#Bash 的 less 命令
less [OPTION]... FELE...
功能
分页查看文件内容。
类型
可执行文件（/usr/bin/less），属于 less。
参数
FILE文件列表，如果没有这个参数或指定为-，则读取标准输入
#操作说明
| 命令 | 说明（中文） |
|---|---|
| h 或 H | 显示帮助信息，总览所有命令。忘记其他命令时记住这条即可。 |
| SPACE / ^V / f / ^F | 向前滚动 N 行，默认滚动一页（窗口大小）。若 N 大于屏幕高度，只显示最后的屏幕内容。注意：某些系统把 ^V 用作特殊转义字符。 |
| z | 与 SPACE 类似，但若指定 N，则把 N 设置为新的窗口大小。 |
| ESC-SPACE | 与 SPACE 类似，但总是滚动整整一屏，即使会越过文件末尾。 |
| ENTER / RETURN / ^N / e / ^E / j / ^J | 向前滚动 N 行，默认 1 行。即使 N 超过屏幕高度，也会完整显示 N 行。 |
| d / ^D | 向前滚动 N 行，默认为屏幕的一半。若指定 N，则此 N 变为随后 d 与 u 的默认值。 |
| b / ^B / ESC-v | 向后滚动 N 行，默认滚动一页。若 N 超出屏幕大小，只显示最后的屏幕内容。 |
| w | 与 ESC-v 类似，但如果指定 N，则设置新的窗口大小。 |
| y / ^Y / ^P / k / ^K | 向后滚动 N 行，默认 1 行。即使 N 超过屏幕高度，也会完整显示 N 行。注意：某些系统把 ^Y 作业控制用途。 |
| u / ^U | 向后滚动 N 行，默认为屏幕的一半。若指定 N，则设置为随后 d/u 的默认 N。 |
| J | 类似 j，但可继续滚动过文件末尾。 |
| K 或 Y | 类似 k，但可继续滚动到文件开头之前。 |
| ESC-) （或→ 方向键） | 向右移动 N 列，默认 1 列。 |
| ESC-( （或← 方向键） | 向左移动 N 列，默认 1 列。注意某些系统把 ( 用作 shell 特殊字符。 |
| ESC-} | 向右移动 N 屏宽，默认一次屏幕宽度。 |
| ESC-{ | 向左移动 N 屏宽，默认一次屏幕宽度。注意某些系统把 { 作为特殊字符。 |
| F | 类似 tail -f：显示文件最新内容。当到达文件末尾时，如果文件继续增长则自动显示新增内容。按 Ctrl-C 退出 F 模式。 |
| ESC-F | 与 F 类似，但如果底部提示抑制，则不提示。 |
| g 或 < | 跳到文件开头；若输入 N，则跳到第 N 行开头。 |
| G 或 > | 跳到文件末尾（等待文件增长）。若输入 N，则跳到第 N 行开头。 |
| p 或 % | 跳转到文件的 N%。例如：50% 跳到文件中间。 |
| m x | 在当前位置设置书签，名称为 x（x 是任意字母）。 |
| ' x | 跳到名称为 x 的书签位置。 |
| '' | 跳回前一位置（双引号，两次）。 |
| /pattern | 向前搜索 pattern。搜索完成后滚动到匹配行顶部。 |
| ?pattern | 向后搜索 pattern。搜索完成后滚动到匹配行底部。 |
| n | 重复最近一次搜索（方向相同）。 |
| N | 重复最近一次搜索（方向相反）。 |
| ESC-n | 重复最近一次搜索，但方向固定为向前。 |
| ESC-N | 重复最近一次搜索，但方向固定为向后。 |
| ESC-/pattern | 搜索但不移动屏幕，仅高亮匹配内容（如果启用了高亮）。 |
| :&pattern | 删除匹配 pattern 的搜索高亮。 |
| Ctrl-G | 显示当前文件名、当前行等信息。再按一次关闭。 |
| f 文件名 | 打开并显示新的文件。 |
| :n | 切换到参数列表中的下一个文件。 |
| :p | 切换到参数列表中的前一个文件。 |
| :e 文件 | 编辑文件（从 LESS 中调到编辑器）。 |
| v | 使用编辑器编辑当前文件（取决于 $EDITOR 环境变量）。 |
| :x | 查看命令行列表中的第一个文件；若指定 N，则查看第 N 个文件。 |
| :d | 从文件列表中删除当前文件。 |
| t | 跳到下一个 tag（如果当前 tag 有多个匹配）。详见 -t 选项说明。 |
| T | 跳到上一个 tag（如果当前 tag 有多个匹配）。 |
| = 或 Ctrl-G 或 :f | 显示当前文件信息，包括文件名、显示底行的行号和字节偏移量。如果可能，还会显示文件长度、总行数及已显示部分百分比。 |
| - | 修改命令行选项的设置，并显示新的设置消息。输入 Ctrl-P 可以不显示消息。支持数字或字符串选项。 |
| -- | 与 - 类似，但使用长选项名。按 ENTER 确认。 |
| -+ | 将选项恢复为默认值，并显示设置消息。不适用于字符串选项。 |
| --+ | 与 -+ 类似，但使用长选项名。 |
| -! | 将选项设置为与默认值相反，并显示消息。不适用于数字或字符串选项。 |
| --! | 与 -! 类似，但使用长选项名。 |
| _ | 显示当前选项设置，但不修改。 |
| __ | 与 _ 类似，但使用长选项名。按 ENTER 确认。 |
| +cmd | 每次查看新文件时执行指定命令。例如 +G 让 less 从文件末尾开始显示。 |
| V | 显示 less 版本号。 |
| q 或 Q 或 :q 或 :Q 或 ZZ | 退出 less。 |
| ! shell-command | 在 shell 中执行指定命令。命令中的 % 被替换为当前文件名，# 被替换为上一个文件名。!! 重复上一次 shell 命令。 |
| ** | <m> shell-command** |
| s filename | 将输入保存到文件。仅在输入为管道时有效，普通文件不可用。 |
#相关命令
| 命令 | 说明 |
|---|---|
| more | 分页查看文件内容 |
#推荐阅读
#手册
LESS(1) General Commands Manual LESS(1)
NAME
less - opposite of more
SYNOPSIS
less -?
less --help
less -V
less --version
less [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-b space] [-h lines] [-j line] [-k keyfile]
[-{oO} logfile] [-p pattern] [-P prompt] [-t tag]
[-T tagsfile] [-x tab,...] [-y lines] [-[z] lines]
[-# shift] [+[+]cmd] [--] [filename]...
