NAME
less
—
view files
SYNOPSIS
less |
[-#?~AaBCcdEeFfGgIiJKLMmNnQqRrSsUuVWwX ]
[-b n]
[-h n]
[-j n]
[-k keyfile]
[-O | -o
logfile] [-P
prompt] [-p
pattern] [-T
tagsfile] [-t
tag] [-x
n,...]
[-y n]
[-z n] [file
...] |
DESCRIPTION
less
is 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, less
displays 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.
Commands are based on both traditional more(1) and vi(1). Commands may be preceded by a decimal number, called N in the descriptions below. The number is used by some commands, as indicated.
This version of less
also acts as
more(1) if it is called as more
, or if the
LESS_IS_MORE
environment variable is set. The main
differences between the two are summarized in the
COMPATIBILITY WITH MORE
section, below.
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
--QUIT-AT-EOF
.
The options are as follows:
-?
|--help
- This option displays a summary of the commands accepted by
less
(the same as theh
command). (Depending on how your shell interprets the question mark, it may be necessary to quote the question mark, thus: ‘
’.)-
\? -A
|--SEARCH-SKIP-SCREEN
- Causes all forward searches (not just non-repeated searches) to start just
after 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 target line. This was the default behavior in
less
versions prior to 441. -a
|--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
repeated searches invoked by the
n
orN
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. -B
|--auto-buffers
- By default, when data is read from a pipe, buffers are allocated
automatically as needed. If a large amount of data is read from the pipe,
this can cause a large amount of memory to be allocated. The
-B
option disables this automatic allocation of buffers for pipes, so that only 64K (or the amount of space specified by the-b
option) is used for the pipe. Warning: use of-B
can result in erroneous display, since only the most recently viewed part of the piped data is kept in memory; any earlier data is lost. -b
n |--buffers
=n- Specifies the amount of buffer space
less
will use for each file, in units of kilobytes (1024 bytes). By default 64K of buffer space is used for each file (unless the file is a pipe; see the-B
option). The-b
option specifies instead that n kilobytes of buffer space should be used for each file. If n is -1, buffer space is unlimited; that is, the entire file can be read into memory. -C
|--CLEAR-SCREEN
- Same as
-c
, for compatibility with older versions ofless
. -c
|--clear-screen
- Causes full screen repaints to be painted from the bottom of the screen. By default, full screen repaints are done from the top line down to avoid the position of the display being moved when using interactive commands.
-d
|--dumb
- The
-d
option 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-d
option does not otherwise change the behavior ofless
on a dumb terminal. -E
|--QUIT-AT-EOF
- Causes
less
to automatically exit the first time it reaches end-of-file. -e
|--quit-at-eof
- Causes
less
to automatically exit the second time it reaches end-of-file. By default, the only way to exitless
is via theq
command. -F
|--quit-if-one-screen
- Causes
less
to automatically exit if the entire file can be displayed on the first screen. -f
|--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. -G
|--HILITE-SEARCH
- The
-G
option suppresses all highlighting of strings found by search commands. -g
|--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 causeless
to run somewhat faster than the default. -h
n |--max-back-scroll
=n- Specifies a maximum number of lines to scroll backward. If it is necessary
to scroll backward more than n lines, the screen is repainted in a forward
direction instead. (If the terminal does not have the ability to scroll
backward, ‘
-h
0’ is implied.) -I
|--IGNORE-CASE
- Like
-i
, but searches ignore case even if the pattern contains uppercase letters. -i
|--ignore-case
- Causes searches to ignore case; that is, uppercase and lowercase are considered identical. This option is ignored if any uppercase letters appear in the search pattern; in other words, if a pattern contains uppercase letters, then that search does not ignore case.
