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hush/miscutils/less.c
Denys Vlasenko 24915117a2 Fixes for warnings in FreeBSD build 
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2011-08-28 05:31:49 +02:00

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/* vi: set sw=4 ts=4: */
/*
* Mini less implementation for busybox
*
* Copyright (C) 2005 by Rob Sullivan <cogito.ergo.cogito@gmail.com>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
/*
* TODO:
* - Add more regular expression support - search modifiers, certain matches, etc.
* - Add more complex bracket searching - currently, nested brackets are
* not considered.
* - Add support for "F" as an input. This causes less to act in
* a similar way to tail -f.
* - Allow horizontal scrolling.
*
* Notes:
* - the inp file pointer is used so that keyboard input works after
* redirected input has been read from stdin
*/
//config:config LESS
//config: bool "less"
//config: default y
//config: help
//config: 'less' is a pager, meaning that it displays text files. It possesses
//config: a wide array of features, and is an improvement over 'more'.
//config:
//config:config FEATURE_LESS_MAXLINES
//config: int "Max number of input lines less will try to eat"
//config: default 9999999
//config: depends on LESS
//config:
//config:config FEATURE_LESS_BRACKETS
//config: bool "Enable bracket searching"
//config: default y
//config: depends on LESS
//config: help
//config: This option adds the capability to search for matching left and right
//config: brackets, facilitating programming.
//config:
//config:config FEATURE_LESS_FLAGS
//config: bool "Enable extra flags"
//config: default y
//config: depends on LESS
//config: help
//config: The extra flags provided do the following:
//config:
//config: The -M flag enables a more sophisticated status line.
//config: The -m flag enables a simpler status line with a percentage.
//config:
//config:config FEATURE_LESS_MARKS
//config: bool "Enable marks"
//config: default y
//config: depends on LESS
//config: help
//config: Marks enable positions in a file to be stored for easy reference.
//config:
//config:config FEATURE_LESS_REGEXP
//config: bool "Enable regular expressions"
//config: default y
//config: depends on LESS
//config: help
//config: Enable regular expressions, allowing complex file searches.
//config:
//config:config FEATURE_LESS_WINCH
//config: bool "Enable automatic resizing on window size changes"
//config: default y
//config: depends on LESS
//config: help
//config: Makes less track window size changes.
//config:
//config:config FEATURE_LESS_ASK_TERMINAL
//config: bool "Use 'tell me cursor position' ESC sequence to measure window"
//config: default y
//config: depends on FEATURE_LESS_WINCH
//config: help
//config: Makes less track window size changes.
//config: If terminal size can't be retrieved and $LINES/$COLUMNS are not set,
//config: this option makes less perform a last-ditch effort to find it:
//config: position cursor to 999,999 and ask terminal to report real
//config: cursor position using "ESC [ 6 n" escape sequence, then read stdin.
//config:
//config: This is not clean but helps a lot on serial lines and such.
//config:
//config:config FEATURE_LESS_DASHCMD
//config: bool "Enable flag changes ('-' command)"
//config: default y
//config: depends on LESS
//config: help
//config: This enables the ability to change command-line flags within
//config: less itself ('-' keyboard command).
//config:
//config:config FEATURE_LESS_LINENUMS
//config: bool "Enable dynamic switching of line numbers"
//config: default y
//config: depends on FEATURE_LESS_DASHCMD
//config: help
//config: Enables "-N" command.
//usage:#define less_trivial_usage
//usage: "[-EMNmh~I?] [FILE]..."
//usage:#define less_full_usage "\n\n"
//usage: "View FILE (or stdin) one screenful at a time\n"
//usage: "\n -E Quit once the end of a file is reached"
//usage: "\n -M,-m Display status line with line numbers"
//usage: "\n and percentage through the file"
//usage: "\n -N Prefix line number to each line"
//usage: "\n -I Ignore case in all searches"
//usage: "\n -~ Suppress ~s displayed past the end of the file"
#include <sched.h> /* sched_yield() */
#include "libbb.h"
#if ENABLE_FEATURE_LESS_REGEXP
#include "xregex.h"
#endif
#define ESC "\033"
/* The escape codes for highlighted and normal text */
#define HIGHLIGHT ESC"[7m"
#define NORMAL ESC"[0m"
/* The escape code to home and clear to the end of screen */
#define CLEAR ESC"[H\033[J"
/* The escape code to clear to the end of line */
#define CLEAR_2_EOL ESC"[K"
enum {
/* Absolute max of lines eaten */
MAXLINES = CONFIG_FEATURE_LESS_MAXLINES,
/* This many "after the end" lines we will show (at max) */
TILDES = 1,
};
/* Command line options */
enum {
FLAG_E = 1 << 0,
FLAG_M = 1 << 1,
FLAG_m = 1 << 2,
FLAG_N = 1 << 3,
FLAG_TILDE = 1 << 4,
FLAG_I = 1 << 5,
FLAG_S = (1 << 6) * ENABLE_FEATURE_LESS_DASHCMD,
/* hijack command line options variable for internal state vars */
LESS_STATE_MATCH_BACKWARDS = 1 << 15,
};
#if !ENABLE_FEATURE_LESS_REGEXP
enum { pattern_valid = 0 };
#endif
struct globals {
int cur_fline; /* signed */
int kbd_fd; /* fd to get input from */
int less_gets_pos;
/* last position in last line, taking into account tabs */
size_t last_line_pos;
unsigned max_fline;
unsigned max_lineno; /* this one tracks linewrap */
unsigned max_displayed_line;
unsigned width;
#if ENABLE_FEATURE_LESS_WINCH
unsigned winch_counter;
#endif
ssize_t eof_error; /* eof if 0, error if < 0 */
ssize_t readpos;
ssize_t readeof; /* must be signed */
const char **buffer;
const char **flines;
const char *empty_line_marker;
unsigned num_files;
unsigned current_file;
char *filename;
char **files;
#if ENABLE_FEATURE_LESS_MARKS
unsigned num_marks;
unsigned mark_lines[15][2];
#endif
#if ENABLE_FEATURE_LESS_REGEXP
unsigned *match_lines;
int match_pos; /* signed! */
int wanted_match; /* signed! */
int num_matches;
regex_t pattern;
smallint pattern_valid;
#endif
#if ENABLE_FEATURE_LESS_ASK_TERMINAL
smallint winsize_err;
#endif
smallint terminated;
struct termios term_orig, term_less;
char kbd_input[KEYCODE_BUFFER_SIZE];
};
#define G (*ptr_to_globals)
#define cur_fline (G.cur_fline )
#define kbd_fd (G.kbd_fd )
#define less_gets_pos (G.less_gets_pos )
#define last_line_pos (G.last_line_pos )
#define max_fline (G.max_fline )
#define max_lineno (G.max_lineno )
#define max_displayed_line (G.max_displayed_line)
#define width (G.width )
#define winch_counter (G.winch_counter )
/* This one is 100% not cached by compiler on read access */
#define WINCH_COUNTER (*(volatile unsigned *)&winch_counter)
#define eof_error (G.eof_error )
#define readpos (G.readpos )
#define readeof (G.readeof )
#define buffer (G.buffer )
#define flines (G.flines )
#define empty_line_marker (G.empty_line_marker )
#define num_files (G.num_files )
#define current_file (G.current_file )
#define filename (G.filename )
#define files (G.files )
#define num_marks (G.num_marks )
#define mark_lines (G.mark_lines )
#if ENABLE_FEATURE_LESS_REGEXP
#define match_lines (G.match_lines )
#define match_pos (G.match_pos )
#define num_matches (G.num_matches )
#define wanted_match (G.wanted_match )
#define pattern (G.pattern )
#define pattern_valid (G.pattern_valid )
#endif
#define terminated (G.terminated )
#define term_orig (G.term_orig )
#define term_less (G.term_less )
#define kbd_input (G.kbd_input )
#define INIT_G() do { \
SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
less_gets_pos = -1; \
empty_line_marker = "~"; \
num_files = 1; \
current_file = 1; \
eof_error = 1; \
terminated = 1; \
IF_FEATURE_LESS_REGEXP(wanted_match = -1;) \
} while (0)
/* flines[] are lines read from stdin, each in malloc'ed buffer.
