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 //config:config MORE
  17 //config:       bool "more"
  18 //config:       default y
  19 //config:       help
  20 //config:         more is a simple utility which allows you to read text one screen
  21 //config:         sized page at a time. If you want to read text that is larger than
  22 //config:         the screen, and you are using anything faster than a 300 baud modem,
  23 //config:         you will probably find this utility very helpful. If you don't have
  24 //config:         any need to reading text files, you can leave this disabled.
  25
  26 //applet:IF_MORE(APPLET(more, BB_DIR_BIN, BB_SUID_DROP))
  27
  28 //kbuild:lib-$(CONFIG_MORE) += more.o
  29
  30 //usage:#define more_trivial_usage
  31 //usage:       "[FILE]..."
  32 //usage:#define more_full_usage "\n\n"
  33 //usage:       "View FILE (or stdin) one screenful at a time"
  34 //usage:
  35 //usage:#define more_example_usage
  36 //usage:       "$ dmesg | more\n"
  37
  38 #include "libbb.h"
  39 #include "common_bufsiz.h"
  40
  41 struct globals {
  42         int tty_fileno;
  43         unsigned terminal_width;
  44         unsigned terminal_height;
  45         struct termios initial_settings;
  46         struct termios new_settings;
  47 } FIX_ALIASING;
  48 #define G (*(struct globals*)bb_common_bufsiz1)
  49 #define INIT_G() do { setup_common_bufsiz(); } while (0)
  50
  51 static void get_wh(void)
  52 {
  53         /* never returns w, h <= 1 */
  54         get_terminal_width_height(G.tty_fileno, &G.terminal_width, &G.terminal_height);
  55         G.terminal_height -= 1;
  56 }
  57
  58 static void tcsetattr_tty_TCSANOW(struct termios *settings)
  59 {
  60         tcsetattr(G.tty_fileno, TCSANOW, settings);
  61 }
  62
  63 static void gotsig(int sig UNUSED_PARAM)
  64 {
  65         /* bb_putchar_stderr doesn't use stdio buffering,
  66          * therefore it is safe in signal handler */
  67         bb_putchar_stderr('\n');
  68         tcsetattr_tty_TCSANOW(&G.initial_settings);
  69         _exit(EXIT_FAILURE);
  70 }
  71
  72 #define CONVERTED_TAB_SIZE 8
  73
  74 int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  75 int more_main(int argc UNUSED_PARAM, char **argv)
  76 {
  77         int c = c; /* for compiler */
  78         int input = 0;
  79         int spaces = 0;
  80         int please_display_more_prompt;
  81         FILE *tty;
  82
  83         INIT_G();
  84
  85         /* Parse options */
  86         /* Accepted but ignored: */
  87         /* -d   Display help instead of ringing bell */
  88         /* -f   Count logical lines (IOW: long lines are not folded) */
  89         /* -l   Do not pause after any line containing a ^L (form feed) */
  90         /* -s   Squeeze blank lines into one */
  91         /* -u   Suppress underlining */
  92         getopt32(argv, "dflsu");
  93         argv += optind;
  94
  95         /* Another popular pager, most, detects when stdout
  96          * is not a tty and turns into cat. This makes sense. */
  97         if (!isatty(STDOUT_FILENO))
  98                 return bb_cat(argv);
  99         tty = fopen_for_read(CURRENT_TTY);
 100         if (!tty)
 101                 return bb_cat(argv);
 102
 103         G.tty_fileno = fileno(tty);
 104         tcgetattr(G.tty_fileno, &G.initial_settings);
 105         G.new_settings = G.initial_settings;
 106         G.new_settings.c_lflag &= ~(ICANON | ECHO);
 107         G.new_settings.c_cc[VMIN] = 1;
 108         G.new_settings.c_cc[VTIME] = 0;
 109         tcsetattr_tty_TCSANOW(&G.new_settings);
 110         bb_signals(BB_FATAL_SIGS, gotsig);
 111
 112         do {
 113                 struct stat st;
 114                 FILE *file;
 115                 int len;
 116                 int lines;
 117
 118                 file = stdin;
 119                 if (*argv) {
 120                         file = fopen_or_warn(*argv, "r");
 121                         if (!file)
 122                                 continue;
 123                 }
 124                 st.st_size = 0;
 125                 fstat(fileno(file), &st);
 126
 127                 get_wh();
 128
 129                 please_display_more_prompt = 0;
 130                 len = 0;
 131                 lines = 0;
 132                 for (;;) {
 133                         int wrap;
 134
 135                         if (spaces)
 136                                 spaces--;
 137                         else {
 138                                 c = getc(file);
 139                                 if (c == EOF) break;
 140                         }
 141  loop_top:
 142                         if (input != 'r' && please_display_more_prompt) {
 143                                 len = printf("--More-- ");
 144                                 if (st.st_size != 0) {
