1LESS(1)                     General Commands Manual                    LESS(1)
2
3
4

NAME

6       less - opposite of more
7

SYNOPSIS

9       less -?
10       less --help
11       less -V
12       less --version
13       less [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
14            [-b space] [-h lines] [-j line] [-k keyfile]
15            [-{oO} logfile] [-p pattern] [-P prompt] [-t tag]
16            [-T tagsfile] [-x tab,...] [-y lines] [-[z] lines]
17            [-# shift] [+[+]cmd] [--] [filename]...
18       (See  the  OPTIONS section for alternate option syntax with long option
19       names.)
20
21

DESCRIPTION

23       Less is a program similar to more (1), but which allows backward  move‐
24       ment in the file as well as forward movement.  Also, less does not have
25       to read the entire input file before  starting,  so  with  large  input
26       files  it  starts  up  faster than text editors like vi (1).  Less uses
27       termcap (or terminfo on some systems), so it can run on  a  variety  of
28       terminals.   There is even limited support for hardcopy terminals.  (On
29       a hardcopy terminal, lines which should be printed at the  top  of  the
30       screen are prefixed with a caret.)
31
32       Commands  are based on both more and vi.  Commands may be preceded by a
33       decimal number, called N in the descriptions below.  The number is used
34       by some commands, as indicated.
35
36

COMMANDS

38       In  the following descriptions, ^X means control-X.  ESC stands for the
39       ESCAPE  key;  for  example  ESC-v  means  the  two  character  sequence
40       "ESCAPE", then "v".
41
42       h or H Help:  display  a  summary of these commands.  If you forget all
43              the other commands, remember this one.
44
45       SPACE or ^V or f or ^F
46              Scroll forward N  lines,  default  one  window  (see  option  -z
47              below).   If  N  is  more  than  the screen size, only the final
48              screenful is displayed.  Warning: some systems use ^V as a  spe‐
49              cial literalization character.
50
51       z      Like  SPACE,  but  if  N is specified, it becomes the new window
52              size.
53
54       ESC-SPACE
55              Like SPACE, but scrolls a full screenful,  even  if  it  reaches
56              end-of-file in the process.
57
58       ENTER or RETURN or ^N or e or ^E or j or ^J
59              Scroll  forward N lines, default 1.  The entire N lines are dis‐
60              played, even if N is more than the screen size.
61
62       d or ^D
63              Scroll forward N lines, default one half of the screen size.  If
64              N  is specified, it becomes the new default for subsequent d and
65              u commands.
66
67       b or ^B or ESC-v
68              Scroll backward N lines,  default  one  window  (see  option  -z
69              below).   If  N  is  more  than  the screen size, only the final
70              screenful is displayed.
71
72       w      Like ESC-v, but if N is specified, it  becomes  the  new  window
73              size.
74
75       y or ^Y or ^P or k or ^K
76              Scroll backward N lines, default 1.  The entire N lines are dis‐
77              played, even if N is more than the screen size.   Warning:  some
78              systems use ^Y as a special job control character.
79
80       u or ^U
81              Scroll  backward  N  lines, default one half of the screen size.
82              If N is specified, it becomes the new default for  subsequent  d
83              and u commands.
84
85       J      Like j, but continues to scroll beyond the end of the file.
86
87       K or Y Like  k,  but  continues  to  scroll beyond the beginning of the
88              file.
89
90       ESC-) or RIGHTARROW
91              Scroll horizontally right N characters, default half the  screen
92              width  (see  the  -#  option).   If  a number N is specified, it
93              becomes the default for future  RIGHTARROW  and  LEFTARROW  com‐
94              mands.   While  the  text  is scrolled, it acts as though the -S
95              option (chop lines) were in effect.
96
97       ESC-( or LEFTARROW
98              Scroll horizontally left N characters, default half  the  screen
99              width  (see  the  -#  option).   If  a number N is specified, it
100              becomes the default for future  RIGHTARROW  and  LEFTARROW  com‐
101              mands.
102
103       ESC-} or ^RIGHTARROW
104              Scroll  horizontally  right  to show the end of the longest dis‐
105              played line.
106
107       ESC-{ or ^LEFTARROW
108              Scroll horizontally left back to the first column.
109
110       r or ^R or ^L
111              Repaint the screen.
112
113       R      Repaint the screen, discarding any buffered  input.   Useful  if
114              the file is changing while it is being viewed.
115
116       F      Scroll  forward, and keep trying to read when the end of file is
117              reached.  Normally this command would be used  when  already  at
118              the  end of the file.  It is a way to monitor the tail of a file
119              which is growing while it is being  viewed.   (The  behavior  is
120              similar to the "tail -f" command.)
121
122       ESC-F  Like  F,  but  as soon as a line is found which matches the last
123              search pattern, the terminal bell is rung and forward  scrolling
124              stops.
125
126       g or < or ESC-<
127              Go to line N in the file, default 1 (beginning of file).  (Warn‐
128              ing: this may be slow if N is large.)
129
130       G or > or ESC->
131              Go to line N in the file, default the end of the  file.   (Warn‐
132              ing:  this  may  be slow if N is large, or if N is not specified
133              and standard input, rather than a file, is being read.)
134
135       ESC-G  Same as G, except if no number N is specified and the  input  is
136              standard  input,  goes  to  the  last  line  which  is currently
137              buffered.
138
139       p or % Go to a position N percent into the file.  N should be between 0
140              and 100, and may contain a decimal point.
141
142       P      Go to the line containing byte offset N in the file.
143
144       {      If a left curly bracket appears in the top line displayed on the
145              screen, the { command  will  go  to  the  matching  right  curly
146              bracket.   The matching right curly bracket is positioned on the
147              bottom line of the screen.  If there is more than one left curly
148              bracket  on  the top line, a number N may be used to specify the
149              N-th bracket on the line.
150
151       }      If a right curly bracket appears in the bottom line displayed on
152              the  screen,  the  }  command will go to the matching left curly
153              bracket.  The matching left curly bracket is positioned  on  the
154              top  line  of the screen.  If there is more than one right curly
155              bracket on the top line, a number N may be used to  specify  the
156              N-th bracket on the line.
157
158       (      Like {, but applies to parentheses rather than curly brackets.
159
160       )      Like }, but applies to parentheses rather than curly brackets.
161
162       [      Like  {, but applies to square brackets rather than curly brack‐
163              ets.
164
165       ]      Like }, but applies to square brackets rather than curly  brack‐
166              ets.
167
168       ESC-^F Followed  by two characters, acts like {, but uses the two char‐
169              acters as open and close brackets, respectively.   For  example,
170              "ESC  ^F < >" could be used to go forward to the > which matches
171              the < in the top displayed line.
172
173       ESC-^B Followed by two characters, acts like }, but uses the two  char‐
174              acters  as  open and close brackets, respectively.  For example,
175              "ESC ^B < >" could be used to go backward to the < which matches
176              the > in the bottom displayed line.
177
178       m      Followed  by  any lowercase or uppercase letter, marks the first
179              displayed line with  that  letter.   If  the  status  column  is
180              enabled  via  the  -J option, the status column shows the marked
181              line.
182
183       M      Acts like m, except the last displayed  line  is  marked  rather
184              than the first displayed line.
185
186       '      (Single  quote.)  Followed by any lowercase or uppercase letter,
187              returns to the position which was previously  marked  with  that
188              letter.   Followed by another single quote, returns to the posi‐
189              tion at which the last "large" movement  command  was  executed.
190              Followed  by a ^ or $, jumps to the beginning or end of the file
191              respectively.  Marks are preserved when a new file is  examined,
192              so the ' command can be used to switch between input files.
193
194       ^X^X   Same as single quote.
195
196       ESC-m  Followed  by  any lowercase or uppercase letter, clears the mark
197              identified by that letter.
198
199       /pattern
200              Search forward in the file for the N-th line containing the pat‐
201              tern.  N defaults to 1.  The pattern is a regular expression, as
202              recognized by the regular expression library  supplied  by  your
203              system.   The search starts at the first line displayed (but see
204              the -a and -j options, which change this).
205
206              Certain characters are special if entered at  the  beginning  of
207              the  pattern;  they modify the type of search rather than become
208              part of the pattern:
209
210              ^N or !
211                     Search for lines which do NOT match the pattern.
212
213              ^E or *
214                     Search multiple files.  That is, if  the  search  reaches
215                     the  END of the current file without finding a match, the
216                     search continues in the next file  in  the  command  line
217                     list.
218
219              ^F or @
220                     Begin  the  search at the first line of the FIRST file in
221                     the command line list, regardless of  what  is  currently
222                     displayed  on  the screen or the settings of the -a or -j
223                     options.
224
225              ^K     Highlight any text which matches the pattern on the  cur‐
226                     rent screen, but don't move to the first match (KEEP cur‐
227                     rent position).
228
229              ^R     Don't interpret regular expression  metacharacters;  that
230                     is, do a simple textual comparison.
231
