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1 .TH LESS 1 "Version 424: 16 Jun 2008"
2 .SH NAME
3 less \- opposite of more
4 .SH SYNOPSIS
5 .B "less \-?"
6 .br
7 .B "less \-\-help"
8 .br
9 .B "less \-V"
10 .br
11 .B "less \-\-version"
12 .br
13 .B "less [\-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]"
14 .br
15 .B " [\-b \fIspace\fP] [\-h \fIlines\fP] [\-j \fIline\fP] [\-k \fIkeyfile\fP]"
16 .br
17 .B " [\-{oO} \fIlogfile\fP] [\-p \fIpattern\fP] [\-P \fIprompt\fP] [\-t \fItag\fP]"
18 .br
19 .B " [\-T \fItagsfile\fP] [\-x \fItab\fP,...] [\-y \fIlines\fP] [\-[z] \fIlines\fP]"
20 .br
21 .B " [\-# \fIshift\fP] [+[+]\fIcmd\fP] [\-\-] [\fIfilename\fP]..."
22 .br
23 (See the OPTIONS section for alternate option syntax with long option names.)
24
25 .SH DESCRIPTION
26 .I Less
27 is a program similar to
28 .I more
29 (1), but which allows backward movement
30 in the file as well as forward movement.
31 Also,
32 .I less
33 does not have to read the entire input file before starting,
34 so with large input files it starts up faster than text editors like
35 .I vi
36 (1).
37 .I Less
38 uses termcap (or terminfo on some systems),
39 so it can run on a variety of terminals.
40 There is even limited support for hardcopy terminals.
41 (On a hardcopy terminal, lines which should be printed at the top
42 of the screen are prefixed with a caret.)
43 .PP
44 Commands are based on both
45 .I more
46 and
47 .I vi.
48 Commands may be preceded by a decimal number,
49 called N in the descriptions below.
50 The number is used by some commands, as indicated.
51
52 .SH COMMANDS
53 In the following descriptions, ^X means control-X.
54 ESC stands for the ESCAPE key; for example ESC-v means the
55 two character sequence "ESCAPE", then "v".
56 .IP "h or H"
57 Help: display a summary of these commands.
58 If you forget all the other commands, remember this one.
59 .IP "SPACE or ^V or f or ^F"
60 Scroll forward N lines, default one window (see option \-z below).
61 If N is more than the screen size, only the final screenful is displayed.
62 Warning: some systems use ^V as a special literalization character.
63 .IP "z"
64 Like SPACE, but if N is specified, it becomes the new window size.
65 .IP "ESC-SPACE"
66 Like SPACE, but scrolls a full screenful, even if it reaches
67 end-of-file in the process.
68 .IP "RETURN or ^N or e or ^E or j or ^J"
69 Scroll forward N lines, default 1.
70 The entire N lines are displayed, even if N is more than the screen size.
71 .IP "d or ^D"
72 Scroll forward N lines, default one half of the screen size.
73 If N is specified, it becomes the new default for
74 subsequent d and u commands.
75 .IP "b or ^B or ESC-v"
76 Scroll backward N lines, default one window (see option \-z below).
77 If N is more than the screen size, only the final screenful is displayed.
78 .IP "w"
79 Like ESC-v, but if N is specified, it becomes the new window size.
80 .IP "y or ^Y or ^P or k or ^K"
81 Scroll backward N lines, default 1.
82 The entire N lines are displayed, even if N is more than the screen size.
83 Warning: some systems use ^Y as a special job control character.
84 .IP "u or ^U"
85 Scroll backward N lines, default one half of the screen size.
86 If N is specified, it becomes the new default for
87 subsequent d and u commands.
88 .IP "ESC-) or RIGHTARROW"
89 Scroll horizontally right N characters, default half the screen width
90 (see the \-# option).
91 If a number N is specified, it becomes the default for future RIGHTARROW
92 and LEFTARROW commands.
93 While the text is scrolled, it acts as though the \-S option
94 (chop lines) were in effect.
95 .IP "ESC-( or LEFTARROW"
96 Scroll horizontally left N characters, default half the screen width
97 (see the \-# option).
98 If a number N is specified, it becomes the default for future RIGHTARROW
99 and LEFTARROW commands.
100 .IP "r or ^R or ^L"
101 Repaint the screen.
102 .IP R
103 Repaint the screen, discarding any buffered input.
104 Useful if the file is changing while it is being viewed.
105 .IP "F"
106 Scroll forward, and keep trying to read when the
107 end of file is reached.
108 Normally this command would be used when already at the end of the file.
109 It is a way to monitor the tail of a file which is growing
110 while it is being viewed.
111 (The behavior is similar to the "tail \-f" command.)
112 .IP "g or < or ESC-<"
113 Go to line N in the file, default 1 (beginning of file).
114 (Warning: this may be slow if N is large.)
115 .IP "G or > or ESC->"
116 Go to line N in the file, default the end of the file.
117 (Warning: this may be slow if N is large,
118 or if N is not specified and
119 standard input, rather than a file, is being read.)
120 .IP "p or %"
121 Go to a position N percent into the file.
122 N should be between 0 and 100, and may contain a decimal point.
123 .IP "P"
124 Go to the line containing byte offset N in the file.
125 .IP "{"
126 If a left curly bracket appears in the top line displayed
127 on the screen,
128 the { command will go to the matching right curly bracket.
129 The matching right curly bracket is positioned on the bottom
130 line of the screen.
131 If there is more than one left curly bracket on the top line,
132 a number N may be used to specify the N-th bracket on the line.
133 .IP "}"
134 If a right curly bracket appears in the bottom line displayed
135 on the screen,
136 the } command will go to the matching left curly bracket.
137 The matching left curly bracket is positioned on the top
138 line of the screen.
139 If there is more than one right curly bracket on the top line,
140 a number N may be used to specify the N-th bracket on the line.
141 .IP "("
142 Like {, but applies to parentheses rather than curly brackets.
143 .IP ")"
144 Like }, but applies to parentheses rather than curly brackets.
145 .IP "["
146 Like {, but applies to square brackets rather than curly brackets.
147 .IP "]"
148 Like }, but applies to square brackets rather than curly brackets.
149 .IP "ESC-^F"
150 Followed by two characters,
151 acts like {, but uses the two characters as open and close brackets,
152 respectively.
153 For example, "ESC ^F < >" could be used to
154 go forward to the > which matches the < in the top displayed line.
155 .IP "ESC-^B"
156 Followed by two characters,
157 acts like }, but uses the two characters as open and close brackets,
158 respectively.
159 For example, "ESC ^B < >" could be used to
160 go backward to the < which matches the > in the bottom displayed line.
161 .IP m
162 Followed by any lowercase letter,
163 marks the current position with that letter.
164 .IP "'"
165 (Single quote.)
166 Followed by any lowercase letter, returns to the position which
167 was previously marked with that letter.
168 Followed by another single quote, returns to the position at
169 which the last "large" movement command was executed.
170 Followed by a ^ or $, jumps to the beginning or end of the
171 file respectively.
172 Marks are preserved when a new file is examined,
173 so the ' command can be used to switch between input files.
174 .IP "^X^X"
175 Same as single quote.
176 .IP /pattern
177 Search forward in the file for the N-th line containing the pattern.
178 N defaults to 1.
179 The pattern is a regular expression, as recognized by
180 the regular expression library supplied by your system.
181 The search starts at the second line displayed
182 (but see the \-a and \-j options, which change this).
183 .sp
184 Certain characters are special
185 if entered at the beginning of the pattern;
186 they modify the type of search rather than become part of the pattern:
187 .RS
188 .IP "^N or !"
189 Search for lines which do NOT match the pattern.
190 .IP "^E or *"
191 Search multiple files.
192 That is, if the search reaches the END of the current file
193 without finding a match,
194 the search continues in the next file in the command line list.
195 .IP "^F or @"
196 Begin the search at the first line of the FIRST file
197 in the command line list,
198 regardless of what is currently displayed on the screen
199 or the settings of the \-a or \-j options.
200 .IP "^K"
201 Highlight any text which matches the pattern on the current screen,
202 but don't move to the first match (KEEP current position).
203 .IP "^R"
204 Don't interpret regular expression metacharacters;
205 that is, do a simple textual comparison.
206 .RE
207 .IP ?pattern
208 Search backward in the file for the N-th line containing the pattern.
209 The search starts at the line immediately before the top line displayed.
210 .sp
211 Certain characters are special as in the / command:
212 .RS
213 .IP "^N or !"
214 Search for lines which do NOT match the pattern.
215 .IP "^E or *"
216 Search multiple files.
217 That is, if the search reaches the beginning of the current file
218 without finding a match,
219 the search continues in the previous file in the command line list.
