Summary of Less command in Unix/Linux

About less
Less is a program similar to more (1), but which allows backward movement in the file as well as forward movement. Also, less does not have to read the entire input file before starting, so with large input files it starts up faster than text editors like vi (1). Less uses termcap (or terminfo on some systems), so it can run on a variety of terminals. There is even limited support for hardcopy terminals. (On a hardcopy terminal, lines which should be printed at the top of the screen are prefixed with a caret.)

Commands are based on both more and vi. Commands may be preceded by a decimal number, called N in the descriptions below. The number is used by some commands, as indicated.

SUMMARY OF LESS COMMANDS

Commands marked with * may be preceded by a number, N.
      Notes in parentheses indicate the behavior if N is given.

  h  H                 Display this help.
  q  :q  Q  :Q  ZZ     Exit.
 ---------------------------------------------------------------------------

                           MOVING

  e  ^E  j  ^N  CR  *  Forward  one line   (or N lines).
  y  ^Y  k  ^K  ^P  *  Backward one line   (or N lines).
  f  ^F  ^V  SPACE  *  Forward  one window (or N lines).
  b  ^B  ESC-v      *  Backward one window (or N lines).
  z                 *  Forward  one window (and set window to N).
  w                 *  Backward one window (and set window to N).
  ESC-SPACE         *  Forward  one window, but don't stop at end-of-file.
  d  ^D             *  Forward  one half-window (and set half-window to N).
  u  ^U             *  Backward one half-window (and set half-window to N).
  ESC-)  RightArrow *  Left  one half screen width (or N positions).
  ESC-(  LeftArrow  *  Right one half screen width (or N positions).

 F                    Forward forever; like "tail -f".
  r  ^R  ^L            Repaint screen.
  R                    Repaint screen, discarding buffered input.
        ---------------------------------------------------
        Default "window" is the screen height.
        Default "half-window" is half of the screen height.
 ---------------------------------------------------------------------------

                          SEARCHING

  /pattern          *  Search forward for (N-th) matching line.
  ?pattern          *  Search backward for (N-th) matching line.
  n                 *  Repeat previous search (for N-th occurrence).
  N                 *  Repeat previous search in reverse direction.
  ESC-n             *  Repeat previous search, spanning files.
  ESC-N             *  Repeat previous search, reverse dir. & spanning files.
  ESC-u                Undo (toggle) search highlighting.
        ---------------------------------------------------
        Search patterns may be modified by one or more of:
        ^N or !  Search for NON-matching lines.
        ^E or *  Search multiple files (pass thru END OF FILE).
        ^F or @  Start search at FIRST file (for /) or last file (for ?).
        ^K       Highlight matches, but don't move (KEEP position).
        ^R       Don't use REGULAR EXPRESSIONS.
 ---------------------------------------------------------------------------

                           JUMPING

  g  <  ESC-<       *  Go to first line in file (or line N).
  G  >  ESC->       *  Go to last line in file (or line N).
  p  %              *  Go to beginning of file (or N percent into file).
  t                 *  Go to the (N-th) next tag.
  T                 *  Go to the (N-th) previous tag.
  {  (  [           *  Find close bracket } ) ].
  }  )  ]           *  Find open bracket { ( [.
  ESC-^F    *  Find close bracket .
  ESC-^B    *  Find open bracket 
        ---------------------------------------------------
        Each "find close bracket" command goes forward to the close bracket
          matching the (N-th) open bracket in the top line.
        Each "find open bracket" command goes backward to the open bracket
          matching the (N-th) close bracket in the bottom line.

  m            Mark the current position with .
  '            Go to a previously marked position.
  ''                   Go to the previous position.
  ^X^X                 Same as '.
        ---------------------------------------------------
        A mark is any upper-case or lower-case letter.

        Certain marks are predefined:
             ^  means  beginning of the file
             $  means  end of the file
 ---------------------------------------------------------------------------

                        CHANGING FILES

  :e [file]            Examine a new file.
  ^X^V                 Same as :e.
  :n                *  Examine the (N-th) next file from the command line.
  :p                *  Examine the (N-th) previous file from the command line.
  :x                *  Examine the first (or N-th) file from the command line.
  :d                   Delete the current file from the command line list.
  =  ^G  :f            Print current file name.
 ---------------------------------------------------------------------------

                    MISCELLANEOUS COMMANDS

  -              Toggle a command line option [see OPTIONS below].
  --             Toggle a command line option, by name.
  _              Display the setting of a command line option.
  __             Display the setting of an option, by name.
  +cmd                 Execute the less cmd each time a new file is examined.

  !command             Execute the shell command with $SHELL.
  |Xcommand            Pipe file between current pos & mark X to shell command.
  v                    Edit the current file with $VISUAL or $EDITOR.
  V                    Print version number of "less".
 ---------------------------------------------------------------------------

                           OPTIONS

        Most options may be changed either on the command line,
        or from within less by using the - or -- command.
        Options may be given in one of two forms: either a single
        character preceded by a -, or a name preceeded by --.

  -?  ........  --help
                  Display help (from command line).
  -a  ........  --search-skip-screen
                  Forward search skips current screen.
  -b [N]  ....  --buffers=[N]
                  Number of buffers.
  -B  ........  --auto-buffers
                  Don't automatically allocate buffers for pipes.
  -c  -C  ....  --clear-screen  --CLEAR-SCREEN
                  Repaint by scrolling/clearing.

  -d  ........  --dumb
                  Dumb terminal.
  -D [xn.n]  .  --color=xn.n
                  Set screen colors. (MS-DOS only)
  -e  -E  ....  --quit-at-eof  --QUIT-AT-EOF
                  Quit at end of file.
  -f  ........  --force
                  Force open non-regular files.
  -F  ........  --quit-if-one-screen
                  Quit if entire file fits on first screen.
  -g  ........  --hilite-search
                  Highlight only last match for searches.
  -G  ........  --HILITE-SEARCH
                  Don't highlight any matches for searches.
  -h [N]  ....  --max-back-scroll=[N]
                  Backward scroll limit.
  -i  ........  --ignore-case
                  Ignore case in searches that do not contain uppercase.
  -I  ........  --IGNORE-CASE
                  Ignore case in all searches.
  -j [N]  ....  --jump-target=[N]
                  Screen position of target lines.
  -J  ........  --status-column
                  Display a status column at left edge of screen.
  -k [file]  .  --lesskey-file=[file]
                  Use a lesskey file.
  -L  ........  --no-lessopen
                  Ignore the LESSOPEN environment variable.
  -m  -M  ....  --long-prompt  --LONG-PROMPT
                  Set prompt style.
  -n  -N  ....  --line-numbers  --LINE-NUMBERS
                  Use line numbers.
  -o [file]  .  --log-file=[file]
                  Copy to log file (standard input only).
  -O [file]  .  --LOG-FILE=[file]
                  Copy to log file (unconditionally overwrite).
  -p [pattern]  --pattern=[pattern]
                  Start at pattern (from command line).
  -P [prompt]   --prompt=[prompt]
                  Define new prompt.
  -q  -Q  ....  --quiet  --QUIET  --silent --SILENT
                  Quiet the terminal bell.
  -r  -R  ....  --raw-control-chars  --RAW-CONTROL-CHARS
                  Output "raw" control characters.
  -s  ........  --squeeze-blank-lines
                  Squeeze multiple blank lines.
  -S  ........  --chop-long-lines
                  Chop long lines.

