本文介绍了使用less命令查看文本文件的基本操作，包括语法、常用参数及全屏、单行和标记导航。less命令提供了向前搜索、显示行号、翻页、退出等便捷功能，是一个强大的文本查看工具。
3.14 less文本查看
3.14.1 语法
less [参数] 文件名
less - opposite of more
3.14.2 常用参数
-
基础操作
【-b <缓冲区大小>】设置缓冲区的大小
【-e】当文件显示结束后，自动离开
【-f】强迫打开特殊文件，例如外围设备代号、目录和二进制文件
【-g】只标识最后搜索的关键词
【-i】忽略搜索时的大小写
【-m】显示类似more命令的百分比
【-N】显示每行的行号
【-o <文件名>】将less输出的内容在指定文件中保存起来
【-Q】不使用警告音
【-s】显示连续空行为一行
【-S】行过长时间将长处部分舍弃
【-x <数字>】将“TAB”键显示为规定的数字空格（设置一个tab表示几个空格） -
阅读导航
【/字符串】：向下搜索“字符串”
【?字符串】：向上搜索“字符串”
【n】重复前一个搜索（与/或？有关）
【N】反向重复前一个搜索（与/或？有关）
【b】向后翻一页
【d】向后翻半页
【h】显示帮助界面
【Q】退出less命令
【u】向前滚动半页
【y】向前滚动一行
【空格键】滚动一页
【回车键】滚动一行
【pagedown】向下翻一页
【pageup】向上翻一页 -
全屏导航
【ctrl+F】向前滚动一屏
【ctrl+B】向后滚动一屏
【ctrl+D】向前滚动半屏
【ctrl+U】向后滚动半屏 -
单行导航
【j】向前移动一行
【k】向后移动一行 -
标记导航
【ma】使用a标记文本的当前位置
【'a】当行标记a处 -
其他
【G】移动到最后一行
【g】移动到第一行
【q/ZZ】退出less命令
【v】进入编辑模式，编辑当前文件
【h】显示less的帮助文档
【&pattern】仅显示匹配模式的行，而不是整个文件
3.14.3 附加（man less）
NAME
less - opposite of more
SYNOPSIS
less -?
less --help
less -V
less --version
less [-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-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 number, called N in the descriptions below. The number is used by some commands, as indicated.
COMMANDS
In the following descriptions, ^X means control-X. ESC stands for the ESCAPE key; for example ESC-v means the two character sequence "ESCAPE", then "v".
h or H Help: display a summary of these commands. If you forget all the other commands, remember this one.
SPACE or ^V or f or ^F
Scroll forward N lines, default one window (see option -z below). If N is more than the screen size, only the final screenful is displayed. Warning: some systems use ^V as
a special literalization character.
z Like SPACE, but if N is specified, it becomes the new window size.
ESC-SPACE
Like SPACE, but scrolls a full screenful, even if it reaches end-of-file in the process.
RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines are displayed, even if N is more than the screen size.
d or ^D
Scroll forward N lines, default one half of the screen size. If N is specified, it becomes the new default for subsequent d and u commands.
b or ^B or ESC-v
Scroll backward N lines, default one window (see option -z below). If N is more than the screen size, only the final screenful is displayed.
w Like ESC-v, but if N is specified, it becomes the new window size.
y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1. The entire N lines are displayed, even if N is more than the screen size. Warning: some systems use ^Y as a special job control charac-
ter.
u or ^U
Scroll backward N lines, default one half of the screen size. If N is specified, it becomes the new default for subsequent d and u commands.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default half the screen width (see the -# option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFT-
ARROW 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 LEFT-
ARROW commands.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input. Useful if the file is changing while it is being viewed.
F Scroll forward, and keep trying to read when the end of file is reached. Normally this command would be used when already at the end of the file. It is a way to monitor the
tail of a file which is growing while it is being viewed. (The behavior is similar to the "tail -f" command.)
g or < or ESC-<
Go to line N in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the file. (Warning: this may be slow if N is large, or if N is not specified and standard input, rather than a file, is being
read.)
p or % Go to a position N percent into the file. N should be between 0 and 100, 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 posi-
tioned 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 second line displayed (but see the -a and -j options, which change this).
Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search reaches the END of the current file without finding a match, the search continues in the next file in the command line
list.
^F or @
Begin the search at the first line of the FIRST file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j
options.
^K Highlight any text which matches the pattern on the 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 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 com-
mand line list.
^F or @
Begin the search at the last line of the last file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j
options.
^K As in forward searches.
^R As in forward searches.
ESC-/pattern
Same as "/*".
