Merge from vendor branch LESS:
[dragonfly.git] / contrib / less-4 / less.nro
CommitLineData
1df93143 1.TH LESS 1 "Version 416: 22 Nov 2007"
131ccf9c
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2.SH NAME
3less \- 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
27is a program similar to
28.I more
29(1), but which allows backward movement
30in the file as well as forward movement.
31Also,
32.I less
33does not have to read the entire input file before starting,
34so with large input files it starts up faster than text editors like
35.I vi
36(1).
37.I Less
38uses termcap (or terminfo on some systems),
39so it can run on a variety of terminals.
40There is even limited support for hardcopy terminals.
41(On a hardcopy terminal, lines which should be printed at the top
42of the screen are prefixed with a caret.)
43.PP
44Commands are based on both
45.I more
46and
47.I vi.
48Commands may be preceded by a decimal number,
49called N in the descriptions below.
50The number is used by some commands, as indicated.
51
52.SH COMMANDS
53In the following descriptions, ^X means control-X.
54ESC stands for the ESCAPE key; for example ESC-v means the
55two character sequence "ESCAPE", then "v".
56.IP "h or H"
57Help: display a summary of these commands.
58If you forget all the other commands, remember this one.
59.IP "SPACE or ^V or f or ^F"
60Scroll forward N lines, default one window (see option \-z below).
61If N is more than the screen size, only the final screenful is displayed.
62Warning: some systems use ^V as a special literalization character.
63.IP "z"
64Like SPACE, but if N is specified, it becomes the new window size.
65.IP "ESC-SPACE"
66Like SPACE, but scrolls a full screenful, even if it reaches
67end-of-file in the process.
68.IP "RETURN or ^N or e or ^E or j or ^J"
69Scroll forward N lines, default 1.
70The entire N lines are displayed, even if N is more than the screen size.
71.IP "d or ^D"
72Scroll forward N lines, default one half of the screen size.
73If N is specified, it becomes the new default for
74subsequent d and u commands.
75.IP "b or ^B or ESC-v"
76Scroll backward N lines, default one window (see option \-z below).
77If N is more than the screen size, only the final screenful is displayed.
78.IP "w"
79Like ESC-v, but if N is specified, it becomes the new window size.
80.IP "y or ^Y or ^P or k or ^K"
81Scroll backward N lines, default 1.
82The entire N lines are displayed, even if N is more than the screen size.
83Warning: some systems use ^Y as a special job control character.
84.IP "u or ^U"
85Scroll backward N lines, default one half of the screen size.
86If N is specified, it becomes the new default for
87subsequent d and u commands.
88.IP "ESC-) or RIGHTARROW"
89Scroll horizontally right N characters, default half the screen width
90(see the \-# option).
91If a number N is specified, it becomes the default for future RIGHTARROW
92and LEFTARROW commands.
93While the text is scrolled, it acts as though the \-S option
94(chop lines) were in effect.
95.IP "ESC-( or LEFTARROW"
96Scroll horizontally left N characters, default half the screen width
97(see the \-# option).
98If a number N is specified, it becomes the default for future RIGHTARROW
99and LEFTARROW commands.
100.IP "r or ^R or ^L"
101Repaint the screen.
102.IP R
103Repaint the screen, discarding any buffered input.
104Useful if the file is changing while it is being viewed.
105.IP "F"
106Scroll forward, and keep trying to read when the
107end of file is reached.
108Normally this command would be used when already at the end of the file.
109It is a way to monitor the tail of a file which is growing
110while it is being viewed.
111(The behavior is similar to the "tail \-f" command.)
112.IP "g or < or ESC-<"
113Go 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->"
116Go to line N in the file, default the end of the file.
117(Warning: this may be slow if N is large,
118or if N is not specified and
119standard input, rather than a file, is being read.)
120.IP "p or %"
121Go to a position N percent into the file.
122N should be between 0 and 100, and may contain a decimal point.
123.IP "P"
124Go to the line containing byte offset N in the file.
125.IP "{"
126If a left curly bracket appears in the top line displayed
127on the screen,
128the { command will go to the matching right curly bracket.
129The matching right curly bracket is positioned on the bottom
130line of the screen.
131If there is more than one left curly bracket on the top line,
132a number N may be used to specify the N-th bracket on the line.
133.IP "}"
134If a right curly bracket appears in the bottom line displayed
135on the screen,
136the } command will go to the matching left curly bracket.
137The matching left curly bracket is positioned on the top
138line of the screen.
139If there is more than one right curly bracket on the top line,
140a number N may be used to specify the N-th bracket on the line.
141.IP "("
142Like {, but applies to parentheses rather than curly brackets.
143.IP ")"
144Like }, but applies to parentheses rather than curly brackets.
145.IP "["
146Like {, but applies to square brackets rather than curly brackets.
147.IP "]"
148Like }, but applies to square brackets rather than curly brackets.
149.IP "ESC-^F"
150Followed by two characters,
151acts like {, but uses the two characters as open and close brackets,
152respectively.
153For example, "ESC ^F < >" could be used to
154go forward to the > which matches the < in the top displayed line.
155.IP "ESC-^B"
156Followed by two characters,
157acts like }, but uses the two characters as open and close brackets,
158respectively.
159For example, "ESC ^B < >" could be used to
160go backward to the < which matches the > in the bottom displayed line.
161.IP m
162Followed by any lowercase letter,
163marks the current position with that letter.
164.IP "'"
165(Single quote.)
166Followed by any lowercase letter, returns to the position which
167was previously marked with that letter.
168Followed by another single quote, returns to the position at
169which the last "large" movement command was executed.
170Followed by a ^ or $, jumps to the beginning or end of the
171file respectively.
172Marks are preserved when a new file is examined,
173so the ' command can be used to switch between input files.
174.IP "^X^X"
175Same as single quote.
176.IP /pattern
177Search forward in the file for the N-th line containing the pattern.
178N defaults to 1.
179The pattern is a regular expression, as recognized by
180the regular expression library supplied by your system.
181The search starts at the second line displayed
182(but see the \-a and \-j options, which change this).
183.sp
184Certain characters are special
185if entered at the beginning of the pattern;
186they modify the type of search rather than become part of the pattern:
187.RS
188.IP "^N or !"
189Search for lines which do NOT match the pattern.
190.IP "^E or *"
191Search multiple files.
192That is, if the search reaches the END of the current file
193without finding a match,
194the search continues in the next file in the command line list.
195.IP "^F or @"
196Begin the search at the first line of the FIRST file
197in the command line list,
198regardless of what is currently displayed on the screen
199or the settings of the \-a or \-j options.
200.IP "^K"
201Highlight any text which matches the pattern on the current screen,
202but don't move to the first match (KEEP current position).
203.IP "^R"
204Don't interpret regular expression metacharacters;
205that is, do a simple textual comparison.
206.RE
207.IP ?pattern
208Search backward in the file for the N-th line containing the pattern.
209The search starts at the line immediately before the top line displayed.
210.sp
211Certain characters are special as in the / command:
212.RS
213.IP "^N or !"
214Search for lines which do NOT match the pattern.
215.IP "^E or *"
216Search multiple files.
217That is, if the search reaches the beginning of the current file
218without finding a match,
219the search continues in the previous file in the command line list.
220.IP "^F or @"
221Begin the search at the last line of the last file
222in the command line list,
223regardless of what is currently displayed on the screen
224or the settings of the \-a or \-j options.
225.IP "^K"
226As in forward searches.
227.IP "^R"
228As in forward searches.
229.RE
230.IP "ESC-/pattern"
231Same as "/*".
232.IP "ESC-?pattern"
233Same as "?*".
234.IP n
235Repeat previous search, for N-th line containing the last pattern.
236If the previous search was modified by ^N, the search is made for the
237N-th line NOT containing the pattern.
238If the previous search was modified by ^E, the search continues
239in the next (or previous) file if not satisfied in the current file.
240If the previous search was modified by ^R, the search is done
241without using regular expressions.
242There is no effect if the previous search was modified by ^F or ^K.
243.IP N
244Repeat previous search, but in the reverse direction.
