|less(3p)||perl pragma to request less of something|
|LESS(1)||General Commands Manual||LESS(1)|
lessis a program similar to the traditional more(1), but with many more features. It displays text one screenful at a time. After showing each screenful, it prompts the user for a command. When showing the last line of a file,
lessdisplays a prompt indicating end of file and the name of the next file to examine, if any. It then waits for input from the user.
This version of
less also acts as
more(1) if it is called as
more, or if the
environment variable is set. The main differences between the two are
summarized in the
COMPATIBILITY WITH MORE
A long option name may be abbreviated as long as the abbreviation
is unambiguous. 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
The options are as follows:
less(the same as the
hcommand). (Depending on how your shell interprets the question mark, it may be necessary to quote the question mark, thus: ‘
lessversions prior to 441.
Ncommands, which start after or before the “target” line respectively; see the
-joption for more about the target line). The
-aoption 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.
-Boption disables this automatic allocation of buffers for pipes, so that only 64K (or the amount of space specified by the
-boption) is used for the pipe. Warning: use of
-Bcan result in erroneous display, since only the most recently viewed part of the piped data is kept in memory; any earlier data is lost.
lesswill use for each file, in units of kilobytes (1024 bytes). By default 64K of buffer space is used for each file (unless the file is a pipe; see the
-boption 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.
-c, for compatibility with older versions of
-doption suppresses the error message normally displayed if the terminal is dumb; that is, if the terminal lacks some important capability, such as the ability to clear the screen or scroll backward. The
-doption does not otherwise change the behavior of
lesson a dumb terminal.
lessto automatically exit the first time it reaches end-of-file.
lessto automatically exit the second time it reaches end-of-file. By default, the only way to exit
lessis via the
lessto automatically exit if the entire file can be displayed on the first screen.
lesswill refuse to open non-regular files.
-Goption suppresses all highlighting of strings found by search commands.
lesswill highlight all strings which match the last search command. The
-goption changes this behavior to highlight only the particular string which was found by the last search command. This can cause
lessto run somewhat faster than the default.
-h0’ is implied.)
-i, but searches ignore case even if the pattern contains uppercase letters.
-Woption is in effect.
-joption is used, forward searches begin at the line immediately after the target line, and backward searches begin at the target line, unless changed by
-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.
lessto exit immediately (with status 2) when an interrupt character (usually
^C) is typed. Normally, an interrupt character causes
lessto 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
lessto open and interpret the named file as a lesskey(1) file. Multiple
-koptions may be specified. If the
LESSKEY_SYSTEMenvironment 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.
LESSOPENenvironment 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.
lessto prompt even more verbosely than more(1).
lessto prompt verbosely, like more(1), with the percent into the file. By default,
lessprompts with a colon.
lessto run more slowly in some cases, especially with a very large input file. Suppressing line numbers with the
-noption will avoid this problem. Using line numbers means: the line number will be displayed in the verbose prompt and in the
=command, and the
vcommand will pass the current line number to the editor (see also the discussion of
LESSEDITin PROMPTS below).
-Ooption is like
-o, but it will overwrite an existing file without asking for confirmation.
If no log file has been specified, the
-O options can be
used from within
less to specify a log file.
Without a file name, they will simply report the name of the log file.
s command is equivalent to specifying
-o from within
lessto 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,
lesswill ask for confirmation before overwriting it.
LESSenvironment variable, rather than being typed in with each
lesscommand. Such an option must either be the last option in the
LESSvariable, or be terminated by a dollar sign.
-Psstring changes the default (short) prompt to string.
-Pmchanges the medium (
-PMchanges the long (
-Phchanges the prompt for the help screen.
-P=changes the message printed by the
-Pwchanges the message printed while waiting for data (in the
-poption on the command line is equivalent to specifying
+/pattern; that is, it tells
lessto start at the first occurrence of pattern in the file.
-r, but only ANSI color escape sequences are output in raw form. Unlike
-r, the screen appearance is maintained correctly in most cases. ANSI color escape sequences are sequences of the form:
ESC [ ... m
where the “...” is zero or more color
specification characters. For the purpose of keeping track of screen
appearance, ANSI color escape sequences are assumed to not move the
cursor. You can make
less think that characters
other than ‘m’ can end ANSI color escape sequences by
setting the environment variable
LESSANSIENDCHARS to the list of characters which
can end a color escape sequence. And you can make
less think that characters 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
-roption is used,
lesscannot 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.
-toption, followed immediately by a tag, will edit the file containing that tag. For this to work, tag information must be available; for example, there may be a file in the current directory called tags, which was previously built by ctags(1) or an equivalent command. The
-toption may also be specified from within
-command) as a way of examining a new file. The command
:tis equivalent to specifying
By default, if neither
-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 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. Text which is overstruck or
underlined can be searched for if neither
-U is in effect.