ESC-?pattern
Same as "?*".
n Repeat previous search, for N-th line containing the last pattern. If the previous search was modified by ^N, the search is made for the N-th line NOT containing the pat-
tern. 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 modi-
fied 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 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-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 file-
name 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 character. On such systems, you may not be able to use ^V.
:n Examine the next file (from the list of files given in the command line). If a number N is specified, the N-th next file is examined.
:p Examine the previous file in the command line list. If a number N is specified, the N-th previous file is examined.
:x Examine the first file in the command line list. If a number N is specified, the N-th file in the list is examined.
:d Remove the current file from the list of files.
t Go to the next tag, if there were more than one matches for the current tag. See the -t option for more details about tags.
T Go to the previous tag, if there were more than one matches for the current tag.
= or ^G or :f
Prints some information about the file being viewed, including its name and the line number and byte offset of the bottom line being displayed. If possible, it also prints
the length of the file, the number of lines in the file and the percent of the file above the last displayed line.
- Followed by one of the command line option letters (see OPTIONS below), this will change the setting of that option and print a message describing the new setting. If a ^P
(CONTROL-P) is entered immediately after the dash, the setting of the option is changed but no message is printed. If the option letter has a numeric value (such as -b or
-h), or a string value (such as -P or -t), a new value may be entered after the option letter. If no new value is entered, a message describing the current setting is
printed and nothing is changed.
-- Like the - command, but takes a long option name (see OPTIONS below) rather than a single option letter. You must press RETURN after typing the option name. A ^P immedi-
ately 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 RETURN after typing the option name.
+cmd Causes the specified cmd to be executed each time a new file is examined. For example, +G causes less to initially display each file starting at the end rather than the
beginning.
V Prints the version number of less being run.
q or Q or :q or :Q or ZZ
Exits less.
The following four commands may or may not be valid, depending on your particular installation.
v Invokes an editor to edit the current file being viewed. The editor is taken from the environment variable VISUAL if defined, or EDITOR if VISUAL is not defined, or defaults
to "vi" if neither VISUAL nor EDITOR is defined. See also the discussion of LESSEDIT under the section on PROMPTS below.
! shell-command
Invokes a shell to run the shell-command given. A percent sign (%) in the command is replaced by the name of the current file. A pound sign (#) is replaced by the name of
the previously examined file. "!!" repeats the last shell command. "!" with no shell command simply invokes a shell. On Unix systems, the shell is taken from the environ-
ment variable SHELL, or defaults to "sh". On MS-DOS and OS/2 systems, the shell is the normal command processor.
| <m> shell-command
<m> represents any mark letter. Pipes a section of the input file to the given shell command. The section of the file to be piped is between the first line on the current
screen and the position marked by the letter. <m> may also be ^ or $ to indicate beginning or end of file respectively. If <m> is . or newline, the current screen is piped.
s filename
Save the input to a file. This only works if the input is a pipe, not an ordinary file.
OPTIONS
Command line options are described below. Most options may be changed while less is running, via the "-" command.
Most options may be given in one of two forms: either a dash followed by a single letter, or two dashes followed by a long option name. A long option name may be abbreviated as
long as the abbreviation is unambiguous. For example, --quit-at-eof may be abbreviated --quit, but not --qui, since both --quit-at-eof and --quiet begin with --qui. Some long
option names are in uppercase, such as --QUIT-AT-EOF, as distinct from --quit-at-eof. Such option names need only have their first letter capitalized; the remainder of the name may
be in either case. For example, --Quit-at-eof is equivalent to --QUIT-AT-EOF.
Options are also taken from the environment variable "LESS". For example, to avoid typing "less -options ..." each time less is invoked, you might tell csh:
setenv LESS "-options"
or if you use sh:
LESS="-options"; export LESS
On MS-DOS, you don’t need the quotes, but you should replace any 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 "-+".
For options like -P or -D which take a following string, a dollar sign ($) must be used to signal the end of the string. For example, to set two -D options on MS-DOS, you must have
a dollar sign between them, like this:
LESS="-Dn9.1$-Ds4.1"
-? or --help
This option displays a summary of the commands accepted by less (the same as the h command). (Depending on how your shell interprets the question mark, it may be necessary
to quote the question mark, thus: "-\?".)
-a or --search-skip-screen
Causes searches to start after the last line displayed on the screen, thus skipping all lines displayed on the screen. By default, searches start at the second line on the
screen (or after the last found line; see the -j option).
-bn or --buffers=n
Specifies the amount of buffer space less will use for each file, in units of kilobytes (1024 bytes). By default 64K of buffer space is used for each file (unless the file
is a pipe; see the -B option). The -b option specifies instead that n kilobytes of buffer space should be used for each file. If n is -1, buffer space is unlimited; that
is, the entire file 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 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.