220 .IP "^F or @"
221 Begin the search at the last line of the last file
222 in the command line list,
223 regardless of what is currently displayed on the screen
224 or the settings of the \-a or \-j options.
225 .IP "^K"
226 As in forward searches.
227 .IP "^R"
228 As in forward searches.
229 .RE
230 .IP "ESC-/pattern"
231 Same as "/*".
232 .IP "ESC-?pattern"
233 Same as "?*".
234 .IP n
235 Repeat previous search, for N-th line containing the last pattern.
236 If the previous search was modified by ^N, the search is made for the
237 N-th line NOT containing the pattern.
238 If the previous search was modified by ^E, the search continues
239 in the next (or previous) file if not satisfied in the current file.
240 If the previous search was modified by ^R, the search is done
241 without using regular expressions.
242 There is no effect if the previous search was modified by ^F or ^K.
243 .IP N
244 Repeat previous search, but in the reverse direction.
245 .IP "ESC-n"
246 Repeat previous search, but crossing file boundaries.
247 The effect is as if the previous search were modified by *.
248 .IP "ESC-N"
249 Repeat previous search, but in the reverse direction
250 and crossing file boundaries.
251 .IP "ESC-u"
252 Undo search highlighting.
253 Turn off highlighting of strings matching the current search pattern.
254 If highlighting is already off because of a previous ESC-u command,
255 turn highlighting back on.
256 Any search command will also turn highlighting back on.
257 (Highlighting can also be disabled by toggling the \-G option;
258 in that case search commands do not turn highlighting back on.)
259 .IP "&pattern"
260 Display only lines which match the pattern;
261 lines which do not match the pattern are not displayed.
262 If pattern is empty (if you type & immediately followed by ENTER),
263 any filtering is turned off, and all lines are displayed.
264 While filtering is in effect, an ampersand is displayed at the
265 beginning of the prompt,
266 as a reminder that some lines in the file may be hidden.
267 .sp
268 Certain characters are special as in the / command:
269 .RS
270 .IP "^N or !"
271 Display only lines which do NOT match the pattern.
272 .IP "^R"
273 Don't interpret regular expression metacharacters;
274 that is, do a simple textual comparison.
275 .RE
276 .IP ":e [filename]"
277 Examine a new file.
278 If the filename is missing, the "current" file (see the :n and :p commands
279 below) from the list of files in the command line is re-examined.
280 A percent sign (%) in the filename is replaced by the name of the
281 current file.
282 A pound sign (#) is replaced by the name of the previously examined file.
283 However, two consecutive percent signs are simply
284 replaced with a single percent sign.
285 This allows you to enter a filename that contains a percent sign
286 in the name.
287 Similarly, two consecutive pound signs are replaced with a single pound sign.
288 The filename is inserted into the command line list of files
289 so that it can be seen by subsequent :n and :p commands.
290 If the filename consists of several files, they are all inserted into
291 the list of files and the first one is examined.
292 If the filename contains one or more spaces,
293 the entire filename should be enclosed in double quotes
294 (also see the \-" option).
295 .IP "^X^V or E"
296 Same as :e.
297 Warning: some systems use ^V as a special literalization character.
298 On such systems, you may not be able to use ^V.
299 .IP ":n"
300 Examine the next file (from the list of files given in the command line).
301 If a number N is specified, the N-th next file is examined.
302 .IP ":p"
303 Examine the previous file in the command line list.
304 If a number N is specified, the N-th previous file is examined.
305 .IP ":x"
306 Examine the first file in the command line list.
307 If a number N is specified, the N-th file in the list is examined.
308 .IP ":d"
309 Remove the current file from the list of files.
310 .IP "t"
311 Go to the next tag, if there were more than one matches for the current tag.
312 See the \-t option for more details about tags.
313 .IP "T"
314 Go to the previous tag, if there were more than one matches for the current tag.
315 .IP "= or ^G or :f"
316 Prints some information about the file being viewed,
317 including its name
318 and the line number and byte offset of the bottom line being displayed.
319 If possible, it also prints the length of the file,
320 the number of lines in the file
321 and the percent of the file above the last displayed line.
322 .IP \-
323 Followed by one of the command line option letters (see OPTIONS below),
324 this will change the setting of that option
325 and print a message describing the new setting.
326 If a ^P (CONTROL-P) is entered immediately after the dash,
327 the setting of the option is changed but no message is printed.
328 If the option letter has a numeric value (such as \-b or \-h),
329 or a string value (such as \-P or \-t),
330 a new value may be entered after the option letter.
331 If no new value is entered, a message describing
332 the current setting is printed and nothing is changed.
333 .IP \-\-
334 Like the \- command, but takes a long option name (see OPTIONS below)
335 rather than a single option letter.
336 You must press RETURN after typing the option name.
337 A ^P immediately after the second dash suppresses printing of a
338 message describing the new setting, as in the \- command.
339 .IP \-+
340 Followed by one of the command line option letters
341 this will reset the option to its default setting
342 and print a message describing the new setting.
343 (The "\-+\fIX\fP" command does the same thing
344 as "\-+\fIX\fP" on the command line.)
345 This does not work for string-valued options.
346 .IP \-\-+
347 Like the \-+ command, but takes a long option name
348 rather than a single option letter.
349 .IP \-!
350 Followed by one of the command line option letters,
351 this will reset the option to the "opposite" of its default setting
352 and print a message describing the new setting.
353 This does not work for numeric or string-valued options.
354 .IP \-\-!
355 Like the \-! command, but takes a long option name
356 rather than a single option letter.
357 .IP _
358 (Underscore.)
359 Followed by one of the command line option letters,
360 this will print a message describing the current setting of that option.
361 The setting of the option is not changed.
362 .IP __
363 (Double underscore.)
364 Like the _ (underscore) command, but takes a long option name
365 rather than a single option letter.
366 You must press RETURN after typing the option name.
367 .IP +cmd
368 Causes the specified cmd to be executed each time a new file is examined.
369 For example, +G causes
370 .I less
371 to initially display each file starting at the end
372 rather than the beginning.
373 .IP V
374 Prints the version number of
375 .I less
376 being run.
377 .IP "q or Q or :q or :Q or ZZ"
378 Exits
379 .I less.
380 .PP
381 The following
382 four
383 commands may or may not be valid, depending on your particular installation.
384 .PP
385 .IP v
386 Invokes an editor to edit the current file being viewed.
387 The editor is taken from the environment variable VISUAL if defined,
388 or EDITOR if VISUAL is not defined,
389 or defaults to "vi" if neither VISUAL nor EDITOR is defined.
390 See also the discussion of LESSEDIT under the section on PROMPTS below.
391 .IP "! shell-command"
392 Invokes a shell to run the shell-command given.
393 A percent sign (%) in the command is replaced by the name of the
394 current file.
395 A pound sign (#) is replaced by the name of the previously examined file.
396 "!!" repeats the last shell command.
397 "!" with no shell command simply invokes a shell.
398 On Unix systems, the shell is taken from the environment variable SHELL,
399 or defaults to "sh".
400 On MS-DOS and OS/2 systems, the shell is the normal command processor.
401 .IP "| <m> shell-command"
402 <m> represents any mark letter.
403 Pipes a section of the input file to the given shell command.
404 The section of the file to be piped is between the first line on
405 the current screen and the position marked by the letter.
406 <m> may also be ^ or $ to indicate beginning or end of file respectively.
407 If <m> is . or newline, the current screen is piped.
408 .IP "s filename"
409 Save the input to a file.
410 This only works if the input is a pipe, not an ordinary file.
411 .PP
412 .SH OPTIONS
413 Command line options are described below.
414 Most options may be changed while
415 .I less
416 is running, via the "\-" command.
417 .PP
418 Most options may be given in one of two forms:
419 either a dash followed by a single letter,
420 or two dashes followed by a long option name.
421 A long option name may be abbreviated as long as
422 the abbreviation is unambiguous.
423 For example, \-\-quit-at-eof may be abbreviated \-\-quit, but not
424 --qui, since both \-\-quit-at-eof and \-\-quiet begin with \-\-qui.
425 Some long option names are in uppercase, such as \-\-QUIT-AT-EOF, as
426 distinct from \-\-quit-at-eof.
427 Such option names need only have their first letter capitalized;
428 the remainder of the name may be in either case.