-J
|--status-column
- Displays a status column at the left edge of the screen. The status column
shows the lines that matched the current search. The status column is also
used if the
-w
or-W
option is in effect. -j
n |--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 recalculated 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, forward searches begin at the line immediately after the target line, and backward searches begin at the target line, unless changed by-a
or-A
. For example, if ‘-j
4’ is used, the target line is the fourth line on the screen, so forward searches begin at the fifth line on the screen. -K
|--quit-on-intr
- Causes
less
to exit immediately (with status 2) when an interrupt character (usually^C
) is typed. Normally, an interrupt character causesless
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 theF
command. -k
keyfile |--lesskey-file
=keyfile- Causes
less
to open and interpret the named file as a lesskey(1) file. Multiple-k
options may be specified. If theLESSKEY
orLESSKEY_SYSTEM
environment variable is set, or if a lesskey file is found in a standard place (see KEY BINDINGS), it is also used as a lesskey file. -L
|--no-lessopen
- Ignore the
LESSOPEN
environment variable (see the INPUT PREPROCESSOR section below). This option can be set from withinless
, but it will apply only to files opened subsequently, not to the file which is currently open. -M
|--LONG-PROMPT
- Causes
less
to prompt even more verbosely than more(1). -m
|--long-prompt
- Causes
less
to prompt verbosely, like more(1), with the percent into the file. By default,less
prompts with a colon. -N
|--LINE-NUMBERS
- Causes a line number to be displayed at the beginning of each line in the display.
-n
|--line-numbers
- Suppresses line numbers. The default (to use line numbers) may cause
less
to run more slowly in some cases, especially with a very large input file. Suppressing line numbers with the-n
option will avoid this problem. Using line numbers means: the line number will be displayed in the verbose prompt and in the=
command, and thev
command will pass the current line number to the editor (see also the discussion ofLESSEDIT
in PROMPTS below). -O
logfile |--LOG-FILE
=logfile- The
-O
option is like-o
, but it will overwrite an existing file without asking for confirmation.If no log file has been specified, the
-o
and-O
options can be used from withinless
to specify a log file. Without a file name, they will simply report the name of the log file. Thes
command is equivalent to specifying-o
from withinless
. -o
logfile |--log-file
=logfile- 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. -P
prompt |--prompt
=prompt- Provides a way to tailor the three prompt styles to your own preference.
This option would normally be put in the
LESS
environment variable, rather than being typed in with eachless
command. Such an option must either be the last option in theLESS
variable, or be terminated by a dollar sign. All prompt strings consist of a sequence of letters and special escape sequences. See the section on PROMPTS for more details. -p
pattern |--pattern
=pattern- The
-p
option on the command line is equivalent to specifying+/
pattern; that is, it tellsless
to start at the first occurrence of pattern in the file. -Q
|--QUIET
|--SILENT
- Causes totally quiet operation: the terminal bell is never rung.
-q
|--quiet
|--silent
- Causes moderately quiet operation: the terminal bell is not rung if an attempt is made to scroll past the end of the file or before the beginning of the file. If the terminal has a visual bell, it is used instead. The bell will be rung on certain other errors, such as typing an invalid character. The default is to ring the terminal bell in all such cases.
-R
|--RAW-CONTROL-CHARS
- Like
-r
, but only ANSI color escape sequences are output in raw form. Unlike-r
, the screen appearance is maintained correctly in most cases. ANSI color escape sequences are sequences of the form:ESC [ ... m
where the “...” is zero or more color specification characters. For the purpose of keeping track of screen appearance, ANSI color escape sequences are assumed to not move the cursor. You can make
less
think that characters other than ‘m’ can end ANSI color escape sequences by setting the environment variableLESSANSIENDCHARS
to the list of characters which can end a color escape sequence. And you can makeless
think that characters other than the standard ones may appear between theESC
and them
by setting the environment variableLESSANSIMIDCHARS
to the list of characters which can appear. -r
|--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. -S
|--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 shown. The default is to wrap long lines; that is, display the remainder on the next line.
-s
|--squeeze-blank-lines
- Causes consecutive blank lines to be squeezed into a single blank line.
-T
tagsfile |--tag-file
=tagsfile- Specifies a tags file to be used instead of tags.
