1 /* vi: set sw=4 ts=4: */
3 * Mini less implementation for busybox
5 * Copyright (C) 2005 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
12 * - Add more regular expression support - search modifiers, certain matches, etc.
13 * - Add more complex bracket searching - currently, nested brackets are
15 * - Add support for "F" as an input. This causes less to act in
16 * a similar way to tail -f.
17 * - Allow horizontal scrolling.
20 * - the inp file pointer is used so that keyboard input works after
21 * redirected input has been read from stdin
28 //config: 'less' is a pager, meaning that it displays text files. It possesses
29 //config: a wide array of features, and is an improvement over 'more'.
31 //config:config FEATURE_LESS_MAXLINES
32 //config: int "Max number of input lines less will try to eat"
33 //config: default 9999999
34 //config: depends on LESS
36 //config:config FEATURE_LESS_BRACKETS
37 //config: bool "Enable bracket searching"
39 //config: depends on LESS
41 //config: This option adds the capability to search for matching left and right
42 //config: brackets, facilitating programming.
44 //config:config FEATURE_LESS_FLAGS
45 //config: bool "Enable -m/-M"
47 //config: depends on LESS
49 //config: The -M/-m flag enables a more sophisticated status line.
51 //config:config FEATURE_LESS_TRUNCATE
52 //config: bool "Enable -S"
54 //config: depends on LESS
56 //config: The -S flag causes long lines to be truncated rather than
59 //config:config FEATURE_LESS_MARKS
60 //config: bool "Enable marks"
62 //config: depends on LESS
64 //config: Marks enable positions in a file to be stored for easy reference.
66 //config:config FEATURE_LESS_REGEXP
67 //config: bool "Enable regular expressions"
69 //config: depends on LESS
71 //config: Enable regular expressions, allowing complex file searches.
73 //config:config FEATURE_LESS_WINCH
74 //config: bool "Enable automatic resizing on window size changes"
76 //config: depends on LESS
78 //config: Makes less track window size changes.
80 //config:config FEATURE_LESS_ASK_TERMINAL
81 //config: bool "Use 'tell me cursor position' ESC sequence to measure window"
83 //config: depends on FEATURE_LESS_WINCH
85 //config: Makes less track window size changes.
86 //config: If terminal size can't be retrieved and $LINES/$COLUMNS are not set,
87 //config: this option makes less perform a last-ditch effort to find it:
88 //config: position cursor to 999,999 and ask terminal to report real
89 //config: cursor position using "ESC [ 6 n" escape sequence, then read stdin.
90 //config: This is not clean but helps a lot on serial lines and such.
92 //config:config FEATURE_LESS_DASHCMD
93 //config: bool "Enable flag changes ('-' command)"
95 //config: depends on LESS
97 //config: This enables the ability to change command-line flags within
98 //config: less itself ('-' keyboard command).
100 //config:config FEATURE_LESS_LINENUMS
101 //config: bool "Enable -N (dynamic switching of line numbers)"
103 //config: depends on FEATURE_LESS_DASHCMD
105 //applet:IF_LESS(APPLET(less, BB_DIR_USR_BIN, BB_SUID_DROP))
107 //kbuild:lib-$(CONFIG_LESS) += less.o
109 //usage:#define less_trivial_usage
110 //usage: "[-E" IF_FEATURE_LESS_REGEXP("I")IF_FEATURE_LESS_FLAGS("Mm")
111 //usage: "N" IF_FEATURE_LESS_TRUNCATE("S") "h~] [FILE]..."
112 //usage:#define less_full_usage "\n\n"
113 //usage: "View FILE (or stdin) one screenful at a time\n"
114 //usage: "\n -E Quit once the end of a file is reached"
115 //usage: IF_FEATURE_LESS_REGEXP(
116 //usage: "\n -I Ignore case in all searches"
118 //usage: IF_FEATURE_LESS_FLAGS(
119 //usage: "\n -M,-m Display status line with line numbers"
120 //usage: "\n and percentage through the file"
122 //usage: "\n -N Prefix line number to each line"
123 //usage: IF_FEATURE_LESS_TRUNCATE(
124 //usage: "\n -S Truncate long lines"
126 //usage: "\n -~ Suppress ~s displayed past EOF"
128 #include <sched.h> /* sched_yield() */
131 #include "common_bufsiz.h"
132 #if ENABLE_FEATURE_LESS_REGEXP
138 /* The escape codes for highlighted and normal text */
139 #define HIGHLIGHT ESC"[7m"
140 #define NORMAL ESC"[0m"
141 /* The escape code to home and clear to the end of screen */
142 #define CLEAR ESC"[H\033[J"
143 /* The escape code to clear to the end of line */
144 #define CLEAR_2_EOL ESC"[K"
147 /* Absolute max of lines eaten */
148 MAXLINES = CONFIG_FEATURE_LESS_MAXLINES,
149 /* This many "after the end" lines we will show (at max) */
153 /* Command line options */
161 FLAG_S = (1 << 6) * ENABLE_FEATURE_LESS_TRUNCATE,
162 /* hijack command line options variable for internal state vars */
163 LESS_STATE_MATCH_BACKWARDS = 1 << 15,
166 #if !ENABLE_FEATURE_LESS_REGEXP
167 enum { pattern_valid = 0 };
171 int cur_fline; /* signed */
172 int kbd_fd; /* fd to get input from */
173 int kbd_fd_orig_flags;
175 /* last position in last line, taking into account tabs */
176 size_t last_line_pos;
178 unsigned max_lineno; /* this one tracks linewrap */
179 unsigned max_displayed_line;
181 #if ENABLE_FEATURE_LESS_WINCH
182 unsigned winch_counter;
184 ssize_t eof_error; /* eof if 0, error if < 0 */
186 ssize_t readeof; /* must be signed */
189 const char *empty_line_marker;
191 unsigned current_file;
194 #if ENABLE_FEATURE_LESS_FLAGS
195 int num_lines; /* a flag if < 0, line count if >= 0 */
196 # define REOPEN_AND_COUNT (-1)
197 # define REOPEN_STDIN (-2)
198 # define NOT_REGULAR_FILE (-3)
200 #if ENABLE_FEATURE_LESS_MARKS
202 unsigned mark_lines[15][2];
204 #if ENABLE_FEATURE_LESS_REGEXP
205 unsigned *match_lines;
206 int match_pos; /* signed! */
207 int wanted_match; /* signed! */
210 smallint pattern_valid;
212 #if ENABLE_FEATURE_LESS_ASK_TERMINAL
213 smallint winsize_err;