429 For example, \-\-Quit-at-eof is equivalent to \-\-QUIT-AT-EOF.
430 .PP
431 Options are also taken from the environment variable "LESS".
432 For example,
433 to avoid typing "less \-options ..." each time
434 .I less
435 is invoked, you might tell
436 .I csh:
437 .sp
438 setenv LESS "-options"
439 .sp
440 or if you use
441 .I sh:
442 .sp
443 LESS="-options"; export LESS
444 .sp
445 On MS-DOS, you don't need the quotes, but you should replace any
446 percent signs in the options string by double percent signs.
447 .sp
448 The environment variable is parsed before the command line,
449 so command line options override the LESS environment variable.
450 If an option appears in the LESS variable, it can be reset
451 to its default value on the command line by beginning the command
452 line option with "\-+".
453 .sp
454 For options like \-P or \-D which take a following string,
455 a dollar sign ($) must be used to signal the end of the string.
456 For example, to set two \-D options on MS-DOS, you must have
457 a dollar sign between them, like this:
458 .sp
459 LESS="-Dn9.1$-Ds4.1"
460 .sp
461 .IP "\-? or \-\-help"
462 This option displays a summary of the commands accepted by
463 .I less
464 (the same as the h command).
465 (Depending on how your shell interprets the question mark,
466 it may be necessary to quote the question mark, thus: "\-\e?".)
467 .IP "\-a or \-\-search-skip-screen"
468 Causes searches to start after the last line
469 displayed on the screen,
470 thus skipping all lines displayed on the screen.
471 By default, searches start at the second line on the screen
472 (or after the last found line; see the \-j option).
473 .IP "\-b\fIn\fP or \-\-buffers=\fIn\fP"
474 Specifies the amount of buffer space
475 .I less
476 will use for each file, in units of kilobytes (1024 bytes).
477 By default 64K of buffer space is used for each file
478 (unless the file is a pipe; see the \-B option).
479 The \-b option specifies instead that \fIn\fP kilobytes of
480 buffer space should be used for each file.
481 If \fIn\fP is \-1, buffer space is unlimited; that is,
482 the entire file can be read into memory.
483 .IP "\-B or \-\-auto-buffers"
484 By default, when data is read from a pipe,
485 buffers are allocated automatically as needed.
486 If a large amount of data is read from the pipe, this can cause
487 a large amount of memory to be allocated.
488 The \-B option disables this automatic allocation of buffers for pipes,
489 so that only 64K
490 (or the amount of space specified by the \-b option)
491 is used for the pipe.
492 Warning: use of \-B can result in erroneous display, since only the
493 most recently viewed part of the piped data is kept in memory;
494 any earlier data is lost.
495 .IP "\-c or \-\-clear-screen"
496 Causes full screen repaints to be painted from the top line down.
497 By default,
498 full screen repaints are done by scrolling from the bottom of the screen.
499 .IP "\-C or \-\-CLEAR-SCREEN"
500 Same as \-c, for compatibility with older versions of
501 .I less.
502 .IP "\-d or \-\-dumb"
503 The \-d option suppresses the error message
504 normally displayed if the terminal is dumb;
505 that is, lacks some important capability,
506 such as the ability to clear the screen or scroll backward.
507 The \-d option does not otherwise change the behavior of
508 .I less
509 on a dumb terminal.
510 .IP "\-D\fBx\fP\fIcolor\fP or \-\-color=\fBx\fP\fIcolor\fP"
511 [MS-DOS only]
512 Sets the color of the text displayed.
513 \fBx\fP is a single character which selects the type of text whose color is
514 being set: n=normal, s=standout, d=bold, u=underlined, k=blink.
515 \fIcolor\fP is a pair of numbers separated by a period.
516 The first number selects the foreground color and the second selects
517 the background color of the text.
518 A single number \fIN\fP is the same as \fIN.0\fP.
519 .IP "\-e or \-\-quit-at-eof"
520 Causes
521 .I less
522 to automatically exit
523 the second time it reaches end-of-file.
524 By default, the only way to exit
525 .I less
526 is via the "q" command.
527 .IP "\-E or \-\-QUIT-AT-EOF"
528 Causes
529 .I less
530 to automatically exit the first time it reaches end-of-file.
531 .IP "\-f or \-\-force"
532 Forces non-regular files to be opened.
533 (A non-regular file is a directory or a device special file.)
534 Also suppresses the warning message when a binary file is opened.
535 By default,
536 .I less
537 will refuse to open non-regular files.
538 Note that some operating systems will not allow directories
539 to be read, even if \-f is set.
540 .IP "\-F or \-\-quit-if-one-screen"
541 Causes
542 .I less
543 to automatically exit
544 if the entire file can be displayed on the first screen.
545 .IP "\-g or \-\-hilite-search"
546 Normally,
547 .I less
548 will highlight ALL strings which match the last search command.
549 The \-g option changes this behavior to highlight only the particular string
550 which was found by the last search command.
551 This can cause
552 .I less
553 to run somewhat faster than the default.
554 .IP "\-G or \-\-HILITE-SEARCH"
555 The \-G option suppresses all highlighting of strings found by search commands.
556 .IP "\-h\fIn\fP or \-\-max-back-scroll=\fIn\fP"
557 Specifies a maximum number of lines to scroll backward.
558 If it is necessary to scroll backward more than \fIn\fP lines,
559 the screen is repainted in a forward direction instead.
560 (If the terminal does not have the ability to scroll
561 backward, \-h0 is implied.)
562 .IP "\-i or \-\-ignore-case"
563 Causes searches to ignore case; that is,
564 uppercase and lowercase are considered identical.
565 This option is ignored if any uppercase letters
566 appear in the search pattern;
567 in other words,
568 if a pattern contains uppercase letters, then that search does not ignore case.
569 .IP "\-I or \-\-IGNORE-CASE"
570 Like \-i, but searches ignore case even if
571 the pattern contains uppercase letters.
572 .IP "\-j\fIn\fP or \-\-jump-target=\fIn\fP"
573 Specifies a line on the screen where the "target" line
574 is to be positioned.
575 The target line is the line specified by any command to
576 search for a pattern, jump to a line number,
577 jump to a file percentage or jump to a tag.
578 The screen line may be specified by a number: the top line on the screen
579 is 1, the next is 2, and so on.
580 The number may be negative to specify a line relative to the bottom
581 of the screen: the bottom line on the screen is \-1, the second
582 to the bottom is \-2, and so on.
583 Alternately, the screen line may be specified as a fraction of the height
584 of the screen, starting with a decimal point: .5 is in the middle of the
585 screen, .3 is three tenths down from the first line, and so on.
586 If the line is specified as a fraction, the actual line number
587 is recalculated if the terminal window is resized, so that the
588 target line remains at the specified fraction of the screen height.
589 If any form of the \-j option is used,
590 forward searches begin at the line immediately after the target line,
591 and backward searches begin at the target line.
592 For example, if "\-j4" is used, the target line is the
593 fourth line on the screen, so forward searches begin at the fifth line
594 on the screen.
595 .IP "\-J or \-\-status-column"
596 Displays a status column at the left edge of the screen.
597 The status column shows the lines that matched the current search.
598 The status column is also used if the \-w or \-W option is in effect.
599 .IP "\-k\fIfilename\fP or \-\-lesskey-file=\fIfilename\fP"
600 Causes
601 .I less
602 to open and interpret the named file as a
603 .I lesskey
604 (1) file.
605 Multiple \-k options may be specified.
606 If the LESSKEY or LESSKEY_SYSTEM environment variable is set, or
607 if a lesskey file is found in a standard place (see KEY BINDINGS),
608 it is also used as a
609 .I lesskey
610 file.
611 .IP "\-K or \-\-quit-on-intr"
612 Causes
613 .I less
614 to exit immediately when an interrupt character (usually ^C) is typed.
615 Normally, an interrupt character causes
616 .I less
617 to stop whatever it is doing and return to its command prompt.
618 Note that use of this option makes it impossible to return to the
619 command prompt from the "F" command.
620 .IP "\-L or \-\-no-lessopen"
621 Ignore the LESSOPEN environment variable
622 (see the INPUT PREPROCESSOR section below).
623 This option can be set from within \fIless\fP,
624 but it will apply only to files opened subsequently, not to the
625 file which is currently open.
626 .IP "\-m or \-\-long-prompt"
627 Causes
628 .I less
629 to prompt verbosely (like \fImore\fP),
630 with the percent into the file.
631 By default,
632 .I less
633 prompts with a colon.
634 .IP "\-M or \-\-LONG-PROMPT"
635 Causes
636 .I less
637 to prompt even more verbosely than
638 .I more.
639 .IP "\-n or \-\-line-numbers"
640 Suppresses line numbers.
641 The default (to use line numbers) may cause
642 .I less
643 to run more slowly in some cases, especially with a very large input file.