-t
tag |--tag
=tag- The
-t
option, followed immediately by a tag, will edit the file containing that tag. For this to work, tag information must be available; for example, there may be a file in the current directory called tags, which was previously built by ctags(1) or an equivalent command. The-t
option may also be specified from withinless
(using the-
command) as a way of examining a new file. The command:t
is equivalent to specifying-t
from withinless
. -U
|--UNDERLINE-SPECIAL
- Causes backspaces, tabs and carriage returns to be treated as control
characters; that is, they are handled as specified by the
-r
option.By default, if neither
-u
nor-U
is given, backspaces which appear adjacent to an underscore character are treated specially: the underlined text is displayed using the 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
nor-U
is in effect. -u
|--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.
-V
|--version
- Displays the version number of
less
. -W
|--HILITE-UNREAD
- Like
-w
, but temporarily highlights the first new line after any forward movement command larger than one line. -w
|--hilite-unread
- Temporarily highlights the first new line after a forward movement of a
full page. The first new line is the line immediately following the line
previously at the bottom of the screen. Also highlights the target line
after a
g
orp
command. The highlight is removed at the next command which causes movement. The entire line is highlighted, unless the-J
option is in effect, in which case only the status column is highlighted. -X
|--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.
-x
n,... |--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,
‘
-x
9,17’ will set tabs at positions 9, 17, 25, 33, etc. The default for n is 8. -y
n |--max-forw-scroll
=n- Specifies a maximum number of lines to scroll forward. If it is necessary
to scroll forward more than n lines, the screen is repainted instead. The
-c
or-C
option may be used to repaint from the top of the screen if desired. By default, any forward movement causes scrolling. -z
n |--window
=n- Changes the default scrolling window size to n
lines. The default is one screenful. The
z
andw
commands can also be used to change the window size. Thez
may 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. --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 anF
commandless
will 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),less
will display the contents of that new file. --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.
--use-backslash
- This option changes the interpretations of options which follow this one.
After 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. -"
cc |--quotes
=cc- Changes the filename quoting character. This may be necessary if you are
trying to name a file which contains both spaces and quote characters. If
cc is 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. If
cc consists of two characters, this changes the open
quote to the first character, and the close quote to the second character.
Filenames containing a space should then be preceded by the open quote
character and followed by the close quote character. Note that even after
the quote characters are changed, this option remains
-"
(a dash followed by a double quote). -~
|--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.
-#
|--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.
--
- A command line argument of
--
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 ‘+’. +
- If a command line option begins with +, the remainder of that option is
taken to be an initial command to
less
. For example,+G
tellsless
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+
numberg; that is, it starts the display at the specified line number (however, see the caveat under theg
command 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.
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
|H
- Help: display a summary of these commands. If you forget all the other commands, remember this one.
SPACE
|^V
|f
|^F
- Scroll forward N lines, default one window (see option
-z
above). 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
|RETURN
|^N
|e
|^E
|j
|^J
- Scroll forward N lines, default 1. The entire N lines are displayed, even if N is more than the screen size.
d
|^D
- Scroll forward N lines, default one half of the screen size. If N is specified, it becomes the new default for subsequent d and u commands.
b
|^B
|ESC-v
- Scroll backward N lines, default one window (see option
-z
above). 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
|^Y
|^P
|k
|^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
|^U
- Scroll backward N lines, default one half of the screen size. If N is specified, it becomes the new default for subsequent d and u commands.
ESC-)
|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-(
|LEFTARROW
- Scroll horizontally left N characters, default half the screen width (see
the
-#
option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW commands. r
|^R
|^L
- Repaint the screen.
R
- Repaint the screen, discarding any buffered input. Useful if the file is changing while it is being viewed.
F
- Scroll forward, and keep trying to read when the end of file is reached. Normally this command would be used when already at the end of the file. It is a way to monitor the tail of a file which is growing while it is being viewed. (The behavior is similar to the "tail -f" command.)
