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 //usage:#define more_trivial_usage
  18 //usage:       "[FILE]..."
  19 //usage:#define more_full_usage "\n\n"
  20 //usage:       "View FILE (or stdin) one screenful at a time"
  21 //usage:
  22 //usage:#define more_example_usage
  23 //usage:       "$ dmesg | more\n"
  24
  25 #include "libbb.h"
  26
  27 /* Support for FEATURE_USE_TERMIOS */
  28
  29 struct globals {
  30         int cin_fileno;
  31         struct termios initial_settings;
  32         struct termios new_settings;
  33 } FIX_ALIASING;
  34 #define G (*(struct globals*)bb_common_bufsiz1)
  35 #define INIT_G() ((void)0)
  36 #define initial_settings (G.initial_settings)
  37 #define new_settings     (G.new_settings    )
  38 #define cin_fileno       (G.cin_fileno      )
  39
  40 #define setTermSettings(fd, argp) \
  41 do { \
  42         if (ENABLE_FEATURE_USE_TERMIOS) \
  43                 tcsetattr(fd, TCSANOW, argp); \
  44 } while (0)
  45 #define getTermSettings(fd, argp) tcgetattr(fd, argp)
  46
  47 static void gotsig(int sig UNUSED_PARAM)
  48 {
  49         /* bb_putchar_stderr doesn't use stdio buffering,
  50          * therefore it is safe in signal handler */
  51         bb_putchar_stderr('\n');
  52         setTermSettings(cin_fileno, &initial_settings);
  53         _exit(EXIT_FAILURE);
  54 }
  55
  56 #define CONVERTED_TAB_SIZE 8
  57
  58 int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  59 int more_main(int argc UNUSED_PARAM, char **argv)
  60 {
  61         int c = c; /* for compiler */
  62         int lines;
  63         int input = 0;
  64         int spaces = 0;
  65         int please_display_more_prompt;
  66         struct stat st;
  67         FILE *file;
  68         FILE *cin;
  69         int len;
  70         unsigned terminal_width;
  71         unsigned terminal_height;
  72
  73         INIT_G();
  74
  75         argv++;
  76         /* Another popular pager, most, detects when stdout
  77          * is not a tty and turns into cat. This makes sense. */
  78         if (!isatty(STDOUT_FILENO))
  79                 return bb_cat(argv);
  80         cin = fopen_for_read(CURRENT_TTY);
  81         if (!cin)
  82                 return bb_cat(argv);
  83
  84         if (ENABLE_FEATURE_USE_TERMIOS) {
  85                 cin_fileno = fileno(cin);
  86                 getTermSettings(cin_fileno, &initial_settings);
  87                 new_settings = initial_settings;
  88                 new_settings.c_lflag &= ~(ICANON | ECHO);
  89                 new_settings.c_cc[VMIN] = 1;
  90                 new_settings.c_cc[VTIME] = 0;
  91                 setTermSettings(cin_fileno, &new_settings);
  92                 bb_signals(0
  93                         + (1 << SIGINT)
  94                         + (1 << SIGQUIT)
  95                         + (1 << SIGTERM)
  96                         , gotsig);
  97         }
  98
  99         do {
 100                 file = stdin;
 101                 if (*argv) {
 102                         file = fopen_or_warn(*argv, "r");
 103                         if (!file)
 104                                 continue;
 105                 }
 106                 st.st_size = 0;
 107                 fstat(fileno(file), &st);
 108
 109                 please_display_more_prompt = 0;
 110                 /* never returns w, h <= 1 */
 111                 get_terminal_width_height(fileno(cin), &terminal_width, &terminal_height);
 112                 terminal_height -= 1;
 113
 114                 len = 0;
 115                 lines = 0;
 116                 while (spaces || (c = getc(file)) != EOF) {
 117                         int wrap;
 118                         if (spaces)
 119                                 spaces--;
 120  loop_top:
 121                         if (input != 'r' && please_display_more_prompt) {
 122                                 len = printf("--More-- ");
 123                                 if (st.st_size != 0) {
 124                                         uoff_t d = (uoff_t)st.st_size / 100;
 125                                         if (d == 0)
 126                                                 d = 1;
 127                                         len += printf("(%u%% of %"OFF_FMT"u bytes)",
 128                                                 (int) ((uoff_t)ftello(file) / d),
 129                                                 st.st_size);
 130                                 }
 131                                 fflush_all();
 132
 133                                 /*
 134                                  * We've just displayed the "--More--" prompt, so now we need
 135                                  * to get input from the user.
 136                                  */
 137                                 for (;;) {
 138                                         input = getc(cin);
 139                                         input = tolower(input);
 140                                         if (!ENABLE_FEATURE_USE_TERMIOS)
 141                                                 printf("\033[A"); /* cursor up */
 142                                         /* Erase the last message */
 143                                         printf("\r%*s\r", len, "");
 144
 145                                         /* Due to various multibyte escape
 146                                          * sequences, it's not ok to accept
 147                                          * any input as a command to scroll
 148                                          * the screen. We only allow known
 149                                          * commands, else we show help msg. */
 150                                         if (input == ' ' || input == '\n' || input == 'q' || input == 'r')
 151                                                 break;
 152                                         len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
 153                                 }
 154                                 len = 0;
 155                                 lines = 0;
 156                                 please_display_more_prompt = 0;
 157
 158                                 if (input == 'q')
 159                                         goto end;
 160
 161                                 /* The user may have resized the terminal.
 162                                  * Re-read the dimensions. */
 163                                 if (ENABLE_FEATURE_USE_TERMIOS) {
 164                                         get_terminal_width_height(cin_fileno, &terminal_width, &terminal_height);
 165                                         terminal_height -= 1;
 166                                 }
 167                         }
 168
 169                         /* Crudely convert tabs into spaces, which are
 170                          * a bajillion times easier to deal with. */
 171                         if (c == '\t') {
 172                                 spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
 173                                 c = ' ';
 174                         }
 175
 176                         /*
 177                          * There are two input streams to worry about here:
 178                          *
 179                          * c    : the character we are reading from the file being "mored"
 180                          * input: a character received from the keyboard
 181                          *
 182                          * If we hit a newline in the _file_ stream, we want to test and
 183                          * see if any characters have been hit in the _input_ stream. This
 184                          * allows the user to quit while in the middle of a file.
 185                          */
 186                         wrap = (++len > terminal_width);
 187                         if (c == '\n' || wrap) {
 188                                 /* Then outputting this character
 189                                  * will move us to a new line. */
 190                                 if (++lines >= terminal_height || input == '\n')
 191                                         please_display_more_prompt = 1;
 192                                 len = 0;
 193                         }
 194                         if (c != '\n' && wrap) {
 195                                 /* Then outputting this will also put a character on
 196                                  * the beginning of that new line. Thus we first want to
 197                                  * display the prompt (if any), so we skip the putchar()
 198                                  * and go back to the top of the loop, without reading
 199                                  * a new character. */
 200                                 goto loop_top;
 201                         }
 202                         /* My small mind cannot fathom backspaces and UTF-8 */
 203                         putchar(c);
 204                         die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
 205                 }
 206                 fclose(file);
 207                 fflush_all();
 208         } while (*argv && *++argv);
 209  end:
 210         setTermSettings(cin_fileno, &initial_settings);
 211         return 0;
 212 }