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less Linux Command Reference Example: less command man page

LESS

NAME

less - opposite of more

SYNOPSIS

less -?
less --help
less -V
less --version
less [-[+]aBcCdeEfFgGiIJLmMnNqQrRsSuUVwWX~]
[-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.)

DESCRIPTION

Less is a program similar to more (1), but which allows backward move-
ment 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.

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 spe-
cial 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 dis-
played, 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 com-
mands. 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 com-
mands.

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. (Warn-
ing: 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 spec-
ify 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 brack-
ets.

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

ESC-^F Followed by two characters, acts like {, but uses the two char-
acters 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 char-
acters 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.

' (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 respec-
tively. Marks are preserved when a new file is examined, so
the ' 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 expres-
sion, as recognized by ed. 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 cur-
rent screen, but don't move to the first match (KEEP
current position).

^R Don't 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 pat-
tern. If the previous search was modified by ^N, the search is
made for the N-th line NOT containing the pattern. If the pre-
vious 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 cross-
ing 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 high-
lighting back on. Any search command will also turn highlight-
ing back on. (Highlighting can also be disabled by toggling
the -G option; in that case search commands do not turn high-
lighting 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. Simi-
larly, 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 exam-
ined. If the filename contains one or more spaces, the entire
filename 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 literal-
ization 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 com-
mand 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 num-
ber 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 describing 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 setting. (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 let-
ters, 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 normal
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 indi-
cate beginning or end of file respectively. 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 don't need the quotes, but you should replace any per-
cent 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 question 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 allo-
cated 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 capabil-
ity, such as the ability to clear the screen or scroll back-
ward. 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 high-
light only the particular 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 lower-
case 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.

-L or --no-lessopen
Ignore the LESSOPEN environment variable (see the INPUT PREPRO-
CESSOR 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 simply 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 occur-
rence 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 beginning 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". Warn-
ing: 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, var-
ious display problems may result, such as long lines being
split in the wrong place.

-R or --RAW-CONTROL-CHARS
Like -r, but tries to keep track of the screen appearance where
possible. This works only if the input consists of normal text
and possibly some ANSI "color" escape sequences, which are
sequences of the form:

ESC [ ... m

where the "..." is zero or more characters other than "m". For
the purpose of keeping track of screen appearance, all control
characters and all 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 char-
acters which can end a color escape sequence.

-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 cur-
rent directory called "tags", which was previously built by
ctags (1) or an equivalent command. If the environment vari-
able LESSGLOBALTAGS is set, it is taken to be the name of a
command compatible with global (1), and that command is exe-
cuted to find the tag. (See http://www.gnu.org/soft-
ware/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 print-
able 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 spe-
cially: the underlined text is displayed using the terminal's
hardware underlining capability. Also, backspaces which appear
between two identical characters are treated specially: the
overstruck text is printed using the terminal's hardware bold-
face capability. Other backspaces are deleted, along with the
preceding 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 under-
lined 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 com-
mand. The highlight is removed at the next command which
causes movement. The entire line is highlighted, unless the -J
option is in effect, in which case only the status column is
highlighted.

-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 con-
tinue 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 deinitializa-
tion 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 key-
pad 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 indi-
cates 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 pre-
ceded by the open quote character and followed by the close
quote character. 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 horizon-
tally 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 argu-
ments. Any arguments following this are interpreted as file-
names. This can be useful 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 com-
mands have an alternate form in [ brackets ] which can be used if a
key does not exist on a particular 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 enter-
ing 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 cur-
sor 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 match-
ing 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 environ-
ment 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 contents of the file are displayed. An input preprocessor is
simply an executable program (or shell script), which writes the con-
tents 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 replace-
ment filename, less uses the original file, as normal. The input pre-
processor 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 replace-
ment file. To set up an input postprocessor, set the LESSCLOSE envi-
ronment variable to a command line which will invoke your input post-
processor. 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 -c $1 >/tmp/less.$$ 2>/dev/null
if [ -s /tmp/less.$$ ]; 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 output. 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 normal. 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 pre-
vious 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 environ-
ment 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.

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 the string "UTF-8"
is found in the LC_ALL, LC_TYPE or LANG environment 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 possi-
ble (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. LESS-
BINFMT may begin with a "*" and one character 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 % fol-
lowed 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>".

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 person-
alized 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 dis-
play 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 equiva-
lently, 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 evalu-
ated. 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 special 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 "Stan-
dard input".

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

This prompt would print the filename, if known. The filename is fol-
lowed 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 literally 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, fol-
lowed 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 ref-
erence, 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 executed 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 invoca-
tion 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 environ-
ment 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 windowing system which supports TIOCGWINSZ
or WIOCGETD, the window system's 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 user's home directory (used to find a lesskey file
on Unix and OS/2 systems).

HOMEDRIVE, HOMEPATH
Concatenation of the HOMEDRIVE and HOMEPATH environment vari-
ables is the name of the user's home directory if the HOME
variable is not set (only in the Windows version).

INIT Name of the user's 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 are assumed to end an ANSI color escape
sequence (default "m").

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 lesse-
cho program is needed to expand metacharacters, such as * and
?, in filenames on Unix systems.

LESSEDIT
Editor prototype string (used for the v command). See discus-
sion 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.

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 com-
mand 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 comple-
tion.

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 system's idea of the screen size takes
precedence over the LINES and COLUMNS environment variables.)

PATH User's 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)

by Margaret Walker on Sun, 07/18/2010 - 00:00

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