Linux文本处理指令less-man帮助手册
LESS(1) General Commands Manual LESS(1)
NAME
less - opposite of more
SYNOPSIS
less -?
less --help
less -V
less --version
less [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-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 movement in the file
as well as forward movement. Also, less does not have to read the entire input file
before starting, so with large input files it starts up faster than text editors like
vi(1). Less uses termcap (or terminfo on some systems), so it can run on a variety
of terminals. There is even limited support for hardcopy terminals. (On a hardcopy
terminal, lines which should be printed at the top of the screen are prefixed with a
caret.)
Commands are based on both more and vi. Commands may be preceded by a decimal num‐
ber, called N in the descriptions below. The number is used by some commands, as in‐
dicated.
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 com‐
mands, 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.
ENTER or RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines are displayed, even if
N is more than the screen size.
d or ^D
Scroll forward N lines, default one half of the screen size. If N is speci‐
fied, 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 speci‐
fied, it becomes the new default for subsequent d and u commands.
J Like j, but continues to scroll beyond the end of the file.
K or Y Like k, but continues to scroll beyond the beginning of the file.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default half the screen width (see the
-# option). If a number N is specified, it becomes the default for future
RIGHTARROW and LEFTARROW commands. While the text is scrolled, it acts as
though the -S option (chop lines) were in effect.
ESC-( or LEFTARROW
Scroll horizontally left N characters, default half the screen width (see the
-# option). If a number N is specified, it becomes the default for future
RIGHTARROW and LEFTARROW commands.
ESC-} or ^RIGHTARROW
Scroll horizontally right to show the end of the longest displayed line.
ESC-{ or ^LEFTARROW
Scroll horizontally left back to the first column.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input. That is, reload the cur‐
rent file. 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. Nor‐
mally 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.) To stop waiting for more
data, enter the interrupt character (usually ^C). On some systems you can
also use ^X.
ESC-F Like F, but as soon as a line is found which matches the last search pattern,
the terminal bell is rung and forward scrolling stops.
g or < or ESC-<
Go to line N in the file, default 1 (beginning of file). (Warning: this may
be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the file. (Warning: this may be
slow if N is large, or if N is not specified and standard input, rather than a
file, is being read.)
ESC-G Same as G, except if no number N is specified and the input is standard input,
goes to the last line which is currently buffered.
p or % Go to a position N percent into the file. N should be between 0 and 100, and
may contain a decimal point.
P Go to the line containing byte offset N in the file.
{ 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 spec‐
ify the N-th bracket on the line.
( Like {, but applies to parentheses rather than curly brackets.
) Like }, but applies to parentheses rather than curly brackets.
[ Like {, but applies to square brackets rather than curly brackets.
] Like }, but applies to square brackets rather than curly brackets.
ESC-^F Followed by two characters, acts like {, but uses the two characters as open
and close brackets, respectively. For example, "ESC ^F < >" could be used to
go forward to the > which matches the < in the top displayed line.
ESC-^B Followed by two characters, acts like }, but uses the two characters as open
and close brackets, respectively. For example, "ESC ^B < >" could be used to
go backward to the < which matches the > in the bottom displayed line.
m Followed by any lowercase or uppercase letter, marks the first displayed line
with that letter. If the status column is enabled via the -J option, the sta‐
tus column shows the marked line.
M Acts like m, except the last displayed line is marked rather than the first
displayed line.
' (Single quote.) Followed by any lowercase or uppercase 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 com‐
mand 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.
ESC-m Followed by any lowercase or uppercase letter, clears the mark identified by
that letter.
/pattern
Search forward in the file for the N-th line containing the pattern. N de‐
faults to 1. The pattern is a regular expression, as recognized by the regu‐
lar expression library supplied by your system. The search starts at the
first line displayed (but see the -a and -j options, which change this).
Certain characters are special if entered at the beginning of the pattern;
they modify the type of search rather than become part of the pattern:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search reaches the END of the
current file without finding a match, the search continues in the next
file in the command line list.
^F or @
Begin the search at the first line of the FIRST file in the command
line list, regardless of what is currently displayed on the screen or
the settings of the -a or -j options.
^K Highlight any text which matches the pattern on the current screen, but
don't move to the first match (KEEP current position).
^R Don't interpret regular expression metacharacters; that is, do a simple
textual comparison.
^W WRAP around the current file. That is, if the search reaches the end
of the current file without finding a match, the search continues from
the first line of the current file up to the line where it started.
?pattern
Search backward in the file for the N-th line containing the pattern. The
search starts at the last line displayed (but see the -a and -j options, which
change this).
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.
^W WRAP around the current file. That is, if the search reaches the be‐
ginning of the current file without finding a match, the search contin‐
ues from the last line of the current file up to the line where it
started.
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 bound‐
aries.
ESC-u Undo search highlighting. Turn off highlighting of strings matching the cur‐
rent search pattern. If highlighting is already off because of a previous
ESC-u command, turn highlighting back on. Any search command will also turn
highlighting back on. (Highlighting can also be disabled by toggling the -G
option; in that case search commands do not turn highlighting back on.)
ESC-U Like ESC-u but also clears the saved search pattern. If the status column is
enabled via the -J option, this clears all search matches marked in the status
column.