216 struct termios term_orig, term_less;
217 char kbd_input[KEYCODE_BUFFER_SIZE];
219 #define G (*ptr_to_globals)
220 #define cur_fline (G.cur_fline )
221 #define kbd_fd (G.kbd_fd )
222 #define less_gets_pos (G.less_gets_pos )
223 #define last_line_pos (G.last_line_pos )
224 #define max_fline (G.max_fline )
225 #define max_lineno (G.max_lineno )
226 #define max_displayed_line (G.max_displayed_line)
227 #define width (G.width )
228 #define winch_counter (G.winch_counter )
229 /* This one is 100% not cached by compiler on read access */
230 #define WINCH_COUNTER (*(volatile unsigned *)&winch_counter)
231 #define eof_error (G.eof_error )
232 #define readpos (G.readpos )
233 #define readeof (G.readeof )
234 #define buffer (G.buffer )
235 #define flines (G.flines )
236 #define empty_line_marker (G.empty_line_marker )
237 #define num_files (G.num_files )
238 #define current_file (G.current_file )
239 #define filename (G.filename )
240 #define files (G.files )
241 #define num_lines (G.num_lines )
242 #define num_marks (G.num_marks )
243 #define mark_lines (G.mark_lines )
244 #if ENABLE_FEATURE_LESS_REGEXP
245 #define match_lines (G.match_lines )
246 #define match_pos (G.match_pos )
247 #define num_matches (G.num_matches )
248 #define wanted_match (G.wanted_match )
249 #define pattern (G.pattern )
250 #define pattern_valid (G.pattern_valid )
252 #define terminated (G.terminated )
253 #define term_orig (G.term_orig )
254 #define term_less (G.term_less )
255 #define kbd_input (G.kbd_input )
256 #define INIT_G() do { \
257 SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
258 less_gets_pos = -1; \
259 empty_line_marker = "~"; \
264 IF_FEATURE_LESS_REGEXP(wanted_match = -1;) \
267 /* flines[] are lines read from stdin, each in malloc'ed buffer.
268 * Line numbers are stored as uint32_t prepended to each line.
269 * Pointer is adjusted so that flines[i] points directly past
270 * line number. Accesor: */
271 #define MEMPTR(p) ((char*)(p) - 4)
272 #define LINENO(p) (*(uint32_t*)((p) - 4))
275 /* Reset terminal input to normal */
276 static void set_tty_cooked(void)
279 tcsetattr(kbd_fd, TCSANOW, &term_orig);
282 /* Move the cursor to a position (x,y), where (0,0) is the
283 top-left corner of the console */
284 static void move_cursor(int line, int row)
286 printf(ESC"[%u;%uH", line, row);
289 static void clear_line(void)
291 printf(ESC"[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
294 static void print_hilite(const char *str)
296 printf(HIGHLIGHT"%s"NORMAL, str);
299 static void print_statusline(const char *str)
302 printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
305 /* Exit the program gracefully */
306 static void less_exit(int code)
309 if (!(G.kbd_fd_orig_flags & O_NONBLOCK))
313 kill_myself_with_sig(- code); /* does not return */
317 #if (ENABLE_FEATURE_LESS_DASHCMD && ENABLE_FEATURE_LESS_LINENUMS) \
318 || ENABLE_FEATURE_LESS_WINCH
319 static void re_wrap(void)
325 int new_cur_fline = 0;
328 const char **old_flines = flines;
330 char **new_flines = NULL;
333 if (option_mask32 & FLAG_N)
346 if (*d == '\t') { /* tab */
348 new_line_pos &= (~7);
352 if (new_line_pos >= w) {
354 /* new line is full, create next one */
357 sz = (d - linebuf) + 1; /* + 1: NUL */
358 d = ((char*)xmalloc(sz + 4)) + 4;
360 memcpy(d, linebuf, sz);
361 new_flines = xrealloc_vector(new_flines, 8, dst_idx);
362 new_flines[dst_idx] = d;
364 if (new_line_pos < w) {
365 /* if we came here thru "goto next_new" */
366 if (src_idx > max_fline)
375 /* *d == NUL: old line ended, go to next old one */
376 free(MEMPTR(old_flines[src_idx]));
377 /* btw, convert cur_fline... */
378 if (cur_fline == src_idx)
379 new_cur_fline = dst_idx;
381 /* no more lines? finish last new line (and exit the loop) */
382 if (src_idx > max_fline)
384 s = old_flines[src_idx];
385 if (lineno != LINENO(s)) {
386 /* this is not a continuation line!
387 * create next _new_ line too */
393 flines = (const char **)new_flines;
395 max_fline = dst_idx - 1;
396 last_line_pos = new_line_pos;
397 cur_fline = new_cur_fline;
398 /* max_lineno is screen-size independent */
399 #if ENABLE_FEATURE_LESS_REGEXP
405 #if ENABLE_FEATURE_LESS_REGEXP
406 static void fill_match_lines(unsigned pos);
408 #define fill_match_lines(pos) ((void)0)
411 static int at_end(void)
413 return (option_mask32 & FLAG_S)
414 ? !(cur_fline <= max_fline &&
415 max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
416 : !(max_fline > cur_fline + max_displayed_line);
419 /* Devilishly complex routine.
421 * Has to deal with EOF and EPIPE on input,
422 * with line wrapping, with last line not ending in '\n'
423 * (possibly not ending YET!), with backspace and tabs.
424 * It reads input again if last time we got an EOF (thus supporting
425 * growing files) or EPIPE (watching output of slow process like make).
428 * flines[] - array of lines already read. Linewrap may cause
429 * one source file line to occupy several flines[n].
430 * flines[max_fline] - last line, possibly incomplete.
431 * terminated - 1 if flines[max_fline] is 'terminated'
432 * (if there was '\n' [which isn't stored itself, we just remember
434 * max_lineno - last line's number, this one doesn't increment
435 * on line wrap, only on "real" new lines.
436 * readbuf[0..readeof-1] - small preliminary buffer.
437 * readbuf[readpos] - next character to add to current line.
438 * last_line_pos - screen line position of next char to be read
439 * (takes into account tabs and backspaces)
440 * eof_error - < 0 error, == 0 EOF, > 0 not EOF/error
442 * "git log -p | less -m" on the kernel git tree is a good test for EAGAINs,
443 * "/search on very long input" and "reaching max line count" corner cases.