232       ?pattern
233              Search  backward  in  the  file for the N-th line containing the
234              pattern.  The search starts at the last line displayed (but  see
235              the -a and -j options, which change this).
236
237              Certain characters are special as in the / command:
238
239              ^N or !
240                     Search for lines which do NOT match the pattern.
241
242              ^E or *
243                     Search  multiple  files.   That is, if the search reaches
244                     the beginning of  the  current  file  without  finding  a
245                     match,  the  search continues in the previous file in the
246                     command line list.
247
248              ^F or @
249                     Begin the search at the last line of the last file in the
250                     command  line  list, regardless of what is currently dis‐
251                     played on the screen or the settings  of  the  -a  or  -j
252                     options.
253
254              ^K     As in forward searches.
255
256              ^R     As in forward searches.
257
258       ESC-/pattern
259              Same as "/*".
260
261       ESC-?pattern
262              Same as "?*".
263
264       n      Repeat  previous  search, for N-th line containing the last pat‐
265              tern.  If the previous search was modified by ^N, the search  is
266              made  for the N-th line NOT containing the pattern.  If the pre‐
267              vious search was modified by ^E, the  search  continues  in  the
268              next  (or  previous)  file if not satisfied in the current file.
269              If the previous search was modified by ^R, the  search  is  done
270              without  using  regular  expressions.  There is no effect if the
271              previous search was modified by ^F or ^K.
272
273       N      Repeat previous search, but in the reverse direction.
274
275       ESC-n  Repeat previous  search,  but  crossing  file  boundaries.   The
276              effect is as if the previous search were modified by *.
277
278       ESC-N  Repeat  previous search, but in the reverse direction and cross‐
279              ing file boundaries.
280
281       ESC-u  Undo search highlighting.   Turn  off  highlighting  of  strings
282              matching the current search pattern.  If highlighting is already
283              off because of a previous ESC-u command, turn highlighting  back
284              on.   Any  search  command  will also turn highlighting back on.
285              (Highlighting can also be disabled by toggling the -G option; in
286              that case search commands do not turn highlighting back on.)
287
288       &pattern
289              Display  only  lines which match the pattern; lines which do not
290              match the pattern are not displayed.  If pattern  is  empty  (if
291              you  type  &  immediately  followed  by ENTER), any filtering is
292              turned off, and all lines are displayed.  While filtering is  in
293              effect,  an  ampersand  is  displayed  at  the  beginning of the
294              prompt, as a reminder that some lines in the file may be hidden.
295
296              Certain characters are special as in the / command:
297
298              ^N or !
299                     Display only lines which do NOT match the pattern.
300
301              ^R     Don't interpret regular expression  metacharacters;  that
302                     is, do a simple textual comparison.
303
304       :e [filename]
305              Examine  a  new file.  If the filename is missing, the "current"
306              file (see the :n and :p commands below) from the list  of  files
307              in  the  command line is re-examined.  A percent sign (%) in the
308              filename is replaced by the name of the current file.   A  pound
309              sign  (#)  is  replaced  by  the name of the previously examined
310              file.   However,  two  consecutive  percent  signs  are   simply
311              replaced with a single percent sign.  This allows you to enter a
312              filename that contains a percent sign in the  name.   Similarly,
313              two  consecutive  pound  signs  are replaced with a single pound
314              sign.  The filename is inserted into the command  line  list  of
315              files  so  that it can be seen by subsequent :n and :p commands.
316              If the filename consists of several files, they are all inserted
317              into  the  list  of files and the first one is examined.  If the
318              filename contains one or more spaces, the entire filename should
319              be enclosed in double quotes (also see the -" option).
320
321       ^X^V or E
322              Same  as :e.  Warning: some systems use ^V as a special literal‐
323              ization character.  On such systems, you may not be able to  use
324              ^V.
325
326       :n     Examine  the next file (from the list of files given in the com‐
327              mand line).  If a number N is specified, the N-th next  file  is
328              examined.
329
330       :p     Examine the previous file in the command line list.  If a number
331              N is specified, the N-th previous file is examined.
332
333       :x     Examine the first file in the command line list.  If a number  N
334              is specified, the N-th file in the list is examined.
335
336       :d     Remove the current file from the list of files.
337
338       t      Go  to the next tag, if there were more than one matches for the
339              current tag.  See the -t option for more details about tags.
340
341       T      Go to the previous tag, if there were more than one matches  for
342              the current tag.
343
344       = or ^G or :f
345              Prints  some  information about the file being viewed, including
346              its name and the line number and byte offset of the bottom  line
347              being  displayed.  If possible, it also prints the length of the
348              file, the number of lines in the file and  the  percent  of  the
349              file above the last displayed line.
350
351       -      Followed  by one of the command line option letters (see OPTIONS
352              below), this will change the setting of that option and print  a
353              message  describing  the  new  setting.   If a ^P (CONTROL-P) is
354              entered immediately after the dash, the setting of the option is
355              changed  but  no message is printed.  If the option letter has a
356              numeric value (such as -b or -h), or a string value (such as  -P
357              or  -t), a new value may be entered after the option letter.  If
358              no new value is entered, a message describing the  current  set‐
359              ting is printed and nothing is changed.
360
361       --     Like  the  -  command, but takes a long option name (see OPTIONS
362              below) rather than a single option letter.  You must press ENTER
363              or  RETURN after typing the option name.  A ^P immediately after
364              the second dash suppresses printing of a message describing  the
365              new setting, as in the - command.
366
367       -+     Followed  by  one  of  the command line option letters this will
368              reset the option to its default  setting  and  print  a  message
369              describing  the  new  setting.  (The "-+X" command does the same
370              thing as "-+X" on the command line.)  This  does  not  work  for
371              string-valued options.
372
373       --+    Like  the -+ command, but takes a long option name rather than a
374              single option letter.
375
376       -!     Followed by one of the command line option  letters,  this  will
377              reset  the  option  to the "opposite" of its default setting and
378              print a message describing the new setting.  This does not  work
379              for numeric or string-valued options.
380
381       --!    Like  the -! command, but takes a long option name rather than a
382              single option letter.
383
384       _      (Underscore.)  Followed by one of the command line  option  let‐
385              ters,  this  will print a message describing the current setting
386              of that option.  The setting of the option is not changed.
387
388       __     (Double underscore.)  Like the _ (underscore) command, but takes
389              a long option name rather than a single option letter.  You must
390              press ENTER or RETURN after typing the option name.
391
392       +cmd   Causes the specified cmd to be executed each time a new file  is
393              examined.  For example, +G causes less to initially display each
394              file starting at the end rather than the beginning.
395
396       V      Prints the version number of less being run.
397
398       q or Q or :q or :Q or ZZ
399              Exits less.
400
401       The following four commands may or may not be valid, depending on  your
402       particular installation.
403
404       v      Invokes  an  editor  to edit the current file being viewed.  The
405              editor is taken from the environment variable VISUAL if defined,
406              or  EDITOR if VISUAL is not defined, or defaults to "vi" if nei‐
407              ther VISUAL nor EDITOR is defined.  See also the  discussion  of
408              LESSEDIT under the section on PROMPTS below.
409
410       ! shell-command
411              Invokes  a shell to run the shell-command given.  A percent sign
412              (%) in the command is replaced by the name of the current  file.
413              A pound sign (#) is replaced by the name of the previously exam‐
414              ined file.  "!!" repeats the last shell command.   "!"  with  no
415              shell  command  simply  invokes  a  shell.  On Unix systems, the
416              shell is taken from the environment variable SHELL, or  defaults
417              to  "sh".   On  MS-DOS and OS/2 systems, the shell is the normal
418              command processor.
419
420       | <m> shell-command
421              <m> represents any mark letter.  Pipes a section  of  the  input
422              file  to the given shell command.  The section of the file to be
423              piped is between the position marked by the letter and the  cur‐
424              rent  screen.  The entire current screen is included, regardless
425              of whether the marked position is before or  after  the  current
426              screen.   <m> may also be ^ or $ to indicate beginning or end of
427              file respectively.  If <m> is . or newline, the  current  screen
428              is piped.
429
430       s filename
431              Save  the  input  to  a file.  This only works if the input is a
432              pipe, not an ordinary file.
433