  -t [tag]  ..  --tag=[tag]
                  Find a tag.
  -T [tagsfile] --tag-file=[tagsfile]
                  Use an alternate tags file.
  -u  -U  ....  --underline-special  --UNDERLINE-SPECIAL
                  Change handling of backspaces.
  -V  ........  --version
                  Display the version number of "less".
  -w  ........  --hilite-unread
                  Highlight first new line after forward-screen.
  -W  ........  --HILITE-UNREAD
                  Highlight first new line after any forward movement.
  -x [N[,...]]  --tabs=[N[,...]]
                  Set tab stops.
  -X  ........  --no-init
                  Don't use termcap init/deinit strings.
                --no-keypad
                  Don't use termcap keypad init/deinit strings.
  -y [N]  ....  --max-forw-scroll=[N]
                  Forward scroll limit.
  -z [N]  ....  --window=[N]
                  Set size of window.
  -" [c[c]]  .  --quotes=[c[c]]
                  Set shell quote characters.
  -~  ........  --tilde
                  Don't display tildes after end of file.
  -# [N]  ....  --shift=[N]
                  Horizontal scroll amount (0 = one half screen width)

 ---------------------------------------------------------------------------

                          LINE EDITING

        These keys can be used to edit text being entered
        on the "command line" at the bottom of the screen.

 RightArrow                       ESC-l     Move cursor right one character.
 LeftArrow                        ESC-h     Move cursor left one character.
 CNTL-RightArrow  ESC-RightArrow  ESC-w     Move cursor right one word.
 CNTL-LeftArrow   ESC-LeftArrow   ESC-b     Move cursor left one word.
 HOME                             ESC-0     Move cursor to start of line.
 END                              ESC-$     Move cursor to end of line.
 BACKSPACE                                  Delete char to left of cursor.
 DELETE                           ESC-x     Delete char under cursor.
 CNTL-BACKSPACE   ESC-BACKSPACE             Delete word to left of cursor.
 CNTL-DELETE      ESC-DELETE      ESC-X     Delete word under cursor.
 CNTL-U           ESC (MS-DOS only)         Delete entire line.
 UpArrow                          ESC-k     Retrieve previous command line.
 DownArrow                        ESC-j     Retrieve next command line.
 TAB                                        Complete filename & cycle.
 SHIFT-TAB                        ESC-TAB   Complete filename & reverse cycle.
 CNTL-L                                     Complete filename, list all.

Frequently used commands of less
[Arrows]/[Page Up]/[Page Down]/[Home]/[End]: Navigation.
[Space bar]: Next page.
b: Previous page.
ng: Jump to line number n. Default is the start of the file.
nG: Jump to line number n. Default is the end of the file.
/pattern: Search for pattern. Regular expressions can be used. [/ = slash] Press / and then Enter to repeat the previous search pattern.
n: Go to next match (after a successful search).
N: Go to previous match.
mletter: Mark the current position with letter.
'letter: Return to position letter. [' = single quote]
'^ or g: Go to start of file.
'$ or G: Go to end of file.
s: Save current content (got from another program like grep) in a file.
=: File information.
F: continually read information from file and follow its end. Useful for logs watching. Use Ctrl+C to exit this mode.
-option: Toggle command-line option -option.
h: Help.
q: Quit.

Full Less Manual

NAME less - opposite of more

SYNOPSIS
less -?
less --help
less -V
less --version
less [-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-b space] [-h lines] [-j line] [-k keyfile]
[-{oO} logfile] [-p pattern] [-P prompt] [-t tag]
[-T tagsfile] [-x tab,...] [-y lines] [-[z] lines]
[-# shift] [+[+]cmd] [--] [filename]...
(See the OPTIONS section for alternate option syntax with long option names.)


COMMANDS
In  the  following  descriptions,  ^X means control-X.  ESC stands for the ESCAPE key; for example ESC-v means the two character sequence "ESCAPE", then
"v".

h or H Help: display a summary of these commands.  If you forget all the other commands, remember this one.

SPACE or ^V or f or ^F
Scroll forward N lines, default one window (see option -z below).  If N is more than the screen size, only  the  final  screenful  is  displayed.
Warning: some systems use ^V as a special literalization character.

z      Like SPACE, but if N is specified, it becomes the new window size.

ESC-SPACE
Like SPACE, but scrolls a full screenful, even if it reaches end-of-file in the process.

RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1.  The entire N lines are displayed, even if N is more than the screen size.

d or ^D
Scroll forward N lines, default one half of the screen size.  If N is specified, it becomes the new default for subsequent d and u commands.

b or ^B or ESC-v
Scroll backward N lines, default one window (see option -z below).  If N is more than the screen size, only the final screenful is displayed.

w      Like ESC-v, but if N is specified, it becomes the new window size.

y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1.  The entire N lines are displayed, even if N is more than the screen size.  Warning: some systems use ^Y as a
special job control character.

u or ^U
Scroll backward N lines, default one half of the screen size.  If N is specified, it becomes the new default for subsequent d and u commands.

ESC-) or RIGHTARROW
Scroll horizontally right N characters, default half the screen width (see the -# option).  If a number N is specified, it  becomes  the  default
for future RIGHTARROW and LEFTARROW commands.  While the text is scrolled, it acts as though the -S option (chop lines) were in effect.

ESC-( or LEFTARROW
Scroll horizontally left N characters, default half the screen width (see the -# option).  If a number N is specified, it becomes the default for
future RIGHTARROW and LEFTARROW commands.

r or ^R or ^L
Repaint the screen.

R      Repaint the screen, discarding any buffered input.  Useful if the file is changing while it is being viewed.

F      Scroll forward, and keep trying to read when the end of file is reached.  Normally this command would be used when already  at  the  end  of  the
file.   It is a way to monitor the tail of a file which is growing while it is being viewed.  (The behavior is similar to the "tail -f" command.)

g or < or ESC-<
              Go to line N in the file, default 1 (beginning of file).  (Warning: this may be slow if N is large.)

       G or > or ESC->
Go to line N in the file, default the end of the file.  (Warning: this may be slow if N is large, or if N is not specified  and  standard  input,
rather than a file, is being read.)

p or % Go to a position N percent into the file.  N should be between 0 and 100.

{      If a left curly bracket appears in the top line displayed on the screen, the { command will go to the matching right curly bracket.  The matching
right curly bracket is positioned on the bottom line of the screen.  If there is more than one left curly bracket on the top line, a number N may
be used to specify the N-th bracket on the line.

}      If  a  right  curly  bracket  appears  in the bottom line displayed on the screen, the } command will go to the matching left curly bracket.  The
matching left curly bracket is positioned on the top line of the screen.  If there is more than one right curly bracket on the top line, a number
N may be used to specify the N-th bracket on the line.

(      Like {, but applies to parentheses rather than curly brackets.

)      Like }, but applies to parentheses rather than curly brackets.

[      Like {, but applies to square brackets rather than curly brackets.

]      Like }, but applies to square brackets rather than curly brackets.

ESC-^F Followed  by  two characters, acts like {, but uses the two characters as open and close brackets, respectively.  For example, "ESC ^F < >" could
be used to go forward to the > which matches the < in the top displayed line.