(See the OPTIONS section for alternate option syntax with long option
names.)
DESCRIPTION
Less is a program similar to more(1), but it has many more features.
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 "ES‐
CAPE", 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 be‐
low). If N is more than the screen size, only the final screen‐
ful is displayed. Warning: some systems use ^V as a special
literalization character.
z Like SPACE, but if N is specified, it becomes the new window
size.
ESC-SPACE
Like SPACE, but scrolls a full screenful, even if it reaches
end-of-file in the process.
ENTER or RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines are dis‐
played, 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 be‐
low). If N is more than the screen size, only the final screen‐
ful 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 dis‐
played, even if N is more than the screen size. Warning: some
systems use ^Y as a special job control character.
u or ^U
Scroll backward N lines, default one half of the screen size.
If N is specified, it becomes the new default for subsequent d
and u commands.
J Like j, but continues to scroll beyond the end of the file.
K or Y Like k, but continues to scroll beyond the beginning of the
file.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default half the screen
width (see the -# option). If a number N is specified, it be‐
comes the default for future RIGHTARROW and LEFTARROW commands.
While the text is scrolled, it acts as though the -S option
(chop lines) were in effect.
ESC-( or LEFTARROW
Scroll horizontally left N characters, default half the screen
width (see the -# option). If a number N is specified, it be‐
comes the default for future RIGHTARROW and LEFTARROW commands.
ESC-} or ^RIGHTARROW
Scroll horizontally right to show the end of the longest dis‐
played line.
ESC-{ or ^LEFTARROW
Scroll horizontally left back to the first column.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input. That is, re‐
load the current file. Useful if the file is changing while it
is being viewed.
F Scroll forward, and keep trying to read when the end of file is
reached. 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.) To stop waiting for more
data, enter the interrupt character (usually ^C). On some sys‐
tems you can also use ^X.
ESC-F Like F, but as soon as a line is found which matches the last
search pattern, the terminal bell is rung and forward scrolling
stops.
g or < or ESC-<
Go to line N in the file, default 1 (beginning of file). (Warn‐
ing: 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. (Warn‐
ing: this may be slow if N is large, or if N is not specified
and standard input, rather than a file, is being read.)
ESC-G Same as G, except if no number N is specified and the input is
standard input, goes to the last line which is currently
buffered.
p or % Go to a position N percent into the file. N should be between 0
and 100, and may contain a decimal point.
P Go to the line containing byte offset N in the file.
{ If a left curly bracket appears in the top line displayed on the
screen, the { command will go to the matching right curly
bracket. The matching right curly bracket is positioned on the
bottom line of the screen. If there is more than one left curly
bracket on the top line, a number N may be used to specify the
N-th bracket on the line.
} If a right curly bracket appears in the bottom line displayed on
the screen, the } command will go to the matching left curly
bracket. The matching left curly bracket is positioned on the
top line of the screen. If there is more than one right curly
bracket on the top line, a number N may be used to 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 brack‐
ets.
] Like }, but applies to square brackets rather than curly brack‐
ets.
ESC-^F Followed by two characters, acts like {, but uses the two char‐
acters 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 char‐
acters as open and close brackets, respectively. For example,
"ESC ^B < >" could be used to go backward to the < which matches
the > in the bottom displayed line.
m Followed by any lowercase or uppercase letter, marks the first
displayed line with that letter. If the status column is en‐
abled via the -J option, the status column shows the marked
line.
M Acts like m, except the last displayed line is marked rather
than the first displayed line.
' (Single quote.) Followed by any lowercase or uppercase letter,
returns to the position which was previously marked with that
letter. Followed by another single quote, returns to the posi‐
tion 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.
ESC-m Followed by any lowercase or uppercase letter, clears the mark
identified by that letter.
/pattern
Search forward in the file for the N-th line containing the pat‐
tern. 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 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 cur‐
rent screen, but don't move to the first match (KEEP cur‐
rent position).
^R Don't interpret regular expression metacharacters; that
is, do a simple textual comparison.
^W WRAP around the current file. That is, if the search
reaches the end of the current file without finding a
match, the search continues from the first line of the
current file up to the line where it started.
?pattern
Search backward in the file for the N-th line containing the
pattern. The search starts at the last line displayed (but see
the -a and -j options, which change this).
Certain characters are special as in the / command:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search reaches
the beginning of the current file without finding a
match, the search continues in the previous file in the
command line list.
^F or @
Begin the search at the last line of the last file in the
command line list, regardless of what is currently dis‐
played on the screen or the settings of the -a or -j op‐
tions.
^K As in forward searches.
^R As in forward searches.
^W WRAP around the current file. That is, if the search
reaches the beginning of the current file without finding
a match, the search continues from the last line of the
current file up to the line where it started.
ESC-/pattern
Same as "/*".
ESC-?pattern
Same as "?*".
n Repeat previous search, for N-th line containing the last pat‐
tern. If the previous search was modified by ^N, the search is
made for the N-th line NOT containing the pattern. If the pre‐
vious 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 ef‐
fect is as if the previous search were modified by *.
ESC-N Repeat previous search, but in the reverse direction and cross‐
ing 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.)
ESC-U Like ESC-u but also clears the saved search pattern. If the
status column is enabled via the -J option, this clears all
search matches marked in the status column.
&pattern
Display only lines which match the pattern; lines which do not
match the 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.
Multiple & commands may be entered, in which case only lines
which match all of the patterns will be displayed.