644 Suppressing line numbers with the \-n option will avoid this problem.
645 Using line numbers means: the line number will be displayed in the verbose
646 prompt and in the = command,
647 and the v command will pass the current line number to the editor
648 (see also the discussion of LESSEDIT in PROMPTS below).
649 .IP "\-N or \-\-LINE-NUMBERS"
650 Causes a line number to be displayed at the beginning of
651 each line in the display.
652 .IP "\-o\fIfilename\fP or \-\-log-file=\fIfilename\fP"
653 Causes
654 .I less
655 to copy its input to the named file as it is being viewed.
656 This applies only when the input file is a pipe,
657 not an ordinary file.
658 If the file already exists,
659 .I less
660 will ask for confirmation before overwriting it.
661 .IP "\-O\fIfilename\fP or \-\-LOG-FILE=\fIfilename\fP"
662 The \-O option is like \-o, but it will overwrite an existing
663 file without asking for confirmation.
664 .sp
665 If no log file has been specified,
666 the \-o and \-O options can be used from within
667 .I less
668 to specify a log file.
669 Without a file name, they will simply report the name of the log file.
670 The "s" command is equivalent to specifying \-o from within
671 .I less.
672 .IP "\-p\fIpattern\fP or \-\-pattern=\fIpattern\fP"
673 The \-p option on the command line is equivalent to
674 specifying +/\fIpattern\fP;
675 that is, it tells
676 .I less
677 to start at the first occurrence of \fIpattern\fP in the file.
678 .IP "\-P\fIprompt\fP or \-\-prompt=\fIprompt\fP"
679 Provides a way to tailor the three prompt
680 styles to your own preference.
681 This option would normally be put in the LESS environment
682 variable, rather than being typed in with each
683 .I less
684 command.
685 Such an option must either be the last option in the LESS variable,
686 or be terminated by a dollar sign.
687 -Ps followed by a string changes the default (short) prompt
688 to that string.
689 -Pm changes the medium (\-m) prompt.
690 -PM changes the long (\-M) prompt.
691 -Ph changes the prompt for the help screen.
692 -P= changes the message printed by the = command.
693 -Pw changes the message printed while waiting for data (in the F command).
694 All prompt strings consist of a sequence of
695 letters and special escape sequences.
696 See the section on PROMPTS for more details.
697 .IP "\-q or \-\-quiet or \-\-silent"
698 Causes moderately "quiet" operation:
699 the terminal bell is not rung
700 if an attempt is made to scroll past the end of the file
701 or before the beginning of the file.
702 If the terminal has a "visual bell", it is used instead.
703 The bell will be rung on certain other errors,
704 such as typing an invalid character.
705 The default is to ring the terminal bell in all such cases.
706 .IP "\-Q or \-\-QUIET or \-\-SILENT"
707 Causes totally "quiet" operation:
708 the terminal bell is never rung.
709 .IP "\-r or \-\-raw-control-chars"
710 Causes "raw" control characters to be displayed.
711 The default is to display control characters using the caret notation;
712 for example, a control-A (octal 001) is displayed as "^A".
713 Warning: when the \-r option is used,
714 .I less
715 cannot keep track of the actual appearance of the screen
716 (since this depends on how the screen responds to
717 each type of control character).
718 Thus, various display problems may result,
719 such as long lines being split in the wrong place.
720 .IP "\-R or \-\-RAW-CONTROL-CHARS"
721 Like \-r, but only ANSI "color" escape sequences are output in "raw" form.
722 Unlike \-r, the screen appearance is maintained correctly in most cases.
723 ANSI "color" escape sequences are sequences of the form:
724 .sp
725 ESC [ ... m
726 .sp
727 where the "..." is zero or more color specification characters
728 For the purpose of keeping track of screen appearance,
729 ANSI color escape sequences are assumed to not move the cursor.
730 You can make
731 .I less
732 think that characters other than "m" can end ANSI color escape sequences
733 by setting the environment variable LESSANSIENDCHARS to the list of
734 characters which can end a color escape sequence.
735 And you can make
736 .I less
737 think that characters other than the standard ones may appear between
738 the ESC and the m by setting the environment variable LESSANSIMIDCHARS
739 to the list of characters which can appear.
740 .IP "\-s or \-\-squeeze-blank-lines"
741 Causes consecutive blank lines to be squeezed into a single blank line.
742 This is useful when viewing
743 .I nroff
744 output.
745 .IP "\-S or \-\-chop-long-lines"
746 Causes lines longer than the screen width to be
747 chopped rather than folded.
748 That is, the portion of a long line that does not fit in
749 the screen width is not shown.
750 The default is to fold long lines; that is, display the remainder
751 on the next line.
752 .IP "\-t\fItag\fP or \-\-tag=\fItag\fP"
753 The \-t option, followed immediately by a TAG,
754 will edit the file containing that tag.
755 For this to work, tag information must be available;
756 for example, there may be a file in the current directory called "tags",
757 which was previously built by
758 .I ctags
759 (1) or an equivalent command.
760 If the environment variable LESSGLOBALTAGS is set, it is taken to be
761 the name of a command compatible with
762 .I global
763 (1), and that command is executed to find the tag.
764 (See http://www.gnu.org/software/global/global.html).
765 The \-t option may also be specified from within
766 .I less
767 (using the \- command) as a way of examining a new file.
768 The command ":t" is equivalent to specifying \-t from within
769 .I less.
770 .IP "\-T\fItagsfile\fP or \-\-tag-file=\fItagsfile\fP"
771 Specifies a tags file to be used instead of "tags".
772 .IP "\-u or \-\-underline-special"
773 Causes backspaces and carriage returns to be treated as printable characters;
774 that is, they are sent to the terminal when they appear in the input.
775 .IP "\-U or \-\-UNDERLINE-SPECIAL"
776 Causes backspaces, tabs and carriage returns to be
777 treated as control characters;
778 that is, they are handled as specified by the \-r option.
779 .sp
780 By default, if neither \-u nor \-U is given,
781 backspaces which appear adjacent to an underscore character
782 are treated specially:
783 the underlined text is displayed
784 using the terminal's hardware underlining capability.
785 Also, backspaces which appear between two identical characters
786 are treated specially:
787 the overstruck text is printed
788 using the terminal's hardware boldface capability.
789 Other backspaces are deleted, along with the preceding character.
790 Carriage returns immediately followed by a newline are deleted.
791 other carriage returns are handled as specified by the \-r option.
792 Text which is overstruck or underlined can be searched for
793 if neither \-u nor \-U is in effect.
794 .IP "\-V or \-\-version"
795 Displays the version number of
796 .I less.
797 .IP "\-w or \-\-hilite-unread"
798 Temporarily highlights the first "new" line after a forward movement
799 of a full page.
800 The first "new" line is the line immediately following the line previously
801 at the bottom of the screen.
802 Also highlights the target line after a g or p command.
803 The highlight is removed at the next command which causes movement.
804 The entire line is highlighted, unless the \-J option is in effect,
805 in which case only the status column is highlighted.
806 .IP "\-W or \-\-HILITE-UNREAD"
807 Like \-w, but temporarily highlights the first new line after any
808 forward movement command larger than one line.
809 .IP "\-x\fIn\fP,... or \-\-tabs=\fIn\fP,..."
810 Sets tab stops.
811 If only one \fIn\fP is specified, tab stops are set at multiples of \fIn\fP.
812 If multiple values separated by commas are specified, tab stops
813 are set at those positions, and then continue with the same spacing as the
814 last two.
815 For example, \fI-x9,17\fP will set tabs at positions 9, 17, 25, 33, etc.
816 The default for \fIn\fP is 8.
817 .IP "\-X or \-\-no-init"
818 Disables sending the termcap initialization and deinitialization strings
819 to the terminal.
820 This is sometimes desirable if the deinitialization string does
821 something unnecessary, like clearing the screen.
822 .IP "\-y\fIn\fP or \-\-max-forw-scroll=\fIn\fP"
823 Specifies a maximum number of lines to scroll forward.
824 If it is necessary to scroll forward more than \fIn\fP lines,
825 the screen is repainted instead.
826 The \-c or \-C option may be used to repaint from the top of
827 the screen if desired.
828 By default, any forward movement causes scrolling.
829 .IP "\-[z]\fIn\fP or \-\-window=\fIn\fP"
830 Changes the default scrolling window size to \fIn\fP lines.
831 The default is one screenful.
832 The z and w commands can also be used to change the window size.
833 The "z" may be omitted for compatibility with some versions of
834 .I more.
835 If the number
836 .I n
837 is negative, it indicates
838 .I n
839 lines less than the current screen size.