       ESC-^B Followed by two characters, acts like }, but uses the two characters as open and close brackets, respectively.  For example, "ESC ^B <  >"  could
be used to go backward to the < which matches the > in the bottom displayed line.

m      Followed by any lowercase letter, marks the current position with that letter.

â      (Single  quote.)   Followed  by  any lowercase letter, returns to the position which was previously marked with that letter.  Followed by another
single quote, returns to the position at which the last "large" movement command was executed.  Followed by a ^ or $, jumps to the  beginning  or
end of the file respectively.  Marks are preserved when a new file is examined, so the â command can be used to switch between input files.

^X^X   Same as single quote.

/pattern
Search forward in the file for the N-th line containing the pattern.  N defaults to 1.  The pattern is a regular expression, as recognized by the
regular expression library supplied by your system.  The search starts at the second line displayed (but see the -a and -j options, which  change
this).

Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern:

^N or !
Search for lines which do NOT match the pattern.

^E or *
Search multiple files.  That is, if the search reaches the END of the current file without finding a match, the search  continues  in  the
next file in the command line list.

^F or @
Begin  the search at the first line of the FIRST file in the command line list, regardless of what is currently displayed on the screen or
the settings of the -a or -j options.

^K     Highlight any text which matches the pattern on the current screen, but donât move to the first match (KEEP current position).

^R     Donât interpret regular expression metacharacters; that is, do a simple textual comparison.

?pattern
Search backward in the file for the N-th line containing the pattern.  The search starts at the line immediately before the top line displayed.

Certain characters are special as in the / command:

^N or !
Search for lines which do NOT match the pattern.

^E or *
Search multiple files.  That is, if the search reaches the beginning of the current file without finding a match, the search continues  in
the previous file in the command line list.

^F or @
Begin  the  search  at the last line of the last file in the command line list, regardless of what is currently displayed on the screen or
the settings of the -a or -j options.

^K     As in forward searches.

^R     As in forward searches.

ESC-/pattern
Same as "/*".

ESC-?pattern
Same as "?*".

n      Repeat previous search, for N-th line containing the last pattern.  If the previous search was modified by ^N, the search is made  for  the  N-th
line NOT containing the pattern.  If the previous search was modified by ^E, the search continues in the next (or previous) file if not satisfied
in the current file.  If the previous search was modified by ^R, the search is done without using regular expressions.  There is no effect if the
previous search was modified by ^F or ^K.

N      Repeat previous search, but in the reverse direction.

ESC-n  Repeat previous search, but crossing file boundaries.  The effect is as if the previous search were modified by *.

ESC-N  Repeat previous search, but in the reverse direction and crossing file boundaries.

ESC-u  Undo  search  highlighting.   Turn  off highlighting of strings matching the current search pattern.  If highlighting is already off because of a
previous ESC-u command, turn highlighting back on.  Any search command will also turn highlighting back on.  (Highlighting can also  be  disabled
by toggling the -G option; in that case search commands do not turn highlighting back on.)

:e [filename]
Examine a new file.  If the filename is missing, the "current" file (see the :n and :p commands below) from the list of files in the command line
is re-examined.  A percent sign (%) in the filename is replaced by the name of the current file.  A pound sign (#) is replaced by the name of the
previously  examined  file.   However,  two consecutive percent signs are simply replaced with a single percent sign.  This allows you to enter a
filename that contains a percent sign in the name.  Similarly, two consecutive pound signs are replaced with a single pound sign.   The  filename
is  inserted  into  the  command line list of files so that it can be seen by subsequent :n and :p commands.  If the filename consists of several
files, they are all inserted into the list of files and the first one is examined.  If the filename contains one or more spaces, the entire file-
name should be enclosed in double quotes (also see the -" option).

^X^V or E
Same as :e.  Warning: some systems use ^V as a special literalization character.  On such systems, you may not be able to use ^V.

:n     Examine the next file (from the list of files given in the command line).  If a number N is specified, the N-th next file is examined.

:p     Examine the previous file in the command line list.  If a number N is specified, the N-th previous file is examined.

:x     Examine the first file in the command line list.  If a number N is specified, the N-th file in the list is examined.

:d     Remove the current file from the list of files.

t      Go to the next tag, if there were more than one matches for the current tag.  See the -t option for more details about tags.

T      Go to the previous tag, if there were more than one matches for the current tag.

= or ^G or :f
Prints  some  information about the file being viewed, including its name and the line number and byte offset of the bottom line being displayed.
If possible, it also prints the length of the file, the number of lines in the file and the percent of the file above the last displayed line.

-      Followed by one of the command line option letters (see OPTIONS below), this will change the setting of that option and print a message  describ-
ing  the new setting.  If a ^P (CONTROL-P) is entered immediately after the dash, the setting of the option is changed but no message is printed.
If the option letter has a numeric value (such as -b or -h), or a string value (such as -P or -t), a new value may be entered  after  the  option
letter.  If no new value is entered, a message describing the current setting is printed and nothing is changed.

--     Like  the - command, but takes a long option name (see OPTIONS below) rather than a single option letter.  You must press RETURN after typing the
option name.  A ^P immediately after the second dash suppresses printing of a message describing the new setting, as in the - command.

-+     Followed by one of the command line option letters this will reset the option to its default setting and print a message describing the new  set-
ting.  (The "-+X" command does the same thing as "-+X" on the command line.)  This does not work for string-valued options.

--+    Like the -+ command, but takes a long option name rather than a single option letter.

-!     Followed  by  one  of  the  command  line option letters, this will reset the option to the "opposite" of its default setting and print a message
describing the new setting.  This does not work for numeric or string-valued options.

--!    Like the -! command, but takes a long option name rather than a single option letter.

_      (Underscore.)  Followed by one of the command line option letters, this will print a message describing the current setting of that option.   The
setting of the option is not changed.

__     (Double  underscore.)   Like  the _ (underscore) command, but takes a long option name rather than a single option letter.  You must press RETURN
after typing the option name.

+cmd   Causes the specified cmd to be executed each time a new file is examined.  For example, +G causes less to initially display each file starting at
the end rather than the beginning.

V      Prints the version number of less being run.

q or Q or :q or :Q or ZZ
Exits less.

The following four commands may or may not be valid, depending on your particular installation.

v      Invokes  an  editor  to  edit  the  current file being viewed.  The editor is taken from the environment variable VISUAL if defined, or EDITOR if
VISUAL is not defined, or defaults to "vi" if neither VISUAL nor EDITOR is defined.  See also the discussion of LESSEDIT  under  the  section  on
PROMPTS below.

! shell-command
Invokes a shell to run the shell-command given.  A percent sign (%) in the command is replaced by the name of the current file.  A pound sign (#)
is replaced by the name of the previously examined file.  "!!" repeats the last shell command.  "!" with no shell command simply invokes a shell.
On  Unix systems, the shell is taken from the environment variable SHELL, or defaults to "sh".  On MS-DOS and OS/2 systems, the shell is the nor-
mal command processor.

|  shell-command
 represents any mark letter.  Pipes a section of the input file to the given shell command.  The section of the file to be  piped  is  between
the  first line on the current screen and the position marked by the letter.   may also be ^ or $ to indicate beginning or end of file respec-
tively.  If  is . or newline, the current screen is piped.

s filename

Save the input to a file.  This only works if the input is a pipe, not an ordinary file.

OPTIONS
Command line options are described below.  Most options may be changed while less is running, via the "-" command.