&pattern
Display only lines which match the pattern; lines which do not match the pat‐
tern are not displayed. If pattern is empty (if you type & immediately fol‐
lowed by ENTER), any filtering is turned off, and all lines are displayed.
While filtering is in effect, an ampersand is displayed at the beginning of
the prompt, as a reminder that some lines in the file may be hidden. Multiple
& commands may be entered, in which case only lines which match all of the
patterns will be displayed.
Certain characters are special as in the / command:
^N or !
Display only lines which do NOT match the pattern.
^R Don't interpret regular expression metacharacters; that is, do a simple
textual comparison.
: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-ex‐
amined. 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 ex‐
amined file. However, two consecutive percent signs are simply replaced with
a single percent sign. This allows you to enter a filename that contains a
percent sign in the name. Similarly, two consecutive pound signs are replaced
with a single pound sign. The filename is inserted into the command line list
of files so that it can be seen by subsequent :n and :p commands. If the
filename consists of several files, they are all inserted into the list of
files and the first one is examined. If the filename contains one or more
spaces, the entire 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 literalization charac‐
ter. 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 speci‐
fied, 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 possi‐
ble, 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 set‐
ting 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 en‐
tered, 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 ENTER or 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 letters, this will
print a message describing the current setting of that option. The setting of
the option is not changed.
__ (Double underscore.) Like the _ (underscore) command, but takes a long option
name rather than a single option letter. You must press ENTER or 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 in‐
stallation.
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 re‐
placed 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 proces‐
sor.
| <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 posi‐
tion marked by the letter and the current screen. The entire current screen
is included, regardless of whether the marked position is before or after the
current screen. <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 or‐
dinary 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 ab‐
breviated 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 percent signs in the
options string by double percent signs.
The environment variable is parsed before the command line, so command line options
override the LESS environment variable. If an option appears in the LESS variable,
it can be reset to its default value on the command line by beginning the command
line option with "-+".
Some options like -k or -D require a string to follow the option letter. The string
for that option is considered to end when a dollar sign ($) is found. For example,
you can set two -D options on MS-DOS like this:
LESS="Dn9.1$Ds4.1"
If the --use-backslash option appears earlier in the options, then a dollar sign or
backslash may be included literally in an option string by preceding it with a back‐
slash. If the --use-backslash option is not in effect, then backslashes are not
treated specially, and there is no way to include a dollar sign in the option string.
-? 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
By default, forward searches start at the top of the displayed screen and
backwards searches start at the bottom of the displayed screen (except for re‐
peated searches invoked by the n or N commands, which start after or before
the "target" line respectively; see the -j option for more about the target
line). The -a option causes forward searches to instead start at the bottom
of the screen and backward searches to start at the top of the screen, thus
skipping all lines displayed on the screen.
-A or --SEARCH-SKIP-SCREEN
Causes all forward searches (not just non-repeated searches) to start just af‐
ter the target line, and all backward searches to start just before the target
line. Thus, forward searches will skip part of the displayed screen (from the
first line up to and including the target line). Similarly backwards searches
will skip the displayed screen from the last line up to and including the tar‐
get line. This was the default behavior in less versions prior to 441.
-bn or --buffers=n
Specifies the amount of buffer space less will use for each file, in units of
kilobytes (1024 bytes). By default 64 KB 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 can be read into
memory.
-B or --auto-buffers
By default, when data is read from a pipe, buffers are allocated automatically
as needed. If a large amount of data is read from the pipe, this can cause a
large amount of memory to be allocated. The -B option disables this automatic
allocation of buffers for pipes, so that only 64 KB (or the amount of space
specified by the -b option) is used for the pipe. Warning: use of -B can re‐
sult in erroneous display, since only the most recently viewed part of the
piped data 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
Same as -c, for compatibility with older versions of less.
-d or --dumb
The -d option suppresses the error message normally displayed if the terminal
is dumb; that is, lacks some important capability, such as the ability to
clear the screen or scroll backward. The -d option does not otherwise change
the behavior of less on a dumb terminal.
-Dxcolor or --color=xcolor
Changes the color of different parts of the displayed text. x is a single
character which selects the type of text whose color is being set:
B Binary characters.
C Control characters.
E Errors and informational messages.
M Mark letters in the status column.
N Line numbers enabled via the -N option.
P Prompts.
R The rscroll character.
S Search results.
W The highlight enabled via the -w option.
d Bold text.
k Blinking text.
s Standout text.
u Underlined text.
The uppercase letters can be used only when the --use-color option is enabled.
When text color is specified by both an uppercase letter and a lowercase let‐
ter, the uppercase letter takes precedence. For example, error messages are
normally displayed as standout text. So if both "s" and "E" are given a
color, the "E" color applies to error messages, and the "s" color applies to
other standout text. The "d" and "u" letters refer to bold and underline text
formed by overstriking with backspaces (see the -u option), not to text using
ANSI escape sequences with the -R option.
A lowercase letter may be followed by a + to indicate that both the normal
format change and the specified color should both be used. For example, -Dug
displays underlined text as green without underlining; the green color has re‐
placed the usual underline formatting. But -Du+g displays underlined text as
both green and in underlined format.
color is either a 4-bit color string or an 8-bit color string:
A 4-bit color string is zero, one or two characters, where the first character
specifies the foreground color and the second specifies the background color
as follows:
b Blue
c Cyan
g Green
k Black
m Magenta
r Red
w White
y Yellow
The corresponding upper-case letter denotes a brighter shade of the color.