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
|<
|ESC-<
- Go to line N in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.)
G
|>
|ESC->
- Go to line N in the file, default the end of the file. (Warning: this may be slow if N is large, or if N is not specified and standard input, rather than a file, is being read.)
p
|%
- 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 specify the N-th bracket on the line.
(
- Like {, but applies to parentheses rather than curly brackets.
)
- Like }, but applies to parentheses rather than curly brackets.
[
- Like {, but applies to square brackets rather than curly brackets.
]
- Like }, but applies to square brackets rather than curly brackets.
ESC-^F
- Followed by two characters, acts like {, but uses the two characters as open and close brackets, respectively. For example, "ESC ^F < >" could be used to go forward to the > which matches the < in the top displayed line.
ESC-^B
- Followed by two characters, acts like }, but uses the two characters as open and close brackets, respectively. For example, "ESC ^B < >" could be used to go backward to the < which matches the > in the bottom displayed line.
m
- Followed by any lowercase letter, marks the current position with that letter.
'
- (Single quote.) Followed by any lowercase letter, returns to the position which was previously marked with that letter. Followed by another single quote, returns to the position at which the last "large" movement command was executed. Followed by a ^ or $, jumps to the beginning or end of the file respectively. Marks are preserved when a new file is examined, so the ' command can be used to switch between input files.
^X^X
- Same as single quote.
/pattern
- Search forward in the file for the N-th line containing the pattern. N
defaults to 1. The pattern is a regular expression, as recognized by the
regular expression library supplied by your system. The search starts at
the 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
|!
- Search for lines which do NOT match the pattern.
^E
|*
- 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
|@
- 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.
?pattern
- Search backward in the file for the N-th line containing the pattern. The
search starts at the line immediately before the top line displayed.
Certain characters are special, as in the / command:
^N
|!
- Search for lines which do NOT match the pattern.
^E
|*
- 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
|@
- Begin the search at the last line of the last file in the command line
list, regardless of what is currently displayed on the screen or the
settings of the
-a
or-j
options. ^K
- As in forward searches.
^R
- As in forward searches.
ESC-/pattern
- Same as "/*".
ESC-?pattern
- Same as "?*".
n
- Repeat previous search, for N-th line containing the last pattern. If the previous search was modified by ^N, the search is made for the N-th line NOT containing the pattern. If the previous search was modified by ^E, the search continues in the next (or previous) file if not satisfied in the current file. If the previous search was modified by ^R, the search is done without using regular expressions. There is no effect if the previous search was modified by ^F or ^K.
N
- Repeat previous search, but in the reverse direction.
ESC-n
- Repeat previous search, but crossing file boundaries. The effect is as if the previous search were modified by *.
ESC-N
- Repeat previous search, but in the reverse direction and crossing file boundaries.
ESC-u
- Undo search highlighting. Turn off highlighting of strings matching the
current search pattern. If highlighting is already off because of a
previous ESC-u command, turn highlighting back on. Any search command will
also turn highlighting back on. (Highlighting can also be disabled by
toggling the
-G
option; in that case search commands do not turn highlighting back on.) &pattern
- Display only lines which match the pattern; lines which do not match the
pattern are not displayed. If pattern is empty (if you type &
immediately followed 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.
Certain characters are special as in the / command:
^N
|!- 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-examined. A percent sign (%) in the filename is
replaced by the name of the current file. A pound sign (#) is replaced by
the name of the previously examined file. However, two consecutive percent
signs are simply replaced with a single percent sign. This allows you to
enter a filename that contains a percent sign in the name. Similarly, two
consecutive pound signs are replaced with a single pound sign. The
filename is inserted into the command line list of files so that it can be
seen by subsequent :n and :p commands. If the filename consists of several
files, they are all inserted into the list of files and the first one is
examined. If the filename contains one or more spaces, the entire filename
should be enclosed in double quotes (also see the
-"
option). ^X^V
|E
- Same as :e. Warning: some systems use ^V as a special literalization character. On such systems, you may not be able to use ^V.