Most options may be given in one of two forms: either a dash followed by a single letter, or two dashes followed by a long option name.  A  long  option
name  may  be  abbreviated  as long as the abbreviation is unambiguous.  For example, --quit-at-eof may be abbreviated --quit, but not --qui, since both
--quit-at-eof and --quiet begin with --qui.  Some long option names are in uppercase, such as  --QUIT-AT-EOF,  as  distinct  from  --quit-at-eof.   Such
option  names  need only have their first letter capitalized; the remainder of the name may be in either case.  For example, --Quit-at-eof is equivalent
to --QUIT-AT-EOF.

Options are also taken from the environment variable "LESS".  For example, to avoid typing "less -options ..." each time less is invoked, you might tell
csh:

setenv LESS "-options"

or if you use sh:

LESS="-options"; export LESS

On MS-DOS, you donât need the quotes, but you should replace any percent signs in the options string by double percent signs.

The environment variable is parsed before the command line, so command line options override the LESS environment variable.  If an option appears in the
LESS variable, it can be reset to its default value on the command line by beginning the command line option with "-+".

For options like -P or -D which take a following string, a dollar sign ($) must be used to signal the end of the string.  For example,  to  set  two  -D
options on MS-DOS, you must have a dollar sign between them, like this:

LESS="-Dn9.1$-Ds4.1"

-? or --help
This  option  displays a summary of the commands accepted by less (the same as the h command).  (Depending on how your shell interprets the ques-
tion mark, it may be necessary to quote the question mark, thus: "-\?".)

-a or --search-skip-screen
Causes searches to start after the last line displayed on the screen, thus skipping all lines displayed on  the  screen.   By  default,  searches
start at the second line on the screen (or after the last found line; see the -j option).

-bn or --buffers=n
Specifies the amount of buffer space less will use for each file, in units of kilobytes (1024 bytes).  By default 64K of buffer space is used for
each file (unless the file is a pipe; see the -B option).  The -b option specifies instead that n kilobytes of buffer space should  be  used  for
each file.  If n is -1, buffer space is unlimited; that is, the entire file is read into memory.

-B or --auto-buffers
By  default, when data is read from a pipe, buffers are allocated automatically as needed.  If a large amount of data is read from the pipe, this
can cause a large amount of memory to be allocated.  The -B option disables this automatic allocation of buffers for pipes, so that only 64K  (or
the  amount  of  space specified by the -b option) is used for the pipe.  Warning: use of -B can result in erroneous display, since only the most
recently viewed part of the file is kept in memory; any earlier data is lost.

-c or --clear-screen
Causes full screen repaints to be painted from the top line down.  By default, full screen repaints are done by scrolling from the bottom of  the

screen.

-C or --CLEAR-SCREEN
The -C option is like -c, but the screen is cleared before it is repainted.

-d or --dumb
The  -d  option  suppresses  the  error message normally displayed if the terminal is dumb; that is, lacks some important capability, such as the
ability to clear the screen or scroll backward.  The -d option does not otherwise change the behavior of less on a dumb terminal.

-Dxcolor or --color=xcolor
[MS-DOS only] Sets the color of the text displayed.  x is a single character which selects the type of text whose color is being  set:  n=normal,
s=standout,  d=bold, u=underlined, k=blink.  color is a pair of numbers separated by a period.  The first number selects the foreground color and
the second selects the background color of the text.  A single number N is the same as N.0.

-e or --quit-at-eof
Causes less to automatically exit the second time it reaches end-of-file.  By default, the only way to exit less is via the "q" command.

-E or --QUIT-AT-EOF
Causes less to automatically exit the first time it reaches end-of-file.

-f or --force
Forces non-regular files to be opened.  (A non-regular file is a directory or a device special file.)  Also suppresses the warning message when a
binary file is opened.  By default, less will refuse to open non-regular files.

-F or --quit-if-one-screen
Causes less to automatically exit if the entire file can be displayed on the first screen.

-g or --hilite-search
Normally, less will highlight ALL strings which match the last search command.  The -g option changes this behavior to highlight only the partic-
ular string which was found by the last search command.  This can cause less to run somewhat faster than the default.

-G or --HILITE-SEARCH
The -G option suppresses all highlighting of strings found by search commands.

-hn or --max-back-scroll=n
Specifies a maximum number of lines to scroll backward.  If it is necessary to scroll backward more than n lines, the screen is  repainted  in  a
forward direction instead.  (If the terminal does not have the ability to scroll backward, -h0 is implied.)

-i or --ignore-case
Causes  searches  to  ignore  case;  that  is, uppercase and lowercase are considered identical.  This option is ignored if any uppercase letters
appear in the search pattern; in other words, if a pattern contains uppercase letters, then that search does not ignore case.

-I or --IGNORE-CASE
Like -i, but searches ignore case even if the pattern contains uppercase letters.

-jn or --jump-target=n
Specifies a line on the screen where the "target" line is to be positioned.  A target line is the object of a text search, tag search, jump to  a
line number, jump to a file percentage, or jump to a marked position.  The screen line is specified by a number: the top line on the screen is 1,
the next is 2, and so on.  The number may be negative to specify a line relative to the bottom of the screen: the bottom line on  the  screen  is
-1,  the  second  to  the  bottom is -2, and so on.  If the -j option is used, searches begin at the line immediately after the target line.  For
example, if "-j4" is used, the target line is the fourth line on the screen, so searches begin at the fifth line on the screen.


-J or --status-column
Displays a status column at the left edge of the screen.  The status column shows the lines that matched the current search.  The  status  column
is also used if the -w or -W option is in effect.

-kfilename or --lesskey-file=filename
Causes  less to open and interpret the named file as a lesskey (1) file.  Multiple -k options may be specified.  If the LESSKEY or LESSKEY_SYSTEM
environment variable is set, or if a lesskey file is found in a standard place (see KEY BINDINGS), it is also used as a lesskey file.

-K or --quit-on-intr
Causes less to exit immediately when an interrupt character (usually ^C) is typed.  Normally, an interrupt character causes less to stop whatever
it is doing and return to its command prompt.

-L or --no-lessopen
Ignore  the LESSOPEN environment variable (see the INPUT PREPROCESSOR section below).  This option can be set from within less, but it will apply
only to files opened subsequently, not to the file which is currently open.

-m or --long-prompt
Causes less to prompt verbosely (like more), with the percent into the file.  By default, less prompts with a colon.

-M or --LONG-PROMPT
Causes less to prompt even more verbosely than more.

-n or --line-numbers
Suppresses line numbers.  The default (to use line numbers) may cause less to run more slowly in some cases, especially with a very  large  input
file.   Suppressing  line numbers with the -n option will avoid this problem.  Using line numbers means: the line number will be displayed in the
verbose prompt and in the = command, and the v command will pass the current line number to the editor (see also the discussion  of  LESSEDIT  in
PROMPTS below).

-N or --LINE-NUMBERS
Causes a line number to be displayed at the beginning of each line in the display.

-ofilename or --log-file=filename
Causes  less  to  copy its input to the named file as it is being viewed.  This applies only when the input file is a pipe, not an ordinary file.
If the file already exists, less will ask for confirmation before overwriting it.

-Ofilename or --LOG-FILE=filename
The -O option is like -o, but it will overwrite an existing file without asking for confirmation.

If no log file has been specified, the -o and -O options can be used from within less to specify a log file.  Without a file name, they will sim-
ply report the name of the log file.  The "s" command is equivalent to specifying -o from within less.