For example, -DNGk displays line numbers as bright green text on a black back‐
ground, and -DEbR displays error messages as blue text on a bright red back‐
ground. If either character is a "-" or is omitted, the corresponding color
is set to that of normal text.
An 8-bit color string is one or two decimal integers separated by a dot, where
the first integer specifies the foreground color and the second specifies the
background color. Each integer is a value between 0 and 255 inclusive which
selects a "CSI 38;5" color value (see
https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_parameters) If either inte‐
ger is a "-" or is omitted, the corresponding color is set to that of normal
text. On MS-DOS versions of less, 8-bit color is not supported; instead, dec‐
imal values are interpreted as 4-bit CHAR_INFO.Attributes values (see
https://docs.microsoft.com/en-us/windows/console/char-info-str).
-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. Note
that some operating systems will not allow directories to be read, even if -f
is set.
-F or --quit-if-one-screen
Causes less to automatically exit if the entire file can be displayed on the
first screen.
-g or --hilite-search
Normally, less will highlight ALL strings which match the last search command.
The -g option changes this behavior to highlight only the particular string
which was found by the last search command. This can cause less to run some‐
what faster than the default.
-G or --HILITE-SEARCH
The -G option suppresses all highlighting of strings found by search commands.
--old-bot
Reverts to the old bottom of screen behavior. This can be sometimes desirable
if the long lines are not wrapped correctly when reaching the bottom of
the terminal, while scrolling forward.
-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 direc‐
tion instead. (If the terminal does not have the ability to scroll backward,
-h0 is implied.)
-i or --ignore-case
Causes searches to ignore case; that is, uppercase and lowercase are consid‐
ered 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 let‐
ters.
-jn or --jump-target=n
Specifies a line on the screen where the "target" line is to be positioned.
The target line is the line specified by any command to search for a pattern,
jump to a line number, jump to a file percentage or jump to a tag. The screen
line may be 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. Alternately, the screen line may be specified as a
fraction of the height of the screen, starting with a decimal point: .5 is in
the middle of the screen, .3 is three tenths down from the first line, and so
on. If the line is specified as a fraction, the actual line number is recal‐
culated if the terminal window is resized, so that the target line remains at
the specified fraction of the screen height. If any form of the -j option is
used, repeated forward searches (invoked with "n" or "N") begin at the line
immediately after the target line, and repeated backward searches begin at the
target line, unless changed by -a or -A. For example, if "-j4" is used, the
target line is the fourth line on the screen, so forward searches begin at the
fifth line on the screen. However nonrepeated searches (invoked with "/" or
"?") always begin at the start or end of the current screen respectively.
-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, and any lines that are marked
(via the m or M command).
-kfilename or --lesskey-file=filename
Causes less to open and interpret the named file as a lesskey(1) binary file.
Multiple -k options may be specified. If the LESSKEY or LESSKEY_SYSTEM envi‐
ronment 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.
--lesskey-src=filename
Causes less to open and interpret the named file as a lesskey(1) source file.
If the LESSKEYIN or LESSKEYIN_SYSTEM environment variable is set, or if a
lesskey source file is found in a standard place (see KEY BINDINGS), it is al‐
so used as a lesskey source file. Prior to version 582, the lesskey program
needed to be run to convert a lesskey source file to a lesskey binary file for
less to use. Newer versions of less read the lesskey source file directly and
ignore the binary file if the source file exists.
-K or --quit-on-intr
Causes less to exit immediately (with status 2) when an interrupt character
(usually ^C) is typed. Normally, an interrupt character causes less to stop
whatever it is doing and return to its command prompt. Note that use of this
option makes it impossible to return to the command prompt from the "F" com‐
mand.
-L or --no-lessopen
Ignore the LESSOPEN environment variable (see the INPUT PREPROCESSOR section
below). This option can be set from within less, but it will apply only to
files opened subsequently, not to the file which is currently open.
-m or --long-prompt
Causes less to prompt verbosely (like more), with the percent into the file.
By default, less prompts with a colon.
-M or --LONG-PROMPT
Causes less to prompt even more verbosely than more.
-n or --line-numbers
Suppresses line numbers. The default (to use line numbers) may cause less to
run more slowly in some cases, especially with a very large input file. Sup‐
pressing 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 edi‐
tor (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 dis‐
play.
-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 ask‐
ing 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 re‐
port the name of the log file. The "s" command is equivalent to specifying -o
from within less.
-ppattern or --pattern=pattern
The -p option on the command line is equivalent to specifying +/pattern; that
is, it tells less to start at the first occurrence of pattern in the file.
-Pprompt or --prompt=prompt
Provides a way to tailor the three prompt styles to your own preference. This
option would normally be put in the LESS environment variable, rather than be‐
ing 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 se‐
quences. 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 at‐
tempt 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. If the
terminal has a "visual bell", it is used in all cases where the terminal bell
would have been rung.