:n
- Examine the next file (from the list of files given in the command line). If a number N is specified, the N-th next file is examined.
:p
- Examine the previous file in the command line list. If a number N is specified, the N-th previous file is examined.
:t
- Go to the specified tag.
: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.
=
|^G
|:f
- Prints some information about the file being viewed, including its name and the line number and byte offset of the bottom line being displayed. If possible, it also prints the length of the file, the number of lines in the file and the percent of the file above the last displayed line.
-
- Followed by one of the command line option letters (see
DESCRIPTION above), this will change
the setting of that option and print a message describing the new setting.
If a ^P (CONTROL-P) is entered immediately after the dash, the setting of
the option is changed but no message is printed. If the option letter has
a numeric value (such as
-b
or-h
), or a string value (such as-P
or-t
), a new value may be entered after the option letter. If no new value is entered, a message describing the current setting is printed and nothing is changed. --
- Like the - command, but takes a long option name (see DESCRIPTION above) 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
|Q
|:q
|:Q
|ZZ
- Exits
less
.
The following four commands may or may not be valid, depending on your particular installation.
v
- Invokes an editor to edit the current file being viewed. The editor is
taken from the environment variable
VISUAL
, if defined, orEDITOR
ifVISUAL
is not defined, or defaults to "vi" if neitherVISUAL
norEDITOR
is defined. See also the discussion of LESSEDIT under the section on PROMPTS below. - |
<m>
shell-command - <m> represents any mark letter. Pipes a section of the input file to the given shell command. The section of the file to be piped is between the first line on the current screen and the position marked by the letter. <m> may also be ^ or $ to indicate beginning or end of file respectively. If <m> is . or newline, the current screen is piped.
s
filename- Save the input to a file. This only works if the input is a pipe, not an ordinary file.
LINE EDITING
When entering command line at the bottom of the screen (for example, a filename for the :e command, or the pattern for a search command), certain keys can be used to manipulate the command line. Most commands have an alternate form in [ brackets ] which can be used if a key does not exist on a particular keyboard. Any of these special keys may be entered literally by preceding it with the "literal" character, either ^V or ^A. A backslash itself may also be entered literally by entering two backslashes.
- LEFTARROW [ESC-h]
- Move the cursor one space to the left.
- RIGHTARROW [ESC-l]
- Move the cursor one space to the right.
- ^LEFTARROW [ESC-b or ESC-LEFTARROW]
- (That is, CONTROL and LEFTARROW simultaneously.) Move the cursor one word to the left.
- ^RIGHTARROW [ESC-w or ESC-RIGHTARROW]
- (That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right.
- HOME [ESC-0]
- Move the cursor to the beginning of the line.
- END [ESC-$]
- Move the cursor to the end of the line.
- BACKSPACE
- Delete the character to the left of the cursor, or cancel the command if the command line is empty.
- DELETE or [ESC-x]
- Delete the character under the cursor.
- ^BACKSPACE [ESC-BACKSPACE]
- (That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor.
- ^DELETE [ESC-X or ESC-DELETE]
- (That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor.
- UPARROW [ESC-k]
- Retrieve the previous command line. 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 through the other matching filenames. If the
completed filename is a directory, a "/" is appended to the
filename. 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 through 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
- Delete the entire command line, or cancel the command if the command line is empty. If you have changed your line-kill character to something other 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
using the program
lesskey(1) to create a lesskey file. This file specifies a set of
command keys and an action associated with each key. You may also use
lesskey to change the line-editing keys (see
LINE EDITING), and to set environment
variables. If the environment variable LESSKEY
is
set, less
uses that as the name of the lesskey file.
Otherwise, less
looks 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, 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 OpenBSD, the system-wide lesskey
file is /etc/sysless.
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 contents of the original
file. However, it will appear to the user as if the original file is opened;
that is, less
will display the original filename as
the name of the current file.