-ppattern or --pattern=pattern
The  -p  option  on the command line is equivalent to specifying +/pattern; that is, it tells less to start at the first occurrence of pattern in
the file.

-Pprompt or --prompt=prompt
Provides a way to tailor the three prompt styles to your own preference.  This option would normally be put in  the  LESS  environment  variable,
rather  than  being  typed  in with each less command.  Such an option must either be the last option in the LESS variable, or be terminated by a
dollar sign.  -Ps followed by a string changes the default (short) prompt to that string.  -Pm changes the medium (-m) prompt.  -PM  changes  the
long  (-M)  prompt.   -Ph  changes  the  prompt  for the help screen.  -P= changes the message printed by the = command.  -Pw changes the message
printed while waiting for data (in the F command).  All prompt strings consist of a sequence of letters and special escape  sequences.   See  the
section on PROMPTS for more details.

-q or --quiet or --silent
Causes  moderately "quiet" operation: the terminal bell is not rung if an attempt is made to scroll past the end of the file or before the begin-
ning of the file.  If the terminal has a "visual bell", it is used instead.  The bell will be rung on certain other errors,  such  as  typing  an
invalid character.  The default is to ring the terminal bell in all such cases.

-Q or --QUIET or --SILENT
Causes totally "quiet" operation: the terminal bell is never rung.

-r or --raw-control-chars
Causes "raw" control characters to be displayed.  The default is to display control characters using the caret notation; for example, a control-A
(octal 001) is displayed as "^A".  Warning: when the -r option is used, less cannot keep track of the actual appearance of the screen (since this
depends on how the screen responds to each type of control character).  Thus, various display problems may result, such as long lines being split
in the wrong place.

-R or --RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences are output in "raw" form.  Unlike -r, the screen  appearance  is  maintained  correctly  in  most
cases.  ANSI "color" escape sequences are sequences of the form:

ESC [ ... m

where the "..." is zero or more color specification characters For the purpose of keeping track of screen appearance, ANSI color escape sequences
are assumed to not move the cursor.  You can make less think that characters other than "m" can end ANSI color escape sequences  by  setting  the
environment  variable LESSANSIENDCHARS to the list of characters which can end a color escape sequence.  And you can make less think that charac-
ters other than the standard ones may appear between the ESC and the m by setting the environment variable LESSANSIMIDCHARS to the list of  char-
acters which can appear.

-s or --squeeze-blank-lines
Causes consecutive blank lines to be squeezed into a single blank line.  This is useful when viewing nroff output.

-S or --chop-long-lines
Causes  lines longer than the screen width to be chopped rather than folded.  That is, the portion of a long line that does not fit in the screen
width is not shown.  The default is to fold long lines; that is, display the remainder on the next line.

-ttag or --tag=tag
The -t option, followed immediately by a TAG, will edit the file containing that tag.  For this to work, tag information must be  available;  for
example,  there  may  be a file in the current directory called "tags", which was previously built by ctags (1) or an equivalent command.  If the
environment variable LESSGLOBALTAGS is set, it is taken to be the name of a command compatible with global (1), and that command is  executed  to
find  the tag.  (See http://www.gnu.org/software/global/global.html).  The -t option may also be specified from within less (using the - command)
as a way of examining a new file.  The command ":t" is equivalent to specifying -t from within less.

-Ttagsfile or --tag-file=tagsfile
Specifies a tags file to be used instead of "tags".

-u or --underline-special
Causes backspaces and carriage returns to be treated as printable characters; that is, they are sent to the terminal  when  they  appear  in  the
input.

-U or --UNDERLINE-SPECIAL
Causes backspaces, tabs and carriage returns to be treated as control characters; that is, they are handled as specified by the -r option.

By default, if neither -u nor -U is given, backspaces which appear adjacent to an underscore character are treated specially: the underlined text
is displayed using the terminalâs hardware underlining capability.  Also, backspaces which appear between two identical  characters  are  treated
specially:  the  overstruck text is printed using the terminalâs hardware boldface capability.  Other backspaces are deleted, along with the pre-
ceding character.  Carriage returns immediately followed by a newline are deleted.  other carriage returns are handled as  specified  by  the  -r
option.  Text which is overstruck or underlined can be searched for if neither -u nor -U is in effect.

-V or --version
Displays the version number of less.

-w or --hilite-unread
Temporarily  highlights the first "new" line after a forward movement of a full page.  The first "new" line is the line immediately following the
line previously at the bottom of the screen.  Also highlights the target line after a g or p command.  The highlight is removed at the next  com-
mand  which  causes  movement.   The entire line is highlighted, unless the -J option is in effect, in which case only the status column is high-
lighted.

-W or --HILITE-UNREAD
Like -w, but temporarily highlights the first new line after any forward movement command larger than one line.

-xn,... or --tabs=n,...
Sets tab stops.  If only one n is specified, tab stops are set at multiples of n.  If multiple values separated  by  commas  are  specified,  tab
stops are set at those positions, and then continue with the same spacing as the last two.  For example, -x9,17 will set tabs at positions 9, 17,
25, 33, etc.  The default for n is 8.

-X or --no-init
Disables sending the termcap initialization and deinitialization strings to the terminal.  This is sometimes desirable  if  the  deinitialization
string does something unnecessary, like clearing the screen.

--no-keypad
Disables sending the keypad initialization and deinitialization strings to the terminal.  This is sometimes useful if the keypad strings make the
numeric keypad behave in an undesirable manner.

-yn or --max-forw-scroll=n
Specifies a maximum number of lines to scroll forward.  If it is necessary to scroll forward more than n lines, the screen is repainted  instead.
The -c or -C option may be used to repaint from the top of the screen if desired.  By default, any forward movement causes scrolling.

-[z]n or --window=n
Changes  the default scrolling window size to n lines.  The default is one screenful.  The z and w commands can also be used to change the window
size.  The "z" may be omitted for compatibility with more.  If the number n is negative, it indicates n lines less than the current screen  size.
For  example,  if the screen is 24 lines, -z-4 sets the scrolling window to 20 lines.  If the screen is resized to 40 lines, the scrolling window
automatically changes to 36 lines.

-"cc or --quotes=cc
Changes the filename quoting character.  This may be necessary if you are trying to name a file which contains both spaces and quote  characters.
Followed  by  a  single character, this changes the quote character to that character.  Filenames containing a space should then be surrounded by
that character rather than by double quotes.  Followed by two characters, changes the open quote to the first character, and the close  quote  to
the  second  character.  Filenames containing a space should then be preceded by the open quote character and followed by the close quote charac-
ter.  Note that even after the quote characters are changed, this option remains -" (a dash followed by a double quote).

-~ or --tilde
Normally lines after end of file are displayed as a single tilde (~).  This option causes lines after end of file to be displayed as blank lines.

-# or --shift
Specifies  the  default number of positions to scroll horizontally in the RIGHTARROW and LEFTARROW commands.  If the number specified is zero, it
sets the default number of positions to one half of the screen width.

--     A command line argument of "--" marks the end of option arguments.  Any arguments following this are interpreted as filenames.  This can be  use-
ful when viewing a file whose name begins with a "-" or "+".