Certain characters are special as in the / command:
^N or !
Display only lines which do NOT match the pattern.
^R Don't interpret regular expression metacharacters; that
is, do a simple textual comparison.
:e [filename]
Examine a new file. If the filename is missing, the "current"
file (see the :n and :p commands below) from the list of files
in the command line is re-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 re‐
placed with a single percent sign. This allows you to enter a
filename that contains a percent sign in the name. Similarly,
two consecutive pound signs are replaced with a single pound
sign. The filename is inserted into the command line list of
files so that it can be seen by subsequent :n and :p commands.
If the filename consists of several files, they are all inserted
into the list of files and the first one is examined. If the
filename contains one or more spaces, the entire filename should
be enclosed in double quotes (also see the -" option).
^X^V or E
Same as :e. Warning: some systems use ^V as a special literal‐
ization 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 com‐
mand 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 en‐
tered 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 set‐
ting is printed and nothing is changed.
-- Like the - command, but takes a long option name (see OPTIONS
below) rather than a single option letter. You must press ENTER
or RETURN after typing the option name. A ^P immediately after
the second dash suppresses printing of a message describing the
new setting, as in the - command.
-+ Followed by one of the command line option letters this will re‐
set the option to its default setting and print a message de‐
scribing 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 let‐
ters, this will print a message describing the current setting
of that option. The setting of the option is not changed.
__ (Double underscore.) Like the _ (underscore) command, but takes
a long option name rather than a single option letter. You must
press ENTER or RETURN after typing the option name.
+cmd Causes the specified cmd to be executed each time a new file is
examined. For example, +G causes less to initially display each
file starting at the end rather than the beginning.
V Prints the version number of less being run.
q or Q or :q or :Q or ZZ
Exits less.
The following four commands may or may not be valid, depending on your
particular 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 nei‐
ther 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 exam‐
ined file. "!!" repeats the last shell command. "!" with no
shell command simply invokes a shell. On Unix systems, the
shell is taken from the environment variable SHELL, or defaults
to "sh". On MS-DOS and OS/2 systems, the shell is the normal
command 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 position marked by the letter and the cur‐
rent screen. The entire current screen is included, regardless
of whether the marked position is before or after the current
screen. <m> may also be ^ or $ to indicate beginning or end of
file respectively. If <m> is . or newline, the current screen
is piped.
s filename
Save the input to a file. This only works if the input is a
pipe, not an 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 un‐
ambiguous. 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 let‐
ter 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 exam‐
ple, 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 per‐
cent 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 ap‐
pears in the LESS variable, it can be reset to its default value on the
command line by beginning the command line option with "-+".
Some options like -k or -D require a string to follow the option let‐
ter. The string for that option is considered to end when a dollar
sign ($) is found. For example, you can set two -D options on MS-DOS
like this:
LESS="Dn9.1$Ds4.1"
If the --use-backslash option appears earlier in the options, then a
dollar sign or backslash may be included literally in an option string
by preceding it with a 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.
-? or --help
This option displays a summary of the commands accepted by less
(the same as the h command). (Depending on how your shell in‐
terprets the question mark, it may be necessary to quote the
question mark, thus: "-\?".)
-a or --search-skip-screen
By default, forward searches start at the top of the displayed
screen and backwards searches start at the bottom of the dis‐
played screen (except for repeated searches invoked by the n or
N commands, which start after or before the "target" line re‐
spectively; see the -j option for more about the target line).
The -a option causes forward searches to instead start at the
bottom of the screen and backward searches to start at the top
of the screen, thus skipping all lines displayed on the screen.
-A or --SEARCH-SKIP-SCREEN
Causes all forward searches (not just non-repeated searches) to
start just 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.
-bn or --buffers=n
Specifies the amount of buffer space less will use for each
file, in units of kilobytes (1024 bytes). By default 64 KB of
buffer space is used for each file (unless the file is a pipe;
see the -B option). The -b option specifies instead that n
kilobytes of buffer space should be used for each file. If n is
-1, buffer space is unlimited; that is, the entire file can be
read into memory.
-B or --auto-buffers
By default, when data is read from a pipe, buffers are allocated
automatically as needed. If a large amount of data is read from
the pipe, this can cause a large amount of memory to be allo‐
cated. The -B option disables this automatic allocation of
buffers for pipes, so that only 64 KB (or the amount of space
specified by the -b option) is used for the pipe. Warning: use
of -B can result in erroneous display, since only the most re‐
cently viewed part of the piped data is kept in memory; any ear‐
lier data is lost.
-c or --clear-screen
Causes full screen repaints to be painted from the top line
down. By default, full screen repaints are done by scrolling
from the bottom of the screen.
-C or --CLEAR-SCREEN
Same as -c, for compatibility with older versions of less.
-d or --dumb
The -d option suppresses the error message normally displayed if
the terminal is dumb; that is, lacks some important capability,
such as the ability to clear the screen or scroll backward. The
-d option does not otherwise change the behavior of less on a
dumb terminal.
-Dxcolor or --color=xcolor
Changes the color of different parts of the displayed text. x
is a single character which selects the type of text whose color
is being set:
B Binary characters.
C Control characters.
E Errors and informational messages.
M Mark letters in the status column.
N Line numbers enabled via the -N option.
P Prompts.
R The rscroll character.
S Search results.
W The highlight enabled via the -w option.
d Bold text.
k Blinking text.
s Standout text.
u Underlined text.
The uppercase letters can be used only when the --use-color op‐
tion is enabled. When text color is specified by both an upper‐
case letter and a lowercase letter, the uppercase letter takes
precedence. For example, error messages are normally displayed
as standout text. So if both "s" and "E" are given a color, the
"E" color applies to error messages, and the "s" color applies
to other standout text. The "d" and "u" letters refer to bold
and underline text formed by overstriking with backspaces (see
the -u option), not to text using ANSI escape sequences with the
-R option.