245.IP "ESC-n"
246Repeat previous search, but crossing file boundaries.
247The effect is as if the previous search were modified by *.
248.IP "ESC-N"
249Repeat previous search, but in the reverse direction
250and crossing file boundaries.
251.IP "ESC-u"
252Undo search highlighting.
253Turn off highlighting of strings matching the current search pattern.
254If highlighting is already off because of a previous ESC-u command,
255turn highlighting back on.
256Any search command will also turn highlighting back on.
257(Highlighting can also be disabled by toggling the \-G option;
258in that case search commands do not turn highlighting back on.)
259.IP ":e [filename]"
260Examine a new file.
261If the filename is missing, the "current" file (see the :n and :p commands
262below) from the list of files in the command line is re-examined.
263A percent sign (%) in the filename is replaced by the name of the
264current file.
265A pound sign (#) is replaced by the name of the previously examined file.
266However, two consecutive percent signs are simply
267replaced with a single percent sign.
268This allows you to enter a filename that contains a percent sign
269in the name.
270Similarly, two consecutive pound signs are replaced with a single pound sign.
271The filename is inserted into the command line list of files
272so that it can be seen by subsequent :n and :p commands.
273If the filename consists of several files, they are all inserted into
274the list of files and the first one is examined.
275If the filename contains one or more spaces,
276the entire filename should be enclosed in double quotes
277(also see the \-" option).
278.IP "^X^V or E"
279Same as :e.
280Warning: some systems use ^V as a special literalization character.
281On such systems, you may not be able to use ^V.
282.IP ":n"
283Examine the next file (from the list of files given in the command line).
284If a number N is specified, the N-th next file is examined.
285.IP ":p"
286Examine the previous file in the command line list.
287If a number N is specified, the N-th previous file is examined.
288.IP ":x"
289Examine the first file in the command line list.
290If a number N is specified, the N-th file in the list is examined.
291.IP ":d"
292Remove the current file from the list of files.
293.IP "t"
294Go to the next tag, if there were more than one matches for the current tag.
295See the \-t option for more details about tags.
296.IP "T"
297Go to the previous tag, if there were more than one matches for the current tag.
298.IP "= or ^G or :f"
299Prints some information about the file being viewed,
300including its name
301and the line number and byte offset of the bottom line being displayed.
302If possible, it also prints the length of the file,
303the number of lines in the file
304and the percent of the file above the last displayed line.
305.IP \-
306Followed by one of the command line option letters (see OPTIONS below),
307this will change the setting of that option
308and print a message describing the new setting.
309If a ^P (CONTROL-P) is entered immediately after the dash,
310the setting of the option is changed but no message is printed.
311If the option letter has a numeric value (such as \-b or \-h),
312or a string value (such as \-P or \-t),
313a new value may be entered after the option letter.
314If no new value is entered, a message describing
315the current setting is printed and nothing is changed.
316.IP \-\-
317Like the \- command, but takes a long option name (see OPTIONS below)
318rather than a single option letter.
319You must press RETURN after typing the option name.
320A ^P immediately after the second dash suppresses printing of a
321message describing the new setting, as in the \- command.
322.IP \-+
323Followed by one of the command line option letters
324this will reset the option to its default setting
325and print a message describing the new setting.
326(The "\-+\fIX\fP" command does the same thing
327as "\-+\fIX\fP" on the command line.)
328This does not work for string-valued options.
329.IP \-\-+
330Like the \-+ command, but takes a long option name
331rather than a single option letter.
332.IP \-!
333Followed by one of the command line option letters,
334this will reset the option to the "opposite" of its default setting
335and print a message describing the new setting.
336This does not work for numeric or string-valued options.
337.IP \-\-!
338Like the \-! command, but takes a long option name
339rather than a single option letter.
340.IP _
341(Underscore.)
342Followed by one of the command line option letters,
343this will print a message describing the current setting of that option.
344The setting of the option is not changed.
345.IP __
346(Double underscore.)
347Like the _ (underscore) command, but takes a long option name
348rather than a single option letter.
349You must press RETURN after typing the option name.
350.IP +cmd
351Causes the specified cmd to be executed each time a new file is examined.
352For example, +G causes
353.I less
354to initially display each file starting at the end
355rather than the beginning.
356.IP V
357Prints the version number of
358.I less
359being run.
360.IP "q or Q or :q or :Q or ZZ"
361Exits
362.I less.
363.PP
364The following
365four
366commands may or may not be valid, depending on your particular installation.
367.PP
368.IP v
369Invokes an editor to edit the current file being viewed.
370The editor is taken from the environment variable VISUAL if defined,
371or EDITOR if VISUAL is not defined,
372or defaults to "vi" if neither VISUAL nor EDITOR is defined.
373See also the discussion of LESSEDIT under the section on PROMPTS below.
374.IP "! shell-command"
375Invokes a shell to run the shell-command given.
376A percent sign (%) in the command is replaced by the name of the
377current file.
378A pound sign (#) is replaced by the name of the previously examined file.
379"!!" repeats the last shell command.
380"!" with no shell command simply invokes a shell.
381On Unix systems, the shell is taken from the environment variable SHELL,
382or defaults to "sh".
383On MS-DOS and OS/2 systems, the shell is the normal command processor.
384.IP "| <m> shell-command"
385<m> represents any mark letter.
386Pipes a section of the input file to the given shell command.
387The section of the file to be piped is between the first line on
388the current screen and the position marked by the letter.
389<m> may also be ^ or $ to indicate beginning or end of file respectively.
390If <m> is . or newline, the current screen is piped.
391.IP "s filename"
392Save the input to a file.
393This only works if the input is a pipe, not an ordinary file.
394.PP
395.SH OPTIONS
396Command line options are described below.
397Most options may be changed while
398.I less
399is running, via the "\-" command.
400.PP
401Most options may be given in one of two forms:
402either a dash followed by a single letter,
403or two dashes followed by a long option name.
404A long option name may be abbreviated as long as
405the abbreviation is unambiguous.
406For example, \-\-quit-at-eof may be abbreviated \-\-quit, but not
407--qui, since both \-\-quit-at-eof and \-\-quiet begin with \-\-qui.
408Some long option names are in uppercase, such as \-\-QUIT-AT-EOF, as
409distinct from \-\-quit-at-eof.
410Such option names need only have their first letter capitalized;
411the remainder of the name may be in either case.
412For example, \-\-Quit-at-eof is equivalent to \-\-QUIT-AT-EOF.
413.PP
414Options are also taken from the environment variable "LESS".
415For example,
416to avoid typing "less \-options ..." each time
417.I less
418is invoked, you might tell
419.I csh:
420.sp
421setenv LESS "-options"
422.sp
423or if you use
424.I sh:
425.sp
426LESS="-options"; export LESS
427.sp
428On MS-DOS, you don't need the quotes, but you should replace any
429percent signs in the options string by double percent signs.
430.sp
431The environment variable is parsed before the command line,
432so command line options override the LESS environment variable.
433If an option appears in the LESS variable, it can be reset
434to its default value on the command line by beginning the command
435line option with "\-+".
436.sp
437For options like \-P or \-D which take a following string,
438a dollar sign ($) must be used to signal the end of the string.
439For example, to set two \-D options on MS-DOS, you must have
440a dollar sign between them, like this:
441.sp
442LESS="-Dn9.1$-Ds4.1"
443.sp
444.IP "\-? or \-\-help"
445This option displays a summary of the commands accepted by
446.I less
447(the same as the h command).
448(Depending on how your shell interprets the question mark,
449it may be necessary to quote the question mark, thus: "\-\e?".)
450.IP "\-a or \-\-search-skip-screen"
451Causes searches to start after the last line
452displayed on the screen,
453thus skipping all lines displayed on the screen.
454By default, searches start at the second line on the screen
455(or after the last found line; see the \-j option).
456.IP "\-b\fIn\fP or \-\-buffers=\fIn\fP"
457Specifies the amount of buffer space
458.I less
459will use for each file, in units of kilobytes (1024 bytes).
460By default 64K of buffer space is used for each file
461(unless the file is a pipe; see the \-B option).