* Line numbers are stored as uint32_t prepended to each line.
* Pointer is adjusted so that flines[i] points directly past
* line number. Accesor: */
#define MEMPTR(p) ((char*)(p) - 4)
#define LINENO(p) (*(uint32_t*)((p) - 4))
/* Reset terminal input to normal */
static void set_tty_cooked(void)
{
fflush_all();
tcsetattr(kbd_fd, TCSANOW, &term_orig);
}
/* Move the cursor to a position (x,y), where (0,0) is the
top-left corner of the console */
static void move_cursor(int line, int row)
{
printf(ESC"[%u;%uH", line, row);
}
static void clear_line(void)
{
printf(ESC"[%u;0H" CLEAR_2_EOL, max_displayed_line + 2);
}
static void print_hilite(const char *str)
{
printf(HIGHLIGHT"%s"NORMAL, str);
}
static void print_statusline(const char *str)
{
clear_line();
printf(HIGHLIGHT"%.*s"NORMAL, width - 1, str);
}
/* Exit the program gracefully */
static void less_exit(int code)
{
set_tty_cooked();
clear_line();
if (code < 0)
kill_myself_with_sig(- code); /* does not return */
exit(code);
}
#if (ENABLE_FEATURE_LESS_DASHCMD && ENABLE_FEATURE_LESS_LINENUMS) \
|| ENABLE_FEATURE_LESS_WINCH
static void re_wrap(void)
{
int w = width;
int new_line_pos;
int src_idx;
int dst_idx;
int new_cur_fline = 0;
uint32_t lineno;
char linebuf[w + 1];
const char **old_flines = flines;
const char *s;
char **new_flines = NULL;
char *d;
if (option_mask32 & FLAG_N)
w -= 8;
src_idx = 0;
dst_idx = 0;
s = old_flines[0];
lineno = LINENO(s);
d = linebuf;
new_line_pos = 0;
while (1) {
*d = *s;
if (*d != '\0') {
new_line_pos++;
if (*d == '\t') /* tab */
new_line_pos += 7;
s++;
d++;
if (new_line_pos >= w) {
int sz;
/* new line is full, create next one */
*d = '\0';
next_new:
sz = (d - linebuf) + 1; /* + 1: NUL */
d = ((char*)xmalloc(sz + 4)) + 4;
LINENO(d) = lineno;
memcpy(d, linebuf, sz);
new_flines = xrealloc_vector(new_flines, 8, dst_idx);
new_flines[dst_idx] = d;
dst_idx++;
if (new_line_pos < w) {
/* if we came here thru "goto next_new" */
if (src_idx > max_fline)
break;
lineno = LINENO(s);
}
d = linebuf;
new_line_pos = 0;
}
continue;
}
/* *d == NUL: old line ended, go to next old one */
free(MEMPTR(old_flines[src_idx]));
/* btw, convert cur_fline... */
if (cur_fline == src_idx)
new_cur_fline = dst_idx;
src_idx++;
/* no more lines? finish last new line (and exit the loop) */
if (src_idx > max_fline)
goto next_new;
s = old_flines[src_idx];
if (lineno != LINENO(s)) {
/* this is not a continuation line!
* create next _new_ line too */
goto next_new;
}
}
free(old_flines);
flines = (const char **)new_flines;
max_fline = dst_idx - 1;
last_line_pos = new_line_pos;
cur_fline = new_cur_fline;
/* max_lineno is screen-size independent */
#if ENABLE_FEATURE_LESS_REGEXP
pattern_valid = 0;
#endif
}
#endif
#if ENABLE_FEATURE_LESS_REGEXP
static void fill_match_lines(unsigned pos);
#else
#define fill_match_lines(pos) ((void)0)
#endif
/* Devilishly complex routine.
*
* Has to deal with EOF and EPIPE on input,
* with line wrapping, with last line not ending in '\n'
* (possibly not ending YET!), with backspace and tabs.
* It reads input again if last time we got an EOF (thus supporting
* growing files) or EPIPE (watching output of slow process like make).
*
* Variables used:
* flines[] - array of lines already read. Linewrap may cause
* one source file line to occupy several flines[n].
* flines[max_fline] - last line, possibly incomplete.
* terminated - 1 if flines[max_fline] is 'terminated'
* (if there was '\n' [which isn't stored itself, we just remember
* that it was seen])
* max_lineno - last line's number, this one doesn't increment
* on line wrap, only on "real" new lines.
* readbuf[0..readeof-1] - small preliminary buffer.
* readbuf[readpos] - next character to add to current line.