840 For example, if the screen is 24 lines, \fI\-z-4\fP sets the
841 scrolling window to 20 lines. If the screen is resized to 40 lines,
842 the scrolling window automatically changes to 36 lines.
843 .IP "\-\fI\(dqcc\fP\ or\ \-\-quotes=\fIcc\fP"
844 Changes the filename quoting character.
845 This may be necessary if you are trying to name a file
846 which contains both spaces and quote characters.
847 Followed by a single character, this changes the quote character to that
848 character.
849 Filenames containing a space should then be surrounded by that character
850 rather than by double quotes.
851 Followed by two characters, changes the open quote to the first character,
852 and the close quote to the second character.
853 Filenames containing a space should then be preceded by the open quote
854 character and followed by the close quote character.
855 Note that even after the quote characters are changed, this option
856 remains \-" (a dash followed by a double quote).
857 .IP "\-~ or \-\-tilde"
858 Normally lines after end of file are displayed as a single tilde (~).
859 This option causes lines after end of file to be displayed as blank lines.
860 .IP "\-# or \-\-shift"
861 Specifies the default number of positions to scroll horizontally
862 in the RIGHTARROW and LEFTARROW commands.
863 If the number specified is zero, it sets the default number of
864 positions to one half of the screen width.
865 .IP "\-\-no-keypad"
866 Disables sending the keypad initialization and deinitialization strings
867 to the terminal.
868 This is sometimes useful if the keypad strings make the numeric
869 keypad behave in an undesirable manner.
870 .IP "\-\-follow-name"
871 Normally, if the input file is renamed while an F command is executing,
872 .I less
873 will continue to display the contents of the original file despite
874 its name change.
875 If \-\-follow-name is specified, during an F command
876 .I less
877 will periodically attempt to reopen the file by name.
878 If the reopen succeeds and the file is a different file from the original
879 (which means that a new file has been created
880 with the same name as the original (now renamed) file),
881 .I less
882 will display the contents of that new file.
883 .IP \-\-
884 A command line argument of "\-\-" marks the end of option arguments.
885 Any arguments following this are interpreted as filenames.
886 This can be useful when viewing a file whose name begins with a "\-" or "+".
887 .IP +
888 If a command line option begins with \fB+\fP,
889 the remainder of that option is taken to be an initial command to
890 .I less.
891 For example, +G tells
892 .I less
893 to start at the end of the file rather than the beginning,
894 and +/xyz tells it to start at the first occurrence of "xyz" in the file.
895 As a special case, +<number> acts like +<number>g;
896 that is, it starts the display at the specified line number
897 (however, see the caveat under the "g" command above).
898 If the option starts with ++, the initial command applies to
899 every file being viewed, not just the first one.
900 The + command described previously
901 may also be used to set (or change) an initial command for every file.
902
903 .SH "LINE EDITING"
904 When entering command line at the bottom of the screen
905 (for example, a filename for the :e command,
906 or the pattern for a search command),
907 certain keys can be used to manipulate the command line.
908 Most commands have an alternate form in [ brackets ] which can be used if
909 a key does not exist on a particular keyboard.
910 (Note that the forms beginning with ESC do not work
911 in some MS-DOS and Windows systems because ESC is the line erase character.)
912 Any of these special keys may be entered literally by preceding
913 it with the "literal" character, either ^V or ^A.
914 A backslash itself may also be entered literally by entering two backslashes.
915 .IP "LEFTARROW [ ESC-h ]"
916 Move the cursor one space to the left.
917 .IP "RIGHTARROW [ ESC-l ]"
918 Move the cursor one space to the right.
919 .IP "^LEFTARROW [ ESC-b or ESC-LEFTARROW ]"
920 (That is, CONTROL and LEFTARROW simultaneously.)
921 Move the cursor one word to the left.
922 .IP "^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]"
923 (That is, CONTROL and RIGHTARROW simultaneously.)
924 Move the cursor one word to the right.
925 .IP "HOME [ ESC-0 ]"
926 Move the cursor to the beginning of the line.
927 .IP "END [ ESC-$ ]"
928 Move the cursor to the end of the line.
929 .IP "BACKSPACE"
930 Delete the character to the left of the cursor,
931 or cancel the command if the command line is empty.
932 .IP "DELETE or [ ESC-x ]"
933 Delete the character under the cursor.
934 .IP "^BACKSPACE [ ESC-BACKSPACE ]"
935 (That is, CONTROL and BACKSPACE simultaneously.)
936 Delete the word to the left of the cursor.
937 .IP "^DELETE [ ESC-X or ESC-DELETE ]"
938 (That is, CONTROL and DELETE simultaneously.)
939 Delete the word under the cursor.
940 .IP "UPARROW [ ESC-k ]"
941 Retrieve the previous command line.
942 .IP "DOWNARROW [ ESC-j ]"
943 Retrieve the next command line.
944 .IP "TAB"
945 Complete the partial filename to the left of the cursor.
946 If it matches more than one filename, the first match
947 is entered into the command line.
948 Repeated TABs will cycle thru the other matching filenames.
949 If the completed filename is a directory, a "/" is appended to the filename.
950 (On MS-DOS systems, a "\e" is appended.)
951 The environment variable LESSSEPARATOR can be used to specify a
952 different character to append to a directory name.
953 .IP "BACKTAB [ ESC-TAB ]"
954 Like, TAB, but cycles in the reverse direction thru the matching filenames.
955 .IP "^L"
956 Complete the partial filename to the left of the cursor.
957 If it matches more than one filename, all matches are entered into
958 the command line (if they fit).
959 .IP "^U (Unix and OS/2) or ESC (MS-DOS)"
960 Delete the entire command line,
961 or cancel the command if the command line is empty.
962 If you have changed your line-kill character in Unix to something
963 other than ^U, that character is used instead of ^U.
964
965 .SH "KEY BINDINGS"
966 You may define your own
967 .I less
968 commands by using the program
969 .I lesskey
970 (1)
971 to create a lesskey file.
972 This file specifies a set of command keys and an action
973 associated with each key.
974 You may also use
975 .I lesskey
976 to change the line-editing keys (see LINE EDITING),
977 and to set environment variables.
978 If the environment variable LESSKEY is set,
979 .I less
980 uses that as the name of the lesskey file.
981 Otherwise,
982 .I less
983 looks in a standard place for the lesskey file:
984 On Unix systems,
985 .I less
986 looks for a lesskey file called "$HOME/.less".
987 On MS-DOS and Windows systems,
988 .I less
989 looks for a lesskey file called "$HOME/_less", and if it is not found there,
990 then looks for a lesskey file called "_less" in any directory specified
991 in the PATH environment variable.
992 On OS/2 systems,
993 .I less
994 looks for a lesskey file called "$HOME/less.ini", and if it is not found,
995 then looks for a lesskey file called "less.ini" in any directory specified
996 in the INIT environment variable, and if it not found there,
997 then looks for a lesskey file called "less.ini" in any directory specified
998 in the PATH environment variable.
999 See the
1000 .I lesskey
1001 manual page for more details.
1002 .P
1003 A system-wide lesskey file may also be set up to provide key bindings.
1004 If a key is defined in both a local lesskey file and in the
1005 system-wide file, key bindings in the local file take precedence over
1006 those in the system-wide file.
1007 If the environment variable LESSKEY_SYSTEM is set,
1008 .I less
1009 uses that as the name of the system-wide lesskey file.
1010 Otherwise,
1011 .I less
1012 looks in a standard place for the system-wide lesskey file:
1013 On Unix systems, the system-wide lesskey file is /usr/local/etc/sysless.
1014 (However, if
1015 .I less
1016 was built with a different sysconf directory than /usr/local/etc,
1017 that directory is where the sysless file is found.)
1018 On MS-DOS and Windows systems, the system-wide lesskey file is c:\e_sysless.
1019 On OS/2 systems, the system-wide lesskey file is c:\esysless.ini.
1020
1021 .SH "INPUT PREPROCESSOR"
1022 You may define an "input preprocessor" for
1023 .I less.
1024 Before
1025 .I less
1026 opens a file, it first gives your input preprocessor a chance to modify the
1027 way the contents of the file are displayed.
1028 An input preprocessor is simply an executable program (or shell script),
1029 which writes the contents of the file to a different file,
1030 called the replacement file.
1031 The contents of the replacement file are then displayed
1032 in place of the contents of the original file.
1033 However, it will appear to the user as if the original file is opened;
1034 that is,
1035 .I less
1036 will display the original filename as the name of the current file.
1037 .PP
1038 An input preprocessor receives one command line argument, the original filename,
1039 as entered by the user.