+      If  a  command  line option begins with +, the remainder of that option is taken to be an initial command to less.  For example, +G tells less to
start at the end of the file rather than the beginning, and +/xyz tells it to start at the first occurrence of "xyz" in the file.  As  a  special
case,  + acts like +g; that is, it starts the display at the specified line number (however, see the caveat under the "g" command
above).  If the option starts with ++, the initial command applies to every file being viewed, not just the first one.  The +  command  described
previously may also be used to set (or change) an initial command for every file.

LINE EDITING
When  entering  command line at the bottom of the screen (for example, a filename for the :e command, or the pattern for a search command), certain keys
can be used to manipulate the command line.  Most commands have an alternate form in [ brackets ] which can be used if a key does not exist on a partic-
ular  keyboard.   (The  bracketed forms do not work in the MS-DOS version.)  Any of these special keys may be entered literally by preceding it with the
"literal" character, either ^V or ^A.  A backslash itself may also be entered literally by entering two backslashes.

LEFTARROW [ ESC-h ]
Move the cursor one space to the left.

RIGHTARROW [ ESC-l ]
Move the cursor one space to the right.

^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.)  Move the cursor one word to the left.

^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.)  Move the cursor one word to the right.

HOME [ ESC-0 ]
Move the cursor to the beginning of the line.

END [ ESC-$ ]
Move the cursor to the end of the line.

BACKSPACE
Delete the character to the left of the cursor, or cancel the command if the command line is empty.

DELETE or [ ESC-x ]
Delete the character under the cursor.

^BACKSPACE [ ESC-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.)  Delete the word to the left of the cursor.

^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.)  Delete the word under the cursor.
UPARROW [ ESC-k ]
Retrieve the previous command line.

DOWNARROW [ ESC-j ]
Retrieve the next command line.

TAB    Complete the partial filename to the left of the cursor.  If it matches more than one filename, the first match is entered into the command line.
Repeated  TABs  will  cycle thru the other matching filenames.  If the completed filename is a directory, a "/" is appended to the filename.  (On
MS-DOS systems, a "\" is appended.)  The environment variable LESSSEPARATOR can be used to specify a different character to append to a directory
name.

BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the matching filenames.

^L     Complete the partial filename to the left of the cursor.  If it matches more than one filename, all matches are entered into the command line (if
they fit).

^U (Unix and OS/2) or ESC (MS-DOS)
Delete the entire command line, or cancel the command if the command line is empty.  If you have changed your  line-kill  character  in  Unix  to
something other than ^U, that character is used instead of ^U.

KEY BINDINGS
You  may  define  your  own  less  commands by using the program lesskey (1) to create a lesskey file.  This file specifies a set of command keys and an
action associated with each key.  You may also use lesskey to change the line-editing keys (see LINE EDITING), and to set environment variables.  If the
environment variable LESSKEY is set, less uses that as the name of the lesskey file.  Otherwise, less looks in a standard place for the lesskey file: On
Unix systems, less looks for a lesskey file called "$HOME/.less".  On MS-DOS and Windows systems, less looks for a lesskey  file  called  "$HOME/_less",
and  if  it  is not found there, then looks for a lesskey file called "_less" in any directory specified in the PATH environment variable.  On OS/2 sys-
tems, less looks for a lesskey file called "$HOME/less.ini", and if it is not found, then looks for a lesskey file called "less.ini"  in  any  directory
specified in the INIT environment variable, and if it not found there, then looks for a lesskey file called "less.ini" in any directory specified in the
PATH environment variable.  See the lesskey manual page for more details.

A system-wide lesskey file may also be set up to provide key bindings.  If a key is defined in both a local lesskey file and in  the  system-wide  file,
key bindings in the local file take precedence over those in the system-wide file.  If the environment variable LESSKEY_SYSTEM is set, less uses that as
the name of the system-wide lesskey file.  Otherwise, less looks in a standard place for the system-wide lesskey file: On Unix systems, the  system-wide
lesskey file is /usr/local/etc/sysless.  (However, if less was built with a different sysconf directory than /usr/local/etc, that directory is where the
sysless file is found.)  On MS-DOS and Windows systems, the system-wide lesskey file is c:\_sysless.  On OS/2 systems, the system-wide lesskey  file  is
c:\sysless.ini.

INPUT PREPROCESSOR
You  may  define an "input preprocessor" for less.  Before less opens a file, it first gives your input preprocessor a chance to modify the way the con-
tents of the file are displayed.  An input preprocessor is simply an executable program (or shell script), which writes the contents of the  file  to  a
different  file,  called  the  replacement file.  The contents of the replacement file are then displayed in place of the contents of the original file.
However, it will appear to the user as if the original file is opened; that is, less will display the original filename as the name of the current file.

An  input  preprocessor  receives  one command line argument, the original filename, as entered by the user.  It should create the replacement file, and
when finished, print the name of the replacement file to its standard output.  If the input preprocessor does not output a  replacement  filename,  less
uses the original file, as normal.  The input preprocessor is not called when viewing standard input.  To set up an input preprocessor, set the LESSOPEN
environment variable to a command line which will invoke your input preprocessor.  This command line should include one occurrence of the  string  "%s",
which will be replaced by the filename when the input preprocessor command is invoked.

When  less  closes  a  file  opened  in such a way, it will call another program, called the input postprocessor, which may perform any desired clean-up
action (such as deleting the replacement file created by LESSOPEN).  This program receives two command line arguments, the original filename as  entered
by  the  user,  and  the name of the replacement file.  To set up an input postprocessor, set the LESSCLOSE environment variable to a command line which
will invoke your input postprocessor.  It may include two occurrences of the string "%s"; the first is replaced with the original name of the  file  and
the second with the name of the replacement file, which was output by LESSOPEN.

For example, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let less view them directly:

lessopen.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -
if [ -s /tmp/less.$$ ]; then
echo /tmp/less.$$
else
rm -f /tmp/less.$$
fi
;;
esac

lessclose.sh:
#! /bin/sh
rm $2

To  use  these  scripts,  put  them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s".  More complex
LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on.

It is also possible to set up an input preprocessor to pipe the file data directly to less, rather than putting the data into a replacement file.   This
avoids  the need to decompress the entire file before starting to view it.  An input preprocessor that works this way is called an input pipe.  An input
pipe, instead of writing the name of a replacement file on its standard output, writes the entire contents of the replacement file on its standard  out-
put.  If the input pipe does not write any characters on its standard output, then there is no replacement file and less uses the original file, as nor-
mal.  To use an input pipe, make the first character in the LESSOPEN environment variable a vertical bar (|) to signify that the input  preprocessor  is
an input pipe.

For example, on many Unix systems, this script will work like the previous example scripts:

lesspipe.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -c $1  2>/dev/null
;;
esac

To  use  this  script, put it where it can be executed and set LESSOPEN="|lesspipe.sh %s".  When an input pipe is used, a LESSCLOSE postprocessor can be
used, but it is usually not necessary since there is no replacement file to clean up.  In this case, the replacement file name passed to  the  LESSCLOSE
postprocessor is "-".

NATIONAL CHARACTER SETS
There are three types of characters in the input file:

normal characters
can be displayed directly to the screen.

control characters
should not be displayed directly, but are expected to be found in ordinary text files (such as backspace and tab).

binary characters
should not be displayed directly and are not expected to be found in text files.