445 static void read_lines(void)
447 char *current_line, *p;
449 char last_terminated = terminated;
450 time_t last_time = 0;
451 int retry_EAGAIN = 2;
452 #if ENABLE_FEATURE_LESS_REGEXP
453 unsigned old_max_fline = max_fline;
456 #define readbuf bb_common_bufsiz1
457 setup_common_bufsiz();
459 /* (careful: max_fline can be -1) */
460 if (max_fline + 1 > MAXLINES)
463 if (option_mask32 & FLAG_N)
466 p = current_line = ((char*)xmalloc(w + 5)) + 4;
467 if (!last_terminated) {
468 const char *cp = flines[max_fline];
471 /* last_line_pos is still valid from previous read_lines() */
477 while (1) { /* read lines until we reach cur_fline or wanted_match */
480 while (1) { /* read chars until we have a line */
482 /* if no unprocessed chars left, eat more */
483 if (readpos >= readeof) {
484 int flags = ndelay_on(0);
490 eof_error = safe_read(STDIN_FILENO, readbuf, COMMON_BUFSIZE);
494 if (t != last_time) {
496 if (--retry_EAGAIN < 0)
501 fcntl(0, F_SETFL, flags); /* ndelay_off(0) */
508 c = readbuf[readpos];
509 /* backspace? [needed for manpages] */
510 /* <tab><bs> is (a) insane and */
511 /* (b) harder to do correctly, so we refuse to do it */
512 if (c == '\x8' && last_line_pos && p[-1] != '\t') {
513 readpos++; /* eat it */
515 /* was buggy (p could end up <= current_line)... */
520 size_t new_last_line_pos = last_line_pos + 1;
522 new_last_line_pos += 7;
523 new_last_line_pos &= (~7);
525 if ((int)new_last_line_pos > w)
527 last_line_pos = new_last_line_pos;
529 /* ok, we will eat this char */
536 /* NUL is substituted by '\n'! */
537 if (c == '\0') c = '\n';
540 } /* end of "read chars until we have a line" loop */
542 //BUG: also triggers on this:
543 // { printf "\nfoo\n"; sleep 1; printf "\nbar\n"; } | less
544 // (resulting in lost empty line between "foo" and "bar" lines)
545 // the "terminated" logic needs fixing (or explaining)
546 /* Corner case: linewrap with only "" wrapping to next line */
547 /* Looks ugly on screen, so we do not store this empty line */
548 if (!last_terminated && !current_line[0]) {
555 last_terminated = terminated;
556 flines = xrealloc_vector(flines, 8, max_fline);
558 flines[max_fline] = (char*)xrealloc(MEMPTR(current_line), strlen(current_line) + 1 + 4) + 4;
559 LINENO(flines[max_fline]) = max_lineno;
563 if (max_fline >= MAXLINES) {
564 eof_error = 0; /* Pretend we saw EOF */
568 #if !ENABLE_FEATURE_LESS_REGEXP
571 if (wanted_match >= num_matches) { /* goto_match called us */
572 fill_match_lines(old_max_fline);
573 old_max_fline = max_fline;
575 if (wanted_match < num_matches)
579 if (eof_error <= 0) {
583 current_line = ((char*)xmalloc(w + 5)) + 4;
586 } /* end of "read lines until we reach cur_fline" loop */
589 if (errno == EAGAIN) {
592 print_statusline(bb_msg_read_error);
595 #if ENABLE_FEATURE_LESS_FLAGS
596 else if (eof_error == 0)
597 num_lines = max_lineno;
600 fill_match_lines(old_max_fline);
601 #if ENABLE_FEATURE_LESS_REGEXP
602 /* prevent us from being stuck in search for a match */
608 #if ENABLE_FEATURE_LESS_FLAGS
609 static int safe_lineno(int fline)
611 if (fline >= max_fline)
612 fline = max_fline - 1;
614 /* also catches empty file (max_fline == 0) */
618 return LINENO(flines[fline]) + 1;
621 /* count number of lines in file */
622 static void update_num_lines(void)
629 /* only do this for regular files */
630 if (num_lines == REOPEN_AND_COUNT || num_lines == REOPEN_STDIN) {
632 fd = open("/proc/self/fd/0", O_RDONLY);
633 if (fd < 0 && num_lines == REOPEN_AND_COUNT) {
634 /* "filename" is valid only if REOPEN_AND_COUNT */
635 fd = open(filename, O_RDONLY);
638 /* somebody stole my file! */
639 num_lines = NOT_REGULAR_FILE;
642 if (fstat(fd, &stbuf) != 0 || !S_ISREG(stbuf.st_mode)) {
643 num_lines = NOT_REGULAR_FILE;
646 while ((len = safe_read(fd, buf, sizeof(buf))) > 0) {
647 for (i = 0; i < len; ++i) {
648 if (buf[i] == '\n' && ++count == MAXLINES)
659 /* Print a status line if -M was specified */
660 static void m_status_print(void)
665 if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
669 printf(HIGHLIGHT"%s", filename);
671 printf(" (file %i of %i)", current_file, num_files);
673 first = safe_lineno(cur_fline);
674 last = (option_mask32 & FLAG_S)
675 ? MIN(first + max_displayed_line, max_lineno)
676 : safe_lineno(cur_fline + max_displayed_line);
677 printf(" lines %i-%i", first, last);
681 printf("/%i", num_lines);
685 if (num_files > 1 && current_file != num_files)
686 printf(" - next: %s", files[current_file]);
687 } else if (num_lines > 0) {
688 percent = (100 * last + num_lines/2) / num_lines;
689 printf(" %i%%", percent <= 100 ? percent : 100);
695 /* Print the status line */
696 static void status_print(void)
700 if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
703 /* Change the status if flags have been set */
704 #if ENABLE_FEATURE_LESS_FLAGS
705 if (option_mask32 & (FLAG_M|FLAG_m)) {
713 if (cur_fline && !at_end()) {
721 printf(HIGHLIGHT"%s (file %i of %i)"NORMAL,
722 p, current_file, num_files);
728 static const char controls[] ALIGN1 =
729 /* NUL: never encountered; TAB: not converted */
730 /**/"\x01\x02\x03\x04\x05\x06\x07\x08" "\x0a\x0b\x0c\x0d\x0e\x0f"
731 "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
732 "\x7f\x9b"; /* DEL and infamous Meta-ESC :( */
733 static const char ctrlconv[] ALIGN1 =
734 /* why 40 instead of 4a below? - it is a replacement for '\n'.
