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