-w, but temporarily highlights the first new line after any forward movement command larger than one line.
pcommand. The highlight is removed at the next command which causes movement. The entire line is highlighted, unless the
-Joption is in effect, in which case only the status column is highlighted.
-x9,17’ will set tabs at positions 9, 17, 25, 33, etc. The default for n is 8.
-Coption may be used to repaint from the top of the screen if desired. By default, any forward movement causes scrolling.
wcommands can also be used to change the window size. The
zmay be omitted for compatibility with some versions of more(1). 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.
Fcommand is executing,
lesswill continue to display the contents of the original file despite its name change. If
--follow-nameis specified, during an
lesswill periodically 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),
lesswill display the contents of that new file.
--use-backslashoption, 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.
-"(a dash followed by a double quote).
--marks the end of option arguments. Any arguments following this are interpreted as filenames. This can be useful when viewing a file whose name begins with a ‘-’ or ‘+’.
less. For example,
lessto start at the end of the file rather than the beginning, and
+/xyztells it to start at the first occurrence of “xyz” in the file. As a special case,
+number acts like
+numberg; that is, it starts the display at the specified line number (however, see the caveat under the
gcommand below). 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.
-zabove). If N is more than the screen size, only the final screenful is displayed. Warning: some systems use ^V as a special literalization character.
-zabove). If N is more than the screen size, only the final screenful is displayed.
-#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
-Soption (chop lines) were in effect.
-#option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW commands.
-joptions, 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:
Certain characters are special, as in the / command:
-Goption; in that case search commands do not turn highlighting back on.)
Certain characters are special as in the / command:
-toption for more details about tags.
-h), or a string value (such as
-t), a new value may be entered after the option letter. If no new value is entered, a message describing the current setting is printed and nothing is changed.
-+X’ on the command line.) This does not work for string-valued options.
lessto initially display each file starting at the end rather than the beginning.
The following four commands may or may not be valid, depending on your particular installation.
VISUAL, if defined, or
VISUALis not defined, or defaults to "vi" if neither
EDITORis defined. See also the discussion of LESSEDIT under the section on PROMPTS below.
LESSSEPARATORcan be used to specify a different character to append to a directory name.
lesscommands by using the program lesskey(1) to create a lesskey file. This file specifies a set of command keys and an action associated with each key. You may also use lesskey to change the line-editing keys (see LINE EDITING), and to set environment variables. If the environment variable
lessuses that as the name of the lesskey file. Otherwise,
lesslooks for a lesskey file called "$HOME/.less". See the lesskey(1) manual page for more details.
A system-wide lesskey file may also be set up to provide key
bindings. If a key is defined in both a local lesskey file and in the
system-wide file, key bindings in the local file take precedence over those
in the system-wide file. If the environment variable
LESSKEY_SYSTEM is set,
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 OpenBSD, the system-wide lesskey
file is /etc/sysless.
lessopens 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,
lesswill 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
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
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
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
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
For example, these two scripts will allow you to keep files in
compressed format, but still let
less view them
#! /bin/sh case "$1" in *.Z) uncompress -c $1 >/tmp/less.$$ 2>/dev/null if [ -s /tmp/less.$$ ]; then echo /tmp/less.$$ else rm -f /tmp/less.$$ fi ;; esac
#! /bin/sh rm $2
To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on.
It is also possible to set up an input preprocessor to pipe the
file data directly to
less, rather than putting the
data into a replacement file. This avoids the need to decompress the entire
file before starting to view it. An input preprocessor that works this way
is called an input pipe. An input pipe, instead of writing the name of a
replacement file on its standard output, writes the entire contents of the
replacement file on its standard output. If the input pipe does not write
any characters on its standard output, then there is no replacement file and
less uses the original file, as normal. To use an
input pipe, make the first character in the
environment variable a vertical bar (|) to signify that the input
preprocessor is an input pipe.
For example, this script will work like the previous example scripts:
#! /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 meaningful. If the exit
status is zero, the output is considered to be replacement text, even if it
empty. If the exit status is nonzero, any output is ignored and the original
file is used. For compatibility with previous versions of
with only one vertical bar, the exit status of the preprocessor is
When an input pipe is used, a LESSCLOSE postprocessor can be used, but it is usually not necessary since there is no replacement file to clean up. In this case, the replacement file name passed to the LESSCLOSE postprocessor is "-".
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.
A "character set" is simply a description of which
characters are to be considered normal, control, and binary.
less will determine the character set to use from
the environment (see locale(1)).
Control and binary characters are displayed in standout (reverse
video). Each such character is displayed in caret notation if possible (e.g.