735 * '\n' is a former NUL - we subst it with @, not J */
736 "\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x40\x4b\x4c\x4d\x4e\x4f"
737 "\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f";
739 static void print_lineno(const char *line)
741 const char *fmt = " ";
742 unsigned n = n; /* for compiler */
744 if (line != empty_line_marker) {
745 /* Width of 7 preserves tab spacing in the text */
747 n = LINENO(line) + 1;
748 if (n > 9999999 && MAXLINES > 9999999) {
757 #if ENABLE_FEATURE_LESS_REGEXP
758 static void print_found(const char *line)
763 regmatch_t match_structs;
766 const char *str = line;
771 n = strcspn(str, controls);
778 n = strspn(str, controls);
785 /* buf[] holds quarantined version of str */
787 /* Each part of the line that matches has the HIGHLIGHT
788 * and NORMAL escape sequences placed around it.
789 * NB: we regex against line, but insert text
790 * from quarantined copy (buf[]) */
796 while (match_status == 0) {
797 char *new = xasprintf("%s%.*s"HIGHLIGHT"%.*s"NORMAL,
798 growline ? growline : "",
799 (int)match_structs.rm_so, str,
800 (int)(match_structs.rm_eo - match_structs.rm_so),
801 str + match_structs.rm_so);
804 str += match_structs.rm_eo;
805 line += match_structs.rm_eo;
808 /* Most of the time doesn't find the regex, optimize for that */
809 match_status = regexec(&pattern, line, 1, &match_structs, eflags);
810 /* if even "" matches, treat it as "not a match" */
811 if (match_structs.rm_so >= match_structs.rm_eo)
815 printf("%s%s\n", growline ? growline : "", str);
819 void print_found(const char *line);
822 static void print_ascii(const char *str)
829 n = strcspn(str, controls);
832 printf("%.*s", (int) n, str);
835 n = strspn(str, controls);
840 else if (*str == (char)0x9b)
841 /* VT100's CSI, aka Meta-ESC. Who's inventor? */
842 /* I want to know who committed this sin */
845 *p++ = ctrlconv[(unsigned char)*str];
854 /* Print the buffer */
855 static void buffer_print(void)
860 for (i = 0; i <= max_displayed_line; i++) {
862 if (option_mask32 & FLAG_N)
863 print_lineno(buffer[i]);
865 print_found(buffer[i]);
867 print_ascii(buffer[i]);
869 if ((option_mask32 & FLAG_E)
871 && (max_fline - cur_fline) <= max_displayed_line
873 less_exit(EXIT_SUCCESS);
878 static void buffer_fill_and_print(void)
881 #if ENABLE_FEATURE_LESS_TRUNCATE
882 int fpos = cur_fline;
884 if (option_mask32 & FLAG_S) {
885 /* Go back to the beginning of this line */
886 while (fpos && LINENO(flines[fpos]) == LINENO(flines[fpos-1]))
891 while (i <= max_displayed_line && fpos <= max_fline) {
892 int lineno = LINENO(flines[fpos]);
893 buffer[i] = flines[fpos];
897 } while ((fpos <= max_fline)
898 && (option_mask32 & FLAG_S)
899 && lineno == LINENO(flines[fpos])
903 for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
904 buffer[i] = flines[cur_fline + i];
907 for (; i <= max_displayed_line; i++) {
908 buffer[i] = empty_line_marker;
913 /* move cur_fline to a given line number, reading lines if necessary */
914 static void goto_lineno(int target)
919 else if (target > LINENO(flines[cur_fline])) {
921 while (LINENO(flines[cur_fline]) != target && cur_fline < max_fline)
923 /* target not reached but more input is available */
924 if (LINENO(flines[cur_fline]) != target && eof_error > 0) {
930 /* search backwards through already-read lines */
931 while (LINENO(flines[cur_fline]) != target && cur_fline > 0)
936 static void cap_cur_fline(void)
938 if ((option_mask32 & FLAG_S)) {
939 if (cur_fline > max_fline)
940 cur_fline = max_fline;
941 if (LINENO(flines[cur_fline]) + max_displayed_line > max_lineno + TILDES) {
942 goto_lineno(max_lineno - max_displayed_line + TILDES);
947 if (cur_fline + max_displayed_line > max_fline + TILDES)
948 cur_fline = max_fline - max_displayed_line + TILDES;
954 /* Move the buffer up and down in the file in order to scroll */
955 static void buffer_down(int nlines)
957 if ((option_mask32 & FLAG_S))
958 goto_lineno(LINENO(flines[cur_fline]) + nlines);
963 buffer_fill_and_print();
966 static void buffer_up(int nlines)
968 if ((option_mask32 & FLAG_S)) {
969 goto_lineno(LINENO(flines[cur_fline]) - nlines);
977 buffer_fill_and_print();
980 /* display a given line where the argument can be either an index into
981 * the flines array or a line number */
982 static void buffer_to_line(int linenum, int is_lineno)
987 goto_lineno(linenum);
992 buffer_fill_and_print();
995 static void buffer_line(int linenum)
997 buffer_to_line(linenum, FALSE);
1000 static void buffer_lineno(int lineno)
1002 buffer_to_line(lineno, TRUE);
1005 static void open_file_and_read_lines(void)
1008 xmove_fd(xopen(filename, O_RDONLY), STDIN_FILENO);
1009 #if ENABLE_FEATURE_LESS_FLAGS
1010 num_lines = REOPEN_AND_COUNT;
1013 /* "less" with no arguments in argv[] */
1014 /* For status line only */
1015 filename = xstrdup(bb_msg_standard_input);
1016 #if ENABLE_FEATURE_LESS_FLAGS
1017 num_lines = REOPEN_STDIN;
1027 /* Reinitialize everything for a new file - free the memory and start over */
1028 static void reinitialize(void)
1033 for (i = 0; i <= max_fline; i++)
1034 free(MEMPTR(flines[i]));
1042 open_file_and_read_lines();
1043 #if ENABLE_FEATURE_LESS_ASK_TERMINAL
1045 printf("\033[999;999H" "\033[6n");
1047 buffer_fill_and_print();
1050 static int64_t getch_nowait(void)
1054 struct pollfd pfd[2];
1056 pfd[0].fd = STDIN_FILENO;
1057 pfd[0].events = POLLIN;
1059 pfd[1].events = POLLIN;
1061 tcsetattr(kbd_fd, TCSANOW, &term_less);
1062 /* NB: select/poll returns whenever read will not block. Therefore:
1063 * if eof is reached, select/poll will return immediately
1064 * because read will immediately return 0 bytes.