462The \-b option specifies instead that \fIn\fP kilobytes of
463buffer space should be used for each file.
464If \fIn\fP is \-1, buffer space is unlimited; that is,
1df93143 465the entire file can be read into memory.
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466.IP "\-B or \-\-auto-buffers"
467By default, when data is read from a pipe,
468buffers are allocated automatically as needed.
469If a large amount of data is read from the pipe, this can cause
470a large amount of memory to be allocated.
471The \-B option disables this automatic allocation of buffers for pipes,
472so that only 64K
473(or the amount of space specified by the \-b option)
474is used for the pipe.
475Warning: use of \-B can result in erroneous display, since only the
1df93143 476most recently viewed part of the piped data is kept in memory;
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477any earlier data is lost.
478.IP "\-c or \-\-clear-screen"
479Causes full screen repaints to be painted from the top line down.
480By default,
481full screen repaints are done by scrolling from the bottom of the screen.
482.IP "\-C or \-\-CLEAR-SCREEN"
483Same as \-c, for compatibility with older versions of
484.I less.
485.IP "\-d or \-\-dumb"
486The \-d option suppresses the error message
487normally displayed if the terminal is dumb;
488that is, lacks some important capability,
489such as the ability to clear the screen or scroll backward.
490The \-d option does not otherwise change the behavior of
491.I less
492on a dumb terminal.
493.IP "\-D\fBx\fP\fIcolor\fP or \-\-color=\fBx\fP\fIcolor\fP"
494[MS-DOS only]
495Sets the color of the text displayed.
496\fBx\fP is a single character which selects the type of text whose color is
497being set: n=normal, s=standout, d=bold, u=underlined, k=blink.
498\fIcolor\fP is a pair of numbers separated by a period.
499The first number selects the foreground color and the second selects
500the background color of the text.
501A single number \fIN\fP is the same as \fIN.0\fP.
502.IP "\-e or \-\-quit-at-eof"
503Causes
504.I less
505to automatically exit
506the second time it reaches end-of-file.
507By default, the only way to exit
508.I less
509is via the "q" command.
510.IP "\-E or \-\-QUIT-AT-EOF"
511Causes
512.I less
513to automatically exit the first time it reaches end-of-file.
514.IP "\-f or \-\-force"
515Forces non-regular files to be opened.
516(A non-regular file is a directory or a device special file.)
517Also suppresses the warning message when a binary file is opened.
518By default,
519.I less
520will refuse to open non-regular files.
521Note that some operating systems will not allow directories
522to be read, even if \-f is set.
523.IP "\-F or \-\-quit-if-one-screen"
524Causes
525.I less
526to automatically exit
527if the entire file can be displayed on the first screen.
528.IP "\-g or \-\-hilite-search"
529Normally,
530.I less
531will highlight ALL strings which match the last search command.
532The \-g option changes this behavior to highlight only the particular string
533which was found by the last search command.
534This can cause
535.I less
536to run somewhat faster than the default.
537.IP "\-G or \-\-HILITE-SEARCH"
538The \-G option suppresses all highlighting of strings found by search commands.
539.IP "\-h\fIn\fP or \-\-max-back-scroll=\fIn\fP"
540Specifies a maximum number of lines to scroll backward.
541If it is necessary to scroll backward more than \fIn\fP lines,
542the screen is repainted in a forward direction instead.
543(If the terminal does not have the ability to scroll
544backward, \-h0 is implied.)
545.IP "\-i or \-\-ignore-case"
546Causes searches to ignore case; that is,
547uppercase and lowercase are considered identical.
548This option is ignored if any uppercase letters
549appear in the search pattern;
550in other words,
551if a pattern contains uppercase letters, then that search does not ignore case.
552.IP "\-I or \-\-IGNORE-CASE"
553Like \-i, but searches ignore case even if
554the pattern contains uppercase letters.
555.IP "\-j\fIn\fP or \-\-jump-target=\fIn\fP"
556Specifies a line on the screen where the "target" line
557is to be positioned.
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558The target line is the line specified by any command to
559search for a pattern, jump to a line number,
560jump to a file percentage or jump to a tag.
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561The screen line may be specified by a number: the top line on the screen
562is 1, the next is 2, and so on.
563The number may be negative to specify a line relative to the bottom
564of the screen: the bottom line on the screen is \-1, the second
565to the bottom is \-2, and so on.
566Alternately, the screen line may be specified as a fraction of the height
567of the screen, starting with a decimal point: .5 is in the middle of the
568screen, .3 is three tenths down from the first line, and so on.
569If the line is specified as a fraction, the actual line number
570is recalculated if the terminal window is resized, so that the
571target line remains at the specified fraction of the screen height.
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572If any form of the \-j option is used,
573forward searches begin at the line immediately after the target line,
574and backward searches begin at the target line.
131ccf9c 575For example, if "\-j4" is used, the target line is the
1df93143 576fourth line on the screen, so forward searches begin at the fifth line
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577on the screen.
578.IP "\-J or \-\-status-column"
579Displays a status column at the left edge of the screen.
580The status column shows the lines that matched the current search.
581The status column is also used if the \-w or \-W option is in effect.
582.IP "\-k\fIfilename\fP or \-\-lesskey-file=\fIfilename\fP"
583Causes
584.I less
585to open and interpret the named file as a
586.I lesskey
587(1) file.
588Multiple \-k options may be specified.
589If the LESSKEY or LESSKEY_SYSTEM environment variable is set, or
590if a lesskey file is found in a standard place (see KEY BINDINGS),
591it is also used as a
592.I lesskey
593file.
594.IP "\-K or \-\-quit-on-intr"
595Causes
596.I less
597to exit immediately when an interrupt character (usually ^C) is typed.
598Normally, an interrupt character causes
599.I less
600to stop whatever it is doing and return to its command prompt.
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601Note that use of this option makes it impossible to return to the
602command prompt from the "F" command.
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603.IP "\-L or \-\-no-lessopen"
604Ignore the LESSOPEN environment variable
605(see the INPUT PREPROCESSOR section below).
606This option can be set from within \fIless\fP,
607but it will apply only to files opened subsequently, not to the
608file which is currently open.
609.IP "\-m or \-\-long-prompt"
610Causes
611.I less
612to prompt verbosely (like \fImore\fP),
613with the percent into the file.
614By default,
615.I less
616prompts with a colon.
617.IP "\-M or \-\-LONG-PROMPT"
618Causes
619.I less
620to prompt even more verbosely than
621.I more.
622.IP "\-n or \-\-line-numbers"
623Suppresses line numbers.
624The default (to use line numbers) may cause
625.I less
626to run more slowly in some cases, especially with a very large input file.
627Suppressing line numbers with the \-n option will avoid this problem.
628Using line numbers means: the line number will be displayed in the verbose
629prompt and in the = command,
630and the v command will pass the current line number to the editor
631(see also the discussion of LESSEDIT in PROMPTS below).
632.IP "\-N or \-\-LINE-NUMBERS"
633Causes a line number to be displayed at the beginning of
634each line in the display.
635.IP "\-o\fIfilename\fP or \-\-log-file=\fIfilename\fP"
636Causes
637.I less
638to copy its input to the named file as it is being viewed.
639This applies only when the input file is a pipe,
640not an ordinary file.
641If the file already exists,
642.I less
643will ask for confirmation before overwriting it.
644.IP "\-O\fIfilename\fP or \-\-LOG-FILE=\fIfilename\fP"
645The \-O option is like \-o, but it will overwrite an existing
646file without asking for confirmation.
647.sp
648If no log file has been specified,
649the \-o and \-O options can be used from within
650.I less
651to specify a log file.
652Without a file name, they will simply report the name of the log file.
653The "s" command is equivalent to specifying \-o from within
654.I less.
655.IP "\-p\fIpattern\fP or \-\-pattern=\fIpattern\fP"
656The \-p option on the command line is equivalent to
657specifying +/\fIpattern\fP;
658that is, it tells
659.I less
660to start at the first occurrence of \fIpattern\fP in the file.