-r or --raw-control-chars
Causes "raw" control characters to be displayed. The default is to display
control characters using the caret notation; for example, a control-A (octal
001) is displayed as "^A". Warning: when the -r option is used, less cannot
keep track of the actual appearance of the screen (since this depends on how
the screen responds to each type of control character). Thus, various display
problems may result, such as long lines being split in the wrong place.
USE OF THE -r OPTION IS NOT RECOMMENDED.
-R or --RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences and OSC 8 hyperlink sequences
are output in "raw" form. Unlike -r, the screen appearance is maintained cor‐
rectly, provided that there are no escape sequences in the file other than
these types of escape sequences. Color escape sequences are only supported
when the color is changed within one line, not across lines. In other words,
the beginning of each line is assumed to be normal (non-colored), regardless
of any escape sequences in previous lines. For the purpose of keeping track
of screen appearance, these escape sequences are assumed to not move the cur‐
sor.
OSC 8 hyperlinks are sequences of the form:
ESC ] 8 ; ... 7
The terminating sequence may be either a BEL character (7) or the two-charac‐
ter sequence "ESC ".
ANSI color escape sequences are sequences of the form:
ESC [ ... m
where the "..." is zero or more color specification characters. You can make
less think that characters other than "m" can end ANSI color escape sequences
by setting the environment variable LESSANSIENDCHARS to the list of characters
which can end a color escape sequence. And you can make less think that char‐
acters other than the standard ones may appear between the ESC and the m by
setting the environment variable LESSANSIMIDCHARS to the list of characters
which can appear.
-s or --squeeze-blank-lines
Causes consecutive blank lines to be squeezed into a single blank line. This
is useful when viewing nroff output.
-S or --chop-long-lines
Causes lines longer than the screen width to be chopped (truncated) rather
than wrapped. That is, the portion of a long line that does not fit in the
screen width is not displayed until you press RIGHT-ARROW. The default is to
wrap long lines; that is, display the remainder on the next line.
-ttag or --tag=tag
The -t option, followed immediately by a TAG, will edit the file containing
that tag. For this to work, tag information must be available; for example,
there may be a file in the current directory called "tags", which was previ‐
ously built by ctags(1) or an equivalent command. If the environment variable
LESSGLOBALTAGS is set, it is taken to be the name of a command compatible with
global(1), and that command is executed to find the tag. (See
http://www.gnu.org/software/global/global.html). The -t option may also be
specified from within less (using the - command) as a way of examining a new
file. The command ":t" is equivalent to specifying -t from within less.
-Ttagsfile or --tag-file=tagsfile
Specifies a tags file to be used instead of "tags".
-u or --underline-special
Causes backspaces and carriage returns to be treated as printable characters;
that is, they are sent to the terminal when they appear in the input.
-U or --UNDERLINE-SPECIAL
Causes backspaces, tabs, carriage returns and "formatting characters" (as de‐
fined by Unicode) 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 dis‐
played using the terminal's hardware underlining capability. Also, backspaces
which appear between two identical characters are treated specially: the over‐
struck text is printed using the terminal's hardware boldface 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. Unicode formatting characters,
such as the Byte Order Mark, are sent to the terminal. Text which is over‐
struck or underlined can be searched for if neither -u nor -U is in effect.
-V or --version
Displays the version number of less.
-w or --hilite-unread
Temporarily highlights the first "new" line after a forward movement of a full
page. The first "new" line is the line immediately following the line previ‐
ously at the bottom of the screen. Also highlights the target line after a g
or p command. The highlight is removed at the next command which causes move‐
ment. 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 move‐
ment command larger than one line.
-xn,... or --tabs=n,...
Sets tab stops. If only one n is specified, tab stops are set at multiples of
n. If multiple values separated by commas are specified, tab stops are set at
those positions, and then continue with the same spacing as the last two. For
example, -x9,17 will set tabs at positions 9, 17, 25, 33, etc. The default
for n is 8.
-X or --no-init
Disables sending the termcap initialization and deinitialization strings to
the terminal. This is sometimes desirable if the deinitialization string does
something unnecessary, like clearing the screen.
-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.
-zn or --window=n or -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 some versions of more. If the
number n is negative, it indicates n lines less than the current screen size.
For example, if the screen is 24 lines, -z-4 sets the scrolling window to 20
lines. If the screen is resized to 40 lines, the scrolling window automati‐
cally changes to 36 lines.
-"cc or --quotes=cc
Changes the filename quoting character. This may be necessary if you are try‐
ing to name a file which contains both spaces and quote characters. Followed
by a single character, this changes the quote character to that character.
Filenames containing a space should then be surrounded by that character
rather than by double quotes. Followed by two characters, changes the open
quote to the first character, and the close quote to the second character.
Filenames containing a space should then be preceded by the open quote charac‐
ter 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 horizontally in the
RIGHTARROW and LEFTARROW commands. If the number specified is zero, it sets
the default number of positions to one half of the screen width. Alternately,
the number may be specified as a fraction of the width of the screen, starting
with a decimal point: .5 is half of the screen width, .3 is three tenths of
the screen width, and so on. If the number is specified as a fraction, the
actual number of scroll positions is recalculated if the terminal window is
resized, so that the actual scroll remains at the specified fraction of the
screen width.
--file-size
If --file-size is specified, less will determine the size of the file immedi‐
ately after opening the file. Normally this is not done, because it can be
slow if the input file is large.