A lowercase letter may be followed by a + to indicate that both
the normal format change and the specified color should both be
used. For example, -Dug displays underlined text as green with‐
out underlining; the green color has replaced the usual under‐
line formatting. But -Du+g displays underlined text as both
green and in underlined format.
color is either a 4-bit color string or an 8-bit color string:
A 4-bit color string is zero, one or two characters, where the
first character specifies the foreground color and the second
specifies the background color as follows:
b Blue
c Cyan
g Green
k Black
m Magenta
r Red
w White
y Yellow
The corresponding upper-case letter denotes a brighter shade of
the color. For example, -DNGk displays line numbers as bright
green text on a black background, and -DEbR displays error mes‐
sages as blue text on a bright red background. If either char‐
acter is a "-" or is omitted, the corresponding color is set to
that of normal text.
An 8-bit color string is one or two decimal integers separated
by a dot, where the first integer specifies the foreground color
and the second specifies the background color. Each integer is
a value between 0 and 255 inclusive which selects a "CSI 38;5"
color value (see
https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_parameters)
If either integer is a "-" or is omitted, the corresponding col‐
or is set to that of normal text. On MS-DOS versions of less,
8-bit color is not supported; instead, decimal values are inter‐
preted as 4-bit CHAR_INFO.Attributes values (see
https://docs.microsoft.com/en-us/windows/console/char-info-str).
-e or --quit-at-eof
Causes less to automatically exit the second time it reaches
end-of-file. By default, the only way to exit less is via the
"q" command.
-E or --QUIT-AT-EOF
Causes less to automatically exit the first time it reaches end-
of-file.
-f or --force
Forces non-regular files to be opened. (A non-regular file is a
directory or a device special file.) Also suppresses the warn‐
ing message when a binary file is opened. By default, less will
refuse to open non-regular files. Note that some operating sys‐
tems 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 dis‐
played 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 high‐
light 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.
-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 upper‐
case 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 com‐
mand 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 speci‐
fied 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 rel‐
ative 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, repeated
forward searches (invoked with "n" or "N") begin at the line im‐
mediately after the target line, and repeated backward searches
begin at the target line, unless changed by -a or -A. For exam‐
ple, if "-j4" is used, the target line is the fourth line on the
screen, so forward searches begin at the fifth line on the
screen. However nonrepeated searches (invoked with "/" or "?")
always begin at the start or end of the current screen respec‐
tively.
-J or --status-column
Displays a status column at the left edge of the screen. The
status column shows the lines that matched the current search,
and any lines that are marked (via the m or M command).
-kfilename or --lesskey-file=filename
Causes less to open and interpret the named file as a lesskey(1)
binary file. Multiple -k options may be specified. If the
LESSKEY or LESSKEY_SYSTEM 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.
--lesskey-src=filename
Causes less to open and interpret the named file as a lesskey(1)
source file. If the LESSKEYIN or LESSKEYIN_SYSTEM environment
variable is set, or if a lesskey source file is found in a stan‐
dard place (see KEY BINDINGS), it is also used as a lesskey
source file. Prior to version 582, the lesskey program needed
to be run to convert a lesskey source file to a lesskey binary
file for less to use. Newer versions of less read the lesskey
source file directly and ignore the binary file if the source
file exists.
-K or --quit-on-intr
Causes less to exit immediately (with status 2) when an inter‐
rupt 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 im‐
possible to return to the command prompt from the "F" command.
-L or --no-lessopen
Ignore the LESSOPEN environment variable (see the INPUT PRE‐
PROCESSOR section below). This option can be set from within
less, but it will apply only to files opened subsequently, not
to the file which is currently open.
-m or --long-prompt
Causes less to prompt verbosely (like more), with the percent
into the file. By default, less prompts with a colon.
-M or --LONG-PROMPT
Causes less to prompt even more verbosely than more.
-n or --line-numbers
Suppresses line numbers. The default (to use line numbers) may
cause less to run more slowly in some cases, especially with a
very large input file. Suppressing line numbers with the -n op‐
tion 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 be‐
low).
-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 occur‐
rence 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 envi‐
ronment variable, rather than being typed in with each less com‐
mand. 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 terminal has a "visual
bell", it is used instead. The bell will be rung on certain
other errors, such as typing an invalid character. The default
is to ring the terminal bell in all such cases.
-Q or --QUIET or --SILENT
Causes totally "quiet" operation: the terminal bell is never
rung. If the terminal has a "visual bell", it is used in all
cases where the terminal bell would have been rung.
-r or --raw-control-chars
Causes "raw" control characters to be displayed. The default is
to display control characters using the caret notation; for ex‐
ample, 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 dis‐
play problems may result, such as long lines being split in the
wrong place.
USE OF THE -r OPTION IS NOT RECOMMENDED.
-R or --RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences and OSC 8 hyper‐
link sequences are output in "raw" form. Unlike -r, the screen
appearance is maintained correctly, provided that there are no
escape sequences in the file other than these types of escape
sequences. Color escape sequences are only supported when the
color is changed within one line, not across lines. In other
words, the beginning of each line is assumed to be normal (non-
colored), regardless of any escape sequences in previous lines.
For the purpose of keeping track of screen appearance, these es‐
cape sequences are assumed to not move the cursor.
OSC 8 hyperlinks are sequences of the form:
ESC ] 8 ; ... \7
The terminating sequence may be either a BEL character (\7) or
the two-character sequence "ESC \".
ANSI color escape sequences are sequences of the form:
ESC [ ... m
where the "..." is zero or more color specification characters.
You can make less think that characters other than "m" can end
ANSI color escape sequences by setting the environment variable
LESSANSIENDCHARS to the list of characters which can end a color
escape sequence. And you can make less think that 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 (trun‐
cated) rather than wrapped. That is, the portion of a long line
that does not fit in the screen width is not displayed until you
press RIGHT-ARROW. The default is to wrap long lines; that is,
display the remainder on the next line.