OPTIONS

435       Command line options are described below.  Most options may be  changed
436       while less is running, via the "-" command.
437
438       Most  options  may be given in one of two forms: either a dash followed
439       by a single letter, or two dashes followed by a long  option  name.   A
440       long  option  name  may  be  abbreviated as long as the abbreviation is
441       unambiguous.  For example, --quit-at-eof may be abbreviated --quit, but
442       not --qui, since both --quit-at-eof and --quiet begin with --qui.  Some
443       long option names are in uppercase, such as --QUIT-AT-EOF, as  distinct
444       from  --quit-at-eof.  Such option names need only have their first let‐
445       ter capitalized; the remainder of the name may be in either case.   For
446       example, --Quit-at-eof is equivalent to --QUIT-AT-EOF.
447
448       Options are also taken from the environment variable "LESS".  For exam‐
449       ple, to avoid typing "less -options ..." each time less is invoked, you
450       might tell csh:
451
452       setenv LESS "-options"
453
454       or if you use sh:
455
456       LESS="-options"; export LESS
457
458       On  MS-DOS,  you don't need the quotes, but you should replace any per‐
459       cent signs in the options string by double percent signs.
460
461       The environment variable is parsed before the command line, so  command
462       line  options  override  the  LESS  environment variable.  If an option
463       appears in the LESS variable, it can be reset to its default  value  on
464       the command line by beginning the command line option with "-+".
465
466       Some  options  like -k or -D require a string to follow the option let‐
467       ter.  The string for that option is considered to  end  when  a  dollar
468       sign  ($)  is found.  For example, you can set two -D options on MS-DOS
469       like this:
470
471       LESS="Dn9.1$Ds4.1"
472
473       If the --use-backslash option appears earlier in the  options,  then  a
474       dollar  sign or backslash may be included literally in an option string
475       by preceding it with a backslash.  If the --use-backslash option is not
476       in  effect, then backslashes are not treated specially, and there is no
477       way to include a dollar sign in the option string.
478
479       -? or --help
480              This option displays a summary of the commands accepted by  less
481              (the  same  as  the  h  command).   (Depending on how your shell
482              interprets the question mark, it may be necessary to  quote  the
483              question mark, thus: "-\?".)
484
485       -a or --search-skip-screen
486              By  default,  forward searches start at the top of the displayed
487              screen and backwards searches start at the bottom  of  the  dis‐
488              played  screen (except for repeated searches invoked by the n or
489              N commands, which  start  after  or  before  the  "target"  line
490              respectively; see the -j option for more about the target line).
491              The -a option causes forward searches to instead  start  at  the
492              bottom  of  the screen and backward searches to start at the top
493              of the screen, thus skipping all lines displayed on the screen.
494
495       -A or --SEARCH-SKIP-SCREEN
496              Causes all forward searches (not just non-repeated searches)  to
497              start  just  after the target line, and all backward searches to
498              start just before the target line.  Thus, forward searches  will
499              skip part of the displayed screen (from the first line up to and
500              including the target line).  Similarly backwards  searches  will
501              skip the displayed screen from the last line up to and including
502              the target line.  This was the default behavior in less versions
503              prior to 441.
504
505       -bn or --buffers=n
506              Specifies  the  amount  of  buffer  space less will use for each
507              file, in units of kilobytes (1024 bytes).  By  default  64 K  of
508              buffer  space  is used for each file (unless the file is a pipe;
509              see the -B option).  The -b  option  specifies  instead  that  n
510              kilobytes of buffer space should be used for each file.  If n is
511              -1, buffer space is unlimited; that is, the entire file  can  be
512              read into memory.
513
514       -B or --auto-buffers
515              By default, when data is read from a pipe, buffers are allocated
516              automatically as needed.  If a large amount of data is read from
517              the  pipe,  this  can cause a large amount of memory to be allo‐
518              cated.  The -B option disables this automatic allocation of buf‐
519              fers for pipes, so that only 64 K (or the amount of space speci‐
520              fied by the -b option) is used for the pipe.  Warning: use of -B
521              can  result  in  erroneous display, since only the most recently
522              viewed part of the piped data is kept  in  memory;  any  earlier
523              data is lost.
524
525       -c or --clear-screen
526              Causes  full  screen  repaints  to  be painted from the top line
527              down.  By default, full screen repaints are  done  by  scrolling
528              from the bottom of the screen.
529
530       -C or --CLEAR-SCREEN
531              Same as -c, for compatibility with older versions of less.
532
533       -d or --dumb
534              The -d option suppresses the error message normally displayed if
535              the terminal is dumb; that is, lacks some important  capability,
536              such as the ability to clear the screen or scroll backward.  The
537              -d option does not otherwise change the behavior of  less  on  a
538              dumb terminal.
539
540       -Dxcolor or --color=xcolor
541              [MS-DOS only] Sets the color of the text displayed.  x is a sin‐
542              gle character which selects the type  of  text  whose  color  is
543              being  set: n=normal, s=standout, d=bold, u=underlined, k=blink.
544              color is a pair of numbers separated by  a  period.   The  first
545              number  selects  the foreground color and the second selects the
546              background color of the text.  A single number N is the same  as
547              N.M,  where  M  is  the  normal background color.  The color may
548              start or end with u to use underline (with the normal color,  if
549              by  itself),  if  the  system supports it (Windows only).  x may
550              also be a to toggle strict ANSI sequence rendering (SGR mode).
551
552
553       -e or --quit-at-eof
554              Causes less to automatically exit the  second  time  it  reaches
555              end-of-file.   By  default, the only way to exit less is via the
556              "q" command.
557
558       -E or --QUIT-AT-EOF
559              Causes less to automatically exit the first time it reaches end-
560              of-file.
561
562       -f or --force
563              Forces non-regular files to be opened.  (A non-regular file is a
564              directory or a device special file.)  Also suppresses the  warn‐
565              ing message when a binary file is opened.  By default, less will
566              refuse to open non-regular files.  Note that some operating sys‐
567              tems will not allow directories to be read, even if -f is set.
568
569       -F or --quit-if-one-screen
570              Causes less to automatically exit if the entire file can be dis‐
571              played on the first screen.
572
573       -g or --hilite-search
574              Normally, less will highlight ALL strings which match  the  last
575              search  command.   The  -g option changes this behavior to high‐
576              light only the particular string which was  found  by  the  last
577              search command.  This can cause less to run somewhat faster than
578              the default.
579
580       -G or --HILITE-SEARCH
581              The -G option suppresses all highlighting of  strings  found  by
582              search commands.
583
584       --old-bot
585              Reverts to the old bottom of screen behavior.  This can be some‐
586              times desirable  if  the  long lines are not wrapped   correctly
587              when  reaching  the  bottom  of  the  terminal,  while scrolling
588              forward.
589
590       -hn or --max-back-scroll=n
591              Specifies a maximum number of lines to scroll backward.   If  it
592              is necessary to scroll backward more than n lines, the screen is
593              repainted in a forward direction instead.  (If the terminal does
594              not have the ability to scroll backward, -h0 is implied.)
595
596       -i or --ignore-case
597              Causes searches to ignore case; that is, uppercase and lowercase
598              are considered identical.  This option is ignored if any  upper‐
599              case  letters appear in the search pattern; in other words, if a
600              pattern contains uppercase letters, then that  search  does  not
601              ignore case.
602
603       -I or --IGNORE-CASE
604              Like  -i,  but searches ignore case even if the pattern contains
605              uppercase letters.
606
607       -jn or --jump-target=n
608              Specifies a line on the screen where the "target" line is to  be
609              positioned.   The  target line is the line specified by any com‐
610              mand to search for a pattern, jump to a line number, jump  to  a
611              file percentage or jump to a tag.  The screen line may be speci‐
612              fied by a number: the top line on the screen is 1, the  next  is
613              2, and so on.  The number may be negative to specify a line rel‐
614              ative to the bottom of the screen: the bottom line on the screen
615              is  -1, the second to the bottom is -2, and so on.  Alternately,
616              the screen line may be specified as a fraction of the height  of
617              the  screen,  starting with a decimal point: .5 is in the middle
618              of the screen, .3 is three tenths down from the first line,  and
619              so  on.  If the line is specified as a fraction, the actual line
620              number is recalculated if the terminal  window  is  resized,  so
621              that  the  target  line remains at the specified fraction of the
622              screen height.  If any form of the -j option is  used,  repeated
623              forward  searches  (invoked  with  "n" or "N") begin at the line
624              immediately  after  the  target  line,  and  repeated   backward
625              searches  begin  at the target line, unless changed by -a or -A.
626              For example, if "-j4" is used, the target  line  is  the  fourth
627              line  on the screen, so forward searches begin at the fifth line
628              on the screen.  However nonrepeated searches (invoked  with  "/"
629              or  "?")  always begin at the start or end of the current screen
630              respectively.
631
632       -J or --status-column
633              Displays a status column at the left edge of  the  screen.   The
634              status  column  shows the lines that matched the current search,
635              and any lines that are marked (via the m  or  M  command).   The
636              status column is also used if the -w or -W option is in effect.
637
638       -kfilename or --lesskey-file=filename
639              Causes  less  to  open and interpret the named file as a lesskey
640              (1) file.  Multiple -k options may be specified.  If the LESSKEY
641              or  LESSKEY_SYSTEM  environment variable is set, or if a lesskey
642              file is found in a standard place (see KEY BINDINGS), it is also
643              used as a lesskey file.
644
645       -K or --quit-on-intr
646              Causes  less  to exit immediately (with status 2) when an inter‐
647              rupt character (usually ^C) is typed.   Normally,  an  interrupt
648              character causes less to stop whatever it is doing and return to
649              its command prompt.  Note that  use  of  this  option  makes  it
650              impossible to return to the command prompt from the "F" command.
651
652       -L or --no-lessopen
653              Ignore  the  LESSOPEN  environment  variable (see the INPUT PRE‐
654              PROCESSOR section below).  This option can be  set  from  within
655              less,  but  it will apply only to files opened subsequently, not
656              to the file which is currently open.
657
658       -m or --long-prompt
659              Causes less to prompt verbosely (like more),  with  the  percent
660              into the file.  By default, less prompts with a colon.
661
662       -M or --LONG-PROMPT
663              Causes less to prompt even more verbosely than more.
664
665       -n or --line-numbers
666              Suppresses  line numbers.  The default (to use line numbers) may
667              cause less to run more slowly in some cases, especially  with  a
668              very  large  input  file.   Suppressing line numbers with the -n
669              option will avoid this problem.  Using line numbers  means:  the
670              line number will be displayed in the verbose prompt and in the =
671              command, and the v command will pass the current line number  to
672              the  editor  (see  also  the  discussion  of LESSEDIT in PROMPTS
673              below).
674
675       -N or --LINE-NUMBERS
676              Causes a line number to be displayed at the  beginning  of  each
677              line in the display.
678
679       -ofilename or --log-file=filename
680              Causes  less  to copy its input to the named file as it is being
681              viewed.  This applies only when the input file is a pipe, not an
682              ordinary  file.   If  the file already exists, less will ask for
683              confirmation before overwriting it.
684
685       -Ofilename or --LOG-FILE=filename
686              The -O option is like -o, but it will overwrite an existing file
687              without asking for confirmation.
688
689              If  no log file has been specified, the -o and -O options can be
690              used from within less to specify a log  file.   Without  a  file
691              name, they will simply report the name of the log file.  The "s"
692              command is equivalent to specifying -o from within less.
693
694       -ppattern or --pattern=pattern
695              The -p option on the command line is  equivalent  to  specifying
696              +/pattern;  that  is, it tells less to start at the first occur‐
697              rence of pattern in the file.
698
699       -Pprompt or --prompt=prompt
700              Provides a way to tailor the three prompt  styles  to  your  own
701              preference.  This option would normally be put in the LESS envi‐
702              ronment variable, rather than being typed in with each less com‐
703              mand.  Such an option must either be the last option in the LESS