1040 It should create the replacement file, and when finished,
1041 print the name of the replacement file to its standard output.
1042 If the input preprocessor does not output a replacement filename,
1043 .I less
1044 uses the original file, as normal.
1045 The input preprocessor is not called when viewing standard input.
1046 To set up an input preprocessor, set the LESSOPEN environment variable
1047 to a command line which will invoke your input preprocessor.
1048 This command line should include one occurrence of the string "%s",
1049 which will be replaced by the filename
1050 when the input preprocessor command is invoked.
1051 .PP
1052 When
1053 .I less
1054 closes a file opened in such a way, it will call another program,
1055 called the input postprocessor,
1056 which may perform any desired clean-up action (such as deleting the
1057 replacement file created by LESSOPEN).
1058 This program receives two command line arguments, the original filename
1059 as entered by the user, and the name of the replacement file.
1060 To set up an input postprocessor, set the LESSCLOSE environment variable
1061 to a command line which will invoke your input postprocessor.
1062 It may include two occurrences of the string "%s";
1063 the first is replaced with the original name of the file and
1064 the second with the name of the replacement file,
1065 which was output by LESSOPEN.
1066 .PP
1067 For example, on many Unix systems, these two scripts will allow you
1068 to keep files in compressed format, but still let
1069 .I less
1070 view them directly:
1071 .PP
1072 lessopen.sh:
1073 .br
1074 #! /bin/sh
1075 .br
1076 case "$1" in
1077 .br
1078 *.Z) uncompress -\c $1 >/tmp/less.$$ 2>/dev/null
1079 .br
1080 if [ \-s /tmp/less.$$ ]; then
1081 .br
1082 echo /tmp/less.$$
1083 .br
1084 else
1085 .br
1086 rm \-f /tmp/less.$$
1087 .br
1088 fi
1089 .br
1090 ;;
1091 .br
1092 esac
1093 .PP
1094 lessclose.sh:
1095 .br
1096 #! /bin/sh
1097 .br
1098 rm $2
1099 .PP
1100 To use these scripts, put them both where they can be executed and
1101 set LESSOPEN="lessopen.sh\ %s", and
1102 LESSCLOSE="lessclose.sh\ %s\ %s".
1103 More complex LESSOPEN and LESSCLOSE scripts may be written
1104 to accept other types of compressed files, and so on.
1105 .PP
1106 It is also possible to set up an input preprocessor to
1107 pipe the file data directly to
1108 .I less,
1109 rather than putting the data into a replacement file.
1110 This avoids the need to decompress the entire file before
1111 starting to view it.
1112 An input preprocessor that works this way is called an input pipe.
1113 An input pipe, instead of writing the name of a replacement file on
1114 its standard output,
1115 writes the entire contents of the replacement file on its standard output.
1116 If the input pipe does not write any characters on its standard output,
1117 then there is no replacement file and
1118 .I less
1119 uses the original file, as normal.
1120 To use an input pipe,
1121 make the first character in the LESSOPEN environment variable a
1122 vertical bar (|) to signify that the input preprocessor is an input pipe.
1123 .PP
1124 For example, on many Unix systems, this script will work like the
1125 previous example scripts:
1126 .PP
1127 lesspipe.sh:
1128 .br
1129 #! /bin/sh
1130 .br
1131 case "$1" in
1132 .br
1133 *.Z) uncompress \-c $1 2>/dev/null
1134 .br
1135 ;;
1136 .br
1137 esac
1138 .br
1139 .PP
1140 To use this script, put it where it can be executed and set
1141 LESSOPEN="|lesspipe.sh %s".
1142 When an input pipe is used, a LESSCLOSE postprocessor can be used,
1143 but it is usually not necessary since there is no replacement file
1144 to clean up.
1145 In this case, the replacement file name passed to the LESSCLOSE
1146 postprocessor is "\-".
1147
1148 .SH "NATIONAL CHARACTER SETS"
1149 There are three types of characters in the input file:
1150 .IP "normal characters"
1151 can be displayed directly to the screen.
1152 .IP "control characters"
1153 should not be displayed directly, but are expected to be found
1154 in ordinary text files (such as backspace and tab).
1155 .IP "binary characters"
1156 should not be displayed directly and are not expected to be found
1157 in text files.
1158 .PP
1159 A "character set" is simply a description of which characters are to
1160 be considered normal, control, and binary.
1161 The LESSCHARSET environment variable may be used to select a character set.
1162 Possible values for LESSCHARSET are:
1163 .IP ascii
1164 BS, TAB, NL, CR, and formfeed are control characters,
1165 all chars with values between 32 and 126 are normal,
1166 and all others are binary.
1167 .IP iso8859
1168 Selects an ISO 8859 character set.
1169 This is the same as ASCII, except characters between 160 and 255 are
1170 treated as normal characters.
1171 .IP latin1
1172 Same as iso8859.
1173 .IP latin9
1174 Same as iso8859.
1175 .IP dos
1176 Selects a character set appropriate for MS-DOS.
1177 .IP ebcdic
1178 Selects an EBCDIC character set.
1179 .IP IBM-1047
1180 Selects an EBCDIC character set used by OS/390 Unix Services.
1181 This is the EBCDIC analogue of latin1. You get similar results
1182 by setting either LESSCHARSET=IBM-1047 or LC_CTYPE=en_US
1183 in your environment.
1184 .IP koi8-r
1185 Selects a Russian character set.
1186 .IP next
1187 Selects a character set appropriate for NeXT computers.
1188 .IP utf-8
1189 Selects the UTF-8 encoding of the ISO 10646 character set.
1190 UTF-8 is special in that it supports multi-byte characters in the input file.
1191 It is the only character set that supports multi-byte characters.
1192 .IP windows
1193 Selects a character set appropriate for Microsoft Windows (cp 1251).
1194 .PP
1195 In rare cases, it may be desired to tailor
1196 .I less
1197 to use a character set other than the ones definable by LESSCHARSET.
1198 In this case, the environment variable LESSCHARDEF can be used
1199 to define a character set.
1200 It should be set to a string where each character in the string represents
1201 one character in the character set.
1202 The character "." is used for a normal character, "c" for control,
1203 and "b" for binary.
1204 A decimal number may be used for repetition.
1205 For example, "bccc4b." would mean character 0 is binary,
1206 1, 2 and 3 are control, 4, 5, 6 and 7 are binary, and 8 is normal.
1207 All characters after the last are taken to be the same as the last,
1208 so characters 9 through 255 would be normal.
1209 (This is an example, and does not necessarily
1210 represent any real character set.)
1211 .PP
1212 This table shows the value of LESSCHARDEF which is equivalent
1213 to each of the possible values for LESSCHARSET:
1214 .sp
1215 ascii\ 8bcccbcc18b95.b
1216 .br
1217 dos\ \ \ 8bcccbcc12bc5b95.b.
1218 .br
1219 ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
1220 .br
1221 \ \ \ \ \ \ 9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
1222 .br
1223 IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
1224 .br
1225 \ \ \ \ \ \ 191.b
1226 .br
1227 iso8859 8bcccbcc18b95.33b.
1228 .br
1229 koi8-r 8bcccbcc18b95.b128.
1230 .br
1231 latin1 8bcccbcc18b95.33b.
1232 .br
1233 next\ \ 8bcccbcc18b95.bb125.bb
1234 .PP
1235 If neither LESSCHARSET nor LESSCHARDEF is set,
1236 but any of the strings "UTF-8", "UTF8", "utf-8" or "utf8"
1237 is found in the LC_ALL, LC_TYPE or LANG
1238 environment variables, then the default character set is utf-8.
1239 .PP
1240 If that string is not found, but your system supports the
1241 .I setlocale
1242 interface,
1243 .I less
1244 will use setlocale to determine the character set.
1245 setlocale is controlled by setting the LANG or LC_CTYPE environment
1246 variables.
1247 .PP
1248 Finally, if the
1249 .I setlocale
1250 interface is also not available, the default character set is latin1.
1251 .PP
1252 Control and binary characters are displayed in standout (reverse video).
1253 Each such character is displayed in caret notation if possible
1254 (e.g. ^A for control-A). Caret notation is used only if
1255 inverting the 0100 bit results in a normal printable character.
1256 Otherwise, the character is displayed as a hex number in angle brackets.
1257 This format can be changed by
1258 setting the LESSBINFMT environment variable.
1259 LESSBINFMT may begin with a "*" and one character to select
1260 the display attribute:
1261 "*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout,
1262 and "*n" is normal.
1263 If LESSBINFMT does not begin with a "*", normal attribute is assumed.
1264 The remainder of LESSBINFMT is a string which may include one
1265 printf-style escape sequence (a % followed by x, X, o, d, etc.).