* last_line_pos - screen line position of next char to be read
* (takes into account tabs and backspaces)
* eof_error - < 0 error, == 0 EOF, > 0 not EOF/error
*/
static void read_lines(void)
{
#define readbuf bb_common_bufsiz1
char *current_line, *p;
int w = width;
char last_terminated = terminated;
#if ENABLE_FEATURE_LESS_REGEXP
unsigned old_max_fline = max_fline;
time_t last_time = 0;
unsigned seconds_p1 = 3; /* seconds_to_loop + 1 */
#endif
if (option_mask32 & FLAG_N)
w -= 8;
IF_FEATURE_LESS_REGEXP(again0:)
p = current_line = ((char*)xmalloc(w + 4)) + 4;
max_fline += last_terminated;
if (!last_terminated) {
const char *cp = flines[max_fline];
strcpy(p, cp);
p += strlen(current_line);
free(MEMPTR(flines[max_fline]));
/* last_line_pos is still valid from previous read_lines() */
} else {
last_line_pos = 0;
}
while (1) { /* read lines until we reach cur_fline or wanted_match */
*p = '\0';
terminated = 0;
while (1) { /* read chars until we have a line */
char c;
/* if no unprocessed chars left, eat more */
if (readpos >= readeof) {
ndelay_on(0);
eof_error = safe_read(STDIN_FILENO, readbuf, sizeof(readbuf));
ndelay_off(0);
readpos = 0;
readeof = eof_error;
if (eof_error <= 0)
goto reached_eof;
}
c = readbuf[readpos];
/* backspace? [needed for manpages] */
/* <tab><bs> is (a) insane and */
/* (b) harder to do correctly, so we refuse to do it */
if (c == '\x8' && last_line_pos && p[-1] != '\t') {
readpos++; /* eat it */
last_line_pos--;
/* was buggy (p could end up <= current_line)... */
*--p = '\0';
continue;
}
{
size_t new_last_line_pos = last_line_pos + 1;
if (c == '\t') {
new_last_line_pos += 7;
new_last_line_pos &= (~7);
}
if ((int)new_last_line_pos >= w)
break;
last_line_pos = new_last_line_pos;
}
/* ok, we will eat this char */
readpos++;
if (c == '\n') {
terminated = 1;
last_line_pos = 0;
break;
}
/* NUL is substituted by '\n'! */
if (c == '\0') c = '\n';
*p++ = c;
*p = '\0';
} /* end of "read chars until we have a line" loop */
/* Corner case: linewrap with only "" wrapping to next line */
/* Looks ugly on screen, so we do not store this empty line */
if (!last_terminated && !current_line[0]) {
last_terminated = 1;
max_lineno++;
continue;
}
reached_eof:
last_terminated = terminated;
flines = xrealloc_vector(flines, 8, max_fline);
flines[max_fline] = (char*)xrealloc(MEMPTR(current_line), strlen(current_line) + 1 + 4) + 4;
LINENO(flines[max_fline]) = max_lineno;
if (terminated)
max_lineno++;
if (max_fline >= MAXLINES) {
eof_error = 0; /* Pretend we saw EOF */
break;
}
if (!(option_mask32 & FLAG_S)
? (max_fline > cur_fline + max_displayed_line)
: (max_fline >= cur_fline
&& max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
) {
#if !ENABLE_FEATURE_LESS_REGEXP
break;
#else
if (wanted_match >= num_matches) { /* goto_match called us */
fill_match_lines(old_max_fline);
old_max_fline = max_fline;
}
if (wanted_match < num_matches)
break;
#endif
}
if (eof_error <= 0) {
if (eof_error < 0) {
if (errno == EAGAIN) {
/* not yet eof or error, reset flag (or else
* we will hog CPU - select() will return
* immediately */
eof_error = 1;
} else {
print_statusline(bb_msg_read_error);
}
}
#if !ENABLE_FEATURE_LESS_REGEXP
break;
#else
if (wanted_match < num_matches) {
break;
} else { /* goto_match called us */
time_t t = time(NULL);
if (t != last_time) {
last_time = t;
if (--seconds_p1 == 0)
break;
}
sched_yield();
goto again0; /* go loop again (max 2 seconds) */
}
#endif
}
max_fline++;
current_line = ((char*)xmalloc(w + 4)) + 4;
p = current_line;
last_line_pos = 0;
} /* end of "read lines until we reach cur_fline" loop */
fill_match_lines(old_max_fline);
#if ENABLE_FEATURE_LESS_REGEXP
/* prevent us from being stuck in search for a match */
wanted_match = -1;
#endif
#undef readbuf
}
#if ENABLE_FEATURE_LESS_FLAGS
/* Interestingly, writing calc_percent as a function saves around 32 bytes
* on my build. */
static int calc_percent(void)
{
unsigned p = (100 * (cur_fline+max_displayed_line+1) + max_fline/2) / (max_fline+1);
return p <= 100 ? p : 100;
}
/* Print a status line if -M was specified */
static void m_status_print(void)
{
int percentage;
if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
return;
clear_line();
printf(HIGHLIGHT"%s", filename);
if (num_files > 1)
printf(" (file %i of %i)", current_file, num_files);
printf(" lines %i-%i/%i ",
cur_fline + 1, cur_fline + max_displayed_line + 1,
max_fline + 1);
if (cur_fline >= (int)(max_fline - max_displayed_line)) {
printf("(END)"NORMAL);
if (num_files > 1 && current_file != num_files)
printf(HIGHLIGHT" - next: %s"NORMAL, files[current_file]);
return;
}
percentage = calc_percent();
printf("%i%%"NORMAL, percentage);
}
#endif
/* Print the status line */
static void status_print(void)
{
const char *p;
if (less_gets_pos >= 0) /* don't touch statusline while input is done! */
return;
/* Change the status if flags have been set */
#if ENABLE_FEATURE_LESS_FLAGS
if (option_mask32 & (FLAG_M|FLAG_m)) {
m_status_print();
return;
}
/* No flags set */
#endif
clear_line();
if (cur_fline && cur_fline < (int)(max_fline - max_displayed_line)) {
bb_putchar(':');
return;
}
p = "(END)";
if (!cur_fline)
p = filename;
if (num_files > 1) {
printf(HIGHLIGHT"%s (file %i of %i)"NORMAL,
p, current_file, num_files);
return;
}
print_hilite(p);
}
static void cap_cur_fline(int nlines)
{
int diff;
if (cur_fline < 0)
cur_fline = 0;
if (cur_fline + max_displayed_line > max_fline + TILDES) {
cur_fline -= nlines;
if (cur_fline < 0)
cur_fline = 0;
diff = max_fline - (cur_fline + max_displayed_line) + TILDES;
/* As the number of lines requested was too large, we just move
* to the end of the file */
if (diff > 0)
cur_fline += diff;
}
}
static const char controls[] ALIGN1 =
/* NUL: never encountered; TAB: not converted */
/**/"\x01\x02\x03\x04\x05\x06\x07\x08" "\x0a\x0b\x0c\x0d\x0e\x0f"
"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
"\x7f\x9b"; /* DEL and infamous Meta-ESC :( */
static const char ctrlconv[] ALIGN1 =
/* why 40 instead of 4a below? - it is a replacement for '\n'.