-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
[MS-DOS only] Sets the color of the text displayed. x is a single character which selects the type of text whose color is being set: n=normal, s=standout, d=bold, u=under-
lined, k=blink. color is a pair of numbers separated by a period. The first number selects the foreground color and the second selects the background color of the text. A
single number N is the same as N.M, where M is the normal background color.
-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 somewhat 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 direction instead. (If
the terminal does not have the ability to scroll backward, -h0 is implied.)
-i or --ignore-case
Causes searches to ignore case; that is, uppercase and 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.
-I or --IGNORE-CASE
Like -i, but searches ignore case even if the pattern contains uppercase letters.
-jn or --jump-target=n
Specifies a line on the screen where the "target" line is to be positioned. The target line is the line specified by any command to search for a pattern, jump to a line num-
ber, 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. 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.
-J or --status-column
Displays a status column at the left edge of the screen. The status column shows the lines that matched the current search. The status column is also used if the -w or -W
option is in effect.
-kfilename or --lesskey-file=filename
Causes less to open and interpret the named file as a lesskey (1) file. Multiple -k options may be specified. If the LESSKEY or LESSKEY_SYSTEM environment variable is set,
or if a lesskey file is found in a standard place (see KEY BINDINGS), it is also used as a lesskey file.
-K or --quit-on-intr
Causes less to exit immediately 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" command.
-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 subse-
quently, not to the file which is currently open.
-m or --long-prompt
Causes less to prompt verbosely (like more), with the percent into the file. By default, less prompts with a colon.
-M or --LONG-PROMPT
Causes less to prompt even more verbosely than more.
-n or --line-numbers
Suppresses line numbers. The default (to use line numbers) may cause less to run more slowly in some cases, especially with a very large input file. Suppressing line num-
bers with the -n option will avoid this problem. Using line numbers means: the line number will be displayed in the verbose prompt and in the = command, and the v command
will pass the current line number to the editor (see also the discussion of LESSEDIT in PROMPTS below).
-N or --LINE-NUMBERS
Causes a line number to be displayed at the beginning of each line in the display.
-ofilename or --log-file=filename
Causes less to copy its input to the named file as it is being viewed. This applies only when the input file is a pipe, not an ordinary file. If the file already exists,
less will ask for confirmation before overwriting it.
-Ofilename or --LOG-FILE=filename
The -O option is like -o, but it will overwrite an existing file without asking for confirmation.
If no log file has been specified, the -o and -O options can be used from within less to specify a log file. Without a file name, they will simply report the name of the log
file. The "s" command is equivalent to specifying -o from within less.
-ppattern or --pattern=pattern
The -p option on the command line is equivalent to specifying +/pattern; that is, it tells less to start at the first 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 being typed in with
each less command. Such an option must either be the last option in the LESS variable, or be terminated by a dollar sign. -Ps followed by a string changes the default
(short) prompt to that string. -Pm changes the medium (-m) prompt. -PM changes the long (-M) prompt. -Ph changes the prompt for the help screen. -P= changes the message
printed by the = command. -Pw changes the message printed while waiting for data (in the F command). All prompt strings consist of a sequence of letters and special escape
sequences. See the section on PROMPTS for more details.
-q or --quiet or --silent
Causes moderately "quiet" operation: the terminal bell is not rung if an attempt is made to scroll past the end of the file or before the beginning of the file. If the ter-
minal has a "visual bell", it is used instead. The bell will be rung on certain other errors, such as typing an invalid character. The default is to ring the terminal bell
in all such cases.
-Q or --QUIET or --SILENT
Causes totally "quiet" operation: the terminal bell is never rung.
-r or --raw-control-chars
Causes "raw" control characters to be displayed. The default is to display control characters using the caret notation; for example, a control-A (octal 001) is displayed as
"^A". 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 con-
trol character). Thus, various display problems may result, such as long lines being split in the wrong place.
-R or --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 variable LESSANSIENDCHARS to the list of char-
acters 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 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 rather than folded. That is, the portion of a long line that does not fit in the screen width is not shown. The
default is to fold long lines; that is, display the remainder on the next line.
-ttag or --tag=tag
The -t option, followed immediately by a TAG, will edit the file containing that tag. For this to work, tag information must be available; for example, there may be a file
in the current directory called "tags", which was previously 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 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 ter-
minal’s hardware underlining capability. Also, backspaces which appear between two identical characters are treated specially: the overstruck text is printed using the ter-
minal’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.
-V or --version
Displays the version number of less.
-w or --hilite-unread
Temporarily highlights the first "new" line after a forward movement of a full page. The first "new" line is the line immediately following the line previously at the bottom
of the screen. Also highlights the target line after a g or p 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.