An input preprocessor receives one command line argument, the
original filename, as entered by the user. It should create the replacement
file, and when finished print the name of the replacement file to its
standard output. If the input preprocessor does not output a replacement
filename, less
uses the original file, as normal.
The input preprocessor is not called when viewing standard input. To set up
an input preprocessor, set the LESSOPEN
environment
variable to a command line which will invoke your input preprocessor. This
command line should include one occurrence of the string "%s",
which will be replaced by the filename when the input preprocessor command
is invoked.
When less
closes a file opened in such a
way, it will call another program, called the input postprocessor, which may
perform any desired clean-up action (such as deleting the replacement file
created by LESSOPEN
). This program receives two
command line arguments, the original filename as entered by the user, and
the name of the replacement file. To set up an input postprocessor, set the
LESSCLOSE
environment variable to a command line
which will invoke your input postprocessor. It may include two occurrences
of the string "%s"; the first is replaced with the original name
of the file and the second with the name of the replacement file, which was
output by LESSOPEN
.
For example, these two scripts will allow you to keep files in
compressed format, but still let less
view them
directly:
lessopen.sh:
#! /bin/sh case "$1" in *.Z) uncompress -c $1 >/tmp/less.$$ 2>/dev/null if [ -s /tmp/less.$$ ]; then echo /tmp/less.$$ else rm -f /tmp/less.$$ fi ;; esac
lessclose.sh:
#! /bin/sh rm $2
To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on.
It is also possible to set up an input preprocessor to pipe the
file data directly to less
, rather than putting the
data into a replacement file. This avoids the need to decompress the entire
file before starting to view it. An input preprocessor that works this way
is called an input pipe. An input pipe, instead of writing the name of a
replacement file on its standard output, writes the entire contents of the
replacement file on its standard output. If the input pipe does not write
any characters on its standard output, then there is no replacement file and
less
uses the original file, as normal. To use an
input pipe, make the first character in the LESSOPEN
environment variable a vertical bar (|) to signify that the input
preprocessor is an input pipe.
For example, 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 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
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 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.
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.
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
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 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
characters.
When the character set is utf-8, the
LESSUTFBINFMT
environment variable acts similarly to
LESSBINFMT but it applies to Unicode code points that were successfully
decoded but are unsuitable for display (e.g., unassigned code points). Its
default value is "<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.
PROMPTS
The -P
option allows you to tailor the
prompt to your preference. The string given to the
-P
option replaces the specified prompt string.
Certain characters in the string are interpreted specially. The prompt
mechanism is rather complicated to provide flexibility, but the ordinary
user need not understand the details of constructing personalized prompt
strings.
A percent sign followed by a single character is expanded according to what the following character is:
- %bX
- Replaced by the byte offset into the current input file. The b is followed
by a single character (shown as X above) which
specifies the line whose byte offset is to be used. If the character is a
"t", the byte offset of the top line in the display is used, an
"m" means use the middle line, a "b" means use the
bottom line, a "B" means use the line just after the bottom
line, and a "j" means use the "target" line, as
specified by the
-j
option. - %B
- Replaced by the size of the current input file.
- %c
- Replaced by the column number of the text appearing in the first column of the screen.
- %dX
- Replaced by the page number of a line in the input file. The line to be used is determined by the X, as with the %b option.
- %D
- Replaced by the number of pages in the input file, or equivalently, the page number of the last line in the input file.
- %E
- Replaced by the name of the editor (from the
VISUAL
environment variable, or theEDITOR
environment variable ifVISUAL
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.
- %i
- Replaced by the index of the current file in the list of input files.
- %lX
- Replaced by the line number of a line in the input file. The line to be used is determined by the X, as with the %b option.
- %L
- Replaced by the line number of the last line in the input file.
- %m
- Replaced by the total number of input files.
- %pX
- Replaced by the percent into the current input file, based on byte offsets. The line used is determined by the X, as with the %b option.