* '\n' is a former NUL - we subst it with @, not J */
"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x40\x4b\x4c\x4d\x4e\x4f"
"\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f";
static void lineno_str(char *nbuf9, const char *line)
{
nbuf9[0] = '\0';
if (option_mask32 & FLAG_N) {
const char *fmt;
unsigned n;
if (line == empty_line_marker) {
memset(nbuf9, ' ', 8);
nbuf9[8] = '\0';
return;
}
/* Width of 7 preserves tab spacing in the text */
fmt = "%7u ";
n = LINENO(line) + 1;
if (n > 9999999) {
n %= 10000000;
fmt = "%07u ";
}
sprintf(nbuf9, fmt, n);
}
}
#if ENABLE_FEATURE_LESS_REGEXP
static void print_found(const char *line)
{
int match_status;
int eflags;
char *growline;
regmatch_t match_structs;
char buf[width];
char nbuf9[9];
const char *str = line;
char *p = buf;
size_t n;
while (*str) {
n = strcspn(str, controls);
if (n) {
if (!str[n]) break;
memcpy(p, str, n);
p += n;
str += n;
}
n = strspn(str, controls);
memset(p, '.', n);
p += n;
str += n;
}
strcpy(p, str);
/* buf[] holds quarantined version of str */
/* Each part of the line that matches has the HIGHLIGHT
and NORMAL escape sequences placed around it.
NB: we regex against line, but insert text
from quarantined copy (buf[]) */
str = buf;
growline = NULL;
eflags = 0;
goto start;
while (match_status == 0) {
char *new = xasprintf("%s%.*s"HIGHLIGHT"%.*s"NORMAL,
growline ? growline : "",
(int)match_structs.rm_so, str,
(int)(match_structs.rm_eo - match_structs.rm_so),
str + match_structs.rm_so);
free(growline);
growline = new;
str += match_structs.rm_eo;
line += match_structs.rm_eo;
eflags = REG_NOTBOL;
start:
/* Most of the time doesn't find the regex, optimize for that */
match_status = regexec(&pattern, line, 1, &match_structs, eflags);
/* if even "" matches, treat it as "not a match" */
if (match_structs.rm_so >= match_structs.rm_eo)
match_status = 1;
}
lineno_str(nbuf9, line);
if (!growline) {
printf(CLEAR_2_EOL"%s%s\n", nbuf9, str);
return;
}
printf(CLEAR_2_EOL"%s%s%s\n", nbuf9, growline, str);
free(growline);
}
#else
void print_found(const char *line);
#endif
static void print_ascii(const char *str)
{
char buf[width];
char nbuf9[9];
char *p;
size_t n;
lineno_str(nbuf9, str);
printf(CLEAR_2_EOL"%s", nbuf9);
while (*str) {
n = strcspn(str, controls);
if (n) {
if (!str[n]) break;
printf("%.*s", (int) n, str);
str += n;
}
n = strspn(str, controls);
p = buf;
do {
if (*str == 0x7f)
*p++ = '?';
else if (*str == (char)0x9b)
/* VT100's CSI, aka Meta-ESC. Who's inventor? */
/* I want to know who committed this sin */
*p++ = '{';
else
*p++ = ctrlconv[(unsigned char)*str];
str++;
} while (--n);
*p = '\0';
print_hilite(buf);
}
puts(str);
}
/* Print the buffer */
static void buffer_print(void)
{
unsigned i;
move_cursor(0, 0);
for (i = 0; i <= max_displayed_line; i++)
if (pattern_valid)
print_found(buffer[i]);
else
print_ascii(buffer[i]);
status_print();
}
static void buffer_fill_and_print(void)
{
unsigned i;
#if ENABLE_FEATURE_LESS_DASHCMD
int fpos = cur_fline;
if (option_mask32 & FLAG_S) {
/* Go back to the beginning of this line */
while (fpos && LINENO(flines[fpos]) == LINENO(flines[fpos-1]))
fpos--;
}
i = 0;
while (i <= max_displayed_line && fpos <= max_fline) {
int lineno = LINENO(flines[fpos]);
buffer[i] = flines[fpos];
i++;
do {
fpos++;
} while ((fpos <= max_fline)
&& (option_mask32 & FLAG_S)
&& lineno == LINENO(flines[fpos])
);
}
#else
for (i = 0; i <= max_displayed_line && cur_fline + i <= max_fline; i++) {
buffer[i] = flines[cur_fline + i];
}
#endif
for (; i <= max_displayed_line; i++) {
buffer[i] = empty_line_marker;
}
buffer_print();
}
/* Move the buffer up and down in the file in order to scroll */
static void buffer_down(int nlines)
{
cur_fline += nlines;
read_lines();
cap_cur_fline(nlines);
buffer_fill_and_print();
}
static void buffer_up(int nlines)
{
cur_fline -= nlines;
if (cur_fline < 0) cur_fline = 0;
read_lines();
buffer_fill_and_print();
}
static void buffer_line(int linenum)
{
if (linenum < 0)
linenum = 0;
cur_fline = linenum;
read_lines();
if (linenum + max_displayed_line > max_fline)
linenum = max_fline - max_displayed_line + TILDES;
if (linenum < 0)
linenum = 0;
cur_fline = linenum;
buffer_fill_and_print();
}
static void open_file_and_read_lines(void)
{
if (filename) {
xmove_fd(xopen(filename, O_RDONLY), STDIN_FILENO);
} else {
/* "less" with no arguments in argv[] */
/* For status line only */
filename = xstrdup(bb_msg_standard_input);
}
readpos = 0;
readeof = 0;
last_line_pos = 0;
terminated = 1;
read_lines();
}
/* Reinitialize everything for a new file - free the memory and start over */
static void reinitialize(void)
{
unsigned i;
if (flines) {
for (i = 0; i <= max_fline; i++)
free(MEMPTR(flines[i]));
free(flines);
flines = NULL;
}
max_fline = -1;
cur_fline = 0;
max_lineno = 0;
open_file_and_read_lines();
#if ENABLE_FEATURE_LESS_ASK_TERMINAL
if (G.winsize_err)
printf("\033[999;999H" "\033[6n");
#endif
buffer_fill_and_print();
}
static int64_t getch_nowait(void)
{
int rd;
int64_t key64;
struct pollfd pfd[2];
pfd[0].fd = STDIN_FILENO;
pfd[0].events = POLLIN;
pfd[1].fd = kbd_fd;
pfd[1].events = POLLIN;
again:
tcsetattr(kbd_fd, TCSANOW, &term_less);
/* NB: select/poll returns whenever read will not block. Therefore:
* if eof is reached, select/poll will return immediately
* because read will immediately return 0 bytes.