704              variable, or be terminated by a dollar sign.
705               -Ps followed by a string changes the default (short) prompt  to
706              that string.
707               -Pm changes the medium (-m) prompt.
708               -PM changes the long (-M) prompt.
709               -Ph changes the prompt for the help screen.
710               -P= changes the message printed by the = command.
711               -Pw  changes the message printed while waiting for data (in the
712              F command).
713
714              All prompt strings consist of a sequence of letters and  special
715              escape sequences.  See the section on PROMPTS for more details.
716
717       -q or --quiet or --silent
718              Causes  moderately  "quiet"  operation: the terminal bell is not
719              rung if an attempt is made to scroll past the end of the file or
720              before the beginning of the file.  If the terminal has a "visual
721              bell", it is used instead.  The bell will  be  rung  on  certain
722              other  errors, such as typing an invalid character.  The default
723              is to ring the terminal bell in all such cases.
724
725       -Q or --QUIET or --SILENT
726              Causes totally "quiet" operation: the  terminal  bell  is  never
727              rung.   If  the  terminal has a "visual bell", it is used in all
728              cases where the terminal bell would have been rung.
729
730       -r or --raw-control-chars
731              Causes "raw" control characters to be displayed.  The default is
732              to  display  control  characters  using  the caret notation; for
733              example, a control-A (octal 001) is displayed as "^A".  Warning:
734              when the -r option is used, less cannot keep track of the actual
735              appearance of the screen (since this depends on how  the  screen
736              responds to each type of control character).  Thus, various dis‐
737              play problems may result, such as long lines being split in  the
738              wrong place.
739
740       -R or --RAW-CONTROL-CHARS
741              Like  -r,  but  only ANSI "color" escape sequences are output in
742              "raw" form.  Unlike -r, the screen appearance is maintained cor‐
743              rectly  in  most  cases.   ANSI  "color"  escape  sequences  are
744              sequences of the form:
745
746                   ESC [ ... m
747
748              where the "..." is zero or more color  specification  characters
749              For  the  purpose  of  keeping  track of screen appearance, ANSI
750              color escape sequences are assumed to not move the cursor.   You
751              can  make less think that characters other than "m" can end ANSI
752              color escape  sequences  by  setting  the  environment  variable
753              LESSANSIENDCHARS to the list of characters which can end a color
754              escape sequence.  And you can make less  think  that  characters
755              other  than the standard ones may appear between the ESC and the
756              m by setting the environment variable  LESSANSIMIDCHARS  to  the
757              list of characters which can appear.
758
759       -s or --squeeze-blank-lines
760              Causes  consecutive  blank  lines  to  be squeezed into a single
761              blank line.  This is useful when viewing nroff output.
762
763       -S or --chop-long-lines
764              Causes lines longer than the screen width to be  chopped  (trun‐
765              cated) rather than wrapped.  That is, the portion of a long line
766              that does not fit in the screen width is not shown.  The default
767              is  to  wrap  long  lines; that is, display the remainder on the
768              next line.
769
770       -ttag or --tag=tag
771              The -t option, followed immediately by a TAG, will edit the file
772              containing  that tag.  For this to work, tag information must be
773              available; for example, there may  be  a  file  in  the  current
774              directory called "tags", which was previously built by ctags (1)
775              or an equivalent command.  If the environment variable LESSGLOB‐
776              ALTAGS  is set, it is taken to be the name of a command compati‐
777              ble with global (1), and that command is executed  to  find  the
778              tag.  (See http://www.gnu.org/software/global/global.html).  The
779              -t option may also be specified from within less  (using  the  -
780              command)  as a way of examining a new file.  The command ":t" is
781              equivalent to specifying -t from within less.
782
783       -Ttagsfile or --tag-file=tagsfile
784              Specifies a tags file to be used instead of "tags".
785
786       -u or --underline-special
787              Causes backspaces and carriage returns to be treated  as  print‐
788              able  characters;  that  is,  they are sent to the terminal when
789              they appear in the input.
790
791       -U or --UNDERLINE-SPECIAL
792              Causes backspaces, tabs, carriage returns and "formatting  char‐
793              acters" (as defined by Unicode) to be treated as control charac‐
794              ters; that is, they are handled as specified by the -r option.
795
796              By default, if neither -u nor  -U  is  given,  backspaces  which
797              appear  adjacent  to  an  underscore  character are treated spe‐
798              cially: the underlined text is displayed  using  the  terminal's
799              hardware  underlining capability.  Also, backspaces which appear
800              between two identical  characters  are  treated  specially:  the
801              overstruck  text  is printed using the terminal's hardware bold‐
802              face capability.  Other backspaces are deleted, along  with  the
803              preceding character.  Carriage returns immediately followed by a
804              newline are deleted.  Other  carriage  returns  are  handled  as
805              specified  by the -r option.  Text which is overstruck or under‐
806              lined can be searched for if neither -u nor -U is in effect.
807
808       -V or --version
809              Displays the version number of less.
810
811       -w or --hilite-unread
812              Temporarily highlights the first  "new"  line  after  a  forward
813              movement of a full page.  The first "new" line is the line imme‐
814              diately following the line  previously  at  the  bottom  of  the
815              screen.  Also highlights the target line after a g or p command.
816              The highlight is removed at the next command which causes  move‐
817              ment.   The  entire line is highlighted, unless the -J option is
818              in effect, in which case only the status column is highlighted.
819
820       -W or --HILITE-UNREAD
821              Like -w, but temporarily highlights the first new line after any
822              forward movement command larger than one line.
823
824       -xn,... or --tabs=n,...
825              Sets  tab  stops.  If only one n is specified, tab stops are set
826              at multiples of n.  If multiple values separated by  commas  are
827              specified,  tab  stops are set at those positions, and then con‐
828              tinue with the same spacing  as  the  last  two.   For  example,
829              -x9,17  will  set  tabs  at  positions  9, 17, 25, 33, etc.  The
830              default for n is 8.
831
832       -X or --no-init
833              Disables sending the termcap initialization and deinitialization
834              strings  to  the  terminal.   This is sometimes desirable if the
835              deinitialization string does something unnecessary, like  clear‐
836              ing the screen.
837
838       -yn or --max-forw-scroll=n
839              Specifies a maximum number of lines to scroll forward.  If it is
840              necessary to scroll forward more than n  lines,  the  screen  is
841              repainted  instead.   The -c or -C option may be used to repaint
842              from the top of the screen if desired.  By default, any  forward
843              movement causes scrolling.
844
845       -zn or --window=n or -n
846              Changes  the  default  scrolling  window  size  to n lines.  The
847              default is one screenful.  The z and w commands can also be used
848              to  change the window size.  The "z" may be omitted for compati‐
849              bility with some versions of more.  If the number n is negative,
850              it  indicates  n  lines  less than the current screen size.  For
851              example, if the screen is 24 lines, -z-4 sets the scrolling win‐
852              dow  to  20  lines.   If  the screen is resized to 40 lines, the
853              scrolling window automatically changes to 36 lines.
854
855       -"cc or --quotes=cc
856              Changes the filename quoting character.  This may  be  necessary
857              if  you are trying to name a file which contains both spaces and
858              quote characters.  Followed by a single character, this  changes
859              the  quote  character to that character.  Filenames containing a
860              space should then be surrounded by that character rather than by
861              double  quotes.   Followed  by  two characters, changes the open
862              quote to the first character, and the close quote to the  second
863              character.  Filenames containing a space should then be preceded
864              by the open quote character and  followed  by  the  close  quote
865              character.   Note  that  even  after  the  quote  characters are
866              changed, this option remains -" (a dash  followed  by  a  double
867              quote).
868
869       -~ or --tilde
870              Normally lines after end of file are displayed as a single tilde
871              (~).  This option causes lines after end of file to be displayed
872              as blank lines.
873
874       -# or --shift
875              Specifies the default number of positions to scroll horizontally
876              in the RIGHTARROW and LEFTARROW commands.  If the number  speci‐
877              fied  is  zero,  it  sets the default number of positions to one
878              half of the screen width.  Alternately, the number may be speci‐
879              fied  as  a fraction of the width of the screen, starting with a
880              decimal point: .5 is half of  the  screen  width,  .3  is  three
881              tenths  of the screen width, and so on.  If the number is speci‐
882              fied as a fraction, the actual number  of  scroll  positions  is
883              recalculated  if  the  terminal  window  is resized, so that the
884              actual scroll remains at the specified fraction  of  the  screen
885              width.
886
887       --follow-name
888              Normally,  if  the  input  file is renamed while an F command is
889              executing, less will continue to display  the  contents  of  the
890              original  file  despite  its  name  change.  If --follow-name is
891              specified, during an F command less will periodically attempt to
892              reopen the file by name.  If the reopen succeeds and the file is
893              a different file from the original (which means that a new  file
894              has  been  created  with  the  same  name  as  the original (now
895              renamed) file), less will display the contents of that new file.
896
897       --mouse
898              Enables mouse input: scrolling the mouse wheel down  moves  for‐
899              ward  in  the file, scrolling the mouse wheel up moves backwards
900              in the file, and clicking the mouse sets the  "#"  mark  to  the
901              line  where the mouse is clicked.  The number of lines to scroll
902              when the wheel is moved can be set by the --wheel-lines  option.
903              Mouse  input  works  only  on  terminals which support X11 mouse
904              reporting, and on the Windows version of less.
905
906       --MOUSE
907              Like --mouse, except the direction scrolled on mouse wheel move‐
908              ment is reversed.
909
910       --no-keypad
911              Disables  sending the keypad initialization and deinitialization
912              strings to the terminal.  This is sometimes useful if the keypad
913              strings make the numeric keypad behave in an undesirable manner.
914
915       --no-histdups
916              This  option  changes the behavior so that if a search string or
917              file name is typed in, and the same string  is  already  in  the
918              history list, the existing copy is removed from the history list
919              before the new one is added.  Thus, a given string  will  appear
920              only  once  in  the history list.  Normally, a string may appear
921              multiple times.
922
923       --rscroll
924              This option changes the character used to mark truncated  lines.
925              It may begin with a two-character attribute indicator like LESS‐
926              BINFMT does.  If there is no attribute  indicator,  standout  is
927              used.  If set to "-", truncated lines are not marked.
928
929       --save-marks
930              Save  marks  in  the  history file, so marks are retained across
931              different invocations of less.
932
933       --use-backslash
934              This option changes the interpretations of options which  follow
935              this one.  After the --use-backslash option, any backslash in an
936              option string is removed and the following  character  is  taken
937              literally.   This  allows a dollar sign to be included in option
938              strings.
939
940       --wheel-lines=n
941              Set the number of lines  to  scroll  when  the  mouse  wheel  is
942              scrolled  and  the  --mouse or --MOUSE option is in effect.  The
943              default is 1 line.
944
945       --     A command line argument of "--" marks the end  of  option  argu‐
946              ments.   Any  arguments  following this are interpreted as file‐
947              names.  This can be useful when viewing a file whose name begins
948              with a "-" or "+".
949
950       +      If  a  command  line option begins with +, the remainder of that
951              option is taken to be an initial command to less.  For  example,
952              +G  tells  less  to start at the end of the file rather than the
953              beginning, and +/xyz tells it to start at the  first  occurrence
954              of  "xyz"  in  the file.  As a special case, +<number> acts like
955              +<number>g; that is, it starts the display at the specified line
956              number  (however,  see  the caveat under the "g" command above).
957              If the option starts with ++, the  initial  command  applies  to
958              every  file being viewed, not just the first one.  The + command
959              described previously may also be used to set (or change) an ini‐
960              tial command for every file.
961
962