^A for control-A). Caret notation is used only if inverting the 0100 bit
results in a normal printable character. Otherwise, the character is
displayed as a hex number in angle brackets. This format can be changed by
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 LESSBINFMT does not begin with a "*", normal
attribute is assumed. The remainder of LESSBINFMT is a string which may
include one printf-style escape sequence (a % followed by x, X, o, d, etc.).
For example, if LESSBINFMT is "*u[%x]", binary characters are
displayed in underlined hexadecimal surrounded by brackets. The default if
no LESSBINFMT is specified is "*s<%02X>". Warning: the
result of expanding the character via LESSBINFMT must be less than 31
When the character set is utf-8, the
LESSUTFBINFMT environment variable acts similarly to
LESSBINFMT but it applies to Unicode code points that were successfully
decoded but are unsuitable for display (e.g., unassigned code points). Its
default value is "<U+%04lX>". Note that LESSUTFBINFMT and
LESSBINFMT share their display attribute setting ("*x") so
specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so
its setting, if any, will have priority. Problematic octets in a UTF-8 file
(octets of a truncated sequence, octets of a complete but non-shortest form
sequence, illegal octets, and stray trailing octets) are displayed
individually using LESSBINFMT so as to facilitate diagnostic of how the
UTF-8 file is ill-formed.
-Poption allows you to tailor the prompt to your preference. The string given to the
-Poption 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:
VISUALenvironment variable, or the
EDITORenvironment variable if
VISUALis not defined). See the discussion of the LESSEDIT feature below.
If any item is unknown (for example, the file size if input is a pipe), a question mark is printed instead.
The format of the prompt string can be changed depending on certain conditions. A question mark followed by a single character acts like an "IF": depending on the following character, a condition is evaluated. If the condition is true, any characters following the question mark and condition character, up to a period, are included in the prompt. If the condition is false, such characters are not included. A colon appearing between the question mark and the period can be used to establish an "ELSE": any characters between the colon and the period are included in the string, if and only if the IF condition is false. Condition characters (which follow a question mark) may be:
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.
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 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 respectively). Each is broken into two lines
here for readability only.
?f%f .?m(file %i of %m) .?e(END) ?x- Next\: %x.: ?pB%pB\%:byte %bB?s/%s...%t ?f%f .?n?m(file %i of %m) ..?ltlines %lt-%lb?L/%L. : byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t
And here is the default message produced by the = command:
?f%f .?m(file %i of %m) .?ltlines %lt-%lb?L/%L. . byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
The prompt expansion features are also used for another purpose:
if an environment variable
LESSEDIT is defined, it
is used as the command to be executed when the v command is invoked. The
LESSEDIT string is expanded in the same way as the prompt strings. The
default value for LESSEDIT is:
%E ?lm+%lm. %f
Note that this expands to the editor name, followed by a + and the
line number, followed by the file name. If your editor does not accept the
"+linenumber" syntax, or has other differences in invocation
LESSEDIT variable can be changed to
modify this default.
LESSSECUREis set to 1,
lessruns in a "secure" mode. This means these features are disabled:
LESS_IS_MOREis set to 1, or if the program is invoked via a file link named "more",
lessbehaves (mostly) in conformance with the POSIX "more" command specification. In this mode, less behaves differently in these ways:
The sense of the
-c option is inverted:
when more(1) changes the display, the
default is to scroll from the bottom of the screen, and the
-c option causes it to paint from the top line
-e option works differently: it causes
more(1) to exit the first time it reaches
EOF, not the second.
-i option acts like the
-I option. The normal behavior of the
-i option is unavailable in this mode.
-m option works differently: if it is
not specified, the medium prompt is used; if it is specified, the short
prompt is used.
-n option acts like the
-z option. The normal behavior of the
-n option is unavailable in this mode.
The parameter to the
-p option is taken to
be a command rather than a search pattern.
Options to suppress error messages when the terminal is dumb
-d), suppress highlighting of strings in search
-G), and disable termcap initialization
-X) are on by default.
LESS environment variables are
ignored, and the
MORE environment variable is used
in its place.
TERMvariable, but may be overridden by window systems which support
VISUALis not set. If neither are set, vi(1) is used.
lessautomatically. Command line options override the
Some options like
-k 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, to separate a prompt
value from any other options with dollar sign between them:
--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 backslash. 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.
less. If set to "-" or "/dev/null", a history file is not used. The default is "-".
lesswill add before each metacharacter in a command sent to the shell. If LESSMETAESCAPE is an empty string, commands containing metacharacters will not be passed to the shell.
lessautomatically when running in more(1) compatible mode.
lessto get the terminal characteristics necessary to manipulate the screen.
EDITORis used; if that is not set, vi(1) is used.
|October 24, 2016||OpenBSD-current|