A  "character  set"  is simply a description of which characters are to be considered normal, control, and binary.  The LESSCHARSET environment variable
may be used to select a character set.  Possible values for LESSCHARSET are:

ascii  BS, TAB, NL, CR, and formfeed are control characters, all chars with values between 32 and 126 are normal, and all others are binary.

iso8859
Selects an ISO 8859 character set.  This is the same as ASCII, except characters between 160 and 255 are treated as normal characters.

latin1 Same as iso8859.

latin9 Same as iso8859.

dos    Selects a character set appropriate for MS-DOS.

ebcdic Selects an EBCDIC character set.

IBM-1047
Selects an EBCDIC character set used by OS/390 Unix Services.  This is the EBCDIC analogue of latin1.  You get similar results by setting  either
LESSCHARSET=IBM-1047 or LC_CTYPE=en_US in your environment.

koi8-r Selects a Russian character set.

next   Selects a character set appropriate for NeXT computers.

utf-8  Selects the UTF-8 encoding of the ISO 10646 character set.

windows
Selects a character set appropriate for Microsoft Windows (cp 1251).

In  special  cases, it may be desired to tailor less to use a character set other than the ones definable by LESSCHARSET.  In this case, the environment
variable LESSCHARDEF can be used to define a character set.  It should be set to a string where each character in the string represents one character in
the character set.  The character "." is used for a normal character, "c" for control, and "b" for binary.  A decimal number may be used for repetition.
For example, "bccc4b." would mean character 0 is binary, 1, 2 and 3 are control, 4, 5, 6 and 7 are binary, and 8 is normal.  All  characters  after  the
last  are  taken  to  be the same as the last, so characters 9 through 255 would be normal.  (This is an example, and does not necessarily represent any
real character set.)

This table shows the value of LESSCHARDEF which is equivalent to each of the possible values for LESSCHARSET:

ascii     8bcccbcc18b95.b
dos       8bcccbcc12bc5b95.b.
ebcdic    5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
IBM-1047  4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
191.b
iso8859   8bcccbcc18b95.33b.
koi8-r    8bcccbcc18b95.b128.
latin1    8bcccbcc18b95.33b.
next      8bcccbcc18b95.bb125.bb

If neither LESSCHARSET nor LESSCHARDEF is set, but any of the strings "UTF-8", "UTF8", "utf-8" or "utf8" is found in the LC_ALL, LC_TYPE or  LANG  envi-
ronment variables, then the default character set is utf-8.

If  that  string  is  not found, but your system supports the setlocale interface, less will use setlocale to determine the character set.  setlocale is
controlled by setting the LANG or LC_CTYPE environment variables.

Finally, if the setlocale interface is also not available, the default character set is latin1.

Control and binary characters are displayed in standout (reverse video).  Each such character is displayed in caret notation if possible  (e.g.  ^A  for
control-A).   Caret notation is used only if inverting the 0100 bit results in a normal printable character.  Otherwise, the character is displayed as a
hex number in angle brackets.  This format can be changed by setting the LESSBINFMT environment variable.  LESSBINFMT may begin with a "*" and one char-
acter to select the display attribute: "*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout, and "*n" is normal.  If LESSBINFMT does not
begin with a "*", normal attribute is assumed.  The remainder of LESSBINFMT is a string which may include one printf-style escape sequence (a % followed
by  x,  X,  o, d, etc.).  For example, if LESSBINFMT is "*u[%x]", binary characters are displayed in underlined hexadecimal surrounded by brackets.  The
default if no LESSBINFMT is specified is "*s<%X>".  The default if no LESSBINFMT is specified is "*s<%02X>".  Warning: the result of expanding the char-
acter via LESSBINFMT must be less than 31 characters.

When  the  character  set  is utf-8, the LESSUTFBINFMT environment variable acts similarly to LESSBINFMT but it applies to Unicode code points that were
successfully decoded but are unsuitable for display (e.g., unassigned code points).  Its default value is  "".   Note  that  LESSUTFBINFMT  and
LESSBINFMT  share  their  display attribute setting ("*x") so specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so its setting, if
any, will have priority.  Problematic octets in a UTF-8 file (octets of a truncated sequence, octets of a complete but non-shortest form sequence, ille-
gal octets, and stray trailing octets) are displayed individually using LESSBINFMT so as to facilitate diagnostic of how the UTF-8 file is ill-formed.

PROMPTS
The  -P  option  allows  you  to tailor the prompt to your preference.  The string given to the -P option replaces the specified prompt string.  Certain
characters in the string are interpreted specially.  The prompt mechanism is rather complicated to provide flexibility, but the ordinary user  need  not
understand the details of constructing personalized prompt strings.

A percent sign followed by a single character is expanded according to what the following character is:

%bX    Replaced  by  the  byte  offset into the current input file.  The b is followed by a single character (shown as X above) which specifies the line
whose byte offset is to be used.  If the character is a "t", the byte offset of the top line in the display is used, an "m" means use the  middle
line,  a  "b" means use the bottom line, a "B" means use the line just after the bottom line, and a "j" means use the "target" line, as specified
by the -j option.

%B     Replaced by the size of the current input file.

%c     Replaced by the column number of the text appearing in the first column of the screen.

%dX    Replaced by the page number of a line in the input file.  The line to be used is determined by the X, as with the %b option.

%D     Replaced by the number of pages in the input file, or equivalently, the page number of the last line in the input file.

%E     Replaced by the name of the editor (from the VISUAL environment variable, or the EDITOR environment variable if VISUAL is not defined).  See  the
discussion of the LESSEDIT feature below.
%f     Replaced by the name of the current input file.

%i     Replaced by the index of the current file in the list of input files.

%lX    Replaced by the line number of a line in the input file.  The line to be used is determined by the X, as with the %b option.

%L     Replaced by the line number of the last line in the input file.

%m     Replaced by the total number of input files.

%pX    Replaced by the percent into the current input file, based on byte offsets.  The line used is determined by the X as with the %b option.

%PX    Replaced by the percent into the current input file, based on line numbers.  The line used is determined by the X as with the %b option.

%s     Same as %B.

%t     Causes any trailing spaces to be removed.  Usually used at the end of the string, but may appear anywhere.

%x     Replaced by the name of the next input file in the list.

If any item is unknown (for example, the file size if input is a pipe), a question mark is printed instead.

The  format  of  the  prompt  string  can be changed depending on certain conditions.  A question mark followed by a single character acts like an "IF":
depending on the following character, a condition is evaluated.  If the condition is true, any characters following  the  question  mark  and  condition
character,  up  to  a  period,  are included in the prompt.  If the condition is false, such characters are not included.  A colon appearing between the
question mark and the period can be used to establish an "ELSE": any characters between the colon and the period are included in the string if and  only
if the IF condition is false.  Condition characters (which follow a question mark) may be:

?a     True if any characters have been included in the prompt so far.

?bX    True if the byte offset of the specified line is known.

?B     True if the size of current input file is known.

?c     True if the text is horizontally shifted (%c is not zero).

?dX    True if the page number of the specified line is known.

?e     True if at end-of-file.

?f     True if there is an input filename (that is, if input is not a pipe).

?lX    True if the line number of the specified line is known.

?L     True if the line number of the last line in the file is known.

?m     True if there is more than one input file.

?n     True if this is the first prompt in a new input file.

?pX    True if the percent into the current input file, based on byte offsets, of the specified line is known.
?PX    True if the percent into the current input file, based on line numbers, of the specified line is known.

?s     Same as "?B".