661.IP "\-P\fIprompt\fP or \-\-prompt=\fIprompt\fP"
662Provides a way to tailor the three prompt
663styles to your own preference.
664This option would normally be put in the LESS environment
665variable, rather than being typed in with each
666.I less
667command.
668Such an option must either be the last option in the LESS variable,
669or be terminated by a dollar sign.
670-Ps followed by a string changes the default (short) prompt
671to that string.
672-Pm changes the medium (\-m) prompt.
673-PM changes the long (\-M) prompt.
674-Ph changes the prompt for the help screen.
675-P= changes the message printed by the = command.
676-Pw changes the message printed while waiting for data (in the F command).
677All prompt strings consist of a sequence of
678letters and special escape sequences.
679See the section on PROMPTS for more details.
680.IP "\-q or \-\-quiet or \-\-silent"
681Causes moderately "quiet" operation:
682the terminal bell is not rung
683if an attempt is made to scroll past the end of the file
684or before the beginning of the file.
685If the terminal has a "visual bell", it is used instead.
686The bell will be rung on certain other errors,
687such as typing an invalid character.
688The default is to ring the terminal bell in all such cases.
689.IP "\-Q or \-\-QUIET or \-\-SILENT"
690Causes totally "quiet" operation:
691the terminal bell is never rung.
692.IP "\-r or \-\-raw-control-chars"
693Causes "raw" control characters to be displayed.
694The default is to display control characters using the caret notation;
695for example, a control-A (octal 001) is displayed as "^A".
696Warning: when the \-r option is used,
697.I less
698cannot keep track of the actual appearance of the screen
699(since this depends on how the screen responds to
700each type of control character).
701Thus, various display problems may result,
702such as long lines being split in the wrong place.
703.IP "\-R or \-\-RAW-CONTROL-CHARS"
704Like \-r, but only ANSI "color" escape sequences are output in "raw" form.
705Unlike \-r, the screen appearance is maintained correctly in most cases.
706ANSI "color" escape sequences are sequences of the form:
707.sp
708 ESC [ ... m
709.sp
710where the "..." is zero or more color specification characters
711For the purpose of keeping track of screen appearance,
712ANSI color escape sequences are assumed to not move the cursor.
713You can make
714.I less
715think that characters other than "m" can end ANSI color escape sequences
716by setting the environment variable LESSANSIENDCHARS to the list of
717characters which can end a color escape sequence.
718And you can make
719.I less
720think that characters other than the standard ones may appear between
721the ESC and the m by setting the environment variable LESSANSIMIDCHARS
722to the list of characters which can appear.
723.IP "\-s or \-\-squeeze-blank-lines"
724Causes consecutive blank lines to be squeezed into a single blank line.
725This is useful when viewing
726.I nroff
727output.
728.IP "\-S or \-\-chop-long-lines"
729Causes lines longer than the screen width to be
730chopped rather than folded.
731That is, the portion of a long line that does not fit in
732the screen width is not shown.
733The default is to fold long lines; that is, display the remainder
734on the next line.
735.IP "\-t\fItag\fP or \-\-tag=\fItag\fP"
736The \-t option, followed immediately by a TAG,
737will edit the file containing that tag.
738For this to work, tag information must be available;
739for example, there may be a file in the current directory called "tags",
740which was previously built by
741.I ctags
742(1) or an equivalent command.
743If the environment variable LESSGLOBALTAGS is set, it is taken to be
744the name of a command compatible with
745.I global
746(1), and that command is executed to find the tag.
747(See http://www.gnu.org/software/global/global.html).
748The \-t option may also be specified from within
749.I less
750(using the \- command) as a way of examining a new file.
751The command ":t" is equivalent to specifying \-t from within
752.I less.
753.IP "\-T\fItagsfile\fP or \-\-tag-file=\fItagsfile\fP"
754Specifies a tags file to be used instead of "tags".
755.IP "\-u or \-\-underline-special"
756Causes backspaces and carriage returns to be treated as printable characters;
757that is, they are sent to the terminal when they appear in the input.
758.IP "\-U or \-\-UNDERLINE-SPECIAL"
759Causes backspaces, tabs and carriage returns to be
760treated as control characters;
761that is, they are handled as specified by the \-r option.
762.sp
763By default, if neither \-u nor \-U is given,
764backspaces which appear adjacent to an underscore character
765are treated specially:
766the underlined text is displayed
767using the terminal's hardware underlining capability.
768Also, backspaces which appear between two identical characters
769are treated specially:
770the overstruck text is printed
771using the terminal's hardware boldface capability.
772Other backspaces are deleted, along with the preceding character.
773Carriage returns immediately followed by a newline are deleted.
774other carriage returns are handled as specified by the \-r option.
775Text which is overstruck or underlined can be searched for
776if neither \-u nor \-U is in effect.
777.IP "\-V or \-\-version"
778Displays the version number of
779.I less.
780.IP "\-w or \-\-hilite-unread"
781Temporarily highlights the first "new" line after a forward movement
782of a full page.
783The first "new" line is the line immediately following the line previously
784at the bottom of the screen.
785Also highlights the target line after a g or p command.
786The highlight is removed at the next command which causes movement.
787The entire line is highlighted, unless the \-J option is in effect,
788in which case only the status column is highlighted.
789.IP "\-W or \-\-HILITE-UNREAD"
790Like \-w, but temporarily highlights the first new line after any
791forward movement command larger than one line.
792.IP "\-x\fIn\fP,... or \-\-tabs=\fIn\fP,..."
793Sets tab stops.
794If only one \fIn\fP is specified, tab stops are set at multiples of \fIn\fP.
795If multiple values separated by commas are specified, tab stops
796are set at those positions, and then continue with the same spacing as the
797last two.
798For example, \fI-x9,17\fP will set tabs at positions 9, 17, 25, 33, etc.
799The default for \fIn\fP is 8.
800.IP "\-X or \-\-no-init"
801Disables sending the termcap initialization and deinitialization strings
802to the terminal.
803This is sometimes desirable if the deinitialization string does
804something unnecessary, like clearing the screen.
131ccf9c
PA
805.IP "\-y\fIn\fP or \-\-max-forw-scroll=\fIn\fP"
806Specifies a maximum number of lines to scroll forward.
807If it is necessary to scroll forward more than \fIn\fP lines,
808the screen is repainted instead.
809The \-c or \-C option may be used to repaint from the top of
810the screen if desired.
811By default, any forward movement causes scrolling.
812.IP "\-[z]\fIn\fP or \-\-window=\fIn\fP"
813Changes the default scrolling window size to \fIn\fP lines.
814The default is one screenful.
815The z and w commands can also be used to change the window size.
816The "z" may be omitted for compatibility with some versions of
817.I more.
818If the number
819.I n
820is negative, it indicates
821.I n
822lines less than the current screen size.
823For example, if the screen is 24 lines, \fI\-z-4\fP sets the
824scrolling window to 20 lines. If the screen is resized to 40 lines,
825the scrolling window automatically changes to 36 lines.
826.IP "\-\fI\(dqcc\fP\ or\ \-\-quotes=\fIcc\fP"
827Changes the filename quoting character.
828This may be necessary if you are trying to name a file
829which contains both spaces and quote characters.
830Followed by a single character, this changes the quote character to that
831character.
832Filenames containing a space should then be surrounded by that character
833rather than by double quotes.
834Followed by two characters, changes the open quote to the first character,
835and the close quote to the second character.
836Filenames containing a space should then be preceded by the open quote
837character and followed by the close quote character.
838Note that even after the quote characters are changed, this option
839remains \-" (a dash followed by a double quote).
840.IP "\-~ or \-\-tilde"
841Normally lines after end of file are displayed as a single tilde (~).
842This option causes lines after end of file to be displayed as blank lines.
843.IP "\-# or \-\-shift"
844Specifies the default number of positions to scroll horizontally
845in the RIGHTARROW and LEFTARROW commands.
846If the number specified is zero, it sets the default number of
847positions to one half of the screen width.
3336a202
PA
848.IP "\-\-no-keypad"
849Disables sending the keypad initialization and deinitialization strings
850to the terminal.
