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 "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.
ENTER or RETURN or ^N or e or ^E or j or ^J Scroll forward N lines, default 1. The entire N lines are displayed, even if N is more than the screen size.
d or ^D Scroll forward N lines, default one half of the screen size. If N is 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 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 becomes the default for future RIGHTARROW and LEFTARROW commands. While the text is scrolled, it acts as though the -S option (chop lines) were in effect.
ESC-( or LEFTARROW Scroll horizontally left N characters, default half the screen width (see the -# option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW commands.
ESC-} or ^RIGHTARROW Scroll horizontally right to show the end of the longest displayed line.
ESC-{ or ^LEFTARROW Scroll horizontally left back to the first column.
r or ^R or ^L Repaint the screen.
R Repaint the screen, discarding any buffered input. That is, reload the 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 systems which support poll(2) you can also use ^X or the character specified by the --intr option. If the input is a pipe and the --exit-follow-on-close option is in effect, less will automatically stop waiting for data when the input side of the pipe is closed.
ESC-F Like F, but as soon as a line is found which matches the last search pattern, the terminal bell is rung and forward scrolling stops.
g or < or ESC-< Go to line N in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.)
G or > or ESC-> Go to line N in the file, default the end of the file. (Warning: this may be slow if N is large, or if N is not specified and standard input, rather than a file, is being read.)
ESC-G Same as G, except if no number N is specified and the input is standard input, goes to the last line which is currently buffered.
p or % Go to a position N percent into the file. N should be between 0 and 100, and may contain a decimal point.
P Go to the line containing byte offset N in the file.
{ If a left curly bracket appears in the top line displayed on the screen, the { command will go to the matching right curly bracket. The matching right curly bracket is positioned on the bottom line of the screen. If there is more than one left curly bracket on the top line, a number N may be used to specify the N-th bracket on the line.
} If a right curly bracket appears in the bottom line displayed on the screen, the } command will go to the matching left curly bracket. The matching left curly bracket is positioned on the top line of the screen. If there is more than one right curly bracket on the bottom 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 or uppercase letter, marks the first displayed line with that letter. If the status column is enabled 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 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.
ESC-m Followed by any lowercase or uppercase letter, clears the mark identified by that letter.
/pattern Search forward in the file for the N-th line containing the pattern. N defaults to 1. The pattern is a regular expression, as recognized by the regular expression library supplied by your system. By default, searching is case-sensitive (uppercase and lowercase are considered different); the -i option can be used to change this. The search starts at the first line displayed (but see the -a and -j options, which change this).
Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern:
^N or ! Search for lines which do NOT match the pattern.
^E or * Search multiple files. That is, if the search reaches the END of the current file without finding a match, the search continues in the next file in the command line list.
^F or @ Begin the search at the first line of the FIRST file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j options.
^K Highlight any text which matches the pattern on the current screen, but don't move to the first match (KEEP current position).
^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison.
^S Followed by a digit N between 1 and 5. Only text which has a non-empty match for the N-th parenthesized SUB-PATTERN will be considered to match the pattern. (Supported only if less is built with one of the regular expression libraries posix, pcre, or pcre2.) Multiple ^S modifiers can be specified, to match more than one sub-pattern.
^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. If the ^W modifier is set, the ^E modifier is ignored.
^L The next character is taken literally; that is, it becomes part of the pattern even if it is one of the above search modifier characters.
?pattern Search backward in the file for the N-th line containing the pattern. The search starts at the last line displayed (but see the -a and -j options, which change this).
Certain characters are special as in the / command:
^N or ! Search for lines which do NOT match the pattern.
^E or * Search multiple files. That is, if the search reaches the beginning of the current file without finding a match, the search continues in the previous file in the command line list.
^F or @ Begin the search at the last line of the last file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j options.
^K As in forward searches.
^R As in forward searches.
^S 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 pattern. If the previous search was modified by ^N, the search is made for the N-th line NOT containing the pattern. If the previous search was modified by ^E, the search continues in the next (or previous) file if not satisfied in the current file. If the previous search was modified by ^R, the search is done without using regular expressions. There is no effect if the previous search was modified by ^F or ^K.
N Repeat previous search, but in the reverse direction.
ESC-n Repeat previous search, but crossing file boundaries. The effect is as if the previous search were modified by *.
ESC-N Repeat previous search, but in the reverse direction and crossing file boundaries.
ESC-u Undo search highlighting. Turn off highlighting of strings matching the current search pattern. If highlighting is already off because of a previous ESC-u command, turn highlighting back on. Any search command will also turn highlighting back on. (Highlighting can also be disabled by toggling the -G option; in that case search commands do not turn highlighting back on.)
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 replaced with a single percent sign. This allows you to enter a filename that contains a percent sign in the name. Similarly, two consecutive pound signs are replaced with a single pound sign. The filename is inserted into the command line list of files so that it can be seen by subsequent :n and :p commands. If the filename consists of several files, they are all inserted into the list of files and the first one is examined. If the filename contains one or more spaces, the entire filename should be enclosed in double quotes (also see the -" option).
^X^V or E Same as :e. Warning: some systems use ^V as a special literalization 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.
^O^N or ^On Search forward in the file for the N-th next OSC 8 hyperlink.
^O^P or ^Op Search backward in the file for the N-th previous OSC 8 hyperlink.
^O^L or ^Ol Jump to the currently selected OSC 8 hyperlink.
= 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 ENTER or RETURN after typing the option name. A ^P immediately after the second dash suppresses printing of a message describing the new setting, as in the - command.