--follow-name
Normally, if the input file is renamed while an F command is executing, less
will continue to display the contents of the original file despite its name
change. If --follow-name is specified, during an F command less will periodi‐
cally attempt to reopen the file by name. If the reopen succeeds and the file
is a different file from the original (which means that a new file has been
created with the same name as the original (now renamed) file), less will dis‐
play the contents of that new file.
--incsearch
Subsequent search commands will be "incremental"; that is, less will advance
to the next line containing the search pattern as each character of the pat‐
tern is typed in.
--line-num-width
Sets the minimum width of the line number field when the -N option is in ef‐
fect. The default is 7 characters.
--mouse
Enables mouse input: scrolling the mouse wheel down moves forward in the file,
scrolling the mouse wheel up moves backwards in the file, and clicking the
mouse sets the "#" mark to the line where the mouse is clicked. The number of
lines to scroll when the wheel is moved can be set by the --wheel-lines op‐
tion. Mouse input works only on terminals which support X11 mouse reporting,
and on the Windows version of less.
--MOUSE
Like --mouse, except the direction scrolled on mouse wheel movement is re‐
versed.
--no-keypad
Disables sending the keypad initialization and deinitialization strings to the
terminal. This is sometimes useful if the keypad strings make the numeric
keypad behave in an undesirable manner.
--no-histdups
This option changes the behavior so that if a search string or file name is
typed in, and the same string is already in the history list, the existing
copy is removed from the history list before the new one is added. Thus, a
given string will appear only once in the history list. Normally, a string
may appear multiple times.
--rscroll
This option changes the character used to mark truncated lines. It may begin
with a two-character attribute indicator like LESSBINFMT does. If there is no
attribute indicator, standout is used. If set to "-", truncated lines are not
marked.
--save-marks
Save marks in the history file, so marks are retained across different invoca‐
tions of less.
--status-col-width
Sets the width of the status column when the -J option is in effect. The de‐
fault is 2 characters.
--use-backslash
This option changes the interpretations of options which follow this one. Af‐
ter the --use-backslash option, any backslash in an option string is removed
and the following character is taken literally. This allows a dollar sign to
be included in option strings.
--use-color
Enables the colored text in various places. The -D option can be used to
change the colors. Colored text works only if the terminal supports ANSI col‐
or escape sequences (as defined in ECMA-48 SGR; see
https://www.ecma-international.org/publications-and-
standards/standards/ecma-48).
--wheel-lines=n
Set the number of lines to scroll when the mouse wheel is scrolled and the
--mouse or --MOUSE option is in effect. The default is 1 line.
-- A command line argument of "--" marks the end of option arguments. Any argu‐
ments following this are interpreted 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 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, +<number> acts like
+<number>g; that is, it starts the display at the specified line number (how‐
ever, 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 a 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 ma‐
nipulate 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. (Note that the
forms beginning with ESC do not work in some MS-DOS and Windows systems because ESC
is the line erase character.) Any of these special keys may be entered literally by
preceding it with the "literal" character, either ^V or ^A. A backslash itself may
also be entered literally by entering two backslashes.
LEFTARROW [ ESC-h ]
Move the cursor one space to the left.
RIGHTARROW [ ESC-l ]
Move the cursor one space to the right.
^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.) Move the cursor one word to
the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to
the right.
HOME [ ESC-0 ]
Move the cursor to the beginning of the line.
END [ ESC-$ ]
Move the cursor to the end of the line.
BACKSPACE
Delete the character to the left of the cursor, or cancel the command if the
command line is empty.
DELETE or [ ESC-x ]
Delete the character under the cursor.
^BACKSPACE [ ESC-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left
of the cursor.
^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.) Delete the word under the cur‐
sor.
UPARROW [ ESC-k ]
Retrieve the previous command line. If you first enter some text and then
press UPARROW, it will retrieve the previous command which begins with that
text.
DOWNARROW [ ESC-j ]
Retrieve the next command line. If you first enter some text and then press
DOWNARROW, it will retrieve the next command which begins with that text.
TAB Complete the partial filename to the left of the cursor. If it matches more
than one filename, the first match is entered into the command line. Repeated
TABs will cycle thru the other matching filenames. If the completed filename
is a directory, a "/" is appended to the filename. (On MS-DOS systems, a ""
is appended.) The environment variable LESSSEPARATOR can be used to specify a
different character to append to a directory name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the matching filenames.
^L Complete the partial filename to the left of the cursor. If it matches more
than one filename, all matches are entered into the command line (if they
fit).
^U (Unix and OS/2) or ESC (MS-DOS)
Delete the entire command line, or cancel the command if the command line is
empty. If you have changed your line-kill character in Unix to something oth‐
er than ^U, that character is used instead of ^U.
^G Delete the entire command line and return to the main prompt.
KEY BINDINGS
You may define your own less commands by creating a lesskey source file. This file
specifies a set of command keys and an action associated with each key. You may also
change the line-editing keys (see LINE EDITING), and to set environment variables.