851This is sometimes useful if the keypad strings make the numeric
852keypad behave in an undesirable manner.
853.IP "\-\-follow-name"
854Normally, if the input file is renamed while an F command is executing,
855.I less
856will continue to display the contents of the original file despite
857its name change.
858If \-\-follow-name is specified, during an F command
859.I less
860will periodically attempt to reopen the file by name.
861If the reopen succeeds and the file is a different file from the original
862(which means that a new file has been created
863with the same name as the original (now renamed) file),
864.I less
865will display the contents of that new file.
131ccf9c
PA
866.IP \-\-
867A command line argument of "\-\-" marks the end of option arguments.
868Any arguments following this are interpreted as filenames.
869This can be useful when viewing a file whose name begins with a "\-" or "+".
870.IP +
871If a command line option begins with \fB+\fP,
872the remainder of that option is taken to be an initial command to
873.I less.
874For example, +G tells
875.I less
876to start at the end of the file rather than the beginning,
877and +/xyz tells it to start at the first occurrence of "xyz" in the file.
878As a special case, +<number> acts like +<number>g;
879that is, it starts the display at the specified line number
880(however, see the caveat under the "g" command above).
881If the option starts with ++, the initial command applies to
882every file being viewed, not just the first one.
883The + command described previously
884may also be used to set (or change) an initial command for every file.
885
886.SH "LINE EDITING"
887When entering command line at the bottom of the screen
888(for example, a filename for the :e command,
889or the pattern for a search command),
890certain keys can be used to manipulate the command line.
891Most commands have an alternate form in [ brackets ] which can be used if
892a key does not exist on a particular keyboard.
893(The bracketed forms do not work in the MS-DOS version.)
894Any of these special keys may be entered literally by preceding
895it with the "literal" character, either ^V or ^A.
896A backslash itself may also be entered literally by entering two backslashes.
897.IP "LEFTARROW [ ESC-h ]"
898Move the cursor one space to the left.
899.IP "RIGHTARROW [ ESC-l ]"
900Move the cursor one space to the right.
901.IP "^LEFTARROW [ ESC-b or ESC-LEFTARROW ]"
902(That is, CONTROL and LEFTARROW simultaneously.)
903Move the cursor one word to the left.
904.IP "^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]"
905(That is, CONTROL and RIGHTARROW simultaneously.)
906Move the cursor one word to the right.
907.IP "HOME [ ESC-0 ]"
908Move the cursor to the beginning of the line.
909.IP "END [ ESC-$ ]"
910Move the cursor to the end of the line.
911.IP "BACKSPACE"
912Delete the character to the left of the cursor,
913or cancel the command if the command line is empty.
914.IP "DELETE or [ ESC-x ]"
915Delete the character under the cursor.
916.IP "^BACKSPACE [ ESC-BACKSPACE ]"
917(That is, CONTROL and BACKSPACE simultaneously.)
918Delete the word to the left of the cursor.
919.IP "^DELETE [ ESC-X or ESC-DELETE ]"
920(That is, CONTROL and DELETE simultaneously.)
921Delete the word under the cursor.
922.IP "UPARROW [ ESC-k ]"
923Retrieve the previous command line.
924.IP "DOWNARROW [ ESC-j ]"
925Retrieve the next command line.
926.IP "TAB"
927Complete the partial filename to the left of the cursor.
928If it matches more than one filename, the first match
929is entered into the command line.
930Repeated TABs will cycle thru the other matching filenames.
931If the completed filename is a directory, a "/" is appended to the filename.
932(On MS-DOS systems, a "\e" is appended.)
933The environment variable LESSSEPARATOR can be used to specify a
934different character to append to a directory name.
935.IP "BACKTAB [ ESC-TAB ]"
936Like, TAB, but cycles in the reverse direction thru the matching filenames.
937.IP "^L"
938Complete the partial filename to the left of the cursor.
939If it matches more than one filename, all matches are entered into
940the command line (if they fit).
941.IP "^U (Unix and OS/2) or ESC (MS-DOS)"
942Delete the entire command line,
943or cancel the command if the command line is empty.
944If you have changed your line-kill character in Unix to something
945other than ^U, that character is used instead of ^U.
946
947.SH "KEY BINDINGS"
948You may define your own
949.I less
950commands by using the program
951.I lesskey
952(1)
953to create a lesskey file.
954This file specifies a set of command keys and an action
955associated with each key.
956You may also use
957.I lesskey
958to change the line-editing keys (see LINE EDITING),
959and to set environment variables.
960If the environment variable LESSKEY is set,
961.I less
962uses that as the name of the lesskey file.
963Otherwise,
964.I less
965looks in a standard place for the lesskey file:
966On Unix systems,
967.I less
968looks for a lesskey file called "$HOME/.less".
969On MS-DOS and Windows systems,
970.I less
971looks for a lesskey file called "$HOME/_less", and if it is not found there,
972then looks for a lesskey file called "_less" in any directory specified
973in the PATH environment variable.
974On OS/2 systems,
975.I less
976looks for a lesskey file called "$HOME/less.ini", and if it is not found,
977then looks for a lesskey file called "less.ini" in any directory specified
978in the INIT environment variable, and if it not found there,
979then looks for a lesskey file called "less.ini" in any directory specified
980in the PATH environment variable.
981See the
982.I lesskey
983manual page for more details.
984.P
985A system-wide lesskey file may also be set up to provide key bindings.
986If a key is defined in both a local lesskey file and in the
987system-wide file, key bindings in the local file take precedence over
988those in the system-wide file.
989If the environment variable LESSKEY_SYSTEM is set,
990.I less
991uses that as the name of the system-wide lesskey file.
992Otherwise,
993.I less
994looks in a standard place for the system-wide lesskey file:
995On Unix systems, the system-wide lesskey file is /usr/local/etc/sysless.
996(However, if
997.I less
998was built with a different sysconf directory than /usr/local/etc,
999that directory is where the sysless file is found.)
1000On MS-DOS and Windows systems, the system-wide lesskey file is c:\e_sysless.
1001On OS/2 systems, the system-wide lesskey file is c:\esysless.ini.
1002
1003.SH "INPUT PREPROCESSOR"
1004You may define an "input preprocessor" for
1005.I less.
1006Before
1007.I less
1008opens a file, it first gives your input preprocessor a chance to modify the
1009way the contents of the file are displayed.
1010An input preprocessor is simply an executable program (or shell script),
1011which writes the contents of the file to a different file,
1012called the replacement file.
1013The contents of the replacement file are then displayed
1014in place of the contents of the original file.
1015However, it will appear to the user as if the original file is opened;
1016that is,
1017.I less
1018will display the original filename as the name of the current file.
1019.PP
1020An input preprocessor receives one command line argument, the original filename,
1021as entered by the user.
1022It should create the replacement file, and when finished,
1023print the name of the replacement file to its standard output.
1024If the input preprocessor does not output a replacement filename,
1025.I less
1026uses the original file, as normal.
1027The input preprocessor is not called when viewing standard input.
1028To set up an input preprocessor, set the LESSOPEN environment variable
1029to a command line which will invoke your input preprocessor.
1030This command line should include one occurrence of the string "%s",
1031which will be replaced by the filename
1032when the input preprocessor command is invoked.
1033.PP
1034When
1035.I less
1036closes a file opened in such a way, it will call another program,
1037called the input postprocessor,
1038which may perform any desired clean-up action (such as deleting the
1039replacement file created by LESSOPEN).
1040This program receives two command line arguments, the original filename
1041as entered by the user, and the name of the replacement file.
1042To set up an input postprocessor, set the LESSCLOSE environment variable
1043to a command line which will invoke your input postprocessor.
1044It may include two occurrences of the string "%s";
1045the first is replaced with the original name of the file and
1046the second with the name of the replacement file,
1047which was output by LESSOPEN.