* Even if select/poll says that input is available, read CAN block
* (switch fd into O_NONBLOCK'ed mode to avoid it)
*/
rd = 1;
/* Are we interested in stdin? */
//TODO: reuse code for determining this
if (!(option_mask32 & FLAG_S)
? !(max_fline > cur_fline + max_displayed_line)
: !(max_fline >= cur_fline
&& max_lineno > LINENO(flines[cur_fline]) + max_displayed_line)
) {
if (eof_error > 0) /* did NOT reach eof yet */
rd = 0; /* yes, we are interested in stdin */
}
/* Position cursor if line input is done */
if (less_gets_pos >= 0)
move_cursor(max_displayed_line + 2, less_gets_pos + 1);
fflush_all();
if (kbd_input[0] == 0) { /* if nothing is buffered */
#if ENABLE_FEATURE_LESS_WINCH
while (1) {
int r;
/* NB: SIGWINCH interrupts poll() */
r = poll(pfd + rd, 2 - rd, -1);
if (/*r < 0 && errno == EINTR &&*/ winch_counter)
return '\\'; /* anything which has no defined function */
if (r) break;
}
#else
safe_poll(pfd + rd, 2 - rd, -1);
#endif
}
/* We have kbd_fd in O_NONBLOCK mode, read inside read_key()
* would not block even if there is no input available */
key64 = read_key(kbd_fd, kbd_input, /*timeout off:*/ -2);
if ((int)key64 == -1) {
if (errno == EAGAIN) {
/* No keyboard input available. Since poll() did return,
* we should have input on stdin */
read_lines();
buffer_fill_and_print();
goto again;
}
/* EOF/error (ssh session got killed etc) */
less_exit(0);
}
set_tty_cooked();
return key64;
}
/* Grab a character from input without requiring the return key.
* May return KEYCODE_xxx values.
* Note that this function works best with raw input. */
static int64_t less_getch(int pos)
{
int64_t key64;
int key;
again:
less_gets_pos = pos;
key = key64 = getch_nowait();
less_gets_pos = -1;
/* Discard Ctrl-something chars.
* (checking only lower 32 bits is a size optimization:
* upper 32 bits are used only by KEYCODE_CURSOR_POS)
*/
if (key >= 0 && key < ' ' && key != 0x0d && key != 8)
goto again;
return key64;
}
static char* less_gets(int sz)
{
int c;
unsigned i = 0;
char *result = xzalloc(1);
while (1) {
c = '\0';
less_gets_pos = sz + i;
c = getch_nowait();
if (c == 0x0d) {
result[i] = '\0';
less_gets_pos = -1;
return result;
}
if (c == 0x7f)
c = 8;
if (c == 8 && i) {
printf("\x8 \x8");
i--;
}
if (c < ' ') /* filters out KEYCODE_xxx too (<0) */
continue;
if (i >= width - sz - 1)
continue; /* len limit */
bb_putchar(c);
result[i++] = c;
result = xrealloc(result, i+1);
}
}
static void examine_file(void)
{
char *new_fname;
print_statusline("Examine: ");
new_fname = less_gets(sizeof("Examine: ") - 1);
if (!new_fname[0]) {
status_print();
err:
free(new_fname);
return;
}
if (access(new_fname, R_OK) != 0) {
print_statusline("Cannot read this file");
goto err;
}
free(filename);
filename = new_fname;
/* files start by = argv. why we assume that argv is infinitely long??
files[num_files] = filename;
current_file = num_files + 1;
num_files++; */
files[0] = filename;
num_files = current_file = 1;
reinitialize();
}
/* This function changes the file currently being paged. direction can be one of the following:
* -1: go back one file
* 0: go to the first file
* 1: go forward one file */
static void change_file(int direction)
{
if (current_file != ((direction > 0) ? num_files : 1)) {
current_file = direction ? current_file + direction : 1;
free(filename);
filename = xstrdup(files[current_file - 1]);
reinitialize();
} else {
print_statusline(direction > 0 ? "No next file" : "No previous file");
}
}
static void remove_current_file(void)
{
unsigned i;
if (num_files < 2)
return;
if (current_file != 1) {
change_file(-1);
for (i = 3; i <= num_files; i++)
files[i - 2] = files[i - 1];
num_files--;
} else {
change_file(1);
for (i = 2; i <= num_files; i++)
files[i - 2] = files[i - 1];
num_files--;
current_file--;
}
}
static void colon_process(void)
{
int keypress;
/* Clear the current line and print a prompt */
print_statusline(" :");
keypress = less_getch(2);
switch (keypress) {
case 'd':
remove_current_file();
break;
case 'e':
examine_file();
break;
#if ENABLE_FEATURE_LESS_FLAGS
case 'f':
m_status_print();
break;
#endif
case 'n':
change_file(1);
break;
case 'p':
change_file(-1);
break;
case 'q':
less_exit(EXIT_SUCCESS);
break;
case 'x':
change_file(0);
break;
}
}
#if ENABLE_FEATURE_LESS_REGEXP
static void normalize_match_pos(int match)
{
if (match >= num_matches)
match = num_matches - 1;
if (match < 0)
match = 0;
match_pos = match;
}
static void goto_match(int match)
{
if (!pattern_valid)
return;
if (match < 0)
match = 0;
/* Try to find next match if eof isn't reached yet */
if (match >= num_matches && eof_error > 0) {
wanted_match = match; /* "I want to read until I see N'th match" */
read_lines();
}
if (num_matches) {
normalize_match_pos(match);
buffer_line(match_lines[match_pos]);
} else {
print_statusline("No matches found");
}
}
static void fill_match_lines(unsigned pos)
{
if (!pattern_valid)
return;
/* Run the regex on each line of the current file */
while (pos <= max_fline) {
/* If this line matches */
if (regexec(&pattern, flines[pos], 0, NULL, 0) == 0
/* and we didn't match it last time */
&& !(num_matches && match_lines[num_matches-1] == pos)
) {
match_lines = xrealloc_vector(match_lines, 4, num_matches);
match_lines[num_matches++] = pos;
}
pos++;
}
}
static void regex_process(void)
{
char *uncomp_regex, *err;
/* Reset variables */
free(match_lines);
match_lines = NULL;
match_pos = 0;
num_matches = 0;
if (pattern_valid) {
regfree(&pattern);
pattern_valid = 0;
}
/* Get the uncompiled regular expression from the user */
clear_line();
bb_putchar((option_mask32 & LESS_STATE_MATCH_BACKWARDS) ? '?' : '/');
uncomp_regex = less_gets(1);
if (!uncomp_regex[0]) {
free(uncomp_regex);
buffer_print();
return;
}
/* Compile the regex and check for errors */
err = regcomp_or_errmsg(&pattern, uncomp_regex,
(option_mask32 & FLAG_I) ? REG_ICASE : 0);
free(uncomp_regex);
if (err) {
print_statusline(err);
free(err);
return;
}
pattern_valid = 1;
match_pos = 0;
fill_match_lines(0);
while (match_pos < num_matches) {
if ((int)match_lines[match_pos] > cur_fline)
break;
match_pos++;
}
if (option_mask32 & LESS_STATE_MATCH_BACKWARDS)
match_pos--;
/* It's possible that no matches are found yet.