 145                                         uoff_t d = (uoff_t)st.st_size / 100;
 146                                         if (d == 0)
 147                                                 d = 1;
 148                                         len += printf("(%u%% of %"OFF_FMT"u bytes)",
 149                                                 (int) ((uoff_t)ftello(file) / d),
 150                                                 st.st_size);
 151                                 }
 152
 153                                 /*
 154                                  * We've just displayed the "--More--" prompt, so now we need
 155                                  * to get input from the user.
 156                                  */
 157                                 for (;;) {
 158                                         fflush_all();
 159                                         input = getc(tty);
 160                                         input = tolower(input);
 161                                         /* Erase the last message */
 162                                         printf("\r%*s\r", len, "");
 163
 164                                         if (input == 'q')
 165                                                 goto end;
 166                                         /* Due to various multibyte escape
 167                                          * sequences, it's not ok to accept
 168                                          * any input as a command to scroll
 169                                          * the screen. We only allow known
 170                                          * commands, else we show help msg. */
 171                                         if (input == ' ' || input == '\n' || input == 'r')
 172                                                 break;
 173                                         len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
 174                                 }
 175                                 len = 0;
 176                                 lines = 0;
 177                                 please_display_more_prompt = 0;
 178
 179                                 /* The user may have resized the terminal.
 180                                  * Re-read the dimensions. */
 181                                 get_wh();
 182                         }
 183
 184                         /* Crudely convert tabs into spaces, which are
 185                          * a bajillion times easier to deal with. */
 186                         if (c == '\t') {
 187                                 spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
 188                                 c = ' ';
 189                         }
 190
 191                         /*
 192                          * There are two input streams to worry about here:
 193                          *
 194                          * c    : the character we are reading from the file being "mored"
 195                          * input: a character received from the keyboard
 196                          *
 197                          * If we hit a newline in the _file_ stream, we want to test and
 198                          * see if any characters have been hit in the _input_ stream. This
 199                          * allows the user to quit while in the middle of a file.
 200                          */
 201                         wrap = (++len > G.terminal_width);
 202                         if (c == '\n' || wrap) {
 203                                 /* Then outputting this character
 204                                  * will move us to a new line. */
 205                                 if (++lines >= G.terminal_height || input == '\n')
 206                                         please_display_more_prompt = 1;
 207                                 len = 0;
 208                         }
 209                         if (c != '\n' && wrap) {
 210                                 /* Then outputting this will also put a character on
 211                                  * the beginning of that new line. Thus we first want to
 212                                  * display the prompt (if any), so we skip the putchar()
 213                                  * and go back to the top of the loop, without reading
 214                                  * a new character. */
 215                                 goto loop_top;
 216                         }
 217                         /* My small mind cannot fathom backspaces and UTF-8 */
 218                         putchar(c);
 219                         die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
 220                 }
 221                 fclose(file);
 222                 fflush_all();
 223         } while (*argv && *++argv);
 224  end:
 225         tcsetattr_tty_TCSANOW(&G.initial_settings);
 226         return 0;
 227 }