1048.PP
1049For example, on many Unix systems, these two scripts will allow you
1050to keep files in compressed format, but still let
1051.I less
1052view them directly:
1053.PP
1054lessopen.sh:
1055.br
1056 #! /bin/sh
1057.br
1058 case "$1" in
1059.br
1060 *.Z) uncompress -\c $1 >/tmp/less.$$ 2>/dev/null
1061.br
1062 if [ \-s /tmp/less.$$ ]; then
1063.br
1064 echo /tmp/less.$$
1065.br
1066 else
1067.br
1068 rm \-f /tmp/less.$$
1069.br
1070 fi
1071.br
1072 ;;
1073.br
1074 esac
1075.PP
1076lessclose.sh:
1077.br
1078 #! /bin/sh
1079.br
1080 rm $2
1081.PP
1082To use these scripts, put them both where they can be executed and
1083set LESSOPEN="lessopen.sh\ %s", and
1084LESSCLOSE="lessclose.sh\ %s\ %s".
1085More complex LESSOPEN and LESSCLOSE scripts may be written
1086to accept other types of compressed files, and so on.
1087.PP
1088It is also possible to set up an input preprocessor to
1089pipe the file data directly to
1090.I less,
1091rather than putting the data into a replacement file.
1092This avoids the need to decompress the entire file before
1093starting to view it.
1094An input preprocessor that works this way is called an input pipe.
1095An input pipe, instead of writing the name of a replacement file on
1096its standard output,
1097writes the entire contents of the replacement file on its standard output.
1098If the input pipe does not write any characters on its standard output,
1099then there is no replacement file and
1100.I less
1101uses the original file, as normal.
1102To use an input pipe,
1103make the first character in the LESSOPEN environment variable a
1104vertical bar (|) to signify that the input preprocessor is an input pipe.
1105.PP
1106For example, on many Unix systems, this script will work like the
1107previous example scripts:
1108.PP
1109lesspipe.sh:
1110.br
1111 #! /bin/sh
1112.br
1113 case "$1" in
1114.br
1115 *.Z) uncompress \-c $1 2>/dev/null
1116.br
1117 ;;
1118.br
1119 esac
1120.br
1121.PP
1122To use this script, put it where it can be executed and set
1123LESSOPEN="|lesspipe.sh %s".
1124When an input pipe is used, a LESSCLOSE postprocessor can be used,
1125but it is usually not necessary since there is no replacement file
1126to clean up.
1127In this case, the replacement file name passed to the LESSCLOSE
1128postprocessor is "\-".
1129
1130.SH "NATIONAL CHARACTER SETS"
1131There are three types of characters in the input file:
1132.IP "normal characters"
1133can be displayed directly to the screen.
1134.IP "control characters"
1135should not be displayed directly, but are expected to be found
1136in ordinary text files (such as backspace and tab).
1137.IP "binary characters"
1138should not be displayed directly and are not expected to be found
1139in text files.
1140.PP
1141A "character set" is simply a description of which characters are to
1142be considered normal, control, and binary.
1143The LESSCHARSET environment variable may be used to select a character set.
1144Possible values for LESSCHARSET are:
1145.IP ascii
1146BS, TAB, NL, CR, and formfeed are control characters,
1147all chars with values between 32 and 126 are normal,
1148and all others are binary.
1149.IP iso8859
1150Selects an ISO 8859 character set.
1151This is the same as ASCII, except characters between 160 and 255 are
1152treated as normal characters.
1153.IP latin1
1154Same as iso8859.
1155.IP latin9
1156Same as iso8859.
1157.IP dos
1158Selects a character set appropriate for MS-DOS.
1159.IP ebcdic
1160Selects an EBCDIC character set.
1161.IP IBM-1047
1162Selects an EBCDIC character set used by OS/390 Unix Services.
1163This is the EBCDIC analogue of latin1. You get similar results
1164by setting either LESSCHARSET=IBM-1047 or LC_CTYPE=en_US
1165in your environment.
1166.IP koi8-r
1167Selects a Russian character set.
1168.IP next
1169Selects a character set appropriate for NeXT computers.
1170.IP utf-8
1171Selects the UTF-8 encoding of the ISO 10646 character set.
1172UTF-8 is special in that it supports multi-byte characters in the input file.
1173It is the only character set that supports multi-byte characters.
1174.IP windows
1175Selects a character set appropriate for Microsoft Windows (cp 1251).
1176.PP
1177In special cases, it may be desired to tailor
1178.I less
1179to use a character set other than the ones definable by LESSCHARSET.
1180In this case, the environment variable LESSCHARDEF can be used
1181to define a character set.
1182It should be set to a string where each character in the string represents
1183one character in the character set.
1184The character "." is used for a normal character, "c" for control,
1185and "b" for binary.
1186A decimal number may be used for repetition.
1187For example, "bccc4b." would mean character 0 is binary,
11881, 2 and 3 are control, 4, 5, 6 and 7 are binary, and 8 is normal.
1189All characters after the last are taken to be the same as the last,
1190so characters 9 through 255 would be normal.
1191(This is an example, and does not necessarily
1192represent any real character set.)
1193.PP
1194This table shows the value of LESSCHARDEF which is equivalent
1195to each of the possible values for LESSCHARSET:
1196.sp
1197 ascii\ 8bcccbcc18b95.b
1198.br
1199 dos\ \ \ 8bcccbcc12bc5b95.b.
1200.br
1201 ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
1202.br
1203 \ \ \ \ \ \ 9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
1204.br
1205 IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
1206.br
1207 \ \ \ \ \ \ 191.b
1208.br
1209 iso8859 8bcccbcc18b95.33b.
1210.br
1211 koi8-r 8bcccbcc18b95.b128.
1212.br
1213 latin1 8bcccbcc18b95.33b.
1214.br
1215 next\ \ 8bcccbcc18b95.bb125.bb
1216.PP
1217If neither LESSCHARSET nor LESSCHARDEF is set,
1218but any of the strings "UTF-8", "UTF8", "utf-8" or "utf8"
1219is found in the LC_ALL, LC_TYPE or LANG
1220environment variables, then the default character set is utf-8.
1221.PP
1222If that string is not found, but your system supports the
1223.I setlocale
1224interface,
1225.I less
1226will use setlocale to determine the character set.
1227setlocale is controlled by setting the LANG or LC_CTYPE environment
1228variables.
1229.PP
1230Finally, if the
1231.I setlocale
1232interface is also not available, the default character set is latin1.
1233.PP
1234Control and binary characters are displayed in standout (reverse video).
1235Each such character is displayed in caret notation if possible
1236(e.g. ^A for control-A). Caret notation is used only if
1237inverting the 0100 bit results in a normal printable character.
1238Otherwise, the character is displayed as a hex number in angle brackets.
1239This format can be changed by
1240setting the LESSBINFMT environment variable.
1241LESSBINFMT may begin with a "*" and one character to select
1242the display attribute:
1243"*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout,
1244and "*n" is normal.
1245If LESSBINFMT does not begin with a "*", normal attribute is assumed.
1246The remainder of LESSBINFMT is a string which may include one
1247printf-style escape sequence (a % followed by x, X, o, d, etc.).
1248For example, if LESSBINFMT is "*u[%x]", binary characters
1249are displayed in underlined hexadecimal surrounded by brackets.
1250The default if no LESSBINFMT is specified is "*s<%X>".
1251The default if no LESSBINFMT is specified is "*s<%02X>".
1252Warning: the result of expanding the character via LESSBINFMT must
1253be less than 31 characters.
1254.PP
1255When the character set is utf-8, the LESSUTFBINFMT environment variable
1256acts similarly to LESSBINFMT but it applies to Unicode code points
1257that were successfully decoded but are unsuitable for display (e.g.,
1258unassigned code points).
1259Its default value is "<U+%04lX>".
1260Note that LESSUTFBINFMT and LESSBINFMT share their display attribute
1261setting ("*x") so specifying one will affect both;
1262LESSUTFBINFMT is read after LESSBINFMT so its setting, if any,
1263will have priority.
1264Problematic octets in a UTF-8 file (octets of a truncated sequence,
1265octets of a complete but non-shortest form sequence, illegal octets,
1266and stray trailing octets)
1267are displayed individually using LESSBINFMT so as to facilitate diagnostic
1268of how the UTF-8 file is ill-formed.
1269
1270.SH "PROMPTS"
1271The \-P option allows you to tailor the prompt to your preference.