-ttag or --tag=tag
The -t option, followed immediately by a TAG, will edit the file
containing that tag. For this to work, tag information must be
available; for example, there may be a file in the current di‐
rectory called "tags", which was previously built by ctags(1) or
an equivalent command. If the environment variable LESSGLOBALT‐
AGS 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 - com‐
mand) 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 print‐
able characters; that is, they are sent to the terminal when
they appear in the input.
-U or --UNDERLINE-SPECIAL
Causes backspaces, tabs, carriage returns and "formatting char‐
acters" (as defined by Unicode) to be treated as control charac‐
ters; that is, they are handled as specified by the -r option.
By default, if neither -u nor -U is given, backspaces which ap‐
pear 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 capabili‐
ty. Other backspaces are deleted, along with the preceding
character. Carriage returns immediately followed by a newline
are deleted. Other carriage returns are handled as specified by
the -r option. Unicode formatting characters, such as the Byte
Order Mark, are sent to the terminal. Text which is overstruck
or underlined can be searched for if neither -u nor -U is in ef‐
fect.
-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 imme‐
diately 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 move‐
ment. The entire line is highlighted, unless the -J option is
in effect, in which case only the status column is highlighted.
-W or --HILITE-UNREAD
Like -w, but temporarily highlights the first new line after any
forward 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 con‐
tinue with the same spacing as the last two. For example,
-x9,17 will set tabs at positions 9, 17, 25, 33, etc. The de‐
fault for n is 8.
-X or --no-init
Disables sending the termcap initialization and deinitialization
strings to the terminal. This is sometimes desirable if the
deinitialization string does something unnecessary, like clear‐
ing 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 re‐
painted instead. The -c or -C option may be used to repaint
from the top of the screen if desired. By default, any forward
movement causes scrolling.
-zn or --window=n or -n
Changes the default scrolling window size to n lines. The de‐
fault is one screenful. The z and w commands can also be used
to change the window size. The "z" may be omitted for compati‐
bility with some versions of more. If the number n is negative,
it indicates n lines less than the current screen size. For ex‐
ample, 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 character, this changes
the quote character to that character. Filenames containing a
space should then be surrounded by that character rather than by
double quotes. Followed by two characters, changes the open
quote to the first character, and the close quote to the second
character. Filenames containing a space should then be preceded
by the open quote 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 speci‐
fied is zero, it sets the default number of positions to one
half of the screen width. Alternately, the number may be speci‐
fied 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 speci‐
fied as a fraction, the actual number of scroll positions is re‐
calculated if the terminal window is resized, so that the actual
scroll remains at the specified fraction of the screen width.
--file-size
If --file-size is specified, less will determine the size of the
file immediately after opening the file. Normally this is not
done, because it can be slow if the input file is large.
--follow-name
Normally, if the input file is renamed while an F command is ex‐
ecuting, less will continue to display the contents of the orig‐
inal file despite its name change. If --follow-name is speci‐
fied, during an F command less will periodically attempt to re‐
open 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 re‐
named) file), less will display the contents of that new file.
--incsearch
Subsequent search commands will be "incremental"; that is, less
will advance to the next line containing the search pattern as
each character of the pattern is typed in.
--line-num-width
Sets the minimum width of the line number field when the -N op‐
tion is in effect. The default is 7 characters.
--mouse
Enables mouse input: scrolling the mouse wheel down moves for‐
ward in the file, scrolling the mouse wheel up moves backwards
in the file, and clicking the mouse sets the "#" mark to the
line where the mouse is clicked. The number of lines to scroll
when the wheel is moved can be set by the --wheel-lines option.
Mouse input works only on terminals which support X11 mouse re‐
porting, and on the Windows version of less.
--MOUSE
Like --mouse, except the direction scrolled on mouse wheel move‐
ment is reversed.
--no-keypad
Disables sending the keypad initialization and deinitialization
strings to the terminal. This is sometimes useful if the keypad
strings make the numeric keypad behave in an undesirable manner.
--no-histdups
This option changes the behavior so that if a search string or
file name is typed in, and the same string is already in the
history list, the existing copy is removed from the history list
before the new one is added. Thus, a given string will appear
only once in the history list. Normally, a string may appear
multiple times.
--rscroll
This option changes the character used to mark truncated lines.
It may begin with a two-character attribute indicator like LESS‐
BINFMT does. If there is no attribute indicator, standout is
used. If set to "-", truncated lines are not marked.
--save-marks
Save marks in the history file, so marks are retained across
different invocations of less.
--status-col-width
Sets the width of the status column when the -J option is in ef‐
fect. The default is 2 characters.
--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.
--use-color
Enables the colored text in various places. The -D option can
be used to change the colors. Colored text works only if the
terminal supports ANSI color escape sequences (as defined in EC‐
MA-48 SGR; see
https://www.ecma-international.org/publications-and-
standards/standards/ecma-48).
--wheel-lines=n
Set the number of lines to scroll when the mouse wheel is
scrolled and the --mouse or --MOUSE option is in effect. The
default is 1 line.
-- A command line argument of "--" marks the end of option argu‐
ments. Any arguments following this are interpreted as file‐
names. 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 ini‐
tial command for every file.
LINE EDITING
When entering a command line at the bottom of the screen (for example,
a filename for the :e command, or the pattern for a search command),
certain keys can be used to 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" 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 cur‐
sor one word to the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.) Move the cur‐
sor 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 com‐
mand which begins with that text.
DOWNARROW [ ESC-j ]
Retrieve the next command line. If you first enter some text
and then press DOWNARROW, it will retrieve the next command
which begins with that text.
TAB Complete the partial filename to the left of the cursor. If it
matches more than one filename, the first match is entered into
the command line. Repeated TABs will cycle thru the other
matching filenames. If the completed filename is a directory, a
"/" is appended to the filename. (On MS-DOS systems, a "\" is
appended.) The environment variable LESSSEPARATOR can be used
to specify a different character to append to a directory name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the matching
filenames.
^L Complete the partial filename to the left of the cursor. If it
matches more than one filename, all matches are entered into the
command line (if they fit).
