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LESS(1) USER COMMANDS LESS(1)
NAME
less - opposite of more
SYNOPSIS
less -?
less -V
less [-[+]aBcCdeEfgGiImMnNqQrsSuUVwX]
[-b _b_u_f_s] [-h _l_i_n_e_s] [-j _l_i_n_e] [-k _k_e_y_f_i_l_e]
[-{oO} _l_o_g_f_i_l_e] [-p _p_a_t_t_e_r_n] [-P _p_r_o_m_p_t] [-t _t_a_g]
[-T _t_a_g_s_f_i_l_e] [-x _t_a_b] [-y _l_i_n_e_s] [-[z] _l_i_n_e_s]
[+[+]_c_m_d] [--] [_f_i_l_e_n_a_m_e]...
DESCRIPTION
_L_e_s_s is a program similar to _m_o_r_e (1), but which allows
backward movement in the file as well as forward movement.
Also, _l_e_s_s does not have to read the entire input file
before starting, so with large input files it starts up fas-
ter than text editors like _v_i (1). _L_e_s_s uses termcap (or
terminfo on some systems), so it can run on a variety of
terminals. There is even limited support for hardcopy ter-
minals. (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 _m_o_r_e and _v_i. Commands may be pre-
ceded 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 for-
get 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
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LESS(1) USER COMMANDS LESS(1)
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-[
Scroll horizontally left N characters, default 8. This
behaves best if you also set the -S option (chop
lines).
ESC-]
Scroll horizontally right N characters, default 8.
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.)
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LESS(1) USER COMMANDS LESS(1)
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, respec-
tively. 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, respec-
tively. For example, "ESC ^B < >" could be used to go
backward to the < which matches the > in the bottom
displayed line.
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LESS(1) USER COMMANDS LESS(1)
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" move-
ment 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
' 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 regu-
lar expression, as recognized by _e_d. 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 begin-
ning 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 find-
ing 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 set-
tings of the -a or -j options.
^K Highlight any text which matches the pattern on
the current 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 contain-
ing the pattern. The search starts at the line immedi-
ately before the top line displayed.
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LESS(1) USER COMMANDS LESS(1)
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 pre-
vious 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
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LESS(1) USER COMMANDS LESS(1)
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.
^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.
= 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
below), this will change the setting of that option and
print a message describing the new setting. 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
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LESS(1) USER COMMANDS LESS(1)
be entered after the option letter. If no new value is
entered, a message describing the current setting is
printed and nothing is changed.
-+ Followed by one of the command line option letters (see
below), this will reset the option to its default set-
ting 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.
-- Followed by one of the command line option letters (see
below), this will reset the option to the "opposite" of
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
numeric or string-valued options.
_ (Underscore.) Followed by one of the command line
option letters (see below), this will print a message
describing the current setting of that option. The
setting of the option is not changed.
+cmd Causes the specified cmd to be executed each time a new
file is examined. For example, +G causes _l_e_s_s to ini-
tially display each file starting at the end rather
than the beginning.
V Prints the version number of _l_e_s_s being run.
q or Q or :q or :Q or ZZ
Exits _l_e_s_s.
The following four commands may or may not be valid, depend-
ing on your particular installation.
v Invokes an editor to edit the current file being
viewed. The editor is taken from the environment vari-
able VISUAL if defined, or EDITOR if VISUAL is not
defined, or defaults to "vi" if neither VISUAL nor EDI-
TOR 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 per-
cent 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
Last change: Version 321: 18 Jul 96 7
LESS(1) USER COMMANDS LESS(1)
normal command processor.
| <m> shell-command
<m> 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.
<m> may also be ^ or $ to indicate beginning or end of
file respectively. If <m> 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 _l_e_s_s is running, via the "-" command.
Options are also taken from the environment variable "LESS".
For example, to avoid typing "less -options ..." each time
_l_e_s_s is invoked, you might tell _c_s_h:
setenv LESS "-options"
or if you use _s_h:
LESS="-options"; export LESS
The environment variable is parsed before the command line,
so command line options override the LESS environment vari-
able. If an option appears in the LESS variable, it can be
reset to its default on the command line by beginning the
command line option with "-+".
For options like -P which take a following string, a dollar
sign ($) may be used to signal the end of the string.
-? This option displays a summary of the commands accepted
by _l_e_s_s (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 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).
-b_n Specifies the number of buffers _l_e_s_s will use for each
file. Buffers are 1K, and by default 10 buffers are
used for each file (except if the file is a pipe; see
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the -B option). The number _n specifies a different
number of buffers to use.
-B 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 dis-
ables this automatic allocation of buffers for pipes,
so that only the number of buffers specified by the -b
option are used. 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 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 The -C option is like -c, but the screen is cleared
before it is repainted.
-d 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 oth-
erwise change the behavior of _l_e_s_s on a dumb terminal).