- %PX
- Replaced by the percent into the current input file, based on line numbers. The line used is determined by the X, as with the %b option.
- %s
- Same as %B.
- %t
- Causes any trailing spaces to be removed. Usually used at the end of the string, but may appear anywhere.
- %x
- Replaced by the name of the next input file in the list.
If any item is unknown (for example, the file size if input is a pipe), a question mark is printed instead.
The format of the prompt string can be changed depending on certain conditions. A question mark followed by a single character acts like an "IF": depending on the following character, a condition is evaluated. If the condition is true, any characters following the question mark and condition character, up to a period, are included in the prompt. If the condition is false, such characters are not included. A colon appearing between the question mark and the period can be used to establish an "ELSE": any characters between the colon and the period are included in the string, if and only if the IF condition is false. Condition characters (which follow a question mark) may be:
- ?a
- True if any characters have been included in the prompt so far.
- ?bX
- True if the byte offset of the specified line is known.
- ?B
- True if the size of the 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(file %i of %m) ..?e(END) ?x- Next\: %x..%t
This prints the filename if this is the first prompt in a file,
followed by the "file N of N" message if there is more than one
input file. Then, if we are at end-of-file, the string "(END)" is
printed followed by the name of the next file, if there is one. Finally, any
trailing spaces are truncated. This is the default prompt. For reference,
here are the defaults for the other two prompts (-m
and -M
respectively). Each is broken into two lines
here for readability only.
?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
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 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).
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 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 down.
The -e
option works differently: it causes
more(1) to exit the first time it reaches EOF, not the second.
The -i
option acts like the
-I
option. The normal behavior of the
-i
option is unavailable in this mode.
The -m
option works differently: if it is
not specified, the medium prompt is used; if it is specified, the short
prompt is used.
The -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
results (-G
), and disable termcap initialization
(-X
) are on by default.
The LESS
environment variables are
ignored, and the MORE
environment variable is used
in its place.
ENVIRONMENT
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 may be overridden by window systems which supportTIOCGWINSZ
. EDITOR
- Specifies the default editor if
VISUAL
is not set. If neither are set, vi(1) is used. HOME
- Name of the user's home directory (used to find a lesskey file).
LANG
- Language for determining the character set.
LC_CTYPE
- The character encoding locale(1). It decides which byte sequences form characters, what their display width is, and which characters are composing or combining characters.
LESS
- Options which are passed to
less
automatically. Command line options override theLESS
environment variable.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:LESS="-Ps--More--$-C -e"
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 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. 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.
LESSCLOSE
- Command line to invoke the (optional) input-postprocessor.
LESSEDIT
- Editor prototype string (used for the v command). See discussion under PROMPTS.
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 "-". LESSHISTSIZE
- The maximum number of commands to save in the history file. The default is 100.
LESSKEY
- Name of the default lesskey(1) file.
LESSKEY_SYSTEM
- Name of the default system-wide lesskey(1) file.
LESSMETACHARS
- List of characters which are considered "metacharacters" by the shell.
LESSMETAESCAPE
- Prefix which
less
will add before each metacharacter in a command sent to the shell. If LESSMETAESCAPE is an empty string, commands containing metacharacters will not be passed to the shell. LESSOPEN
- Command line to invoke the (optional) input-preprocessor.
LESSSECURE
- Runs less in "secure" mode. See discussion under SECURITY.
LESSSEPARATOR
- String to be appended to a directory name in filename completion.
LESSUTFBINFMT
- Format for displaying non-printable Unicode code points.
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 may be overridden by window
systems which support
TIOCGWINSZ
. MORE
- Options which are passed to
less
automatically when running in more(1) compatible mode. SHELL
- The shell used to expand filenames.
TERM
- Specifies the terminal type. Used by
less
to get the terminal characteristics necessary to manipulate the screen. VISUAL
- Specifies the default editor. If not set,
EDITOR
is used; if that is not set, vi(1) is used.
SEE ALSO
AUTHORS
Mark Nudelman.