^U (Unix and OS/2) or ESC (MS-DOS)
Delete the entire command line, or cancel the command if the
command line is empty. If you have changed your line-kill char‐
acter in Unix 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 creating a lesskey source
file. This file specifies a set of command keys and an action associ‐
ated with each key. You may also change the line-editing keys (see
LINE EDITING), and to set environment variables. If the environment
variable LESSKEYIN is set, less uses that as the name of the lesskey
source file. Otherwise, less looks in a standard place for the lesskey
source file: On Unix systems, less looks for a lesskey file called
"$XDG_CONFIG_HOME/lesskey" or "$HOME/.lesskey". On MS-DOS and Windows
systems, less looks for a lesskey file called "$HOME/_lesskey", and if
it is not found there, then looks for a lesskey file called "_lesskey"
in any directory specified in the PATH environment variable. On OS/2
systems, less looks for a lesskey file called "$HOME/lesskey.ini", and
if it is not found, then looks for a lesskey file called "lesskey.ini"
in any directory specified in the INIT environment variable, and if it
not found there, then looks for a lesskey file called "lesskey.ini" in
any directory specified in the PATH environment variable. See the
lesskey manual page for more details.
A system-wide lesskey source file may also be set up to provide key
bindings. If a key is defined in both a local lesskey file and in the
system-wide file, key bindings in the local file take precedence over
those in the system-wide file. If the environment variable
LESSKEYIN_SYSTEM is set, less uses that as the name of the system-wide
lesskey file. Otherwise, less looks in a standard place for the sys‐
tem-wide lesskey file: On Unix systems, the system-wide lesskey file is
/usr/local/etc/syslesskey. (However, if less was built with a differ‐
ent sysconf directory than /usr/local/etc, that directory is where the
sysless file is found.) On MS-DOS and Windows systems, the system-wide
lesskey file is c:\_syslesskey. On OS/2 systems, the system-wide
lesskey file is c:\syslesskey.ini.
Previous versions of less (before v582) used lesskey files with a bina‐
ry format, produced by the lesskey program. It is no longer necessary
to use the lesskey program.
INPUT PREPROCESSOR
You may define an "input preprocessor" for less. Before less opens a
file, it first gives your input preprocessor a chance to modify the way
the contents of the file are displayed. An input preprocessor is sim‐
ply an executable program (or shell script), which writes the contents
of the file to a different file, called the replacement file. The con‐
tents of the replacement file are then displayed in place of the con‐
tents of the original file. However, it will appear to the user as if
the original file is opened; that is, less will display the original
filename as the name of the current file.
An input preprocessor receives one command line argument, the original
filename, as entered by the user. It should create the replacement
file, and when finished, print the name of the replacement file to its
standard output. If the input preprocessor does not output a replace‐
ment filename, less uses the original file, as normal. The input pre‐
processor is not called when viewing standard input. To set up an in‐
put 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 re‐
placed by the filename when the input preprocessor command is invoked.
When less closes a file opened in such a way, it will call another pro‐
gram, 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 orig‐
inal 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 re‐
placed 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 "$1" in
*.Z) TEMPFILE=$(mktemp)
uncompress -c $1 >$TEMPFILE 2>/dev/null
if [ -s $TEMPFILE ]; then
echo $TEMPFILE
else
rm -f $TEMPFILE
fi
;;
esac
lessclose.sh:
#! /bin/sh
rm $2
To use these scripts, put them both where they can be executed and set
LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More
complex LESSOPEN and LESSCLOSE scripts may be written to accept other
types of compressed files, and so on.
It is also possible to set up an input preprocessor to pipe the file
data directly to less, rather than putting the data into a replacement
file. This avoids the need to decompress the entire file before start‐
ing 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 replace‐
ment file on its standard output, writes the entire contents of the re‐
placement file on its standard output. If the input pipe does not
write any characters on its standard output, then there is no replace‐
ment 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. As with non-pipe input preprocessors, the command string must
contain one occurrence of %s, which is replaced with the filename of
the input file.
For example, on many Unix systems, this script will work like the pre‐
vious 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 in‐
terpreted 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 is
empty. If the exit status is nonzero, any output is ignored and the
original file is used. For compatibility with previous versions of
less, if LESSOPEN starts with only one vertical bar, the exit status of
the preprocessor is ignored.
When an input pipe is used, a LESSCLOSE postprocessor can be used, but
it is usually not necessary since there is no replacement file to clean
up. In this case, the replacement file name passed to the LESSCLOSE
postprocessor is "-".
For compatibility with previous versions of less, the input preproces‐
sor 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 charac‐
ters 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. The LESSCHARSET environment
variable may be used to select a character set. Possible values for
LESSCHARSET are:
ascii BS, TAB, NL, CR, and formfeed are control characters, all chars
with values between 32 and 126 are normal, and all others are
binary.
iso8859
Selects an ISO 8859 character set. This is the same as ASCII,
except characters between 160 and 255 are treated as normal
characters.
latin1 Same as iso8859.
latin9 Same as iso8859.
dos Selects a character set appropriate for MS-DOS.
ebcdic Selects an EBCDIC character set.
IBM-1047
Selects an EBCDIC character set used by OS/390 Unix Services.
This is the EBCDIC analogue of latin1. You get similar results
by setting either LESSCHARSET=IBM-1047 or LC_CTYPE=en_US in your
environment.
koi8-r Selects a Russian character set.
next Selects a character set appropriate for NeXT computers.
utf-8 Selects the UTF-8 encoding of the ISO 10646 character set.
UTF-8 is special in that it supports multi-byte characters in
the input file. It is the only character set that supports mul‐
ti-byte characters.
windows
Selects a character set appropriate for Microsoft Windows (cp
1251).
