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 /* Support for FEATURE_USE_TERMIOS */
  42
  43 struct globals {
  44         int cin_fileno;
  45         struct termios initial_settings;
  46         struct termios new_settings;
  47 } FIX_ALIASING;
  48 #define G (*(struct globals*)bb_common_bufsiz1)
  49 #define initial_settings (G.initial_settings)
  50 #define new_settings     (G.new_settings    )
  51 #define cin_fileno       (G.cin_fileno      )
  52 #define INIT_G() do { setup_common_bufsiz(); } while (0)
  53
  54 #define setTermSettings(fd, argp) \
  55 do { \
  56         if (ENABLE_FEATURE_USE_TERMIOS) \
  57                 tcsetattr(fd, TCSANOW, argp); \
  58 } while (0)
  59 #define getTermSettings(fd, argp) tcgetattr(fd, argp)
  60
  61 static void gotsig(int sig UNUSED_PARAM)
  62 {
  63         /* bb_putchar_stderr doesn't use stdio buffering,
  64          * therefore it is safe in signal handler */
  65         bb_putchar_stderr('\n');
  66         setTermSettings(cin_fileno, &initial_settings);
  67         _exit(EXIT_FAILURE);
  68 }
  69
  70 #define CONVERTED_TAB_SIZE 8
  71
  72 int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  73 int more_main(int argc UNUSED_PARAM, char **argv)
  74 {
  75         int c = c; /* for compiler */
  76         int lines;
  77         int input = 0;
  78         int spaces = 0;
  79         int please_display_more_prompt;
  80         struct stat st;
  81         FILE *file;
  82         FILE *cin;
  83         int len;
  84         unsigned terminal_width;
  85         unsigned terminal_height;
  86
  87         INIT_G();
  88
  89         /* Parse options */
  90         /* Accepted but ignored: */
  91         /* -d   Display help instead of ringing bell is pressed */
  92         /* -f   Count logical lines (IOW: long lines are not folded) */
  93         /* -l   Do not pause after any line containing a ^L (form feed) */
  94         /* -s   Squeeze blank lines into one */
  95         /* -u   Suppress underlining */
  96         getopt32(argv, "dflsu");
  97         argv += optind;
  98
  99         /* Another popular pager, most, detects when stdout
 100          * is not a tty and turns into cat. This makes sense. */
 101         if (!isatty(STDOUT_FILENO))
 102                 return bb_cat(argv);
 103         cin = fopen_for_read(CURRENT_TTY);
 104         if (!cin)
 105                 return bb_cat(argv);
 106
 107         if (ENABLE_FEATURE_USE_TERMIOS) {
 108                 cin_fileno = fileno(cin);
 109                 getTermSettings(cin_fileno, &initial_settings);
 110                 new_settings = initial_settings;
 111                 new_settings.c_lflag &= ~(ICANON | ECHO);
 112                 new_settings.c_cc[VMIN] = 1;
 113                 new_settings.c_cc[VTIME] = 0;
 114                 setTermSettings(cin_fileno, &new_settings);
 115                 bb_signals(0
 116                         + (1 << SIGINT)
 117                         + (1 << SIGQUIT)
 118                         + (1 << SIGTERM)
 119                         , gotsig);
 120         }
 121
 122         do {
 123                 file = stdin;
 124                 if (*argv) {
 125                         file = fopen_or_warn(*argv, "r");
 126                         if (!file)
 127                                 continue;
 128                 }
 129                 st.st_size = 0;
 130                 fstat(fileno(file), &st);
 131
 132                 please_display_more_prompt = 0;
 133                 /* never returns w, h <= 1 */
 134                 get_terminal_width_height(fileno(cin), &terminal_width, &terminal_height);
 135                 terminal_height -= 1;
 136
 137                 len = 0;
 138                 lines = 0;
 139                 while (spaces || (c = getc(file)) != EOF) {
 140                         int wrap;
 141                         if (spaces)
 142                                 spaces--;
 143  loop_top:
 144                         if (input != 'r' && please_display_more_prompt) {
 145                                 len = printf("--More-- ");
 146                                 if (st.st_size != 0) {
 147                                         uoff_t d = (uoff_t)st.st_size / 100;
 148                                         if (d == 0)
 149                                                 d = 1;
 150                                         len += printf("(%u%% of %"OFF_FMT"u bytes)",
 151                                                 (int) ((uoff_t)ftello(file) / d),
 152                                                 st.st_size);
 153                                 }
 154                                 fflush_all();
 155
 156                                 /*
 157                                  * We've just displayed the "--More--" prompt, so now we need
 158                                  * to get input from the user.
 159                                  */
 160                                 for (;;) {
 161                                         input = getc(cin);
 162                                         input = tolower(input);
 163                                         if (!ENABLE_FEATURE_USE_TERMIOS)
 164                                                 printf("\033[A"); /* cursor up */
 165                                         /* Erase the last message */
 166                                         printf("\r%*s\r", len, "");
 167
 168                                         /* Due to various multibyte escape
 169                                          * sequences, it's not ok to accept
 170                                          * any input as a command to scroll
 171                                          * the screen. We only allow known
 172                                          * commands, else we show help msg. */
 173                                         if (input == ' ' || input == '\n' || input == 'q' || input == 'r')
 174                                                 break;
 175                                         len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
 176                                 }
 177                                 len = 0;
 178                                 lines = 0;
 179                                 please_display_more_prompt = 0;
 180
 181                                 if (input == 'q')
 182                                         goto end;
 183
 184                                 /* The user may have resized the terminal.
 185                                  * Re-read the dimensions. */
 186                                 if (ENABLE_FEATURE_USE_TERMIOS) {
 187                                         get_terminal_width_height(cin_fileno, &terminal_width, &terminal_height);
 188                                         terminal_height -= 1;
 189                                 }
 190                         }
 191
 192                         /* Crudely convert tabs into spaces, which are
 193                          * a bajillion times easier to deal with. */
 194                         if (c == '\t') {
 195                                 spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
 196                                 c = ' ';
 197                         }
 198
 199                         /*
 200                          * There are two input streams to worry about here:
 201                          *
 202                          * c    : the character we are reading from the file being "mored"
 203                          * input: a character received from the keyboard
 204                          *
 205                          * If we hit a newline in the _file_ stream, we want to test and
 206                          * see if any characters have been hit in the _input_ stream. This
 207                          * allows the user to quit while in the middle of a file.
 208                          */
 209                         wrap = (++len > terminal_width);
 210                         if (c == '\n' || wrap) {
 211                                 /* Then outputting this character
 212                                  * will move us to a new line. */
 213                                 if (++lines >= terminal_height || input == '\n')
 214                                         please_display_more_prompt = 1;
 215                                 len = 0;
 216                         }
 217                         if (c != '\n' && wrap) {
 218                                 /* Then outputting this will also put a character on
 219                                  * the beginning of that new line. Thus we first want to
 220                                  * display the prompt (if any), so we skip the putchar()
 221                                  * and go back to the top of the loop, without reading
 222                                  * a new character. */
 223                                 goto loop_top;
 224                         }
 225                         /* My small mind cannot fathom backspaces and UTF-8 */
 226                         putchar(c);
 227                         die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
 228                 }
 229                 fclose(file);
 230                 fflush_all();
 231         } while (*argv && *++argv);
 232  end:
 233         setTermSettings(cin_fileno, &initial_settings);
 234         return 0;
 235 }