1065 * Even if select/poll says that input is available, read CAN block
1066 * (switch fd into O_NONBLOCK'ed mode to avoid it)
1069 /* Are we interested in stdin? */
1071 if (eof_error > 0) /* did NOT reach eof yet */
1072 rd = 0; /* yes, we are interested in stdin */
1074 /* Position cursor if line input is done */
1075 if (less_gets_pos >= 0)
1076 move_cursor(max_displayed_line + 2, less_gets_pos + 1);
1079 if (kbd_input[0] == 0) { /* if nothing is buffered */
1080 #if ENABLE_FEATURE_LESS_WINCH
1083 /* NB: SIGWINCH interrupts poll() */
1084 r = poll(pfd + rd, 2 - rd, -1);
1085 if (/*r < 0 && errno == EINTR &&*/ winch_counter)
1086 return '\\'; /* anything which has no defined function */
1090 safe_poll(pfd + rd, 2 - rd, -1);
1094 /* We have kbd_fd in O_NONBLOCK mode, read inside read_key()
1095 * would not block even if there is no input available */
1096 key64 = read_key(kbd_fd, kbd_input, /*timeout off:*/ -2);
1097 if ((int)key64 == -1) {
1098 if (errno == EAGAIN) {
1099 /* No keyboard input available. Since poll() did return,
1100 * we should have input on stdin */
1102 buffer_fill_and_print();
1105 /* EOF/error (ssh session got killed etc) */
1112 /* Grab a character from input without requiring the return key.
1113 * May return KEYCODE_xxx values.
1114 * Note that this function works best with raw input. */
1115 static int64_t less_getch(int pos)
1121 less_gets_pos = pos;
1122 key = key64 = getch_nowait();
1125 /* Discard Ctrl-something chars.
1126 * (checking only lower 32 bits is a size optimization:
1127 * upper 32 bits are used only by KEYCODE_CURSOR_POS)
1129 if (key >= 0 && key < ' ' && key != 0x0d && key != 8)
1135 static char* less_gets(int sz)
1139 char *result = xzalloc(1);
1143 less_gets_pos = sz + i;
1156 if (c < ' ') /* filters out KEYCODE_xxx too (<0) */
1158 if (i >= width - sz - 1)
1159 continue; /* len limit */
1162 result = xrealloc(result, i+1);
1166 static void examine_file(void)
1170 print_statusline("Examine: ");
1171 new_fname = less_gets(sizeof("Examine: ") - 1);
1172 if (!new_fname[0]) {
1178 if (access(new_fname, R_OK) != 0) {
1179 print_statusline("Cannot read this file");
1183 filename = new_fname;
1184 /* files start by = argv. why we assume that argv is infinitely long??
1185 files[num_files] = filename;
1186 current_file = num_files + 1;
1188 files[0] = filename;
1189 num_files = current_file = 1;
1193 /* This function changes the file currently being paged. direction can be one of the following:
1194 * -1: go back one file
1195 * 0: go to the first file
1196 * 1: go forward one file */
1197 static void change_file(int direction)
1199 if (current_file != ((direction > 0) ? num_files : 1)) {
1200 current_file = direction ? current_file + direction : 1;
1202 filename = xstrdup(files[current_file - 1]);
1205 print_statusline(direction > 0 ? "No next file" : "No previous file");
1209 static void remove_current_file(void)
1216 if (current_file != 1) {
1218 for (i = 3; i <= num_files; i++)
1219 files[i - 2] = files[i - 1];
1223 for (i = 2; i <= num_files; i++)
1224 files[i - 2] = files[i - 1];
1230 static void colon_process(void)
1234 /* Clear the current line and print a prompt */
1235 print_statusline(" :");
1237 keypress = less_getch(2);
1240 remove_current_file();
1245 #if ENABLE_FEATURE_LESS_FLAGS
1257 less_exit(EXIT_SUCCESS);
1265 #if ENABLE_FEATURE_LESS_REGEXP
1266 static void normalize_match_pos(int match)
1268 if (match >= num_matches)
1269 match = num_matches - 1;
1275 static void goto_match(int match)
1281 /* Try to find next match if eof isn't reached yet */
1282 if (match >= num_matches && eof_error > 0) {
1283 wanted_match = match; /* "I want to read until I see N'th match" */
1287 normalize_match_pos(match);
1288 buffer_line(match_lines[match_pos]);
1290 print_statusline("No matches found");
1294 static void fill_match_lines(unsigned pos)
1298 /* Run the regex on each line of the current file */
1299 while (pos <= max_fline) {
1300 /* If this line matches */
1301 if (regexec(&pattern, flines[pos], 0, NULL, 0) == 0
1302 /* and we didn't match it last time */
1303 && !(num_matches && match_lines[num_matches-1] == pos)
1305 match_lines = xrealloc_vector(match_lines, 4, num_matches);
1306 match_lines[num_matches++] = pos;
1312 static void regex_process(void)
1314 char *uncomp_regex, *err;
1316 /* Reset variables */
1321 if (pattern_valid) {
1326 /* Get the uncompiled regular expression from the user */
1328 bb_putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
1329 uncomp_regex = less_gets(1);
1330 if (!uncomp_regex[0]) {
1336 /* Compile the regex and check for errors */
1337 err = regcomp_or_errmsg(&pattern, uncomp_regex,
1338 (option_mask32 & FLAG_I) ? REG_ICASE : 0);
1341 print_statusline(err);
1348 fill_match_lines(0);
1349 while (match_pos < num_matches) {
1350 if ((int)match_lines[match_pos] > cur_fline)
1354 if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
1357 /* It's possible that no matches are found yet.