-Dx_c_o_l_o_r
[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. _c_o_l_o_r 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 Causes _l_e_s_s to automatically exit the second time it
reaches end-of-file. By default, the only way to exit
_l_e_s_s is via the "q" command.
-E Causes _l_e_s_s to automatically exit the first time it
reaches end-of-file.
-f 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, _l_e_s_s will refuse to open non-
regular files.
-g Normally, _l_e_s_s will highlight ALL strings which match
the last search command. The -g option changes this
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behavior to highlight only the particular string which
was found by the last search command. This can cause
_l_e_s_s to run somewhat faster than the default.
-G The -G option suppresses all highlighting of strings
found by search commands.
-h_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 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 upper-
case letters, then that search does not ignore case.
-I Like -i, but searches ignore case even if the pattern
contains uppercase letters.
-j_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 bot-
tom 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.
-k_f_i_l_e_n_a_m_e
Causes _l_e_s_s to open and interpret the named file as a
_l_e_s_s_k_e_y (1) file. Multiple -k options may be speci-
fied. If the LESSKEY environment variable is set, or
if a lesskey file is found in a standard place (see KEY
BINDINGS), it is also used as a _l_e_s_s_k_e_y file.
-m Causes _l_e_s_s to prompt verbosely (like _m_o_r_e), with the
percent into the file. By default, _l_e_s_s prompts with a
colon.
-M Causes _l_e_s_s to prompt even more verbosely than _m_o_r_e.
-n Suppresses line numbers. The default (to use line
numbers) may cause _l_e_s_s to run more slowly in some
cases, especially with a very large input file.
Last change: Version 321: 18 Jul 96 10
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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 Causes a line number to be displayed at the beginning
of each line in the display.
-o_f_i_l_e_n_a_m_e
Causes _l_e_s_s 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, _l_e_s_s will ask for confirmation before overwrit-
ing it.
-O_f_i_l_e_n_a_m_e
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 _l_e_s_s 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 _l_e_s_s.
-p_p_a_t_t_e_r_n
The -p option on the command line is equivalent to
specifying +/_p_a_t_t_e_r_n; that is, it tells _l_e_s_s to start
at the first occurrence of _p_a_t_t_e_r_n in the file.
-P_p_r_o_m_p_t
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 _l_e_s_s 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 = com-
mand. All prompt strings consist of a sequence of
letters and special escape sequences. See the section
on PROMPTS for more details.
-q 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
Last change: Version 321: 18 Jul 96 11
LESS(1) USER COMMANDS LESS(1)
errors, such as typing an invalid character. The
default is to ring the terminal bell in all such cases.
-Q Causes totally "quiet" operation: the terminal bell is
never rung.
-r 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, _l_e_s_s 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.
-s Causes consecutive blank lines to be squeezed into a
single blank line. This is useful when viewing _n_r_o_f_f
output.
-S Causes lines longer than the screen width to be chopped
rather than folded. That is, the remainder of a long
line is simply discarded. The default is to fold long
lines; that is, display the remainder on the next line.
-t_t_a_g
The -t option, followed immediately by a TAG, will edit
the file containing that tag. For this to work, there
must be a file called "tags" in the current directory,
which was previously built by the _c_t_a_g_s (1) command.
This option may also be specified from within _l_e_s_s
(using the - command) as a way of examining a new file.
The command ":t" is equivalent to specifying -t from
within _l_e_s_s.
-T_t_a_g_s_f_i_l_e
Specifies a tags file to be used instead of "tags".
-u 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 Causes backspaces, tabs and carriage returns to be
treated as control characters; that is, they are han-
dled 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 terminal's hardware underlining capability.
Also, backspaces which appear between two identical
characters are treated specially: the overstruck text
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LESS(1) USER COMMANDS LESS(1)
is printed using the terminal's hardware boldface capa-
bility. Other backspaces are deleted, along with the
preceding character. Carriage returns immediately fol-
lowed 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 nei-
ther -u nor -U is in effect.
-V Displays the version number of _l_e_s_s.
-w Causes blank lines to be used to represent lines past
the end of the file. By default, a tilde character (~)
is used.
-x_n Sets tab stops every _n positions. The default for _n is
8.
-X Disables sending the termcap initialization and deini-
tialization strings to the terminal. This is sometimes
desirable if the deinitialization string does something
unnecessary, like clearing the screen.
-y_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
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 _m_o_r_e. 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.
-- A command line argument of "--" marks the end of option
arguments. Any arguments following this are inter-
preted as filenames. 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
_l_e_s_s. For example, +G tells _l_e_s_s 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, +<number> acts like +<number>g; that
is, it starts the display at the specified line number
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LESS(1) USER COMMANDS LESS(1)
(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
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 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 can-
cel 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 ]
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(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 cur-
sor. 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.
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 cur-
sor. If it matches more than one filename, all matches
are entered into the command line (if they fit).