1272The string given to the \-P option replaces the specified prompt string.
1273Certain characters in the string are interpreted specially.
1274The prompt mechanism is rather complicated to provide flexibility,
1275but the ordinary user need not understand the details of constructing
1276personalized prompt strings.
1277.sp
1278A percent sign followed by a single character is expanded
1279according to what the following character is:
1280.IP "%b\fIX\fP"
1281Replaced by the byte offset into the current input file.
1282The b is followed by a single character (shown as \fIX\fP above)
1283which specifies the line whose byte offset is to be used.
1284If the character is a "t", the byte offset of the top line in the
1285display is used,
1286an "m" means use the middle line,
1287a "b" means use the bottom line,
1288a "B" means use the line just after the bottom line,
1289and a "j" means use the "target" line, as specified by the \-j option.
1290.IP "%B"
1291Replaced by the size of the current input file.
1292.IP "%c"
1293Replaced by the column number of the text appearing in the first
1294column of the screen.
1295.IP "%d\fIX\fP"
1296Replaced by the page number of a line in the input file.
1297The line to be used is determined by the \fIX\fP, as with the %b option.
1298.IP "%D"
1299Replaced by the number of pages in the input file,
1300or equivalently, the page number of the last line in the input file.
1301.IP "%E"
1302Replaced by the name of the editor (from the VISUAL environment variable,
1303or the EDITOR environment variable if VISUAL is not defined).
1304See the discussion of the LESSEDIT feature below.
1305.IP "%f"
1306Replaced by the name of the current input file.
1307.IP "%i"
1308Replaced by the index of the current file in the list of
1309input files.
1310.IP "%l\fIX\fP"
1311Replaced by the line number of a line in the input file.
1312The line to be used is determined by the \fIX\fP, as with the %b option.
1313.IP "%L"
1314Replaced by the line number of the last line in the input file.
1315.IP "%m"
1316Replaced by the total number of input files.
1317.IP "%p\fIX\fP"
1318Replaced by the percent into the current input file, based on byte offsets.
1319The line used is determined by the \fIX\fP as with the %b option.
1320.IP "%P\fIX\fP"
1321Replaced by the percent into the current input file, based on line numbers.
1322The line used is determined by the \fIX\fP as with the %b option.
1323.IP "%s"
1324Same as %B.
1325.IP "%t"
1326Causes any trailing spaces to be removed.
1327Usually used at the end of the string, but may appear anywhere.
1328.IP "%x"
1329Replaced by the name of the next input file in the list.
1330.PP
1331If any item is unknown (for example, the file size if input
1332is a pipe), a question mark is printed instead.
1333.PP
1334The format of the prompt string can be changed
1335depending on certain conditions.
1336A question mark followed by a single character acts like an "IF":
1337depending on the following character, a condition is evaluated.
1338If the condition is true, any characters following the question mark
1339and condition character, up to a period, are included in the prompt.
1340If the condition is false, such characters are not included.
1341A colon appearing between the question mark and the
1342period can be used to establish an "ELSE": any characters between
1343the colon and the period are included in the string if and only if
1344the IF condition is false.
1345Condition characters (which follow a question mark) may be:
1346.IP "?a"
1347True if any characters have been included in the prompt so far.
1348.IP "?b\fIX\fP"
1349True if the byte offset of the specified line is known.
1350.IP "?B"
1351True if the size of current input file is known.
1352.IP "?c"
1353True if the text is horizontally shifted (%c is not zero).
1354.IP "?d\fIX\fP"
1355True if the page number of the specified line is known.
1356.IP "?e"
1357True if at end-of-file.
1358.IP "?f"
1359True if there is an input filename
1360(that is, if input is not a pipe).
1361.IP "?l\fIX\fP"
1362True if the line number of the specified line is known.
1363.IP "?L"
1364True if the line number of the last line in the file is known.
1365.IP "?m"
1366True if there is more than one input file.
1367.IP "?n"
1368True if this is the first prompt in a new input file.
1369.IP "?p\fIX\fP"
1370True if the percent into the current input file, based on byte offsets,
1371of the specified line is known.
1372.IP "?P\fIX\fP"
1373True if the percent into the current input file, based on line numbers,
1374of the specified line is known.
1375.IP "?s"
1376Same as "?B".
1377.IP "?x"
1378True if there is a next input file
1379(that is, if the current input file is not the last one).
1380.PP
1381Any characters other than the special ones
1382(question mark, colon, period, percent, and backslash)
1383become literally part of the prompt.
1384Any of the special characters may be included in the prompt literally
1385by preceding it with a backslash.
1386.PP
1387Some examples:
1388.sp
1389?f%f:Standard input.
1390.sp
1391This prompt prints the filename, if known;
1392otherwise the string "Standard input".
1393.sp
1394?f%f .?ltLine %lt:?pt%pt\e%:?btByte %bt:-...
1395.sp
1396This prompt would print the filename, if known.
1397The filename is followed by the line number, if known,
1398otherwise the percent if known, otherwise the byte offset if known.
1399Otherwise, a dash is printed.
1400Notice how each question mark has a matching period,
1401and how the % after the %pt
1402is included literally by escaping it with a backslash.
1403.sp
1404?n?f%f\ .?m(file\ %i\ of\ %m)\ ..?e(END)\ ?x-\ Next\e:\ %x..%t
1405.sp
1406This prints the filename if this is the first prompt in a file,
1407followed by the "file N of N" message if there is more
1408than one input file.
1409Then, if we are at end-of-file, the string "(END)" is printed
1410followed by the name of the next file, if there is one.
1411Finally, any trailing spaces are truncated.
1412This is the default prompt.
1413For reference, here are the defaults for
1414the other two prompts (\-m and \-M respectively).
1415Each is broken into two lines here for readability only.
1416.nf
1417.sp
1418?n?f%f\ .?m(file\ %i\ of\ %m)\ ..?e(END)\ ?x-\ Next\e:\ %x.:
1419 ?pB%pB\e%:byte\ %bB?s/%s...%t
1420.sp
1421?f%f\ .?n?m(file\ %i\ of\ %m)\ ..?ltlines\ %lt-%lb?L/%L.\ :
1422 byte\ %bB?s/%s.\ .?e(END)\ ?x-\ Next\e:\ %x.:?pB%pB\e%..%t
1423.sp
1424.fi
1425And here is the default message produced by the = command:
1426.nf
1427.sp
1428?f%f\ .?m(file\ %i\ of\ %m)\ .?ltlines\ %lt-%lb?L/%L.\ .
1429 byte\ %bB?s/%s.\ ?e(END)\ :?pB%pB\e%..%t
1430.fi
1431.PP
1432The prompt expansion features are also used for another purpose:
1433if an environment variable LESSEDIT is defined, it is used
1434as the command to be executed when the v command is invoked.
1435The LESSEDIT string is expanded in the same way as the prompt strings.
1436The default value for LESSEDIT is:
1437.nf
1438.sp
1439 %E\ ?lm+%lm.\ %f
1440.sp
1441.fi
1442Note that this expands to the editor name, followed by a + and the
1443line number, followed by the file name.
1444If your editor does not accept the "+linenumber" syntax, or has other
1445differences in invocation syntax, the LESSEDIT variable can be
1446changed to modify this default.
1447
1448.SH SECURITY
1449When the environment variable LESSSECURE is set to 1,
1450.I less
1451runs in a "secure" mode.
1452This means these features are disabled:
1453.RS
1454.IP "!"
1455the shell command
1456.IP "|"
1457the pipe command
1458.IP ":e"
1459the examine command.
1460.IP "v"
1461the editing command
1462.IP "s \-o"
1463log files
1464.IP "\-k"
1465use of lesskey files
1466.IP "\-t"
1467use of tags files
1468.IP " "
1469metacharacters in filenames, such as *
1470.IP " "
1471filename completion (TAB, ^L)
1472.RE
1473.PP
1474Less can also be compiled to be permanently in "secure" mode.