1358 * goto_match() will read input looking for match,
1360 goto_match(match_pos);
1364 static void number_process(int first_digit)
1369 char num_input[sizeof(int)*4]; /* more than enough */
1371 num_input[0] = first_digit;
1373 /* Clear the current line, print a prompt, and then print the digit */
1375 printf(":%c", first_digit);
1377 /* Receive input until a letter is given */
1379 while (i < sizeof(num_input)-1) {
1380 keypress = less_getch(i + 1);
1381 if ((unsigned)keypress > 255 || !isdigit(keypress))
1383 num_input[i] = keypress;
1384 bb_putchar(keypress);
1388 num_input[i] = '\0';
1389 num = bb_strtou(num_input, NULL, 10);
1390 /* on format error, num == -1 */
1391 if (num < 1 || num > MAXLINES) {
1396 /* We now know the number and the letter entered, so we process them */
1398 case KEYCODE_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
1401 case KEYCODE_UP: case 'b': case 'w': case 'y': case 'u':
1404 case 'g': case '<': case 'G': case '>':
1405 buffer_lineno(num - 1);
1408 #if ENABLE_FEATURE_LESS_FLAGS
1410 num = num * (num_lines > 0 ? num_lines : max_lineno) / 100;
1412 num = num * max_lineno / 100;
1416 #if ENABLE_FEATURE_LESS_REGEXP
1418 goto_match(match_pos + num);
1421 option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
1425 option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
1432 #if ENABLE_FEATURE_LESS_DASHCMD
1433 static void flag_change(void)
1439 keypress = less_getch(1);
1443 option_mask32 ^= FLAG_M;
1446 option_mask32 ^= FLAG_m;
1449 option_mask32 ^= FLAG_E;
1452 option_mask32 ^= FLAG_TILDE;
1454 #if ENABLE_FEATURE_LESS_TRUNCATE
1456 option_mask32 ^= FLAG_S;
1457 buffer_fill_and_print();
1460 #if ENABLE_FEATURE_LESS_LINENUMS
1462 option_mask32 ^= FLAG_N;
1464 buffer_fill_and_print();
1471 static void show_flag_status(void)
1478 keypress = less_getch(1);
1482 flag_val = option_mask32 & FLAG_M;
1485 flag_val = option_mask32 & FLAG_m;
1488 flag_val = option_mask32 & FLAG_TILDE;
1491 flag_val = option_mask32 & FLAG_N;
1494 flag_val = option_mask32 & FLAG_E;
1502 printf(HIGHLIGHT"The status of the flag is: %u"NORMAL, flag_val != 0);
1506 #endif /* ENABLE_FEATURE_LESS_DASHCMD */
1508 static void save_input_to_file(void)
1510 const char *msg = "";
1515 print_statusline("Log file: ");
1516 current_line = less_gets(sizeof("Log file: ")-1);
1517 if (current_line[0]) {
1518 fp = fopen_for_write(current_line);
1520 msg = "Error opening log file";
1523 for (i = 0; i <= max_fline; i++)
1524 fprintf(fp, "%s\n", flines[i]);
1529 print_statusline(msg);
1533 #if ENABLE_FEATURE_LESS_MARKS
1534 static void add_mark(void)
1538 print_statusline("Mark: ");
1539 letter = less_getch(sizeof("Mark: ") - 1);
1541 if (isalpha(letter)) {
1542 /* If we exceed 15 marks, start overwriting previous ones */
1543 if (num_marks == 14)
1546 mark_lines[num_marks][0] = letter;
1547 mark_lines[num_marks][1] = cur_fline;
1550 print_statusline("Invalid mark letter");
1554 static void goto_mark(void)
1559 print_statusline("Go to mark: ");
1560 letter = less_getch(sizeof("Go to mark: ") - 1);
1563 if (isalpha(letter)) {
1564 for (i = 0; i <= num_marks; i++)
1565 if (letter == mark_lines[i][0]) {
1566 buffer_line(mark_lines[i][1]);
1569 if (num_marks == 14 && letter != mark_lines[14][0])
1570 print_statusline("Mark not set");
1572 print_statusline("Invalid mark letter");
1576 #if ENABLE_FEATURE_LESS_BRACKETS
1577 static char opp_bracket(char bracket)
1580 case '{': case '[': /* '}' == '{' + 2. Same for '[' */
1582 case '(': /* ')' == '(' + 1 */
1594 static void match_right_bracket(char bracket)
1596 unsigned i = cur_fline;
1599 || strchr(flines[i], bracket) == NULL
1601 print_statusline("No bracket in top line");
1605 bracket = opp_bracket(bracket);
1606 for (; i < max_fline; i++) {
1607 if (strchr(flines[i], bracket) != NULL) {
1609 * Line with matched right bracket becomes
1612 buffer_line(i - max_displayed_line);
1616 print_statusline("No matching bracket found");
1619 static void match_left_bracket(char bracket)
1621 int i = cur_fline + max_displayed_line;
1624 || strchr(flines[i], bracket) == NULL
1626 print_statusline("No bracket in bottom line");
1630 bracket = opp_bracket(bracket);
1631 for (; i >= 0; i--) {
1632 if (strchr(flines[i], bracket) != NULL) {
1634 * Line with matched left bracket becomes
1635 * first visible line
1641 print_statusline("No matching bracket found");
1643 #endif /* FEATURE_LESS_BRACKETS */
1645 static void keypress_process(int keypress)
1648 case KEYCODE_DOWN: case 'e': case 'j': case 0x0d:
1651 case KEYCODE_UP: case 'y': case 'k':
1654 case KEYCODE_PAGEDOWN: case ' ': case 'z': case 'f':
1655 buffer_down(max_displayed_line + 1);
1657 case KEYCODE_PAGEUP: case 'w': case 'b':
1658 buffer_up(max_displayed_line + 1);
1661 buffer_down((max_displayed_line + 1) / 2);
1664 buffer_up((max_displayed_line + 1) / 2);
1666 case KEYCODE_HOME: case 'g': case 'p': case '<': case '%':
1669 case KEYCODE_END: case 'G': case '>':
1670 cur_fline = MAXLINES;
1672 buffer_line(cur_fline);
1675 less_exit(EXIT_SUCCESS);
1677 #if ENABLE_FEATURE_LESS_MARKS
1688 /* TODO: (1) also bind ^R, ^L to this?
1689 * (2) re-measure window size?