* goto_match() will read input looking for match,
* if needed */
goto_match(match_pos);
}
#endif
static void number_process(int first_digit)
{
unsigned i;
int num;
int keypress;
char num_input[sizeof(int)*4]; /* more than enough */
num_input[0] = first_digit;
/* Clear the current line, print a prompt, and then print the digit */
clear_line();
printf(":%c", first_digit);
/* Receive input until a letter is given */
i = 1;
while (i < sizeof(num_input)-1) {
keypress = less_getch(i + 1);
if ((unsigned)keypress > 255 || !isdigit(num_input[i]))
break;
num_input[i] = keypress;
bb_putchar(keypress);
i++;
}
num_input[i] = '\0';
num = bb_strtou(num_input, NULL, 10);
/* on format error, num == -1 */
if (num < 1 || num > MAXLINES) {
buffer_print();
return;
}
/* We now know the number and the letter entered, so we process them */
switch (keypress) {
case KEYCODE_DOWN: case 'z': case 'd': case 'e': case ' ': case '\015':
buffer_down(num);
break;
case KEYCODE_UP: case 'b': case 'w': case 'y': case 'u':
buffer_up(num);
break;
case 'g': case '<': case 'G': case '>':
cur_fline = num + max_displayed_line;
read_lines();
buffer_line(num - 1);
break;
case 'p': case '%':
num = num * (max_fline / 100); /* + max_fline / 2; */
cur_fline = num + max_displayed_line;
read_lines();
buffer_line(num);
break;
#if ENABLE_FEATURE_LESS_REGEXP
case 'n':
goto_match(match_pos + num);
break;
case '/':
option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
regex_process();
break;
case '?':
option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
regex_process();
break;
#endif
}
}
#if ENABLE_FEATURE_LESS_DASHCMD
static void flag_change(void)
{
int keypress;
clear_line();
bb_putchar('-');
keypress = less_getch(1);
switch (keypress) {
case 'M':
option_mask32 ^= FLAG_M;
break;
case 'm':
option_mask32 ^= FLAG_m;
break;
case 'E':
option_mask32 ^= FLAG_E;
break;
case '~':
option_mask32 ^= FLAG_TILDE;
break;
case 'S':
option_mask32 ^= FLAG_S;
buffer_fill_and_print();
break;
#if ENABLE_FEATURE_LESS_LINENUMS
case 'N':
option_mask32 ^= FLAG_N;
re_wrap();
buffer_fill_and_print();
break;
#endif
}
}
#ifdef BLOAT
static void show_flag_status(void)
{
int keypress;
int flag_val;
clear_line();
bb_putchar('_');
keypress = less_getch(1);
switch (keypress) {
case 'M':
flag_val = option_mask32 & FLAG_M;
break;
case 'm':
flag_val = option_mask32 & FLAG_m;
break;
case '~':
flag_val = option_mask32 & FLAG_TILDE;
break;
case 'N':
flag_val = option_mask32 & FLAG_N;
break;
case 'E':
flag_val = option_mask32 & FLAG_E;
break;
default:
flag_val = 0;
break;
}
clear_line();
printf(HIGHLIGHT"The status of the flag is: %u"NORMAL, flag_val != 0);
}
#endif
#endif /* ENABLE_FEATURE_LESS_DASHCMD */
static void save_input_to_file(void)
{
const char *msg = "";
char *current_line;
unsigned i;
FILE *fp;
print_statusline("Log file: ");
current_line = less_gets(sizeof("Log file: ")-1);
if (current_line[0]) {
fp = fopen_for_write(current_line);
if (!fp) {
msg = "Error opening log file";
goto ret;
}
for (i = 0; i <= max_fline; i++)
fprintf(fp, "%s\n", flines[i]);
fclose(fp);
msg = "Done";
}
ret:
print_statusline(msg);
free(current_line);
}
#if ENABLE_FEATURE_LESS_MARKS
static void add_mark(void)
{
int letter;
print_statusline("Mark: ");
letter = less_getch(sizeof("Mark: ") - 1);
if (isalpha(letter)) {
/* If we exceed 15 marks, start overwriting previous ones */
if (num_marks == 14)
num_marks = 0;
mark_lines[num_marks][0] = letter;
mark_lines[num_marks][1] = cur_fline;
num_marks++;
} else {
print_statusline("Invalid mark letter");
}
}
static void goto_mark(void)
{
int letter;
int i;
print_statusline("Go to mark: ");
letter = less_getch(sizeof("Go to mark: ") - 1);
clear_line();
if (isalpha(letter)) {
for (i = 0; i <= num_marks; i++)
if (letter == mark_lines[i][0]) {
buffer_line(mark_lines[i][1]);
break;
}
if (num_marks == 14 && letter != mark_lines[14][0])
print_statusline("Mark not set");
} else
print_statusline("Invalid mark letter");
}
#endif
#if ENABLE_FEATURE_LESS_BRACKETS
static char opp_bracket(char bracket)
{
switch (bracket) {
case '{': case '[': /* '}' == '{' + 2. Same for '[' */
bracket++;
case '(': /* ')' == '(' + 1 */
bracket++;
break;
case '}': case ']':
bracket--;
case ')':
bracket--;
break;
};
return bracket;
}
static void match_right_bracket(char bracket)
{
unsigned i;
if (strchr(flines[cur_fline], bracket) == NULL) {
print_statusline("No bracket in top line");
return;
}
bracket = opp_bracket(bracket);
for (i = cur_fline + 1; i < max_fline; i++) {
if (strchr(flines[i], bracket) != NULL) {
buffer_line(i);
return;
}
}
print_statusline("No matching bracket found");
}
static void match_left_bracket(char bracket)
{
int i;
if (strchr(flines[cur_fline + max_displayed_line], bracket) == NULL) {
print_statusline("No bracket in bottom line");
return;
}
bracket = opp_bracket(bracket);
for (i = cur_fline + max_displayed_line; i >= 0; i--) {
if (strchr(flines[i], bracket) != NULL) {
buffer_line(i);
return;
}
}
print_statusline("No matching bracket found");
}
#endif /* FEATURE_LESS_BRACKETS */
static void keypress_process(int keypress)
{
switch (keypress) {
case KEYCODE_DOWN: case 'e': case 'j': case 0x0d:
buffer_down(1);
break;
case KEYCODE_UP: case 'y': case 'k':
buffer_up(1);
break;
case KEYCODE_PAGEDOWN: case ' ': case 'z': case 'f':
buffer_down(max_displayed_line + 1);
break;
case KEYCODE_PAGEUP: case 'w': case 'b':
buffer_up(max_displayed_line + 1);
break;
case 'd':
buffer_down((max_displayed_line + 1) / 2);
break;
case 'u':
buffer_up((max_displayed_line + 1) / 2);
break;
case KEYCODE_HOME: case 'g': case 'p': case '<': case '%':
buffer_line(0);
break;
case KEYCODE_END: case 'G': case '>':
cur_fline = MAXLINES;
read_lines();
buffer_line(cur_fline);
break;
case 'q': case 'Q':
less_exit(EXIT_SUCCESS);
break;
#if ENABLE_FEATURE_LESS_MARKS
case 'm':
add_mark();
buffer_print();
break;
case '\'':
goto_mark();
buffer_print();
break;
#endif
case 'r': case 'R':
/* TODO: (1) also bind ^R, ^L to this?