^U (Unix) 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 _l_e_s_s commands by using the program
_l_e_s_s_k_e_y (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 _l_e_s_s_k_e_y to change the line-editing keys
(see LINE EDITING), and to set environment variables. If
the environment variable LESSKEY is set, _l_e_s_s uses that as
the name of the lesskey file. Otherwise, _l_e_s_s looks in a
standard place for the lesskey file: On Unix systems, _l_e_s_s
looks for a lesskey file called "$HOME/.less". On MS-DOS
systems, _l_e_s_s looks for a lesskey file called "$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 systems, _l_e_s_s 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 _l_e_s_s_k_e_y manual page for more
details.
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INPUT PREPROCESSOR
You may define an "input preprocessor" for _l_e_s_s. Before _l_e_s_s
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 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, _l_e_s_s 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,
_l_e_s_s uses the original file, as normal. The input prepro-
cessor 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 _l_e_s_s 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
_l_e_s_s 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
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;;
esac
lessclose.sh:
#! /bin/sh
rm $2
To use these scripts, put them both where they can be exe-
cuted 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 _l_e_s_s, 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 _l_e_s_s uses the original
file, as normal. To use an input pipe, make the first char-
acter 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 LESS-
CLOSE 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
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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 charac-
ters 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
The default character set. BS, TAB, NL, CR, and
formfeed are control characters, all chars with values
between 127 and 255 are binary, and all others are nor-
mal.
latin1
Selects the ISO 8859/1 character set. latin-1 is the
same as ASCII, except characters between 161 and 255
are treated as normal characters.
dos Selects a character set appropriate for MS-DOS.
koi8-r
Selects a Russian character set.
next Selects a character set appropriate for NeXT computers.
In special cases, it may be desired to tailor _l_e_s_s 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
latin1 8bcccbcc18b95.33b.
dos 8bcccbcc12bc5b95.b.
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koi8-r 8bcccbcc18b95.b128.
next 8bcccbcc18b95.bb125.bb
If neither LESSCHARSET nor LESSCHARDEF is set, but your sys-
tem supports the _s_e_t_l_o_c_a_l_e interface, _l_e_s_s will use setlo-
cale to determine the character set. setlocale is con-
trolled by setting the LANG or LC_CTYPE environment vari-
ables.
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 nota-
tion 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 vari-
able. LESSBINFMT 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 nor-
mal. If LESSBINFMT does not begin with a "*", normal attri-
bute 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 hex-
adecimal surrounded by brackets. The default if no LESS-
BINFMT is specified is "*d<%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 personalized
prompt strings.
A percent sign followed by a single character is expanded
according to what the following character is:
%b_X 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 speci-
fied by the -j option.
%B Replaced by the size of the current input file.
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%E Replaced by the name of the editor (from the VISUAL
environment variable, or the EDITOR environment vari-
able 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.
%l_X 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.
%p_X Replaced by the percent into the current input file.
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 condi-
tion 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.
?b_X True if the byte offset of the specified line is known.
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?B True if the size of current input file 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).
?l_X 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.
?p_X True if the percent into the current input file 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 "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 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, 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
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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 rea-
dability 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) ..?ltline %lt?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) .?ltline %lt?L/%L. .
byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
The prompt expansion features are also used for another pur-
pose: 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 invocation syntax, the LESSEDIT vari-
able can be changed to modify this default.
SECURITY
When the environment variable LESSSECURE is set to 1, _l_e_s_s
runs in a "secure" mode. This means these features are dis-
abled:
! 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
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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 _l_e_s_s_k_e_y (1) file.
COLUMNS
Sets the number of columns on the screen. Takes pre-
cedence 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 less-
key file on Unix systems).
INIT Name of the user's init directory (used to find a less-
key 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 _l_e_s_s automatically.
LESSBINFMT
Format for displaying non-printable, non-control char-
acters.
LESSCHARDEF
Defines a character set.
LESSCHARSET
Selects a predefined character set.
LESSCLOSE
Command line to invoke the (optional) input-
postprocessor.
LESSEDIT
Editor prototype string (used for the v command). See
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discussion under PROMPTS.
LESSKEY
Name of the default lesskey(1) file.
LESSOPEN
Command line to invoke the (optional) input-
preprocessor.
LESSSECURE
Runs less in "secure" mode. See discussion under SECU-
RITY.
LINES
Sets the number of lines on the screen. Takes pre-
cedence over the number of lines specified by the TERM
variable.
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 _l_e_s_s 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 number of the line at the top of the screen, but the
byte and percent of the line 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.
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On some systems, _s_e_t_l_o_c_a_l_e claims that characters 0 thru 31
are control characters rather than binary characters. This
causes _l_e_s_s to treat some binary files as ordinary, non-
binary files. To workaround this problem, set the environ-
ment variable LESSCHARSET to "ascii" (or whatever character
set is appropriate).
COPYRIGHT
Copyright (c) 1984,1985,1989,1994,1995,1996 Mark Nudelman
Comments to: markn@3do.com
Last change: Version 321: 18 Jul 96 25