1266 For example, if LESSBINFMT is "*u[%x]", binary characters
1267 are displayed in underlined hexadecimal surrounded by brackets.
1268 The default if no LESSBINFMT is specified is "*s<%X>".
1269 The default if no LESSBINFMT is specified is "*s<%02X>".
1270 Warning: the result of expanding the character via LESSBINFMT must
1271 be less than 31 characters.
1272 .PP
1273 When the character set is utf-8, the LESSUTFBINFMT environment variable
1274 acts similarly to LESSBINFMT but it applies to Unicode code points
1275 that were successfully decoded but are unsuitable for display (e.g.,
1276 unassigned code points).
1277 Its default value is "<U+%04lX>".
1278 Note that LESSUTFBINFMT and LESSBINFMT share their display attribute
1279 setting ("*x") so specifying one will affect both;
1280 LESSUTFBINFMT is read after LESSBINFMT so its setting, if any,
1281 will have priority.
1282 Problematic octets in a UTF-8 file (octets of a truncated sequence,
1283 octets of a complete but non-shortest form sequence, illegal octets,
1284 and stray trailing octets)
1285 are displayed individually using LESSBINFMT so as to facilitate diagnostic
1286 of how the UTF-8 file is ill-formed.
1287
1288 .SH "PROMPTS"
1289 The \-P option allows you to tailor the prompt to your preference.
1290 The string given to the \-P option replaces the specified prompt string.
1291 Certain characters in the string are interpreted specially.
1292 The prompt mechanism is rather complicated to provide flexibility,
1293 but the ordinary user need not understand the details of constructing
1294 personalized prompt strings.
1295 .sp
1296 A percent sign followed by a single character is expanded
1297 according to what the following character is:
1298 .IP "%b\fIX\fP"
1299 Replaced by the byte offset into the current input file.
1300 The b is followed by a single character (shown as \fIX\fP above)
1301 which specifies the line whose byte offset is to be used.
1302 If the character is a "t", the byte offset of the top line in the
1303 display is used,
1304 an "m" means use the middle line,
1305 a "b" means use the bottom line,
1306 a "B" means use the line just after the bottom line,
1307 and a "j" means use the "target" line, as specified by the \-j option.
1308 .IP "%B"
1309 Replaced by the size of the current input file.
1310 .IP "%c"
1311 Replaced by the column number of the text appearing in the first
1312 column of the screen.
1313 .IP "%d\fIX\fP"
1314 Replaced by the page number of a line in the input file.
1315 The line to be used is determined by the \fIX\fP, as with the %b option.
1316 .IP "%D"
1317 Replaced by the number of pages in the input file,
1318 or equivalently, the page number of the last line in the input file.
1319 .IP "%E"
1320 Replaced by the name of the editor (from the VISUAL environment variable,
1321 or the EDITOR environment variable if VISUAL is not defined).
1322 See the discussion of the LESSEDIT feature below.
1323 .IP "%f"
1324 Replaced by the name of the current input file.
1325 .IP "%i"
1326 Replaced by the index of the current file in the list of
1327 input files.
1328 .IP "%l\fIX\fP"
1329 Replaced by the line number of a line in the input file.
1330 The line to be used is determined by the \fIX\fP, as with the %b option.
1331 .IP "%L"
1332 Replaced by the line number of the last line in the input file.
1333 .IP "%m"
1334 Replaced by the total number of input files.
1335 .IP "%p\fIX\fP"
1336 Replaced by the percent into the current input file, based on byte offsets.
1337 The line used is determined by the \fIX\fP as with the %b option.
1338 .IP "%P\fIX\fP"
1339 Replaced by the percent into the current input file, based on line numbers.
1340 The line used is determined by the \fIX\fP as with the %b option.
1341 .IP "%s"
1342 Same as %B.
1343 .IP "%t"
1344 Causes any trailing spaces to be removed.
1345 Usually used at the end of the string, but may appear anywhere.
1346 .IP "%x"
1347 Replaced by the name of the next input file in the list.
1348 .PP
1349 If any item is unknown (for example, the file size if input
1350 is a pipe), a question mark is printed instead.
1351 .PP
1352 The format of the prompt string can be changed
1353 depending on certain conditions.
1354 A question mark followed by a single character acts like an "IF":
1355 depending on the following character, a condition is evaluated.
1356 If the condition is true, any characters following the question mark
1357 and condition character, up to a period, are included in the prompt.
1358 If the condition is false, such characters are not included.
1359 A colon appearing between the question mark and the
1360 period can be used to establish an "ELSE": any characters between
1361 the colon and the period are included in the string if and only if
1362 the IF condition is false.
1363 Condition characters (which follow a question mark) may be:
1364 .IP "?a"
1365 True if any characters have been included in the prompt so far.
1366 .IP "?b\fIX\fP"
1367 True if the byte offset of the specified line is known.
1368 .IP "?B"
1369 True if the size of current input file is known.
1370 .IP "?c"
1371 True if the text is horizontally shifted (%c is not zero).
1372 .IP "?d\fIX\fP"
1373 True if the page number of the specified line is known.
1374 .IP "?e"
1375 True if at end-of-file.
1376 .IP "?f"
1377 True if there is an input filename
1378 (that is, if input is not a pipe).
1379 .IP "?l\fIX\fP"
1380 True if the line number of the specified line is known.
1381 .IP "?L"
1382 True if the line number of the last line in the file is known.
1383 .IP "?m"
1384 True if there is more than one input file.
1385 .IP "?n"
1386 True if this is the first prompt in a new input file.
1387 .IP "?p\fIX\fP"
1388 True if the percent into the current input file, based on byte offsets,
1389 of the specified line is known.
1390 .IP "?P\fIX\fP"
1391 True if the percent into the current input file, based on line numbers,
1392 of the specified line is known.
1393 .IP "?s"
1394 Same as "?B".
1395 .IP "?x"
1396 True if there is a next input file
1397 (that is, if the current input file is not the last one).
1398 .PP
1399 Any characters other than the special ones
1400 (question mark, colon, period, percent, and backslash)
1401 become literally part of the prompt.
1402 Any of the special characters may be included in the prompt literally
1403 by preceding it with a backslash.
1404 .PP
1405 Some examples:
1406 .sp
1407 ?f%f:Standard input.
1408 .sp
1409 This prompt prints the filename, if known;
1410 otherwise the string "Standard input".
1411 .sp
1412 ?f%f .?ltLine %lt:?pt%pt\e%:?btByte %bt:-...
1413 .sp
1414 This prompt would print the filename, if known.
1415 The filename is followed by the line number, if known,
1416 otherwise the percent if known, otherwise the byte offset if known.
1417 Otherwise, a dash is printed.
1418 Notice how each question mark has a matching period,
1419 and how the % after the %pt
1420 is included literally by escaping it with a backslash.
1421 .sp
1422 ?n?f%f\ .?m(file\ %i\ of\ %m)\ ..?e(END)\ ?x-\ Next\e:\ %x..%t
1423 .sp
1424 This prints the filename if this is the first prompt in a file,
1425 followed by the "file N of N" message if there is more
1426 than one input file.
1427 Then, if we are at end-of-file, the string "(END)" is printed
1428 followed by the name of the next file, if there is one.
1429 Finally, any trailing spaces are truncated.
1430 This is the default prompt.
1431 For reference, here are the defaults for
1432 the other two prompts (\-m and \-M respectively).
1433 Each is broken into two lines here for readability only.
1434 .nf
1435 .sp
1436 ?n?f%f\ .?m(file\ %i\ of\ %m)\ ..?e(END)\ ?x-\ Next\e:\ %x.:
1437 ?pB%pB\e%:byte\ %bB?s/%s...%t
1438 .sp
1439 ?f%f\ .?n?m(file\ %i\ of\ %m)\ ..?ltlines\ %lt-%lb?L/%L.\ :
1440 byte\ %bB?s/%s.\ .?e(END)\ ?x-\ Next\e:\ %x.:?pB%pB\e%..%t
1441 .sp
1442 .fi
1443 And here is the default message produced by the = command:
1444 .nf
1445 .sp
1446 ?f%f\ .?m(file\ %i\ of\ %m)\ .?ltlines\ %lt-%lb?L/%L.\ .
1447 byte\ %bB?s/%s.\ ?e(END)\ :?pB%pB\e%..%t
1448 .fi
1449 .PP
1450 The prompt expansion features are also used for another purpose:
1451 if an environment variable LESSEDIT is defined, it is used
1452 as the command to be executed when the v command is invoked.
