,
  42          * therefore it is safe in signal handler */
  43         bb_putchar_stderr('\n');
  44         setTermSettings(cin_fileno, &initial_settings);
  45         _exit(EXIT_FAILURE);
  46 }
  47
  48 #define CONVERTED_TAB_SIZE 8
  49
  50 int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  51 int more_main(int argc UNUSED_PARAM, char **argv)
  52 {
  53         int c = c; /* for compiler */
  54         int lines;
  55         int input = 0;
  56         int spaces = 0;
  57         int please_display_more_prompt;
  58         struct stat st;
  59         FILE *file;
  60         FILE *cin;
  61         int len;
  62         unsigned terminal_width;
  63         unsigned terminal_height;
  64
  65         INIT_G();
  66
  67         argv++;
  68         /* Another popular pager, most, detects when stdout
  69          * is not a tty and turns into cat. This makes sense. */
  70         if (!isatty(STDOUT_FILENO))
  71                 return bb_cat(argv);
  72         cin = fopen_for_read(CURRENT_TTY);
  73         if (!cin)
  74                 return bb_cat(argv);
  75
  76         if (ENABLE_FEATURE_USE_TERMIOS) {
  77                 cin_fileno = fileno(cin);
  78                 getTermSettings(cin_fileno, &initial_settings);
  79                 new_settings = initial_settings;
  80                 new_settings.c_lflag &= ~ICANON;
  81                 new_settings.c_lflag &= ~ECHO;
  82                 new_settings.c_cc[VMIN] = 1;
  83                 new_settings.c_cc[VTIME] = 0;
  84                 setTermSettings(cin_fileno, &new_settings);
  85                 bb_signals(0
  86                         + (1 << SIGINT)
  87                         + (1 << SIGQUIT)
  88                         + (1 << SIGTERM)
  89                         , gotsig);
  90         }
  91
  92         do {
  93                 file = stdin;
  94                 if (*argv) {
  95                         file = fopen_or_warn(*argv, "r");
  96                         if (!file)
  97                                 continue;
  98                 }
  99                 st.st_size = 0;
 100                 fstat(fileno(file), &st);
 101
 102                 please_display_more_prompt = 0;
 103                 /* never returns w, h <= 1 */
 104                 get_terminal_width_height(fileno(cin), &terminal_width, &terminal_height);
 105                 terminal_height -= 1;
 106
 107                 len = 0;
 108                 lines = 0;
 109                 while (spaces || (c = getc(file)) != EOF) {
 110                         int wrap;
 111                         if (spaces)
 112                                 spaces--;
 113  loop_top:
 114                         if (input != 'r' && please_display_more_prompt) {
 115                                 len = printf("--More-- ");
 116                                 if (st.st_size != 0) {
 117                                         uoff_t d = (uoff_t)st.st_size / 100;
 118                                         if (d == 0)
 119                                                 d = 1;
 120                                         len += printf("(%u%% of %"OFF_FMT"u bytes)",
 121                                                 (int) ((uoff_t)ftello(file) / d),
 122                                                 st.st_size);
 123                                 }
 124                                 fflush_all();
 125
 126                                 /*
 127                                  * We've just displayed the "--More--" prompt, so now we need
 128                                  * to get input from the user.
 129                                  */
 130                                 for (;;) {
 131                                         input = getc(cin);
 132                                         input = tolower(input);
 133                                         if (!ENABLE_FEATURE_USE_TERMIOS)
 134                                                 printf("\033[A"); /* cursor up */
 135                                         /* Erase the last message */
 136                                         printf("\r%*s\r", len, "");
 137
 138                                         /* Due to various multibyte escape
 139                                          * sequences, it's not ok to accept
 140                                          * any input as a command to scroll
 141                                          * the screen. We only allow known
 142                                          * commands, else we show help msg. */
 143                                         if (input == ' ' || input == '\n' || input == 'q' || input == 'r')
 144                                                 break;
 145                                         len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
 146                                 }
 147                                 len = 0;
 148                                 lines = 0;
 149                                 please_display_more_prompt = 0;
 150
 151                                 if (input == 'q')
 152                                         goto end;
 153
 154                                 /* The user may have resized the terminal.
 155                                  * Re-read the dimensions. */
 156                                 if (ENABLE_FEATURE_USE_TERMIOS) {
 157                                         get_terminal_width_height(cin_fileno, &terminal_width, &terminal_height);
 158                                         terminal_height -= 1;
 159                                 }
 160                         }
 161
 162                         /* Crudely convert tabs into spaces, which are
 163                          * a bajillion times easier to deal with. */
 164                         if (c == '\t') {
 165                                 spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
 166                                 c = ' ';
 167                         }
 168
 169                         /*
 170                          * There are two input streams to worry about here:
 171                          *
 172                          * c    : the character we are reading from the file being "mored"
 173                          * input: a character received from the keyboard
 174                          *
 175                          * If we hit a newline in the _file_ stream, we want to test and
 176                          * see if any characters have been hit in the _input_ stream. This
 177                          * allows the user to quit while in the middle of a file.
 178                          */
 179                         wrap = (++len > terminal_width);
 180                         if (c == '\n' || wrap) {
 181                                 /* Then outputting this character
 182                                  * will move us to a new line. */
 183                                 if (++lines >= terminal_height || input == '\n')
 184                                         please_display_more_prompt = 1;
 185                                 len = 0;
 186                         }
 187                         if (c != '\n' && wrap) {
 188                                 /* Then outputting this will also put a character on
 189                                  * the beginning of that new line. Thus we first want to
 190                                  * display the prompt (if any), so we skip the putchar()
 191                                  * and go back to the top of the loop, without reading
 192                                  * a new character. */
 193                                 goto loop_top;
 194                         }
 195                         /* My small mind cannot fathom backspaces and UTF-8 */
 196                         putchar(c);
 197                         die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
 198                 }
 199                 fclose(file);
 200                 fflush_all();
 201         } while (*argv && *++argv);
 202  end:
 203         setTermSettings(cin_fileno, &initial_settings);
 204         return 0;
 205 }