LINE EDITING

964       When  entering command line at the bottom of the screen (for example, a
965       filename for the :e command, or the pattern for a search command), cer‐
966       tain  keys  can  be used to manipulate the command line.  Most commands
967       have an alternate form in [ brackets ] which can be used if a key  does
968       not  exist  on  a  particular keyboard.  (Note that the forms beginning
969       with ESC do not work in some MS-DOS and Windows systems because ESC  is
970       the  line  erase  character.)  Any of these special keys may be entered
971       literally by preceding it with the "literal" character,  either  ^V  or
972       ^A.   A  backslash itself may also be entered literally by entering two
973       backslashes.
974
975       LEFTARROW [ ESC-h ]
976              Move the cursor one space to the left.
977
978       RIGHTARROW [ ESC-l ]
979              Move the cursor one space to the right.
980
981       ^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
982              (That is, CONTROL and LEFTARROW simultaneously.)  Move the  cur‐
983              sor one word to the left.
984
985       ^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
986              (That is, CONTROL and RIGHTARROW simultaneously.)  Move the cur‐
987              sor one word to the right.
988
989       HOME [ ESC-0 ]
990              Move the cursor to the beginning of the line.
991
992       END [ ESC-$ ]
993              Move the cursor to the end of the line.
994
995       BACKSPACE
996              Delete the character to the left of the cursor,  or  cancel  the
997              command if the command line is empty.
998
999       DELETE or [ ESC-x ]
1000              Delete the character under the cursor.
1001
1002       ^BACKSPACE [ ESC-BACKSPACE ]
1003              (That  is,  CONTROL  and  BACKSPACE simultaneously.)  Delete the
1004              word to the left of the cursor.
1005
1006       ^DELETE [ ESC-X or ESC-DELETE ]
1007              (That is, CONTROL and DELETE simultaneously.)  Delete  the  word
1008              under the cursor.
1009
1010       UPARROW [ ESC-k ]
1011              Retrieve  the  previous  command  line.  If you first enter some
1012              text and then press UPARROW, it will retrieve the previous  com‐
1013              mand which begins with that text.
1014
1015       DOWNARROW [ ESC-j ]
1016              Retrieve  the  next  command line.  If you first enter some text
1017              and then press DOWNARROW, it  will  retrieve  the  next  command
1018              which begins with that text.
1019
1020       TAB    Complete  the partial filename to the left of the cursor.  If it
1021              matches more than one filename, the first match is entered  into
1022              the  command  line.   Repeated  TABs  will  cycle thru the other
1023              matching filenames.  If the completed filename is a directory, a
1024              "/"  is  appended to the filename.  (On MS-DOS systems, a "\" is
1025              appended.)  The environment variable LESSSEPARATOR can  be  used
1026              to specify a different character to append to a directory name.
1027
1028       BACKTAB [ ESC-TAB ]
1029              Like, TAB, but cycles in the reverse direction thru the matching
1030              filenames.
1031
1032       ^L     Complete the partial filename to the left of the cursor.  If  it
1033              matches more than one filename, all matches are entered into the
1034              command line (if they fit).
1035
1036       ^U (Unix and OS/2) or ESC (MS-DOS)
1037              Delete the entire command line, or cancel  the  command  if  the
1038              command line is empty.  If you have changed your line-kill char‐
1039              acter in Unix to something other than ^U, that character is used
1040              instead of ^U.
1041
1042       ^G     Delete the entire command line and return to the main prompt.
1043
1044

KEY BINDINGS

1046       You  may define your own less commands by using the program lesskey (1)
1047       to create a lesskey file.  This file specifies a set  of  command  keys
1048       and  an  action  associated with each key.  You may also use lesskey to
1049       change the line-editing keys (see LINE EDITING), and to set environment
1050       variables.   If the environment variable LESSKEY is set, less uses that
1051       as the name of the lesskey file.  Otherwise, less looks in  a  standard
1052       place  for  the lesskey file: On Unix systems, less looks for a lesskey
1053       file called "$HOME/.less".  On MS-DOS and Windows systems,  less  looks
1054       for  a lesskey file called "$HOME/_less", and if it is not found there,
1055       then looks for a lesskey file called "_less" in any directory specified
1056       in  the  PATH  environment variable.  On OS/2 systems, less looks for a
1057       lesskey file called "$HOME/less.ini", and if  it  is  not  found,  then
1058       looks  for  a lesskey file called "less.ini" in any directory specified
1059       in the INIT environment variable, and if it not found there, then looks
1060       for  a lesskey file called "less.ini" in any directory specified in the
1061       PATH environment variable.   See  the  lesskey  manual  page  for  more
1062       details.
1063
1064       A  system-wide lesskey file may also be set up to provide key bindings.
1065       If a key is defined in both a local lesskey file and in the system-wide
1066       file,  key bindings in the local file take precedence over those in the
1067       system-wide file.  If the environment variable LESSKEY_SYSTEM  is  set,
1068       less uses that as the name of the system-wide lesskey file.  Otherwise,
1069       less looks in a standard place for the  system-wide  lesskey  file:  On
1070       Unix  systems,  the system-wide lesskey file is /usr/local/etc/sysless.
1071       (However, if less was built with a  different  sysconf  directory  than
1072       /usr/local/etc, that directory is where the sysless file is found.)  On
1073       MS-DOS and Windows systems, the system-wide lesskey  file  is  c:\_sys‐
1074       less.  On OS/2 systems, the system-wide lesskey file is c:\sysless.ini.
1075
1076