1697 save_input_to_file();
1702 #if ENABLE_FEATURE_LESS_FLAGS
1707 #if ENABLE_FEATURE_LESS_REGEXP
1709 option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
1713 goto_match(match_pos + 1);
1716 goto_match(match_pos - 1);
1719 option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
1723 #if ENABLE_FEATURE_LESS_DASHCMD
1734 #if ENABLE_FEATURE_LESS_BRACKETS
1735 case '{': case '(': case '[':
1736 match_right_bracket(keypress);
1738 case '}': case ')': case ']':
1739 match_left_bracket(keypress);
1747 if (isdigit(keypress))
1748 number_process(keypress);
1751 static void sig_catcher(int sig)
1756 #if ENABLE_FEATURE_LESS_WINCH
1757 static void sigwinch_handler(int sig UNUSED_PARAM)
1763 int less_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1764 int less_main(int argc, char **argv)
1771 /* TODO: -x: do not interpret backspace, -xx: tab also
1772 * -xxx: newline also
1773 * -w N: assume width N (-xxx -w 32: hex viewer of sorts)
1774 * -s: condense many empty lines to one
1775 * (used by some setups for manpage display)
1777 getopt32(argv, "EMmN~I" IF_FEATURE_LESS_TRUNCATE("S") /*ignored:*/"s");
1783 /* Another popular pager, most, detects when stdout
1784 * is not a tty and turns into cat. This makes sense. */
1785 if (!isatty(STDOUT_FILENO))
1786 return bb_cat(argv);
1789 if (isatty(STDIN_FILENO)) {
1790 /* Just "less"? No args and no redirection? */
1791 bb_error_msg("missing filename");
1795 filename = xstrdup(files[0]);
1798 if (option_mask32 & FLAG_TILDE)
1799 empty_line_marker = "";
1801 /* Some versions of less can survive w/o controlling tty,
1802 * try to do the same. This also allows to specify an alternative
1803 * tty via "less 1<>TTY".
1805 * We prefer not to use STDOUT_FILENO directly,
1806 * since we want to set this fd to non-blocking mode,
1807 * and not interfere with other processes which share stdout with us.
1809 tty_name = xmalloc_ttyname(STDOUT_FILENO);
1811 tty_fd = open(tty_name, O_RDONLY);
1816 /* Try controlling tty */
1818 tty_fd = open(CURRENT_TTY, O_RDONLY);
1820 /* If all else fails, less 481 uses stdout. Mimic that */
1821 tty_fd = STDOUT_FILENO;
1824 G.kbd_fd_orig_flags = ndelay_on(tty_fd);
1825 kbd_fd = tty_fd; /* save in a global */
1827 tcgetattr(kbd_fd, &term_orig);
1828 term_less = term_orig;
1829 term_less.c_lflag &= ~(ICANON | ECHO);
1830 term_less.c_iflag &= ~(IXON | ICRNL);
1831 /*term_less.c_oflag &= ~ONLCR;*/
1832 term_less.c_cc[VMIN] = 1;
1833 term_less.c_cc[VTIME] = 0;
1835 IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
1836 /* 20: two tabstops + 4 */
1837 if (width < 20 || max_displayed_line < 3)
1838 return bb_cat(argv);
1839 max_displayed_line -= 2;
1841 /* We want to restore term_orig on exit */
1842 bb_signals(BB_FATAL_SIGS, sig_catcher);
1843 #if ENABLE_FEATURE_LESS_WINCH
1844 signal(SIGWINCH, sigwinch_handler);
1847 buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
1852 #if ENABLE_FEATURE_LESS_WINCH
1853 while (WINCH_COUNTER) {
1856 IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
1857 IF_FEATURE_LESS_ASK_TERMINAL(got_size:)
1858 /* 20: two tabstops + 4 */
1861 if (max_displayed_line < 3)
1862 max_displayed_line = 3;
1863 max_displayed_line -= 2;
1865 buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
1866 /* Avoid re-wrap and/or redraw if we already know
1867 * we need to do it again. These ops are expensive */
1873 buffer_fill_and_print();
1874 /* This took some time. Loop back and check,
1875 * were there another SIGWINCH? */
1877 keypress = less_getch(-1); /* -1: do not position cursor */
1878 # if ENABLE_FEATURE_LESS_ASK_TERMINAL
1879 if ((int32_t)keypress == KEYCODE_CURSOR_POS) {
1880 uint32_t rc = (keypress >> 32);
1881 width = (rc & 0x7fff);
1882 max_displayed_line = ((rc >> 16) & 0x7fff);
1887 keypress = less_getch(-1); /* -1: do not position cursor */
1889 keypress_process(keypress);
1894 Help text of less version 418 is below.
1895 If you are implementing something, keeping
1896 key and/or command line switch compatibility is a good idea:
1899 SUMMARY OF LESS COMMANDS
1901 Commands marked with * may be preceded by a number, N.
1902 Notes in parentheses indicate the behavior if N is given.
1903 h H Display this help.
1905 ---------------------------------------------------------------------------
1907 e ^E j ^N CR * Forward one line (or N lines).
1908 y ^Y k ^K ^P * Backward one line (or N lines).
1909 f ^F ^V SPACE * Forward one window (or N lines).
1910 b ^B ESC-v * Backward one window (or N lines).
1911 z * Forward one window (and set window to N).
1912 w * Backward one window (and set window to N).
1913 ESC-SPACE * Forward one window, but don't stop at end-of-file.
1914 d ^D * Forward one half-window (and set half-window to N).
1915 u ^U * Backward one half-window (and set half-window to N).
1916 ESC-) RightArrow * Left one half screen width (or N positions).
1917 ESC-( LeftArrow * Right one half screen width (or N positions).
1918 F Forward forever; like "tail -f".
1919 r ^R ^L Repaint screen.
1920 R Repaint screen, discarding buffered input.
1921 ---------------------------------------------------
1922 Default "window" is the screen height.
1923 Default "half-window" is half of the screen height.
1924 ---------------------------------------------------------------------------
1926 /pattern * Search forward for (N-th) matching line.
1927 ?pattern * Search backward for (N-th) matching line.
1928 n * Repeat previous search (for N-th occurrence).
1929 N * Repeat previous search in reverse direction.
1930 ESC-n * Repeat previous search, spanning files.
1931 ESC-N * Repeat previous search, reverse dir. & spanning files.
1932 ESC-u Undo (toggle) search highlighting.
1933 ---------------------------------------------------
1934 Search patterns may be modified by one or more of:
1935 ^N or ! Search for NON-matching lines.
1936 ^E or * Search multiple files (pass thru END OF FILE).
1937 ^F or @ Start search at FIRST file (for /) or last file (for ?).
1938 ^K Highlight matches, but don't move (KEEP position).
1939 ^R Don't use REGULAR EXPRESSIONS.
1940 ---------------------------------------------------------------------------
1942 g < ESC-< * Go to first line in file (or line N).
1943 G > ESC-> * Go to last line in file (or line N).
1944 p % * Go to beginning of file (or N percent into file).
1945 t * Go to the (N-th) next tag.
1946 T * Go to the (N-th) previous tag.
1947 { ( [ * Find close bracket } ) ].
1948 } ) ] * Find open bracket { ( [.