1475
1476.SH "COMPATIBILITY WITH MORE"
1477If the environment variable LESS_IS_MORE is set to 1,
1478or if the program is invoked via a file link named "more",
1479.I less
1480behaves (mostly) in conformance with the POSIX "more" command specification.
1481In this mode, less behaves differently in these ways:
1482.PP
1483The \-e option works differently.
1484If the \-e option is not set,
1485.I less
1486behaves as if the \-E option were set.
1487If the \-e option is set,
1488.I less
1489behaves as if the \-e and \-F options were set.
1490.PP
1491The \-m option works differently.
1492If the \-m option is not set, the medium prompt is used,
1493and it is prefixed with the string "--More--".
1494If the \-m option is set, the short prompt is used.
1495.PP
1496The \-n option acts like the \-z option.
1497The normal behavior of the \-n option is unavailable in this mode.
1498.PP
1499The parameter to the \-p option is taken to be a
1500.I less
1501command rather than a search pattern.
1502.PP
1503The LESS environment variable is ignored,
1504and the MORE environment variable is used in its place.
1505
1506.SH "ENVIRONMENT VARIABLES"
1507Environment variables may be specified either in the system environment
1508as usual, or in a
1509.I lesskey
1510(1) file.
1511If environment variables are defined in more than one place,
1512variables defined in a local lesskey file take precedence over
1513variables defined in the system environment, which take precedence
1514over variables defined in the system-wide lesskey file.
1515.IP COLUMNS
1516Sets the number of columns on the screen.
1517Takes precedence over the number of columns specified by the TERM variable.
1518(But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD,
1519the window system's idea of the screen size takes precedence over the
1520LINES and COLUMNS environment variables.)
1521.IP EDITOR
1522The name of the editor (used for the v command).
1523.IP HOME
1524Name of the user's home directory
1525(used to find a lesskey file on Unix and OS/2 systems).
1526.IP "HOMEDRIVE, HOMEPATH"
1527Concatenation of the HOMEDRIVE and HOMEPATH environment variables is
1528the name of the user's home directory if the HOME variable is not set
1529(only in the Windows version).
1530.IP INIT
1531Name of the user's init directory (used to find a lesskey file on OS/2 systems).
1532.IP LANG
1533Language for determining the character set.
1534.IP LC_CTYPE
1535Language for determining the character set.
1536.IP LESS
1537Options which are passed to
1538.I less
1539automatically.
1540.IP LESSANSIENDCHARS
1541Characters which may end an ANSI color escape sequence
1542(default "m").
1543.IP LESSANSIMIDCHARS
1544Characters which may appear between the ESC character and the
1545end character in an ANSI color escape sequence
1546(default "0123456789;[?!"'#%()*+\ ".
1547.IP LESSBINFMT
1548Format for displaying non-printable, non-control characters.
1549.IP LESSCHARDEF
1550Defines a character set.
1551.IP LESSCHARSET
1552Selects a predefined character set.
1553.IP LESSCLOSE
1554Command line to invoke the (optional) input-postprocessor.
1555.IP LESSECHO
1556Name of the lessecho program (default "lessecho").
1557The lessecho program is needed to expand metacharacters, such as * and ?,
1558in filenames on Unix systems.
1559.IP LESSEDIT
1560Editor prototype string (used for the v command).
1561See discussion under PROMPTS.
1562.IP LESSGLOBALTAGS
1563Name of the command used by the \-t option to find global tags.
1564Normally should be set to "global" if your system has the
1565.I global
1566(1) command. If not set, global tags are not used.
1567.IP LESSHISTFILE
1568Name of the history file used to remember search commands and
1569shell commands between invocations of
1570.I less.
1571If set to "\-" or "/dev/null", a history file is not used.
1572The default is "$HOME/.lesshst" on Unix systems, "$HOME/_lesshst" on
1573DOS and Windows systems, or "$HOME/lesshst.ini" or "$INIT/lesshst.ini"
1574on OS/2 systems.
1575.IP LESSHISTSIZE
1576The maximum number of commands to save in the history file.
1577The default is 100.
1578.IP LESSKEY
1579Name of the default lesskey(1) file.
1580.IP LESSKEY_SYSTEM
1581Name of the default system-wide lesskey(1) file.
1582.IP LESSMETACHARS
1583List of characters which are considered "metacharacters" by the shell.
1584.IP LESSMETAESCAPE
1585Prefix which less will add before each metacharacter in a
1586command sent to the shell.
1587If LESSMETAESCAPE is an empty string, commands containing
1588metacharacters will not be passed to the shell.
1589.IP LESSOPEN
1590Command line to invoke the (optional) input-preprocessor.
1591.IP LESSSECURE
1592Runs less in "secure" mode.
1593See discussion under SECURITY.
1594.IP LESSSEPARATOR
1595String to be appended to a directory name in filename completion.
1596.IP LESSUTFBINFMT
1597Format for displaying non-printable Unicode code points.
1598.IP LESS_IS_MORE
1599Emulate the
1600.I more
1601(1) command.
1602.IP LINES
1603Sets the number of lines on the screen.
1604Takes precedence over the number of lines specified by the TERM variable.
1605(But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD,
1606the window system's idea of the screen size takes precedence over the
1607LINES and COLUMNS environment variables.)
1608.IP PATH
1609User's search path (used to find a lesskey file
1610on MS-DOS and OS/2 systems).
1611.IP SHELL
1612The shell used to execute the ! command, as well as to expand filenames.
1613.IP TERM
1614The type of terminal on which
1615.I less
1616is being run.
1617.IP VISUAL
1618The name of the editor (used for the v command).
1619
1620.SH "SEE ALSO"
1621lesskey(1)
1622
1623.SH WARNINGS
1624The = command and prompts (unless changed by \-P)
1625report the line numbers of the lines at the top and bottom of the screen,
1626but the byte and percent of the line after the one at the bottom of the screen.
1627.PP
1628On certain older terminals (the so-called "magic cookie" terminals),
1629search highlighting will cause an erroneous display.
1630On such terminals, search highlighting is disabled by default
1631to avoid possible problems.
1632.PP
1633When searching in a binary file, text which follows a null byte
1634may not be found.
1635This problem does not occur when searching with regular expressions turned
1636off via ^R, and also does not occur when
1637.I less
1638is compiled to use the PCRE regular expression library.
1639.PP
1640In certain cases, when search highlighting is enabled and
1641a search pattern begins with a ^,
1642more text than the matching string may be highlighted.
1643(This problem does not occur when less is compiled to use the POSIX
1644regular expression package.)
1645.PP
1646On some systems,
1647.I setlocale
1648claims that ASCII characters 0 thru 31 are control characters
1649rather than binary characters.
1650This causes
1651.I less
1652to treat some binary files as ordinary, non-binary files.
1653To workaround this problem, set the environment variable
1654LESSCHARSET to "ascii" (or whatever character set is appropriate).
1655.PP
1656This manual is too long.
1657.PP
1658See http://www.greenwoodsoftware.com/less for the latest list of known bugs in less.
1659
1660.SH COPYRIGHT
1661Copyright (C) 1984-2007 Mark Nudelman
1662.PP
1663less is part of the GNU project and is free software.
1664You can redistribute it and/or modify it
1665under the terms of either
1666(1) the GNU General Public License as published by
1667the Free Software Foundation; or (2) the Less License.
1668See the file README in the less distribution for more details
1669regarding redistribution.
1670You should have received a copy of the GNU General Public License
1671along with the source for less; see the file COPYING.
1672If not, write to the Free Software Foundation, 59 Temple Place,
1673Suite 330, Boston, MA 02111-1307, USA.
1674You should also have received a copy of the Less License;
1675see the file LICENSE.
1676.PP
1677less is distributed in the hope that it will be useful, but
1678WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1679or FITNESS FOR A PARTICULAR PURPOSE.
1680See the GNU General Public License for more details.
1681
1682.SH AUTHOR
1683.PP
1684Mark Nudelman <markn@greenwoodsoftware.com>
1685.br
1686Send bug reports or comments to the above address or to
1687.br
1688bug-less@gnu.org.
1689.br
1690For more information, see the less homepage at
1691.br
1692http://www.greenwoodsoftware.com/less.