INPUT PREPROCESSOR

1078       You  may  define an "input preprocessor" for less.  Before less opens a
1079       file, it first gives your input preprocessor a chance to modify the way
1080       the  contents of the file are displayed.  An input preprocessor is sim‐
1081       ply an executable program (or shell script), which writes the  contents
1082       of the file to a different file, called the replacement file.  The con‐
1083       tents of the replacement file are then displayed in place of  the  con‐
1084       tents  of the original file.  However, it will appear to the user as if
1085       the original file is opened; that is, less will  display  the  original
1086       filename as the name of the current file.
1087
1088       An  input preprocessor receives one command line argument, the original
1089       filename, as entered by the user.  It  should  create  the  replacement
1090       file,  and when finished, print the name of the replacement file to its
1091       standard output.  If the input preprocessor does not output a  replace‐
1092       ment  filename, less uses the original file, as normal.  The input pre‐
1093       processor is not called when viewing standard  input.   To  set  up  an
1094       input  preprocessor, set the LESSOPEN environment variable to a command
1095       line which will invoke your  input  preprocessor.   This  command  line
1096       should  include  one  occurrence  of  the  string  "%s",  which will be
1097       replaced by  the  filename  when  the  input  preprocessor  command  is
1098       invoked.
1099
1100       When less closes a file opened in such a way, it will call another pro‐
1101       gram, called the input postprocessor, which  may  perform  any  desired
1102       clean-up  action  (such  as  deleting  the  replacement file created by
1103       LESSOPEN).  This program receives two command line arguments, the orig‐
1104       inal  filename  as entered by the user, and the name of the replacement
1105       file.  To set up an input postprocessor, set the LESSCLOSE  environment
1106       variable  to a command line which will invoke your input postprocessor.
1107       It may include two  occurrences  of  the  string  "%s";  the  first  is
1108       replaced  with  the  original  name of the file and the second with the
1109       name of the replacement file, which was output by LESSOPEN.
1110
1111       For example, on many Unix systems, these two scripts will allow you  to
1112       keep files in compressed format, but still let less view them directly:
1113
1114       lessopen.sh:
1115            #! /bin/sh
1116            case "$1" in
1117            *.Z) TEMPFILE=$(mktemp)
1118                 uncompress -c $1  >$TEMPFILE  2>/dev/null
1119                 if [ -s $TEMPFILE ]; then
1120                      echo $TEMPFILE
1121                 else
1122                      rm -f $TEMPFILE
1123                 fi
1124                 ;;
1125            esac
1126
1127       lessclose.sh:
1128            #! /bin/sh
1129            rm $2
1130
1131       To  use these scripts, put them both where they can be executed and set
1132       LESSOPEN="lessopen.sh %s",  and  LESSCLOSE="lessclose.sh %s %s".   More
1133       complex  LESSOPEN  and LESSCLOSE scripts may be written to accept other
1134       types of compressed files, and so on.
1135
1136       It is also possible to set up an input preprocessor to  pipe  the  file
1137       data  directly to less, rather than putting the data into a replacement
1138       file.  This avoids the need to decompress the entire file before start‐
1139       ing to view it.  An input preprocessor that works this way is called an
1140       input pipe.  An input pipe, instead of writing the name of  a  replace‐
1141       ment  file  on  its  standard output, writes the entire contents of the
1142       replacement file on its standard output.  If the input  pipe  does  not
1143       write  any characters on its standard output, then there is no replace‐
1144       ment file and less uses the original file, as normal.  To use an  input
1145       pipe,  make  the first character in the LESSOPEN environment variable a
1146       vertical bar (|) to signify that the input  preprocessor  is  an  input
1147       pipe.   As  with  non-pipe input preprocessors, the command string must
1148       contain one occurrence of %s, which is replaced with  the  filename  of
1149       the input file.
1150
1151       For  example, on many Unix systems, this script will work like the pre‐
1152       vious example scripts:
1153
1154       lesspipe.sh:
1155            #! /bin/sh
1156            case "$1" in
1157            *.Z) uncompress -c $1  2>/dev/null
1158                 ;;
1159            *)   exit 1
1160                 ;;
1161            esac
1162            exit $?
1163
1164       To  use  this  script,  put  it  where  it  can  be  executed  and  set
1165       LESSOPEN="|lesspipe.sh %s".
1166
1167       Note  that  a  preprocessor  cannot output an empty file, since that is
1168       interpreted as meaning there is no replacement, and the  original  file
1169       is used.  To avoid this, if LESSOPEN starts with two vertical bars, the
1170       exit status of the script becomes meaningful.  If the  exit  status  is
1171       zero,  the  output  is considered to be replacement text, even if it is
1172       empty.  If the exit status is nonzero, any output is  ignored  and  the
1173       original  file  is  used.   For compatibility with previous versions of
1174       less, if LESSOPEN starts with only one vertical bar, the exit status of
1175       the preprocessor is ignored.
1176
1177       When  an input pipe is used, a LESSCLOSE postprocessor can be used, but
1178       it is usually not necessary since there is no replacement file to clean
1179       up.   In  this  case, the replacement file name passed to the LESSCLOSE
1180       postprocessor is "-".
1181
1182       For compatibility with previous versions of less, the input  preproces‐
1183       sor or pipe is not used if less is viewing standard input.  However, if
1184       the first character of LESSOPEN is a dash (-), the  input  preprocessor
1185       is  used  on  standard input as well as other files.  In this case, the
1186       dash is not considered to be part  of  the  preprocessor  command.   If
1187       standard input is being viewed, the input preprocessor is passed a file
1188       name consisting of a single dash.  Similarly, if the first two  charac‐
1189       ters  of  LESSOPEN  are vertical bar and dash (|-) or two vertical bars
1190       and a dash (||-), the input pipe is used on standard input as  well  as
1191       other files.  Again, in this case the dash is not considered to be part
1192       of the input pipe command.
1193
1194       There are used following files to set up default preprocessor:
1195            /etc/profile.d/less.sh
1196            /etc/profile.d/less.csh
1197       These files set up /usr/bin/lesspipe.sh as a default  filter.  An  user
1198       defined filter can be specified in ~/.lessfilter. This file should have
1199       an execute bit set and accept only one parameter,  which  represents  a
1200       filename.  If  the user defined filter process the file, zero should be
1201       returned. Otherwise ~/.lessfilter tries to handle the file.
1202
1203

