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 #include "common_bufsiz.h"
  27
  28 /* Support for FEATURE_USE_TERMIOS */
  29
  30 struct globals {
  31         int cin_fileno;
  32         struct termios initial_settings;
  33         struct termios new_settings;
  34 } FIX_ALIASING;
  35 #define G (*(struct globals*)bb_common_bufsiz1)
  36 #define initial_settings (G.initial_settings)
  37 #define new_settings     (G.new_settings    )
  38 #define cin_fileno       (G.cin_fileno      )
  39 #define INIT_G() do { setup_common_bufsiz(); } while (0)
  40
  41 #define setTermSettings(fd, argp) \
  42 do { \
  43         if (ENABLE_FEATURE_USE_TERMIOS) \
  44                 tcsetattr(fd, TCSANOW, argp); \
  45 } while (0)
  46 #define getTermSettings(fd, argp) tcgetattr(fd, argp)
  47
  48 static void gotsig(int sig UNUSED_PARAM)
  49 {
  50         /* bb_putchar_stderr doesn't use stdio buffering,
  51          * therefore it is safe in signal handler */
  52         bb_putchar_stderr('\n');
  53         setTermSettings(cin_fileno, &initial_settings);
  54         _exit(EXIT_FAILURE);
  55 }
  56
  57 #define CONVERTED_TAB_SIZE 8
  58
  59 int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  60 int more_main(int argc UNUSED_PARAM, char **argv)
  61 {
  62         int c = c; /* for compiler */
  63         int lines;
  64         int input = 0;
  65         int spaces = 0;
  66         int please_display_more_prompt;
  67         struct stat st;
  68         FILE *file;
  69         FILE *cin;
  70         int len;
  71         unsigned terminal_width;
  72         unsigned terminal_height;
  73
  74         INIT_G();
  75
  76         /* Parse options */
  77         /* Accepted but ignored: */
  78         /* -d   Display help instead of ringing bell is pressed */
  79         /* -f   Count logical lines (IOW: long lines are not folded) */
  80         /* -l   Do not pause after any line containing a ^L (form feed) */
  81         /* -s   Squeeze blank lines into one */
  82         /* -u   Suppress underlining */
  83         getopt32(argv, "dflsu");
  84         argv += optind;
  85
  86         /* Another popular pager, most, detects when stdout
  87          * is not a tty and turns into cat. This makes sense. */
  88         if (!isatty(STDOUT_FILENO))
  89                 return bb_cat(argv);
  90         cin = fopen_for_read(CURRENT_TTY);
  91         if (!cin)
  92                 return bb_cat(argv);
  93
  94         if (ENABLE_FEATURE_USE_TERMIOS) {
  95                 cin_fileno = fileno(cin);
  96                 getTermSettings(cin_fileno, &initial_settings);
  97                 new_settings = initial_settings;
  98                 new_settings.c_lflag &= ~(ICANON | ECHO);
  99                 new_settings.c_cc[VMIN] = 1;
 100                 new_settings.c_cc[VTIME] = 0;
 101                 setTermSettings(cin_fileno, &new_settings);
 102                 bb_signals(0
 103                         + (1 << SIGINT)
 104                         + (1 << SIGQUIT)
 105                         + (1 << SIGTERM)
 106                         , gotsig);
 107         }
 108
 109         do {
 110                 file = stdin;
 111                 if (*argv) {
 112                         file = fopen_or_warn(*argv, "r");
 113                         if (!file)
 114                                 continue;
 115                 }
 116                 st.st_size = 0;
 117                 fstat(fileno(file), &st);
 118
 119                 please_display_more_prompt = 0;
 120                 /* never returns w, h <= 1 */
 121                 get_terminal_width_height(fileno(cin), &terminal_width, &terminal_height);
 122                 terminal_height -= 1;
 123
 124                 len = 0;
 125                 lines = 0;
 126                 while (spaces || (c = getc(file)) != EOF) {
 127                         int wrap;
 128                         if (spaces)
 129                                 spaces--;
 130  loop_top:
 131                         if (input != 'r' && please_display_more_prompt) {
 132                                 len = printf("--More-- ");
 133                                 if (st.st_size != 0) {
 134                                         uoff_t d = (uoff_t)st.st_size / 100;
 135                                         if (d == 0)
 136                                                 d = 1;
 137                                         len += printf("(%u%% of %"OFF_FMT"u bytes)",
 138                                                 (int) ((uoff_t)ftello(file) / d),
 139                                                 st.st_size);
 140                                 }
 141                                 fflush_all();
 142
 143                                 /*
 144                                  * We've just displayed the "--More--" prompt, so now we need
 145                                  * to get input from the user.
 146                                  */
 147                                 for (;;) {
 148                                         input = getc(cin);
 149                                         input = tolower(input);
 150                                         if (!ENABLE_FEATURE_USE_TERMIOS)
 151                                                 printf("\033[A"); /* cursor up */
 152                                         /* Erase the last message */
 153                                         printf("\r%*s\r", len, "");
 154
 155                                         /* Due to various multibyte escape
 156                                          * sequences, it's not ok to accept
 157                                          * any input as a command to scroll
 158                                          * the screen. We only allow known
 159                                          * commands, else we show help msg. */
 160                                         if (input == ' ' || input == '\n' || input == 'q' || input == 'r')
 161                                                 break;
 162                                         len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
 163                                 }
 164                                 len = 0;
 165                                 lines = 0;
 166                                 please_display_more_prompt = 0;
 167
 168                                 if (input == 'q')
 169                                         goto end;
 170
 171                                 /* The user may have resized the terminal.
 172                                  * Re-read the dimensions. */
 173                                 if (ENABLE_FEATURE_USE_TERMIOS) {
 174                                         get_terminal_width_height(cin_fileno, &terminal_width, &terminal_height);
 175                                         terminal_height -= 1;
 176                                 }
 177                         }
 178
 179                         /* Crudely convert tabs into spaces, which are
 180                          * a bajillion times easier to deal with. */
 181                         if (c == '\t') {
 182                                 spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
 183                                 c = ' ';
 184                         }
 185
 186                         /*
 187                          * There are two input streams to worry about here:
 188                          *
 189                          * c    : the character we are reading from the file being "mored"
 190                          * input: a character received from the keyboard
 191                          *
 192                          * If we hit a newline in the _file_ stream, we want to test and
 193                          * see if any characters have been hit in the _input_ stream. This
 194                          * allows the user to quit while in the middle of a file.
 195                          */
 196                         wrap = (++len > terminal_width);
 197                         if (c == '\n' || wrap) {
 198                                 /* Then outputting this character
 199                                  * will move us to a new line. */
 200                                 if (++lines >= terminal_height || input == '\n')
 201                                         please_display_more_prompt = 1;
 202                                 len = 0;
 203                         }
 204                         if (c != '\n' && wrap) {
 205                                 /* Then outputting this will also put a character on
 206                                  * the beginning of that new line. Thus we first want to
 207                                  * display the prompt (if any), so we skip the putchar()
 208                                  * and go back to the top of the loop, without reading
 209                                  * a new character. */
 210                                 goto loop_top;
 211                         }
 212                         /* My small mind cannot fathom backspaces and UTF-8 */
 213                         putchar(c);
 214                         die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
 215                 }
 216                 fclose(file);
 217                 fflush_all();
 218         } while (*argv && *++argv);
 219  end:
 220         setTermSettings(cin_fileno, &initial_settings);
 221         return 0;
 222 }