?x     True if there is a next input file (that is, if the current input file is not the last one).

Any  characters other than the special ones (question mark, colon, period, percent, and backslash) become literally part of the prompt.  Any of the spe-
cial characters may be included in the prompt literally by preceding it with a backslash.

Some examples:

?f%f:Standard input.

This prompt prints the filename, if known; otherwise the string "Standard input".

?f%f .?ltLine %lt:?pt%pt\%:?btByte %bt:-...

This prompt would print the filename, if known.  The filename is followed by the line number, if known, otherwise the percent if  known,  otherwise  the
byte  offset if known.  Otherwise, a dash is printed.  Notice how each question mark has a matching period, and how the % after the %pt is included lit-
erally by escaping it with a backslash.

?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x..%t

This prints the filename if this is the first prompt in a file, followed by the "file N of N" message if there is more than one input file.  Then, if we
are  at  end-of-file, the string "(END)" is printed followed by the name of the next file, if there is one.  Finally, any trailing spaces are truncated.
This is the default prompt.  For reference, here are the defaults for the other two prompts (-m and -M respectively).  Each is  broken  into  two  lines
here for readability only.

?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x.:
?pB%pB\%:byte %bB?s/%s...%t

?f%f .?n?m(file %i of %m) ..?ltlines %lt-%lb?L/%L. :
byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t

And here is the default message produced by the = command:

?f%f .?m(file %i of %m) .?ltlines %lt-%lb?L/%L. .
byte %bB?s/%s. ?e(END) :?pB%pB\%..%t

The  prompt  expansion  features are also used for another purpose: if an environment variable LESSEDIT is defined, it is used as the command to be exe-
cuted when the v command is invoked.  The LESSEDIT string is expanded in the same way as the prompt strings.  The default value for LESSEDIT is:

%E ?lm+%lm. %f

Note that this expands to the editor name, followed by a + and the line number, followed by  the  file  name.   If  your  editor  does  not  accept  the
"+linenumber" syntax, or has other differences in invocation syntax, the LESSEDIT variable can be changed to modify this default.

SECURITY
When the environment variable LESSSECURE is set to 1, less runs in a "secure" mode.  This means these features are disabled:
!      the shell command

|      the pipe command

:e     the examine command.

v      the editing command

s  -o  log files

-k     use of lesskey files

-t     use of tags files

metacharacters in filenames, such as *

filename completion (TAB, ^L)

Less can also be compiled to be permanently in "secure" mode.

ENVIRONMENT VARIABLES
Environment  variables  may  be  specified either in the system environment as usual, or in a lesskey (1) file.  If environment variables are defined in
more than one place, variables defined in a local lesskey file take precedence over variables defined in the system environment, which  take  precedence
over variables defined in the system-wide lesskey file.

COLUMNS
Sets  the  number of columns on the screen.  Takes precedence over the number of columns specified by the TERM variable.  (But if you have a win-
dowing system which supports TIOCGWINSZ or WIOCGETD, the window systemâs idea of the screen size takes precedence  over  the  LINES  and  COLUMNS
environment variables.)

EDITOR The name of the editor (used for the v command).

HOME   Name of the userâs home directory (used to find a lesskey file on Unix and OS/2 systems).

HOMEDRIVE, HOMEPATH
Concatenation  of the HOMEDRIVE and HOMEPATH environment variables is the name of the userâs home directory if the HOME variable is not set (only
in the Windows version).

INIT   Name of the userâs init directory (used to find a lesskey file on OS/2 systems).

LANG   Language for determining the character set.

LC_CTYPE
Language for determining the character set.

LESS   Options which are passed to less automatically.

LESSANSIENDCHARS
Characters which may end an ANSI color escape sequence (default "m").

LESSANSIMIDCHARS
Characters which may appear between the ESC character and the end character in an ANSI color escape sequence (default  "0123456789;[?!"â#%()*+ ".

LESSBINFMT
Format for displaying non-printable, non-control characters.

LESSCHARDEF
Defines a character set.

LESSCHARSET
Selects a predefined character set.

LESSCLOSE
Command line to invoke the (optional) input-postprocessor.

LESSECHO
Name  of  the  lessecho  program (default "lessecho").  The lessecho program is needed to expand metacharacters, such as * and ?, in filenames on
Unix systems.

LESSEDIT
Editor prototype string (used for the v command).  See discussion under PROMPTS.

LESSGLOBALTAGS
Name of the command used by the -t option to find global tags.  Normally should be set to "global" if your system has the global (1) command.  If
not set, global tags are not used.

LESSHISTFILE
Name  of  the history file used to remember search commands and shell commands between invocations of less.  If set to "-", a history file is not
used.   The  default  is  "$HOME/.lesshst"  on  Unix  systems,  "$HOME/_lesshst"  on  DOS  and  Windows  systems,   or   "$HOME/lesshst.ini"   or
"$INIT/lesshst.ini" on OS/2 systems.

LESSHISTSIZE
The maximum number of commands to save in the history file.  The default is 100.

LESSKEY
Name of the default lesskey(1) file.

LESSKEY_SYSTEM
Name of the default system-wide lesskey(1) file.

LESSMETACHARS
List of characters which are considered "metacharacters" by the shell.

LESSMETAESCAPE
Prefix  which  less will add before each metacharacter in a command sent to the shell.  If LESSMETAESCAPE is an empty string, commands containing
metacharacters will not be passed to the shell.

LESSOPEN
Command line to invoke the (optional) input-preprocessor.

LESSSECURE
Runs less in "secure" mode.  See discussion under SECURITY.

LESSSEPARATOR
String to be appended to a directory name in filename completion.

LESSUTFBINFMT
Format for displaying non-printable Unicode code points.

LINES  Sets the number of lines on the screen.  Takes precedence over the number of lines specified by the TERM variable.  (But if you have a  windowing
system which supports TIOCGWINSZ or WIOCGETD, the window systemâs idea of the screen size takes precedence over the LINES and COLUMNS environment
variables.)

PATH   Userâs search path (used to find a lesskey file on MS-DOS and OS/2 systems).

SHELL  The shell used to execute the ! command, as well as to expand filenames.

TERM   The type of terminal on which less is being run.

VISUAL The name of the editor (used for the v command).

SEE ALSO
lesskey(1)

WARNINGS
The = command and prompts (unless changed by -P) report the line numbers of the lines at the top and bottom of the screen, but the byte and  percent  of
the line after the one at the bottom of the screen.

If  the :e command is used to name more than one file, and one of the named files has been viewed previously, the new files may be entered into the list
in an unexpected order.

On certain older terminals (the so-called "magic cookie" terminals), search highlighting will cause an erroneous display.   On  such  terminals,  search
highlighting is disabled by default to avoid possible problems.

In  certain  cases,  when  search  highlighting  is enabled and a search pattern begins with a ^, more text than the matching string may be highlighted.
(This problem does not occur when less is compiled to use the POSIX regular expression package.)

When viewing text containing ANSI color escape sequences using the -R option, searching will not find  text  containing  an  embedded  escape  sequence.
Also, search highlighting may change the color of some of the text which follows the highlighted text.

On  some systems, setlocale claims that ASCII characters 0 thru 31 are control characters rather than binary characters.  This causes less to treat some
binary files as ordinary, non-binary files.  To workaround this problem, set the environment variable LESSCHARSET to "ascii" (or whatever character  set
is appropriate).