-W or --HILITE-UNREAD
Like -w, but temporarily highlights the first new line after any forward movement command larger than one line.
-xn,... or --tabs=n,...
Sets tab stops. If only one n is specified, tab stops are set at multiples of n. If multiple values separated by commas are specified, tab stops are set at those positions,
and then 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 unneces-
sary, 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.
-[z]n or --window=n
Changes the default scrolling window size to n lines. The default is one screenful. The z and w commands can also be used to change the window size. The "z" may be omitted
for compatibility with 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 automatically changes to 36 lines.
-"cc or --quotes=cc
Changes the filename quoting character. This may be necessary if you are trying to name a file which contains both spaces and quote characters. Followed by a single charac-
ter, 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 character and followed by the close quote character. Note that even after the quote characters are changed, this option remains -" (a dash followed by a double quote).
-~ or --tilde
Normally lines after end of file are displayed as a single tilde (~). This option causes lines after end of file to be displayed as blank lines.
-# or --shift
Specifies the default number of positions to scroll 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.
--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.
--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 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.
-- 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 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 (however, see the caveat under the "g" command above). If the option starts with ++, the initial command applies to every file being
viewed, not just the first one. The + command described previously may also be used to set (or change) an initial command for every file.
LINE EDITING
When entering command line at the bottom of the screen (for example, a filename for the :e command, or the pattern for a search command), certain keys can be used to manipulate the
command line. Most commands have an alternate form in [ brackets ] which can be used if a key does not exist on a particular keyboard. (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" charac-
ter, 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.
DOWNARROW [ ESC-j ]
Retrieve the next command line.
TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match is entered into the command line. Repeated TABs will cycle
thru the other matching filenames. If the completed filename is a directory, a "/" is appended to the filename. (On MS-DOS systems, a "\" is appended.) The environment
variable LESSSEPARATOR can be used to specify a different character to append to a directory name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the 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 other than ^U, that
character is used instead of ^U.
KEY BINDINGS
You may define your own less commands by using the program lesskey (1) to create a lesskey file. This file specifies a set of command keys and an action associated with each key.
You may also use lesskey to change the line-editing keys (see LINE EDITING), and to set environment variables. If the environment variable LESSKEY is set, less uses that as the
name of the lesskey file. Otherwise, less looks in a standard place for the lesskey file: On Unix systems, less looks for a lesskey file called "$HOME/.less". On MS-DOS and Win-
dows systems, less looks for a lesskey file called "$HOME/_less", and if it is not found there, then looks for a lesskey file called "_less" in any directory specified in the PATH
environment variable. On OS/2 systems, less looks for a lesskey file called "$HOME/less.ini", and if it is not found, then looks for a lesskey file called "less.ini" in any direc-
tory specified in the INIT environment variable, and if it not found there, then looks for a lesskey file called "less.ini" in any directory specified in the PATH environment vari-
able. See the lesskey manual page for more details.
A system-wide lesskey file may also be set up to provide key bindings. If a key is defined in both a local lesskey file and in the system-wide file, key bindings in the local file
take precedence over those in the system-wide file. If the environment variable LESSKEY_SYSTEM is set, less uses that as the name of the system-wide lesskey file. Otherwise, less
looks in a standard place for the system-wide lesskey file: On Unix systems, the system-wide lesskey file is /usr/local/etc/sysless. (However, if less was built with a different
sysconf directory than /usr/local/etc, that directory is where the sysless file is found.) On MS-DOS and Windows systems, the system-wide lesskey file is c:\_sysless. On OS/2 sys-
tems, the system-wide lesskey file is c:\sysless.ini.
INPUT PREPROCESSOR
You may define an "input preprocessor" for less. Before less opens a file, it first gives your input preprocessor a chance to modify the way the contents of the file are displayed.
An input preprocessor is simply an executable program (or shell script), which writes the 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, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let less view them directly:
lessopen.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -
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
BACKSPACE
Delete the character to the left of the cursor, or cancel the command if the command line is empty.
DELETE or [ ESC-x ]
Delete the character under the cursor.
^BACKSPACE [ ESC-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor.
^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor.
UPARROW [ ESC-k ]
Retrieve the previous command line.
DOWNARROW [ ESC-j ]
Retrieve the next command line.
TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match is entered into the command line. Repeated TABs will cycle
thru the other matching filenames. If the completed filename is a directory, a "/" is appended to the filename. (On MS-DOS systems, a "\" is appended.) The environment
variable LESSSEPARATOR can be used to specify a different character to append to a directory name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the 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 other than ^U, that
character is used instead of ^U.
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