If the environment variable LESSKEYIN is set, less uses that as the name of the
lesskey source file. Otherwise, less looks in a standard place for the lesskey
source file: On Unix systems, less looks for a lesskey file called "$XDG_CON‐
FIG_HOME/lesskey" or "$HOME/.lesskey". On MS-DOS and Windows systems, less looks for
a lesskey file called "$HOME/_lesskey", and if it is not found there, then looks for
a lesskey file called "_lesskey" in any directory specified in the PATH environment
variable. On OS/2 systems, less looks for a lesskey file called "$HOME/lesskey.ini",
and if it is not found, then looks for a lesskey file called "lesskey.ini" in any di‐
rectory specified in the INIT environment variable, and if it not found there, then
looks for a lesskey file called "lesskey.ini" in any directory specified in the PATH
environment variable. See the lesskey manual page for more details.
A system-wide lesskey source 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 envi‐
ronment variable LESSKEYIN_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/sys‐
lesskey. (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:\_syslesskey. On OS/2 systems,
the system-wide lesskey file is c:syslesskey.ini.
Previous versions of less (before v582) used lesskey files with a binary format, pro‐
duced by the lesskey program. It is no longer necessary to use the lesskey program.
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 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 con‐
tents of the original file. However, it will appear to the user as if the original
file is opened; that is, less will display the original filename as the name of the
current file.
An input preprocessor receives one command line argument, the original filename, as
entered by the user. It should create the replacement file, and when finished, print
the name of the replacement file to its standard output. If the input preprocessor
does not output a replacement filename, less uses the original file, as normal. The
input preprocessor is not called when viewing standard input. To set up an input
preprocessor, set the LESSOPEN environment variable to a command line which will in‐
voke 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 com‐
mand 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 com‐
mand 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 environ‐
ment 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 out‐
put 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 "$1" in
*.Z) TEMPFILE=$(mktemp)
uncompress -c $1 >$TEMPFILE 2>/dev/null
if [ -s $TEMPFILE ]; then
echo $TEMPFILE
else
rm -f $TEMPFILE
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 re‐
placement file on its standard output. If the input pipe does not write any charac‐
ters 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 preproces‐
sor is an input pipe. As with non-pipe input preprocessors, the command string must
contain one occurrence of %s, which is replaced with the filename of the input file.
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
;;
*) exit 1
;;
esac
exit $?
To use this script, put it where it can be executed and set LESSOPEN="|lesspipe.sh
%s".
Note that a preprocessor cannot output an empty file, since that is interpreted as
meaning there is no replacement, and the original file is used. To avoid this, if
LESSOPEN starts with two vertical bars, the exit status of the script becomes mean‐
ingful. If the exit status is zero, the output is considered to be replacement text,
even if it is empty. If the exit status is nonzero, any output is ignored and the
original file is used. For compatibility with previous versions of less, if LESSOPEN
starts with only one vertical bar, the exit status of the preprocessor is ignored.
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 re‐
placement file name passed to the LESSCLOSE postprocessor is "-".
For compatibility with previous versions of less, the input preprocessor or pipe is
not used if less is viewing standard input. However, if the first character of
LESSOPEN is a dash (-), the input preprocessor is used on standard input as well as
other files. In this case, the dash is not considered to be part of the preprocessor
command. If standard input is being viewed, the input preprocessor is passed a file
name consisting of a single dash. Similarly, if the first two characters of LESSOPEN
are vertical bar and dash (|-) or two vertical bars and a dash (||-), the input pipe
is used on standard input as well as other files. Again, in this case the dash is
not considered to be part of the input pipe command.
There are used following files to set up default preprocessor:
/etc/profile.d/less.sh
/etc/profile.d/less.csh
These files set up /usr/bin/lesspipe.sh as a default filter. An user defined filter
can be specified in ~/.lessfilter. This file should have an execute bit set and ac‐
cept only one parameter, which represents a filename. If the user defined filter
process the file, zero should be returned. Otherwise ~/.lessfilter tries to handle
the file.
NATIONAL CHARACTER SETS
There are three types of characters in the input file:
normal characters
can be displayed directly to the screen.
control characters
should not be displayed directly, but are expected to be found in ordinary
text files (such as backspace and tab).
binary characters
should not be displayed directly and are not expected to be found in text
files.
A "character set" is simply a description of which characters are to be considered
normal, control, and binary. The LESSCHARSET environment variable may be used to se‐
lect 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 charac‐
ters 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 LESS‐
CHARSET=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. UTF-8 is special
in that it supports multi-byte characters in the input file. It is the only
character set that supports multi-byte characters.
windows
Selects a character set appropriate for Microsoft Windows (cp 1251).
In rare 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 char‐
acter 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 num‐
ber may be used for repetition. For example, "bccc4b." would mean character 0 is bi‐
nary, 1, 2 and 3 are control, 4, 5, 6 and 7 are binary, and 8 is normal. All charac‐
ters after the last are taken to be the same as the last, so characters 9 through 255
would be normal. (This is an example, and does not necessarily represent any real
character set.)
This table shows the value of LESSCHARDEF which is equivalent to each of the possible
values for LESSCHARSET:
ascii 8bcccbcc18b95.b
dos 8bcccbcc12bc5b95.b.
ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
191.b
iso8859 8bcccbcc18b95.33b.
koi8-r 8bcccbcc18b95.b128.
latin1 8bcccbcc18b95.33b.
next 8bcccbcc18b95.bb125.bb
If neither LESSCHARSET nor LESSCHARDEF is set, but any of the strings "UTF-8",
"UTF8", "utf-8" or "utf8" is found in the LC_ALL, LC_CTYPE or LANG environment vari‐
ables, 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 set‐
ting the LANG or LC_CTYPE environment variables.