In rare cases, it may be desired to tailor less to use a character set
other than the ones definable by LESSCHARSET. In this case, the envi‐
ronment variable LESSCHARDEF can be used to define a character set. It
should be set to a string where each character in the string represents
one character in the character set. The character "." is used for a
normal character, "c" for control, and "b" for binary. A decimal num‐
ber may be used for repetition. For example, "bccc4b." would mean
character 0 is binary, 1, 2 and 3 are control, 4, 5, 6 and 7 are bina‐
ry, and 8 is normal. All characters after the last are taken to be the
same as the last, so characters 9 through 255 would be normal. (This
is an example, and does not necessarily represent any real character
set.)
This table shows the value of LESSCHARDEF which is equivalent to each
of the possible values for LESSCHARSET:
ascii 8bcccbcc18b95.b
dos 8bcccbcc12bc5b95.b.
ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
191.b
iso8859 8bcccbcc18b95.33b.
koi8-r 8bcccbcc18b95.b128.
latin1 8bcccbcc18b95.33b.
next 8bcccbcc18b95.bb125.bb
If neither LESSCHARSET nor LESSCHARDEF is set, but any of the strings
"UTF-8", "UTF8", "utf-8" or "utf8" is found in the LC_ALL, LC_CTYPE or
LANG environment variables, then the default character set is utf-8.
If that string is not found, but your system supports the setlocale in‐
terface, less will use setlocale to determine the character set. set‐
locale is controlled by setting the LANG or LC_CTYPE environment vari‐
ables.
Finally, if the setlocale interface is also not available, the default
character set is latin1.
Control and binary characters are displayed in standout (reverse
video). Each such character is displayed in caret notation if possible
(e.g. ^A for control-A). Caret notation is used only if inverting the
0100 bit results in a normal printable character. Otherwise, the char‐
acter 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 re‐
sult 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., unas‐
signed 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, invalid octets, and stray
trailing octets) are displayed individually using LESSBINFMT so as to
facilitate diagnostic of how the UTF-8 file is ill-formed.
PROMPTS
The -P option allows you to tailor the prompt to your preference. The
string given to the -P option replaces the specified prompt string.
Certain characters in the string are interpreted specially. The prompt
mechanism is rather complicated to provide flexibility, but the ordi‐
nary 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 spec‐
ifies the line whose byte offset is to be used. If the charac‐
ter 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 bot‐
tom 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 equiva‐
lently, the page number of the last line in the input file.
%E Replaced by the name of the editor (from the VISUAL environment
variable, or the EDITOR environment variable if VISUAL is not
defined). See the discussion of the LESSEDIT feature below.
%f Replaced by the name of the current input file.
%F Replaced by the last component of the name of the current input
file.
%g Replaced by the shell-escaped name of the current input file.
This is useful when the expanded string will be used in a shell
command, such as in LESSEDIT.
%i Replaced by the index of the current file in the list of input
files.
%lX Replaced by the line number of a line in the input file. The
line to be used is determined by the X, as with the %b option.
%L Replaced by the line number of the last line in the input file.
%m Replaced by the total number of input files.
%pX Replaced by the percent into the current input file, based on
byte offsets. The line used is determined by the X as with the
%b option.
%PX Replaced by the percent into the current input file, based on
line numbers. The line used is determined by the X as with the
%b option.
%s Same as %B.
%t Causes any trailing spaces to be removed. Usually used at the
end of the string, but may appear anywhere.
%T Normally expands to the word "file". However if viewing files
via a tags list using the -t option, it expands to the word
"tag".
%x Replaced by the name of the next input file in the list.
If any item is unknown (for example, the file size if input is a pipe),
a question mark is printed instead.
The format of the prompt string can be changed depending on certain
conditions. A question mark followed by a single character acts like
an "IF": depending on the following character, a condition is evaluat‐
ed. If the condition is true, any characters following the question
mark and condition character, up to a period, are included in the
prompt. If the condition is false, such characters are not included.
A colon appearing between the question mark and the period can be used
to establish an "ELSE": any characters between the colon and the period
are included in the string if and only if the IF condition is false.
Condition characters (which follow a question mark) may be:
?a True if any characters have been included in the prompt so far.
?bX True if the byte offset of the specified line is known.
?B True if the size of current input file is known.
?c True if the text is horizontally shifted (%c is not zero).
?dX True if the page number of the specified line is known.
?e True if at end-of-file.
?f True if there is an input filename (that is, if input is not a
pipe).
?lX True if the line number of the specified line is known.
?L True if the line number of the last line in the file is known.
?m True if there is more than one input file.
?n True if this is the first prompt in a new input file.
?pX True if the percent into the current input file, based on byte
offsets, of the specified line is known.
?PX True if the percent into the current input file, based on line
numbers, of the specified line is known.
?s Same as "?B".
?x True if there is a next input file (that is, if the current in‐
put file is not the last one).
Any characters other than the special ones (question mark, colon, peri‐
od, 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 "Stan‐
dard input".
?f%f .?ltLine %lt:?pt%pt\%:?btByte %bt:-...
This prompt would print the filename, if known. The filename is fol‐
lowed by the line number, if known, otherwise the percent if known,
otherwise the byte offset if known. Otherwise, a dash is printed. No‐
tice how each question mark has a matching period, and how the % after
the %pt is included literally by escaping it with a backslash.
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\: %x..%t";
This prints the filename if this is the first prompt in a file, fol‐
lowed 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 refer‐
ence, here are the defaults for the other two prompts (-m and -M re‐
spectively). Each is broken into two lines here for readability only.
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\: %x.:
?pB%pB\%:byte %bB?s/%s...%t
?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%lb?L/%L. :
byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t
And here is the default message produced by the = command:
?f%f .?m(%T %i of %m) .?ltlines %lt-%lb?L/%L. .
byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
The prompt expansion features are also used for another purpose: if an
environment variable LESSEDIT is defined, it is used as the command to
be executed when the v command is invoked. The LESSEDIT string is ex‐
panded in the same way as the prompt strings. The default value for
LESSEDIT is:
%E ?lm+%lm. %g
Note that this expands to the editor name, followed by a + and the line
number, followed by the shell-escaped file name. If your editor does
not accept the "+linenumber" syntax, or has other differences in invo‐
cation syntax, the LESSEDIT variable can be changed to modify this de‐
fault.