NATIONAL CHARACTER SETS

1205       There are three types of characters in the input file:
1206
1207       normal characters
1208              can be displayed directly to the screen.
1209
1210       control characters
1211              should not be displayed directly, but are expected to  be  found
1212              in ordinary text files (such as backspace and tab).
1213
1214       binary characters
1215              should  not  be  displayed  directly  and are not expected to be
1216              found in text files.
1217
1218       A "character set" is simply a description of which characters are to be
1219       considered  normal,  control,  and binary.  The LESSCHARSET environment
1220       variable may be used to select a character set.   Possible  values  for
1221       LESSCHARSET are:
1222
1223       ascii  BS,  TAB, NL, CR, and formfeed are control characters, all chars
1224              with values between 32 and 126 are normal, and  all  others  are
1225              binary.
1226
1227       iso8859
1228              Selects  an  ISO 8859 character set.  This is the same as ASCII,
1229              except characters between 160 and  255  are  treated  as  normal
1230              characters.
1231
1232       latin1 Same as iso8859.
1233
1234       latin9 Same as iso8859.
1235
1236       dos    Selects a character set appropriate for MS-DOS.
1237
1238       ebcdic Selects an EBCDIC character set.
1239
1240       IBM-1047
1241              Selects  an  EBCDIC  character set used by OS/390 Unix Services.
1242              This is the EBCDIC analogue of latin1.  You get similar  results
1243              by setting either LESSCHARSET=IBM-1047 or LC_CTYPE=en_US in your
1244              environment.
1245
1246       koi8-r Selects a Russian character set.
1247
1248       next   Selects a character set appropriate for NeXT computers.
1249
1250       utf-8  Selects the UTF-8 encoding  of  the  ISO  10646  character  set.
1251              UTF-8  is  special  in that it supports multi-byte characters in
1252              the input file.  It is the  only  character  set  that  supports
1253              multi-byte characters.
1254
1255       windows
1256              Selects  a  character  set appropriate for Microsoft Windows (cp
1257              1251).
1258
1259       In rare cases, it may be desired to tailor less to use a character  set
1260       other  than the ones definable by LESSCHARSET.  In this case, the envi‐
1261       ronment variable LESSCHARDEF can be used to define a character set.  It
1262       should be set to a string where each character in the string represents
1263       one character in the character set.  The character "." is  used  for  a
1264       normal  character, "c" for control, and "b" for binary.  A decimal num‐
1265       ber may be used for repetition.   For  example,  "bccc4b."  would  mean
1266       character  0  is  binary,  1,  2  and  3 are control, 4, 5, 6 and 7 are
1267       binary, and 8 is normal.  All characters after the last are taken to be
1268       the  same  as  the  last,  so characters 9 through 255 would be normal.
1269       (This is an example, and does not necessarily represent any real  char‐
1270       acter set.)
1271
1272       This  table  shows the value of LESSCHARDEF which is equivalent to each
1273       of the possible values for LESSCHARSET:
1274
1275            ascii     8bcccbcc18b95.b
1276            dos       8bcccbcc12bc5b95.b.
1277            ebcdic    5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
1278                      9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
1279            IBM-1047  4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
1280                      191.b
1281            iso8859   8bcccbcc18b95.33b.
1282            koi8-r    8bcccbcc18b95.b128.
1283            latin1    8bcccbcc18b95.33b.
1284            next      8bcccbcc18b95.bb125.bb
1285
1286       If neither LESSCHARSET nor LESSCHARDEF is set, but any of  the  strings
1287       "UTF-8",  "UTF8", "utf-8" or "utf8" is found in the LC_ALL, LC_CTYPE or
1288       LANG environment variables, then the default character set is utf-8.
1289
1290       If that string is not found, but your  system  supports  the  setlocale
1291       interface,  less  will  use  setlocale  to determine the character set.
1292       setlocale is controlled by setting the  LANG  or  LC_CTYPE  environment
1293       variables.
1294
1295       Finally,  if the setlocale interface is also not available, the default
1296       character set is latin1.
1297
1298       Control and  binary  characters  are  displayed  in  standout  (reverse
1299       video).  Each such character is displayed in caret notation if possible
1300       (e.g. ^A for control-A).  Caret notation is used only if inverting  the
1301       0100 bit results in a normal printable character.  Otherwise, the char‐
1302       acter is displayed as a hex number in angle brackets.  This format  can
1303       be  changed by setting the LESSBINFMT environment variable.  LESSBINFMT
1304       may begin with a "*" and one character to select the display attribute:
1305       "*k"  is  blinking, "*d" is bold, "*u" is underlined, "*s" is standout,
1306       and "*n" is normal.  If LESSBINFMT does not begin with  a  "*",  normal
1307       attribute  is  assumed.   The remainder of LESSBINFMT is a string which
1308       may include one printf-style escape sequence (a % followed by x, X,  o,
1309       d,  etc.).   For  example, if LESSBINFMT is "*u[%x]", binary characters
1310       are displayed in underlined hexadecimal surrounded  by  brackets.   The
1311       default  if  no  LESSBINFMT  is  specified is "*s<%02X>".  Warning: the
1312       result of expanding the character via LESSBINFMT must be less  than  31
1313       characters.
1314
1315       When the character set is utf-8, the LESSUTFBINFMT environment variable
1316       acts similarly to LESSBINFMT but it applies to Unicode code points that
1317       were  successfully  decoded but are unsuitable for display (e.g., unas‐
1318       signed code points).  Its default  value  is  "<U+%04lX>".   Note  that
1319       LESSUTFBINFMT  and  LESSBINFMT  share  their  display attribute setting
1320       ("*x") so specifying one will affect both; LESSUTFBINFMT is read  after
1321       LESSBINFMT  so  its  setting,  if any, will have priority.  Problematic
1322       octets in a UTF-8 file (octets of a truncated  sequence,  octets  of  a
1323       complete  but  non-shortest  form  sequence,  illegal octets, and stray
1324       trailing octets) are displayed individually using LESSBINFMT so  as  to
1325       facilitate diagnostic of how the UTF-8 file is ill-formed.
1326
1327

PROMPTS

1329       The  -P option allows you to tailor the prompt to your preference.  The
1330       string given to the -P option replaces  the  specified  prompt  string.
1331       Certain characters in the string are interpreted specially.  The prompt
1332       mechanism is rather complicated to provide flexibility, but  the  ordi‐
1333       nary  user need not understand the details of constructing personalized
1334       prompt strings.
1335
1336       A percent sign followed by a single character is expanded according  to
1337       what the following character is:
1338
1339       %bX    Replaced  by the byte offset into the current input file.  The b
1340              is followed by a single character (shown as X above) which spec‐
1341              ifies  the line whose byte offset is to be used.  If the charac‐
1342              ter is a "t", the byte offset of the top line in the display  is
1343              used, an "m" means use the middle line, a "b" means use the bot‐
1344              tom line, a "B" means use the line just after the  bottom  line,
1345              and  a  "j"  means use the "target" line, as specified by the -j
1346              option.
1347
1348       %B     Replaced by the size of the current input file.
1349
1350       %c     Replaced by the column number of the text appearing in the first
1351              column of the screen.
1352
1353       %dX    Replaced  by  the  page number of a line in the input file.  The
1354              line to be used is determined by the X, as with the %b option.
1355
1356       %D     Replaced by the number of pages in the input  file,  or  equiva‐
1357              lently, the page number of the last line in the input file.
1358
1359       %E     Replaced  by the name of the editor (from the VISUAL environment
1360              variable, or the EDITOR environment variable if  VISUAL  is  not
1361              defined).  See the discussion of the LESSEDIT feature below.
1362
1363       %f     Replaced by the name of the current input file.
1364
1365       %F     Replaced  by the last component of the name of the current input
1366              file.
1367
1368       %g     Replaced by the shell-escaped name of the  current  input  file.
1369              This  is useful when the expanded string will be used in a shell
1370              command, such as in LESSEDIT.
1371
1372       %i     Replaced by the index of the current file in the list  of  input
1373              files.
1374
1375       %lX    Replaced  by  the  line number of a line in the input file.  The
1376              line to be used is determined by the X, as with the %b option.
1377
1378       %L     Replaced by the line number of the last line in the input file.
1379
1380       %m     Replaced by the total number of input files.
1381
1382       %pX    Replaced by the percent into the current input  file,  based  on
1383              byte  offsets.  The line used is determined by the X as with the
1384              %b option.
1385
1386       %PX    Replaced by the percent into the current input  file,  based  on
1387              line  numbers.  The line used is determined by the X as with the
1388              %b option.
1389
1390       %s     Same as %B.
1391
1392       %t     Causes any trailing spaces to be removed.  Usually used  at  the
1393              end of the string, but may appear anywhere.
1394
1395       %T     Normally  expands  to the word "file".  However if viewing files
1396              via a tags list using the -t option,  it  expands  to  the  word
1397              "tag".
1398
1399       %x     Replaced by the name of the next input file in the list.
1400
1401       If any item is unknown (for example, the file size if input is a pipe),
1402       a question mark is printed instead.
1403
1404       The format of the prompt string can be  changed  depending  on  certain
1405       conditions.   A  question mark followed by a single character acts like
1406       an "IF": depending on the following character, a  condition  is  evalu‐
1407       ated.   If the condition is true, any characters following the question
1408       mark and condition character, up to  a  period,  are  included  in  the
1409       prompt.   If  the condition is false, such characters are not included.
1410       A colon appearing between the question mark and the period can be  used
1411       to establish an "ELSE": any characters between the colon and the period
1412       are included in the string if and only if the IF  condition  is  false.
1413       Condition characters (which follow a question mark) may be:
1414
1415       ?a     True if any characters have been included in the prompt so far.
1416
1417       ?bX    True if the byte offset of the specified line is known.
1418
1419       ?B     True if the size of current input file is known.
1420
1421       ?c     True if the text is horizontally shifted (%c is not zero).
1422
1423       ?dX    True if the page number of the specified line is known.
1424
1425       ?e     True if at end-of-file.
1426
1427       ?f     True  if  there is an input filename (that is, if input is not a
1428              pipe).
1429
1430       ?lX    True if the line number of the specified line is known.
1431
1432       ?L     True if the line number of the last line in the file is known.
1433
1434       ?m     True if there is more than one input file.
1435
1436       ?n     True if this is the first prompt in a new input file.
1437
1438       ?pX    True if the percent into the current input file, based  on  byte
1439              offsets, of the specified line is known.
1440
1441       ?PX    True  if  the percent into the current input file, based on line
1442              numbers, of the specified line is known.
1443
1444       ?s     Same as "?B".
1445
1446       ?x     True if there is a next input file  (that  is,  if  the  current
1447              input file is not the last one).
1448
1449       Any  characters  other  than  the  special  ones (question mark, colon,
1450       period, percent, and backslash) become literally part  of  the  prompt.
1451       Any  of  the special characters may be included in the prompt literally
1452       by preceding it with a backslash.
1453
1454       Some examples:
1455
1456       ?f%f:Standard input.
1457
1458       This prompt prints the filename, if known; otherwise the string  "Stan‐
1459       dard input".
1460
1461       ?f%f .?ltLine %lt:?pt%pt\%:?btByte %bt:-...
1462
1463       This  prompt  would print the filename, if known.  The filename is fol‐
1464       lowed by the line number, if known, otherwise  the  percent  if  known,
1465       otherwise  the  byte  offset  if  known.  Otherwise, a dash is printed.
1466       Notice how each question mark has a matching  period,  and  how  the  %
1467       after the %pt is included literally by escaping it with a backslash.
1468
1469       ?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\: %x..%t";
1470
1471       This  prints  the  filename if this is the first prompt in a file, fol‐
1472       lowed by the "file N of N" message if there  is  more  than  one  input
1473       file.   Then,  if  we are at end-of-file, the string "(END)" is printed
1474       followed by the name of the next file, if there is one.   Finally,  any
1475       trailing spaces are truncated.  This is the default prompt.  For refer‐
1476       ence, here are the defaults for  the  other  two  prompts  (-m  and  -M
1477       respectively).   Each  is  broken  into  two lines here for readability
1478       only.
1479
1480       ?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\: %x.:
1481            ?pB%pB\%:byte %bB?s/%s...%t
1482
1483       ?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%lb?L/%L. :
1484            byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t
1485
1486       And here is the default message produced by the = command:
1487
1488       ?f%f .?m(%T %i of %m) .?ltlines %lt-%lb?L/%L. .
1489            byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
1490
1491       The prompt expansion features are also used for another purpose: if  an
1492       environment  variable LESSEDIT is defined, it is used as the command to
1493       be executed when the v command is  invoked.   The  LESSEDIT  string  is
1494       expanded  in the same way as the prompt strings.  The default value for
1495       LESSEDIT is:
1496
1497            %E ?lm+%lm. %g
1498
1499       Note that this expands to the editor name, followed by a + and the line
1500       number,  followed  by the shell-escaped file name.  If your editor does
1501       not accept the "+linenumber" syntax, or has other differences in  invo‐
1502       cation  syntax,  the  LESSEDIT  variable  can be changed to modify this
1503       default.
1504
1505