Finally, if the setlocale interface is also not available, the default character set
is latin1.
Control and binary characters are displayed in standout (reverse video). Each such
character is displayed in caret notation if possible (e.g. ^A for control-A). Caret
notation is used only if inverting the 0100 bit results in a normal printable charac‐
ter. Otherwise, the character is displayed as a hex number in angle brackets. This
format can be changed by setting the LESSBINFMT environment variable. LESSBINFMT may
begin with a "*" and one character to select the display attribute: "*k" is blinking,
"*d" is bold, "*u" is underlined, "*s" is standout, and "*n" is normal. If LESS‐
BINFMT 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 charac‐
ters are displayed in underlined hexadecimal surrounded by brackets. The default if
no LESSBINFMT is specified is "*s<%02X>". Warning: the result of expanding the char‐
acter via LESSBINFMT must be less than 31 characters.
When the character set is utf-8, the LESSUTFBINFMT environment variable acts similar‐
ly to LESSBINFMT but it applies to Unicode code points that were successfully decoded
but are unsuitable for display (e.g., unassigned code points). Its default value is
"<U+%04lX>". Note that LESSUTFBINFMT and LESSBINFMT share their display attribute
setting ("*x") so specifying one will affect both; LESSUTFBINFMT is read after LESS‐
BINFMT so its setting, if any, will have priority. Problematic octets in a UTF-8
file (octets of a truncated sequence, octets of a complete but non-shortest form se‐
quence, invalid octets, and stray trailing octets) are displayed individually using
LESSBINFMT so as to facilitate diagnostic of how the UTF-8 file is ill-formed.
PROMPTS
The -P option allows you to tailor the prompt to your preference. The string given
to the -P option replaces the specified prompt string. Certain characters in the
string are interpreted specially. The prompt mechanism is rather complicated to pro‐
vide flexibility, but the ordinary user need not understand the details of construct‐
ing personalized prompt strings.
A percent sign followed by a single character is expanded according to what the fol‐
lowing 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 off‐
set is to be used. If the character is a "t", the byte offset of the top line
in the display is used, an "m" means use the middle line, a "b" means use the
bottom line, a "B" means use the line just after the bottom line, and a "j"
means use the "target" line, as specified by the -j option.
%B Replaced by the size of the current input file.
%c Replaced by the column number of the text appearing in the first column of the
screen.
%dX Replaced by the page number of a line in the input file. The line to be used
is determined by the X, as with the %b option.
%D Replaced by the number of pages in the input file, or equivalently, the page
number of the last line in the input file.
%E Replaced by the name of the editor (from the VISUAL environment variable, or
the EDITOR environment variable if VISUAL is not defined). See the discussion
of the LESSEDIT feature below.
%f Replaced by the name of the current input file.
%F Replaced by the last component of the name of the current input file.
%g Replaced by the shell-escaped name of the current input file. This is useful
when the expanded string will be used in a shell command, such as in LESSEDIT.
%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.
%T Normally expands to the word "file". However if viewing files via a tags list
using the -t option, it expands to the word "tag".
%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 fol‐
lowing character, a condition is evaluated. If the condition is true, any characters
following the question mark and condition character, up to a period, are included in
the prompt. If the condition is false, such characters are not included. A colon
appearing between the question mark and the period can be used to establish an
"ELSE": any characters between the colon and the period are included in the string if
and only if the IF condition is false. Condition characters (which follow a question
mark) may be:
?a True if any characters have been included in the prompt so far.
?bX True if the byte offset of the specified line is known.
?B True if the size of current input file is known.
?c True if the text is horizontally shifted (%c is not zero).
?dX True if the page number of the specified line is known.
?e True if at end-of-file.
?f True if there is an input filename (that is, if input is not a pipe).
?lX True if the line number of the specified line is known.
?L True if the line number of the last line in the file is known.
?m True if there is more than one input file.
?n True if this is the first prompt in a new input file.
?pX True if the percent into the current input file, based on byte offsets, of the
specified line is known.
?PX True if the percent into the current input file, based on line numbers, of the
specified line is known.
?s Same as "?B".
?x True if there is a next input file (that is, if the current input file is not
the last one).
Any characters other than the special ones (question mark, colon, period, percent,
and backslash) become literally part of the prompt. Any of the 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(%T %i of %m) ..?e(END) ?x- Next: %x..%t";
This prints the filename if this is the first prompt in a file, followed by the "file
N of N" message if there is more than one input file. Then, if we are at end-of-
file, the string "(END)" is printed followed by the name of the next file, if there
is one. Finally, any trailing spaces are truncated. This is the default prompt.
For reference, here are the defaults for the other two prompts (-m and -M respective‐
ly). Each is broken into two lines here for readability only.
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next: %x.:
?pB%pB\%:byte %bB?s/%s...%t
?f%f .?n?m(%T %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(%T %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. %g
Note that this expands to the editor name, followed by a + and the line number, fol‐
lowed by the shell-escaped file name. If your editor does not accept the "+linenum‐
ber" syntax, or has other differences in invocation syntax, the LESSEDIT variable can
be changed to modify this default.