1453 The LESSEDIT string is expanded in the same way as the prompt strings.
1454 The default value for LESSEDIT is:
1455 .nf
1456 .sp
1457 %E\ ?lm+%lm.\ %f
1458 .sp
1459 .fi
1460 Note that this expands to the editor name, followed by a + and the
1461 line number, followed by the file name.
1462 If your editor does not accept the "+linenumber" syntax, or has other
1463 differences in invocation syntax, the LESSEDIT variable can be
1464 changed to modify this default.
1465
1466 .SH SECURITY
1467 When the environment variable LESSSECURE is set to 1,
1468 .I less
1469 runs in a "secure" mode.
1470 This means these features are disabled:
1471 .RS
1472 .IP "!"
1473 the shell command
1474 .IP "|"
1475 the pipe command
1476 .IP ":e"
1477 the examine command.
1478 .IP "v"
1479 the editing command
1480 .IP "s \-o"
1481 log files
1482 .IP "\-k"
1483 use of lesskey files
1484 .IP "\-t"
1485 use of tags files
1486 .IP " "
1487 metacharacters in filenames, such as *
1488 .IP " "
1489 filename completion (TAB, ^L)
1490 .RE
1491 .PP
1492 Less can also be compiled to be permanently in "secure" mode.
1493
1494 .SH "COMPATIBILITY WITH MORE"
1495 If the environment variable LESS_IS_MORE is set to 1,
1496 or if the program is invoked via a file link named "more",
1497 .I less
1498 behaves (mostly) in conformance with the POSIX "more" command specification.
1499 In this mode, less behaves differently in these ways:
1500 .PP
1501 The \-e option works differently.
1502 If the \-e option is not set,
1503 .I less
1504 behaves as if the \-E option were set.
1505 If the \-e option is set,
1506 .I less
1507 behaves as if the \-e and \-F options were set.
1508 .PP
1509 The \-m option works differently.
1510 If the \-m option is not set, the medium prompt is used,
1511 and it is prefixed with the string "--More--".
1512 If the \-m option is set, the short prompt is used.
1513 .PP
1514 The \-n option acts like the \-z option.
1515 The normal behavior of the \-n option is unavailable in this mode.
1516 .PP
1517 The parameter to the \-p option is taken to be a
1518 .I less
1519 command rather than a search pattern.
1520 .PP
1521 The LESS environment variable is ignored,
1522 and the MORE environment variable is used in its place.
1523
1524 .SH "ENVIRONMENT VARIABLES"
1525 Environment variables may be specified either in the system environment
1526 as usual, or in a
1527 .I lesskey
1528 (1) file.
1529 If environment variables are defined in more than one place,
1530 variables defined in a local lesskey file take precedence over
1531 variables defined in the system environment, which take precedence
1532 over variables defined in the system-wide lesskey file.
1533 .IP COLUMNS
1534 Sets the number of columns on the screen.
1535 Takes precedence over the number of columns specified by the TERM variable.
1536 (But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD,
1537 the window system's idea of the screen size takes precedence over the
1538 LINES and COLUMNS environment variables.)
1539 .IP EDITOR
1540 The name of the editor (used for the v command).
1541 .IP HOME
1542 Name of the user's home directory
1543 (used to find a lesskey file on Unix and OS/2 systems).
1544 .IP "HOMEDRIVE, HOMEPATH"
1545 Concatenation of the HOMEDRIVE and HOMEPATH environment variables is
1546 the name of the user's home directory if the HOME variable is not set
1547 (only in the Windows version).
1548 .IP INIT
1549 Name of the user's init directory (used to find a lesskey file on OS/2 systems).
1550 .IP LANG
1551 Language for determining the character set.
1552 .IP LC_CTYPE
1553 Language for determining the character set.
1554 .IP LESS
1555 Options which are passed to
1556 .I less
1557 automatically.
1558 .IP LESSANSIENDCHARS
1559 Characters which may end an ANSI color escape sequence
1560 (default "m").
1561 .IP LESSANSIMIDCHARS
1562 Characters which may appear between the ESC character and the
1563 end character in an ANSI color escape sequence
1564 (default "0123456789;[?!"'#%()*+\ ".
1565 .IP LESSBINFMT
1566 Format for displaying non-printable, non-control characters.
1567 .IP LESSCHARDEF
1568 Defines a character set.
1569 .IP LESSCHARSET
1570 Selects a predefined character set.
1571 .IP LESSCLOSE
1572 Command line to invoke the (optional) input-postprocessor.
1573 .IP LESSECHO
1574 Name of the lessecho program (default "lessecho").
1575 The lessecho program is needed to expand metacharacters, such as * and ?,
1576 in filenames on Unix systems.
1577 .IP LESSEDIT
1578 Editor prototype string (used for the v command).
1579 See discussion under PROMPTS.
1580 .IP LESSGLOBALTAGS
1581 Name of the command used by the \-t option to find global tags.
1582 Normally should be set to "global" if your system has the
1583 .I global
1584 (1) command. If not set, global tags are not used.
1585 .IP LESSHISTFILE
1586 Name of the history file used to remember search commands and
1587 shell commands between invocations of
1588 .I less.
1589 If set to "\-" or "/dev/null", a history file is not used.
1590 The default is "$HOME/.lesshst" on Unix systems, "$HOME/_lesshst" on
1591 DOS and Windows systems, or "$HOME/lesshst.ini" or "$INIT/lesshst.ini"
1592 on OS/2 systems.
1593 .IP LESSHISTSIZE
1594 The maximum number of commands to save in the history file.
1595 The default is 100.
1596 .IP LESSKEY
1597 Name of the default lesskey(1) file.
1598 .IP LESSKEY_SYSTEM
1599 Name of the default system-wide lesskey(1) file.
1600 .IP LESSMETACHARS
1601 List of characters which are considered "metacharacters" by the shell.
1602 .IP LESSMETAESCAPE
1603 Prefix which less will add before each metacharacter in a
1604 command sent to the shell.
1605 If LESSMETAESCAPE is an empty string, commands containing
1606 metacharacters will not be passed to the shell.
1607 .IP LESSOPEN
1608 Command line to invoke the (optional) input-preprocessor.
1609 .IP LESSSECURE
1610 Runs less in "secure" mode.
1611 See discussion under SECURITY.
1612 .IP LESSSEPARATOR
1613 String to be appended to a directory name in filename completion.
1614 .IP LESSUTFBINFMT
1615 Format for displaying non-printable Unicode code points.
1616 .IP LESS_IS_MORE
1617 Emulate the
1618 .I more
1619 (1) command.
1620 .IP LINES
1621 Sets the number of lines on the screen.
1622 Takes precedence over the number of lines specified by the TERM variable.
1623 (But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD,
1624 the window system's idea of the screen size takes precedence over the
1625 LINES and COLUMNS environment variables.)
1626 .IP PATH
1627 User's search path (used to find a lesskey file
1628 on MS-DOS and OS/2 systems).
1629 .IP SHELL
1630 The shell used to execute the ! command, as well as to expand filenames.
1631 .IP TERM
1632 The type of terminal on which
1633 .I less
1634 is being run.
1635 .IP VISUAL
1636 The name of the editor (used for the v command).
1637
1638 .SH "SEE ALSO"
1639 lesskey(1)
1640
1641 .SH COPYRIGHT
1642 Copyright (C) 1984-2008 Mark Nudelman
1643 .PP
1644 less is part of the GNU project and is free software.
1645 You can redistribute it and/or modify it
1646 under the terms of either
1647 (1) the GNU General Public License as published by
1648 the Free Software Foundation; or (2) the Less License.
1649 See the file README in the less distribution for more details
1650 regarding redistribution.
1651 You should have received a copy of the GNU General Public License
1652 along with the source for less; see the file COPYING.
1653 If not, write to the Free Software Foundation, 59 Temple Place,
1654 Suite 330, Boston, MA 02111-1307, USA.
1655 You should also have received a copy of the Less License;
1656 see the file LICENSE.
1657 .PP
1658 less is distributed in the hope that it will be useful, but
1659 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1660 or FITNESS FOR A PARTICULAR PURPOSE.
1661 See the GNU General Public License for more details.
1662
1663 .SH AUTHOR
1664 .PP
1665 Mark Nudelman <markn@greenwoodsoftware.com>
1666 .br
1667 See http://www.greenwoodsoftware.com/less/bugs.html for the latest list of known bugs in less.
1668 .br
1669 Send bug reports or comments to the above address or to
1670 .br
1671 bug-less@gnu.org.
1672 .br
1673 For more information, see the less homepage at
1674 .br
1675 http://www.greenwoodsoftware.com/less.