SECURITY

1507       When the environment variable LESSSECURE is set to 1, less  runs  in  a
1508       "secure" mode.  This means these features are disabled:
1509
1510              !      the shell command
1511
1512              |      the pipe command
1513
1514              :e     the examine command.
1515
1516              v      the editing command
1517
1518              s  -o  log files
1519
1520              -k     use of lesskey files
1521
1522              -t     use of tags files
1523
1524                     metacharacters in filenames, such as *
1525
1526                     filename completion (TAB, ^L)
1527
1528       Less can also be compiled to be permanently in "secure" mode.
1529
1530

COMPATIBILITY WITH MORE

1532       If the environment variable LESS_IS_MORE is set to 1, or if the program
1533       is invoked via a file link named "more", less behaves (mostly) in  con‐
1534       formance  with  the  POSIX "more" command specification.  In this mode,
1535       less behaves differently in these ways:
1536
1537       The -e option works differently.  If the -e option  is  not  set,  less
1538       behaves  as  if  the -e option were set.  If the -e option is set, less
1539       behaves as if the -E option were set.
1540
1541       The -m option works differently.  If the -m  option  is  not  set,  the
1542       medium  prompt  is used, and it is prefixed with the string "--More--".
1543       If the -m option is set, the short prompt is used.
1544
1545       The -n option acts like the -z option.  The normal behavior of  the  -n
1546       option is unavailable in this mode.
1547
1548       The  parameter  to  the  -p option is taken to be a less command rather
1549       than a search pattern.
1550
1551       The LESS environment variable is  ignored,  and  the  MORE  environment
1552       variable is used in its place.
1553
1554

ENVIRONMENT VARIABLES

1556       Environment variables may be specified either in the system environment
1557       as usual, or in a lesskey  (1)  file.   If  environment  variables  are
1558       defined  in  more  than one place, variables defined in a local lesskey
1559       file take precedence over variables defined in the system  environment,
1560       which take precedence over variables defined in the system-wide lesskey
1561       file.
1562
1563       COLUMNS
1564              Sets the number of columns on the screen.  Takes precedence over
1565              the  number  of columns specified by the TERM variable.  (But if
1566              you  have  a  windowing  system  which  supports  TIOCGWINSZ  or
1567              WIOCGETD,  the  window  system's  idea  of the screen size takes
1568              precedence over the LINES and COLUMNS environment variables.)
1569
1570       EDITOR The name of the editor (used for the v command).
1571
1572       HOME   Name of the user's home directory (used to find a  lesskey  file
1573              on Unix and OS/2 systems).
1574
1575       HOMEDRIVE, HOMEPATH
1576              Concatenation  of  the  HOMEDRIVE and HOMEPATH environment vari‐
1577              ables is the name of the user's home directory if the HOME vari‐
1578              able is not set (only in the Windows version).
1579
1580       INIT   Name  of  the user's init directory (used to find a lesskey file
1581              on OS/2 systems).
1582
1583       LANG   Language for determining the character set.
1584
1585       LC_CTYPE
1586              Language for determining the character set.
1587
1588       LESS   Options which are passed to less automatically.
1589
1590       LESSANSIENDCHARS
1591              Characters which may end an ANSI color escape sequence  (default
1592              "m").
1593
1594       LESSANSIMIDCHARS
1595              Characters  which  may  appear between the ESC character and the
1596              end  character  in  an  ANSI  color  escape  sequence   (default
1597              "0123456789:;[?!"'#%()*+ ".
1598
1599       LESSBINFMT
1600              Format for displaying non-printable, non-control characters.
1601
1602       LESSCHARDEF
1603              Defines a character set.
1604
1605       LESSCHARSET
1606              Selects a predefined character set.
1607
1608       LESSCLOSE
1609              Command line to invoke the (optional) input-postprocessor.
1610
1611       LESSECHO
1612              Name of the lessecho program (default "lessecho").  The lessecho
1613              program is needed to expand metacharacters, such as * and ?,  in
1614              filenames on Unix systems.
1615
1616       LESSEDIT
1617              Editor  prototype  string (used for the v command).  See discus‐
1618              sion under PROMPTS.
1619
1620       LESSGLOBALTAGS
1621              Name of the command used by the -t option to find  global  tags.
1622              Normally should be set to "global" if your system has the global
1623              (1) command.  If not set, global tags are not used.
1624
1625       LESSHISTFILE
1626              Name of the history file used to remember  search  commands  and
1627              shell  commands  between  invocations of less.  If set to "-" or
1628              "/dev/null", a  history  file  is  not  used.   The  default  is
1629              "$HOME/.lesshst"  on  Unix  systems, "$HOME/_lesshst" on DOS and
1630              Windows systems, or "$HOME/lesshst.ini"  or  "$INIT/lesshst.ini"
1631              on OS/2 systems.
1632
1633       LESSHISTSIZE
1634              The maximum number of commands to save in the history file.  The
1635              default is 100.
1636
1637       LESSKEY
1638              Name of the default lesskey(1) file.
1639
1640       LESSKEY_SYSTEM
1641              Name of the default system-wide lesskey(1) file.
1642
1643       LESSMETACHARS
1644              List of characters which are considered "metacharacters" by  the
1645              shell.
1646
1647       LESSMETAESCAPE
1648              Prefix  which  less will add before each metacharacter in a com‐
1649              mand sent to the shell.  If LESSMETAESCAPE is an  empty  string,
1650              commands  containing  metacharacters  will  not be passed to the
1651              shell.
1652
1653       LESSOPEN
1654              Command line to invoke the (optional) input-preprocessor.
1655
1656       LESSSECURE
1657              Runs less in "secure" mode.  See discussion under SECURITY.
1658
1659       LESSSEPARATOR
1660              String to be appended to a directory name  in  filename  comple‐
1661              tion.
1662
1663       LESSUTFBINFMT
1664              Format for displaying non-printable Unicode code points.
1665
1666       LESS_IS_MORE
1667              Emulate the more (1) command.
1668
1669       LINES  Sets  the  number of lines on the screen.  Takes precedence over
1670              the number of lines specified by the TERM variable.  (But if you
1671              have  a  windowing system which supports TIOCGWINSZ or WIOCGETD,
1672              the window system's idea of the  screen  size  takes  precedence
1673              over the LINES and COLUMNS environment variables.)
1674
1675       MORE   Options  which  are passed to less automatically when running in
1676              more compatible mode.
1677
1678       PATH   User's search path (used to find a lesskey file  on  MS-DOS  and
1679              OS/2 systems).
1680
1681       SHELL  The  shell  used  to execute the ! command, as well as to expand
1682              filenames.
1683
1684       TERM   The type of terminal on which less is being run.
1685
1686       VISUAL The name of the editor (used for the v command).
1687
1688

SEE ALSO

1690       lesskey(1)
1691
1692
1694       Copyright (C) 1984-2019  Mark Nudelman
1695
1696       less is part of the GNU project and is free software.  You  can  redis‐
1697       tribute  it and/or modify it under the terms of either (1) the GNU Gen‐
1698       eral Public License as published by the Free  Software  Foundation;  or
1699       (2) the Less License.  See the file README in the less distribution for
1700       more details regarding redistribution.  You should have received a copy
1701       of  the  GNU General Public License along with the source for less; see
1702       the file COPYING.  If not, write to the Free  Software  Foundation,  59
1703       Temple  Place, Suite 330, Boston, MA  02111-1307, USA.  You should also
1704       have received a copy of the Less License; see the file LICENSE.
1705
1706       less is distributed in the hope that it will be useful, but WITHOUT ANY
1707       WARRANTY;  without even the implied warranty of MERCHANTABILITY or FIT‐
1708       NESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License  for
1709       more details.
1710
1711

AUTHOR

1713       Mark Nudelman
1714       Report bugs at https://github.com/gwsw/less/issues.
1715       For more information, see the less homepage at
1716       http://www.greenwoodsoftware.com/less.
1717
1718
1719
1720                           Version 551: 11 Jun 2019                    LESS(1)
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