SECURITY
When the environment variable LESSSECURE is set to 1, less runs in a "secure" mode.
This means these features are disabled:
! the shell command
| the pipe command
:e the examine command.
v the editing command
s -o log files
-k use of lesskey files
-t use of tags files
metacharacters in filenames, such as *
filename completion (TAB, ^L)
Less can also be compiled to be permanently in "secure" mode.
COMPATIBILITY WITH MORE
If the environment variable LESS_IS_MORE is set to 1, or if the program is invoked
via a file link named "more", less behaves (mostly) in conformance with the POSIX
"more" command specification. In this mode, less behaves differently in these ways:
The -e option works differently. If the -e option is not set, less behaves as if the
-e option were set. If the -e option is set, less behaves as if the -E option were
set.
The -m option works differently. If the -m option is not set, the medium prompt is
used, and it is prefixed with the string "--More--". If the -m option is set, the
short prompt is used.
The -n option acts like the -z option. The normal behavior of the -n option is un‐
available in this mode.
The parameter to the -p option is taken to be a less command rather than a search
pattern.
The LESS environment variable is ignored, and the MORE environment variable is used
in its place.
ENVIRONMENT VARIABLES
Environment variables may be specified either in the system environment as usual, or
in a lesskey(1) file. If environment variables are defined in more than one place,
variables defined in a local lesskey file take precedence over variables defined in
the system environment, which take precedence over variables defined in the system-
wide lesskey file.
COLUMNS
Sets the number of columns on the screen. Takes precedence over the number of
columns specified by the TERM variable. (But if you have a 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 variables is the name
of the user's home directory if the HOME variable is not set (only in the Win‐
dows version).
INIT Name of the user's init directory (used to find a lesskey file on OS/2 sys‐
tems).
LANG Language for determining the character set.
LC_CTYPE
Language for determining the character set.
LESS Options which are passed to less automatically.
LESSANSIENDCHARS
Characters which may end an ANSI color escape sequence (default "m").
LESSANSIMIDCHARS
Characters which may appear between the ESC character and the end character in
an ANSI color escape sequence (default "0123456789:;[?!"'#%()*+ ".
LESSBINFMT
Format for displaying non-printable, non-control characters.
LESSCHARDEF
Defines a character set.
LESSCHARSET
Selects a predefined character set.
LESSCLOSE
Command line to invoke the (optional) input-postprocessor.
LESSECHO
Name of the lessecho program (default "lessecho"). The lessecho program is
needed to expand metacharacters, such as * and ?, in filenames on Unix sys‐
tems.
LESSEDIT
Editor prototype string (used for the v command). See discussion under
PROMPTS.
LESSGLOBALTAGS
Name of the command used by the -t option to find global tags. Normally
should be set to "global" if your system has the global(1) command. If not
set, global tags are not used.
LESSHISTFILE
Name of the history file used to remember search commands and shell commands
between invocations of less. If set to "-" or "/dev/null", a history file is
not used. The default is "$XDG_DATA_HOME/lesshst" or "$HOME/.lesshst" on Unix
systems, "$HOME/_lesshst" on DOS and Windows systems, or "$HOME/lesshst.ini"
or "$INIT/lesshst.ini" on OS/2 systems.
LESSHISTSIZE
The maximum number of commands to save in the history file. The default is
100.
LESSKEYIN
Name of the default lesskey source file.
LESSKEY
Name of the default lesskey binary file. (Not used if "$LESSKEYIN" exists.)
LESSKEYIN_SYSTEM
Name of the default system-wide lesskey source file.
LESSKEY_SYSTEM
Name of the default system-wide lesskey binary file. (Not used if
"$LESSKEYIN_SYSTEM" exists.)
LESSMETACHARS
List of characters which are considered "metacharacters" by the shell.
LESSMETAESCAPE
Prefix which less will add before each metacharacter in a command sent to the
shell. If LESSMETAESCAPE is an empty string, commands containing metacharac‐
ters will not be passed to the shell.
LESSOPEN
Command line to invoke the (optional) input-preprocessor.
LESSSECURE
Runs less in "secure" mode. See discussion under SECURITY.
LESSSEPARATOR
String to be appended to a directory name in filename completion.
LESSUTFBINFMT
Format for displaying non-printable Unicode code points.
LESS_IS_MORE
Emulate the more(1) command.
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.)
MORE Options which are passed to less automatically when running in more compatible
mode.
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)
COPYRIGHT
Copyright (C) 1984-2021 Mark Nudelman
less is part of the GNU project and is free software. You can redistribute it and/or
modify it under the terms of either (1) the GNU General Public License as published
by the Free Software Foundation; or (2) the Less License. See the file README in the
less distribution for more details regarding redistribution. You should have re‐
ceived a copy of the GNU General Public License along with the source for less; see
the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place,
Suite 330, Boston, MA 02111-1307, USA. You should also have received a copy of the
Less License; see the file LICENSE.
less is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
POSE. See the GNU General Public License for more details.
AUTHOR
Mark Nudelman
Report bugs at https://github.com/gwsw/less/issues.
For more information, see the less homepage at
https://greenwoodsoftware.com/less
Version 590: 03 Jun 2021 LESS(1)