1949 ESC-^F <c1> <c2> * Find close bracket <c2>.
1950 ESC-^B <c1> <c2> * Find open bracket <c1>
1951 ---------------------------------------------------
1952 Each "find close bracket" command goes forward to the close bracket
1953 matching the (N-th) open bracket in the top line.
1954 Each "find open bracket" command goes backward to the open bracket
1955 matching the (N-th) close bracket in the bottom line.
1956 m<letter> Mark the current position with <letter>.
1957 '<letter> Go to a previously marked position.
1958 '' Go to the previous position.
1960 ---------------------------------------------------
1961 A mark is any upper-case or lower-case letter.
1962 Certain marks are predefined:
1963 ^ means beginning of the file
1964 $ means end of the file
1965 ---------------------------------------------------------------------------
1967 :e [file] Examine a new file.
1969 :n * Examine the (N-th) next file from the command line.
1970 :p * Examine the (N-th) previous file from the command line.
1971 :x * Examine the first (or N-th) file from the command line.
1972 :d Delete the current file from the command line list.
1973 = ^G :f Print current file name.
1974 ---------------------------------------------------------------------------
1975 MISCELLANEOUS COMMANDS
1976 -<flag> Toggle a command line option [see OPTIONS below].
1977 --<name> Toggle a command line option, by name.
1978 _<flag> Display the setting of a command line option.
1979 __<name> Display the setting of an option, by name.
1980 +cmd Execute the less cmd each time a new file is examined.
1981 !command Execute the shell command with $SHELL.
1982 |Xcommand Pipe file between current pos & mark X to shell command.
1983 v Edit the current file with $VISUAL or $EDITOR.
1984 V Print version number of "less".
1985 ---------------------------------------------------------------------------
1987 Most options may be changed either on the command line,
1988 or from within less by using the - or -- command.
1989 Options may be given in one of two forms: either a single
1990 character preceded by a -, or a name preceded by --.
1992 Display help (from command line).
1993 -a ........ --search-skip-screen
1994 Forward search skips current screen.
1995 -b [N] .... --buffers=[N]
1997 -B ........ --auto-buffers
1998 Don't automatically allocate buffers for pipes.
1999 -c ........ --clear-screen
2000 Repaint by clearing rather than scrolling.
2003 -D [xn.n] . --color=xn.n
2004 Set screen colors. (MS-DOS only)
2005 -e -E .... --quit-at-eof --QUIT-AT-EOF
2006 Quit at end of file.
2008 Force open non-regular files.
2009 -F ........ --quit-if-one-screen
2010 Quit if entire file fits on first screen.
2011 -g ........ --hilite-search
2012 Highlight only last match for searches.
2013 -G ........ --HILITE-SEARCH
2014 Don't highlight any matches for searches.
2015 -h [N] .... --max-back-scroll=[N]
2016 Backward scroll limit.
2017 -i ........ --ignore-case
2018 Ignore case in searches that do not contain uppercase.
2019 -I ........ --IGNORE-CASE
2020 Ignore case in all searches.
2021 -j [N] .... --jump-target=[N]
2022 Screen position of target lines.
2023 -J ........ --status-column
2024 Display a status column at left edge of screen.
2025 -k [file] . --lesskey-file=[file]
2027 -L ........ --no-lessopen
2028 Ignore the LESSOPEN environment variable.
2029 -m -M .... --long-prompt --LONG-PROMPT
2031 -n -N .... --line-numbers --LINE-NUMBERS
2032 Don't use line numbers.
2033 -o [file] . --log-file=[file]
2034 Copy to log file (standard input only).
2035 -O [file] . --LOG-FILE=[file]
2036 Copy to log file (unconditionally overwrite).
2037 -p [pattern] --pattern=[pattern]
2038 Start at pattern (from command line).
2039 -P [prompt] --prompt=[prompt]
2041 -q -Q .... --quiet --QUIET --silent --SILENT
2042 Quiet the terminal bell.
2043 -r -R .... --raw-control-chars --RAW-CONTROL-CHARS
2044 Output "raw" control characters.
2045 -s ........ --squeeze-blank-lines
2046 Squeeze multiple blank lines.
2047 -S ........ --chop-long-lines
2049 -t [tag] .. --tag=[tag]
2051 -T [tagsfile] --tag-file=[tagsfile]
2052 Use an alternate tags file.
2053 -u -U .... --underline-special --UNDERLINE-SPECIAL
2054 Change handling of backspaces.
2055 -V ........ --version
2056 Display the version number of "less".
2057 -w ........ --hilite-unread
2058 Highlight first new line after forward-screen.
2059 -W ........ --HILITE-UNREAD
2060 Highlight first new line after any forward movement.
2061 -x [N[,...]] --tabs=[N[,...]]
2063 -X ........ --no-init
2064 Don't use termcap init/deinit strings.
2066 Don't use termcap keypad init/deinit strings.
2067 -y [N] .... --max-forw-scroll=[N]
2068 Forward scroll limit.
2069 -z [N] .... --window=[N]
2071 -" [c[c]] . --quotes=[c[c]]
2072 Set shell quote characters.
2074 Don't display tildes after end of file.
2075 -# [N] .... --shift=[N]
2076 Horizontal scroll amount (0 = one half screen width)
2078 ---------------------------------------------------------------------------
2080 These keys can be used to edit text being entered
2081 on the "command line" at the bottom of the screen.
2082 RightArrow ESC-l Move cursor right one character.
2083 LeftArrow ESC-h Move cursor left one character.
2084 CNTL-RightArrow ESC-RightArrow ESC-w Move cursor right one word.
2085 CNTL-LeftArrow ESC-LeftArrow ESC-b Move cursor left one word.
2086 HOME ESC-0 Move cursor to start of line.
2087 END ESC-$ Move cursor to end of line.
2088 BACKSPACE Delete char to left of cursor.
2089 DELETE ESC-x Delete char under cursor.
2090 CNTL-BACKSPACE ESC-BACKSPACE Delete word to left of cursor.
2091 CNTL-DELETE ESC-DELETE ESC-X Delete word under cursor.
2092 CNTL-U ESC (MS-DOS only) Delete entire line.
2093 UpArrow ESC-k Retrieve previous command line.
2094 DownArrow ESC-j Retrieve next command line.
2095 TAB Complete filename & cycle.
2096 SHIFT-TAB ESC-TAB Complete filename & reverse cycle.
2097 CNTL-L Complete filename, list all.