SECURITY
When the environment variable LESSSECURE is set to 1, less runs in a
"secure" mode. This means these features are disabled:
! the shell command
| the pipe command
:e the examine command.
v the editing command
s -o log files
-k use of lesskey files
-t use of tags files
metacharacters in filenames, such as *
filename completion (TAB, ^L)
Less can also be compiled to be permanently in "secure" mode.
COMPATIBILITY WITH MORE
If the environment variable LESS_IS_MORE is set to 1, or if the program
is invoked via a file link named "more", less behaves (mostly) in con‐
formance with the POSIX "more" command specification. In this mode,
less behaves differently in these ways:
The -e option works differently. If the -e option is not set, less be‐
haves as if the -e option were set. If the -e option is set, less be‐
haves as if the -E option were set.
The -m option works differently. If the -m option is not set, the
medium prompt is used, and it is prefixed with the string "--More--".
If the -m option is set, the short prompt is used.
The -n option acts like the -z option. The normal behavior of the -n
option is unavailable in this mode.
The parameter to the -p option is taken to be a less command rather
than a search pattern.
The LESS environment variable is ignored, and the MORE environment
variable is used in its place.
ENVIRONMENT VARIABLES
Environment variables may be specified either in the system environment
as usual, or in a lesskey(1) file. If environment variables are de‐
fined in more than one place, variables defined in a local lesskey file
take precedence over variables defined in the system environment, which
take precedence over variables defined in the system-wide lesskey file.
COLUMNS
Sets the number of columns on the screen. Takes precedence over
the number of columns specified by the TERM variable. (But if
you have a windowing system which supports TIOCGWINSZ or
WIOCGETD, the window system's idea of the screen size takes
precedence over the LINES and COLUMNS environment variables.)
EDITOR The name of the editor (used for the v command).
HOME Name of the user's home directory (used to find a lesskey file
on Unix and OS/2 systems).
HOMEDRIVE, HOMEPATH
Concatenation of the HOMEDRIVE and HOMEPATH environment vari‐
ables is the name of the user's home directory if the HOME vari‐
able is not set (only in the Windows version).
INIT Name of the user's init directory (used to find a lesskey file
on OS/2 systems).
LANG Language for determining the character set.
LC_CTYPE
Language for determining the character set.
LESS Options which are passed to less automatically.
LESSANSIENDCHARS
Characters which may end an ANSI color escape sequence (default
"m").
LESSANSIMIDCHARS
Characters which may appear between the ESC character and the
end character in an ANSI color escape sequence (default
"0123456789:;[?!"'#%()*+ ".
LESSBINFMT
Format for displaying non-printable, non-control characters.
LESSCHARDEF
Defines a character set.
LESSCHARSET
Selects a predefined character set.
LESSCLOSE
Command line to invoke the (optional) input-postprocessor.
LESSECHO
Name of the lessecho program (default "lessecho"). The lessecho
program is needed to expand metacharacters, such as * and ?, in
filenames on Unix systems.
LESSEDIT
Editor prototype string (used for the v command). See discus‐
sion under PROMPTS.
LESSGLOBALTAGS
Name of the command used by the -t option to find global tags.
Normally should be set to "global" if your system has the glob‐
al(1) command. If not set, global tags are not used.
LESSHISTFILE
Name of the history file used to remember search commands and
shell commands between invocations of less. If set to "-" or
"/dev/null", a history file is not used. The default is
"$XDG_DATA_HOME/lesshst" or "$HOME/.lesshst" on Unix systems,
"$HOME/_lesshst" on DOS and Windows systems, or
"$HOME/lesshst.ini" or "$INIT/lesshst.ini" on OS/2 systems.
LESSHISTSIZE
The maximum number of commands to save in the history file. The
default is 100.
LESSKEYIN
Name of the default lesskey source file.
LESSKEY
Name of the default lesskey binary file. (Not used if
"$LESSKEYIN" exists.)
LESSKEYIN_SYSTEM
Name of the default system-wide lesskey source file.
LESSKEY_SYSTEM
Name of the default system-wide lesskey binary file. (Not used
if "$LESSKEYIN_SYSTEM" exists.)
LESSMETACHARS
List of characters which are considered "metacharacters" by the
shell.
LESSMETAESCAPE
Prefix which less will add before each metacharacter in a com‐
mand 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 comple‐
tion.
LESSUTFBINFMT
Format for displaying non-printable Unicode code points.
LESS_IS_MORE
Emulate the more(1) command.
LINES Sets the number of lines on the screen. Takes precedence over
the number of lines specified by the TERM variable. (But if you
have a windowing system which supports TIOCGWINSZ or WIOCGETD,
the window system's idea of the screen size takes precedence
over the LINES and COLUMNS environment variables.)
MORE Options which are passed to less automatically when running in
more compatible mode.
PATH User's search path (used to find a lesskey file on MS-DOS and
OS/2 systems).
SHELL The shell used to execute the ! command, as well as to expand
filenames.
TERM The type of terminal on which less is being run.
VISUAL The name of the editor (used for the v command).
SEE ALSO
lesskey(1)
COPYRIGHT
Copyright (C) 1984-2021 Mark Nudelman
less is part of the GNU project and is free software. You can redis‐
tribute it and/or modify it under the terms of either (1) the GNU Gen‐
eral Public License as published by the Free Software Foundation; or
(2) the Less License. See the file README in the less distribution for
more details regarding redistribution. You should have received a copy
of the GNU General Public License along with the source for less; see
the file COPYING. If not, write to the Free Software Foundation, 59
Temple Place, Suite 330, Boston, MA 02111-1307, USA. You should also
have received a copy of the Less License; see the file LICENSE.
less is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FIT‐
NESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
AUTHOR
Mark Nudelman
Report bugs at https://github.com/gwsw/less/issues.
For more information, see the less homepage at
https://greenwoodsoftware.com/less
Version 590: 03 Jun 2021 LESS(1)