* (2) re-measure window size?
*/
buffer_print();
break;
/*case 'R':
full_repaint();
break;*/
case 's':
save_input_to_file();
break;
case 'E':
examine_file();
break;
#if ENABLE_FEATURE_LESS_FLAGS
case '=':
m_status_print();
break;
#endif
#if ENABLE_FEATURE_LESS_REGEXP
case '/':
option_mask32 &= ~LESS_STATE_MATCH_BACKWARDS;
regex_process();
break;
case 'n':
goto_match(match_pos + 1);
break;
case 'N':
goto_match(match_pos - 1);
break;
case '?':
option_mask32 |= LESS_STATE_MATCH_BACKWARDS;
regex_process();
break;
#endif
#if ENABLE_FEATURE_LESS_DASHCMD
case '-':
flag_change();
buffer_print();
break;
#ifdef BLOAT
case '_':
show_flag_status();
break;
#endif
#endif
#if ENABLE_FEATURE_LESS_BRACKETS
case '{': case '(': case '[':
match_right_bracket(keypress);
break;
case '}': case ')': case ']':
match_left_bracket(keypress);
break;
#endif
case ':':
colon_process();
break;
}
if (isdigit(keypress))
number_process(keypress);
}
static void sig_catcher(int sig)
{
less_exit(- sig);
}
#if ENABLE_FEATURE_LESS_WINCH
static void sigwinch_handler(int sig UNUSED_PARAM)
{
winch_counter++;
}
#endif
int less_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int less_main(int argc, char **argv)
{
INIT_G();
/* TODO: -x: do not interpret backspace, -xx: tab also */
/* -xxx: newline also */
/* -w N: assume width N (-xxx -w 32: hex viewer of sorts) */
getopt32(argv, "EMmN~I" IF_FEATURE_LESS_DASHCMD("S"));
argc -= optind;
argv += optind;
num_files = argc;
files = argv;
/* Another popular pager, most, detects when stdout
* is not a tty and turns into cat. This makes sense. */
if (!isatty(STDOUT_FILENO))
return bb_cat(argv);
if (!num_files) {
if (isatty(STDIN_FILENO)) {
/* Just "less"? No args and no redirection? */
bb_error_msg("missing filename");
bb_show_usage();
}
} else {
filename = xstrdup(files[0]);
}
if (option_mask32 & FLAG_TILDE)
empty_line_marker = "";
kbd_fd = open(CURRENT_TTY, O_RDONLY);
if (kbd_fd < 0)
return bb_cat(argv);
ndelay_on(kbd_fd);
tcgetattr(kbd_fd, &term_orig);
term_less = term_orig;
term_less.c_lflag &= ~(ICANON | ECHO);
term_less.c_iflag &= ~(IXON | ICRNL);
/*term_less.c_oflag &= ~ONLCR;*/
term_less.c_cc[VMIN] = 1;
term_less.c_cc[VTIME] = 0;
IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
/* 20: two tabstops + 4 */
if (width < 20 || max_displayed_line < 3)
return bb_cat(argv);
max_displayed_line -= 2;
/* We want to restore term_orig on exit */
bb_signals(BB_FATAL_SIGS, sig_catcher);
#if ENABLE_FEATURE_LESS_WINCH
signal(SIGWINCH, sigwinch_handler);
#endif
buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
reinitialize();
while (1) {
int64_t keypress;
#if ENABLE_FEATURE_LESS_WINCH
while (WINCH_COUNTER) {
again:
winch_counter--;
IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
IF_FEATURE_LESS_ASK_TERMINAL(got_size:)
/* 20: two tabstops + 4 */
if (width < 20)
width = 20;
if (max_displayed_line < 3)
max_displayed_line = 3;
max_displayed_line -= 2;
free(buffer);
buffer = xmalloc((max_displayed_line+1) * sizeof(char *));
/* Avoid re-wrap and/or redraw if we already know
* we need to do it again. These ops are expensive */
if (WINCH_COUNTER)
goto again;
re_wrap();
if (WINCH_COUNTER)
goto again;
buffer_fill_and_print();
/* This took some time. Loop back and check,
* were there another SIGWINCH? */
}
keypress = less_getch(-1); /* -1: do not position cursor */
# if ENABLE_FEATURE_LESS_ASK_TERMINAL
if ((int32_t)keypress == KEYCODE_CURSOR_POS) {
uint32_t rc = (keypress >> 32);
width = (rc & 0x7fff);
max_displayed_line = ((rc >> 16) & 0x7fff);
goto got_size;
}
# endif
#else
keypress = less_getch(-1); /* -1: do not position cursor */
#endif
keypress_process(keypress);
}
}
/*
Help text of less version 418 is below.
If you are implementing something, keeping
key and/or command line switch compatibility is a good idea:
SUMMARY OF LESS COMMANDS
Commands marked with * may be preceded by a number, N.
Notes in parentheses indicate the behavior if N is given.
h H Display this help.
q :q Q :Q ZZ Exit.
---------------------------------------------------------------------------
MOVING
e ^E j ^N CR * Forward one line (or N lines).
y ^Y k ^K ^P * Backward one line (or N lines).
f ^F ^V SPACE * Forward one window (or N lines).
b ^B ESC-v * Backward one window (or N lines).
z * Forward one window (and set window to N).
w * Backward one window (and set window to N).
ESC-SPACE * Forward one window, but don't stop at end-of-file.
d ^D * Forward one half-window (and set half-window to N).
u ^U * Backward one half-window (and set half-window to N).
ESC-) RightArrow * Left one half screen width (or N positions).
ESC-( LeftArrow * Right one half screen width (or N positions).
F Forward forever; like "tail -f".
r ^R ^L Repaint screen.
R Repaint screen, discarding buffered input.
---------------------------------------------------
Default "window" is the screen height.
Default "half-window" is half of the screen height.
---------------------------------------------------------------------------
SEARCHING
/pattern * Search forward for (N-th) matching line.
?pattern * Search backward for (N-th) matching line.
n * Repeat previous search (for N-th occurrence).
N * Repeat previous search in reverse direction.
ESC-n * Repeat previous search, spanning files.
ESC-N * Repeat previous search, reverse dir. & spanning files.
ESC-u Undo (toggle) search highlighting.
---------------------------------------------------
Search patterns may be modified by one or more of:
^N or ! Search for NON-matching lines.
^E or * Search multiple files (pass thru END OF FILE).
^F or @ Start search at FIRST file (for /) or last file (for ?).
^K Highlight matches, but don't move (KEEP position).
^R Don't use REGULAR EXPRESSIONS.
---------------------------------------------------------------------------
JUMPING
g < ESC-< * Go to first line in file (or line N).
G > ESC-> * Go to last line in file (or line N).
p % * Go to beginning of file (or N percent into file).
t * Go to the (N-th) next tag.
T * Go to the (N-th) previous tag.
{ ( [ * Find close bracket } ) ].
} ) ] * Find open bracket { ( [.
ESC-^F <c1> <c2> * Find close bracket <c2>.
ESC-^B <c1> <c2> * Find open bracket <c1>
---------------------------------------------------
Each "find close bracket" command goes forward to the close bracket
matching the (N-th) open bracket in the top line.
Each "find open bracket" command goes backward to the open bracket
matching the (N-th) close bracket in the bottom line.
m<letter> Mark the current position with <letter>.
'<letter> Go to a previously marked position.
'' Go to the previous position.
^X^X Same as '.
---------------------------------------------------
A mark is any upper-case or lower-case letter.
Certain marks are predefined:
^ means beginning of the file
$ means end of the file
---------------------------------------------------------------------------
CHANGING FILES
:e [file] Examine a new file.
^X^V Same as :e.
:n * Examine the (N-th) next file from the command line.
:p * Examine the (N-th) previous file from the command line.
:x * Examine the first (or N-th) file from the command line.
:d Delete the current file from the command line list.
= ^G :f Print current file name.
---------------------------------------------------------------------------
MISCELLANEOUS COMMANDS
-<flag> Toggle a command line option [see OPTIONS below].
--<name> Toggle a command line option, by name.
_<flag> Display the setting of a command line option.
__<name> Display the setting of an option, by name.
+cmd Execute the less cmd each time a new file is examined.
!command Execute the shell command with $SHELL.
|Xcommand Pipe file between current pos & mark X to shell command.
v Edit the current file with $VISUAL or $EDITOR.
V Print version number of "less".
---------------------------------------------------------------------------
OPTIONS
Most options may be changed either on the command line,
or from within less by using the - or -- command.
Options may be given in one of two forms: either a single
character preceded by a -, or a name preceeded by --.
-? ........ --help
Display help (from command line).
-a ........ --search-skip-screen
Forward search skips current screen.
-b [N] .... --buffers=[N]
Number of buffers.
-B ........ --auto-buffers
Don't automatically allocate buffers for pipes.
-c ........ --clear-screen
Repaint by clearing rather than scrolling.
-d ........ --dumb
Dumb terminal.
-D [xn.n] . --color=xn.n
Set screen colors. (MS-DOS only)
-e -E .... --quit-at-eof --QUIT-AT-EOF
Quit at end of file.
-f ........ --force
Force open non-regular files.
-F ........ --quit-if-one-screen
Quit if entire file fits on first screen.
-g ........ --hilite-search
Highlight only last match for searches.
-G ........ --HILITE-SEARCH
Don't highlight any matches for searches.
-h [N] .... --max-back-scroll=[N]
Backward scroll limit.
-i ........ --ignore-case
Ignore case in searches that do not contain uppercase.
-I ........ --IGNORE-CASE
Ignore case in all searches.
-j [N] .... --jump-target=[N]
Screen position of target lines.
-J ........ --status-column
Display a status column at left edge of screen.
-k [file] . --lesskey-file=[file]
Use a lesskey file.
-L ........ --no-lessopen
Ignore the LESSOPEN environment variable.
-m -M .... --long-prompt --LONG-PROMPT
Set prompt style.
-n -N .... --line-numbers --LINE-NUMBERS
Don't use line numbers.
-o [file] . --log-file=[file]
Copy to log file (standard input only).
-O [file] . --LOG-FILE=[file]
Copy to log file (unconditionally overwrite).
-p [pattern] --pattern=[pattern]
Start at pattern (from command line).
-P [prompt] --prompt=[prompt]
Define new prompt.
-q -Q .... --quiet --QUIET --silent --SILENT
Quiet the terminal bell.
-r -R .... --raw-control-chars --RAW-CONTROL-CHARS
Output "raw" control characters.
-s ........ --squeeze-blank-lines
Squeeze multiple blank lines.
-S ........ --chop-long-lines
Chop long lines.
-t [tag] .. --tag=[tag]
Find a tag.
-T [tagsfile] --tag-file=[tagsfile]
Use an alternate tags file.
-u -U .... --underline-special --UNDERLINE-SPECIAL
Change handling of backspaces.
-V ........ --version
Display the version number of "less".
-w ........ --hilite-unread
Highlight first new line after forward-screen.
-W ........ --HILITE-UNREAD
Highlight first new line after any forward movement.
-x [N[,...]] --tabs=[N[,...]]
Set tab stops.
-X ........ --no-init
Don't use termcap init/deinit strings.
--no-keypad
Don't use termcap keypad init/deinit strings.
-y [N] .... --max-forw-scroll=[N]
Forward scroll limit.
-z [N] .... --window=[N]
Set size of window.
-" [c[c]] . --quotes=[c[c]]
Set shell quote characters.
-~ ........ --tilde
Don't display tildes after end of file.
-# [N] .... --shift=[N]
Horizontal scroll amount (0 = one half screen width)
---------------------------------------------------------------------------
LINE EDITING
These keys can be used to edit text being entered
on the "command line" at the bottom of the screen.
RightArrow ESC-l Move cursor right one character.
LeftArrow ESC-h Move cursor left one character.
CNTL-RightArrow ESC-RightArrow ESC-w Move cursor right one word.
CNTL-LeftArrow ESC-LeftArrow ESC-b Move cursor left one word.
HOME ESC-0 Move cursor to start of line.
END ESC-$ Move cursor to end of line.
BACKSPACE Delete char to left of cursor.
DELETE ESC-x Delete char under cursor.
CNTL-BACKSPACE ESC-BACKSPACE Delete word to left of cursor.
CNTL-DELETE ESC-DELETE ESC-X Delete word under cursor.
CNTL-U ESC (MS-DOS only) Delete entire line.
UpArrow ESC-k Retrieve previous command line.
DownArrow ESC-j Retrieve next command line.
TAB Complete filename & cycle.
SHIFT-TAB ESC-TAB Complete filename & reverse cycle.
CNTL-L Complete filename, list all.
*/
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