-+ Followed by one of the command line option letters this will reset the option to its default setting and print a message describing the new setting. (The "-+X" command does the same thing as "-+X" on the command line.) This does not work for string- valued options.
--+: Like the -+ command, but takes a long option name rather than a single option letter.
-! Followed by one of the command line option letters, this will reset the option to the "opposite" of its default setting and print a message describing the new setting. This does not work for numeric or string-valued options.
--!: Like the -! command, but takes a long option name rather than a single option letter.
_ (Underscore.) Followed by one of the command line option letters, this will print a message describing the current setting of that option. The setting of the option is not changed.
__ (Double underscore.) Like the _ (underscore) command, but takes a long option name rather than a single option letter. You must press ENTER or RETURN after typing the option name.
+cmd Causes the specified cmd to be executed each time a new file is examined. For example, +G causes less to initially display each file starting at the end rather than the beginning.
V Prints the version number of less being run.
q or Q or :q or :Q or ZZ Exits less.
The following seven 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. If a ^P (CONTROL-P) is entered immediately after the !, no "done" message is printed after the shell command is executed. On Unix systems, the shell is taken from the environment variable SHELL, or defaults to "sh". On MS- DOS, Windows, and OS/2 systems, the shell is the normal command processor.
shell-command
Similar to the "!" command, except that the command is expanded in the same way as prompt strings. For example, the name of the current file would be given as "%f".
|
s filename Save the input to a file. This works only if the input is a pipe, not an ordinary file.
^O^O Run a shell command to open the URI in the current OSC 8 hyperlink, selected by a previous ^O^N or ^O^P command. To find the shell command, the environment variable named "LESS_OSC8_xxx" is read, where "xxx" is the scheme from the URI (the part before the first colon), or is empty if there is no colon in the URI. The value of the environment variable is then expanded in the same way as prompt strings (in particular, any instance of "%o" is replaced with the URI) to produce an OSC 8 "handler" shell command. The standard output from the handler is an "opener" shell command which is then executed to open the URI.
There are two special cases:
If the URI begins with "#", the remainder of the URI is taken to be the
value of the id parameter in another OSC 8 link in the same file, and ^O^O will simply jump to that link.
If the opener begins with the characters ":e" followed by whitespace and
a filename, then instead of running the opener as a shell command, the specified filename is opened in the current instance of less.
In a simple case where the opener accepts the complete URI as a command line parameter, the handler may be as simple as
echo mybrowser '%o'
In other cases, the URI may need to be modified, so the handler may have to do some manipulation of the %o value.
If the LESS_OSC8_xxx variable is not set, the variable LESS_OSC8_ANY is tried. If neither LESS_OSC8_xxx nor LESS_OSC8_ANY is set, links using the "xxx" scheme cannot be opened. However, there are default handlers for the schemes "man" (used when LESS_OSC8_man is not set) and "file" (used when LESS_OSC8_file is not set), which should work on systems which provide the sed(1) command and a shell with syntax compatible with the Bourne shell sh(1). If you use LESS_OSC8_ANY to override LESS_OSC8_file, you must set LESS_OSC8_file to "-" to indicate that the default value should not be used, and likewise for LESS_OSC8_man.
The URI passed to an OSC8 handler via %o is guaranteed not to contain any single quote or double quote characters, but it may contain any other shell metacharacters such as semicolons, dollar signs, ampersands, etc. The handler should take care to appropriately quote parameters in the opener command, to prevent execution of unintended shell commands in the case of opening a URI which contains shell metacharacters. Also, since the handler command is expanded like a command prompt, any metacharacters interpreted by prompt expansion (such as percent, dot, colon, backslash, etc.) must be escaped with a backslash (see the PROMPTS section for details).
^X When the "Waiting for data" message is displayed, such as while in the F command, pressing ^X will stop less from waiting and return to a prompt. This may cause less to think that the file ends at the current position, so it may be necessary to use the R or F command to see more data. The --intr option can be used to specify a different character to use instead of ^X. This command works only on systems that support the poll(2) function. On systems without poll(2), the interrupt character (usually ^C) can be used instead.
Options
Command line options are described below. Most options may be changed while less is running, via the "-" command.
Some 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 and Windows, you don't need the quotes, but you should be careful that any percent signs in the options string are not interpreted as an environment variable expansion.
The environment variable is parsed before the command line, so command line options override the LESS environment variable. If an option appears in the LESS variable, it can be reset to its default value on the command line by beginning the command line option with "-+".
Some options like -k or -D require a string to follow the option letter. The string for that option is considered to end when a dollar sign ($) is found. For example, you can set two -D options like this:
LESS="Dnwb$Dsbw"
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 interprets the question mark, it may be necessary to quote the question mark, thus: "-?".)
-a or --search-skip-screen By default, forward searches start at the top of the displayed screen and backwards searches start at the bottom of the displayed screen (except for repeated searches invoked by the n or N commands, which start after or before the "target" line respectively; see the -j option for more about the target line). The -a option causes forward searches to instead start at the bottom of the screen and backward searches to start at the top of the screen, thus skipping all lines displayed on the screen.
-A or --SEARCH-SKIP-SCREEN Causes all forward searches (not just non-repeated searches) to start just 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 Varsayılan olarak, bir borudan (pipe) veri okunduğunda arabellekler gerektiğinde otomatik olarak tahsis edilir. Borudan büyük miktarda veri okunursa, bu durum büyük miktarda bellek tahsis edilmesine neden olabilir. -B seçeneği, borular için bu otomatik arabellek tahsisini devre dışı bırakır, böylece boru için yalnızca 64 KB (veya -b seçeneğiyle belirtilen alan miktarı) kullanılır. Uyarı: -B seçeneğinin kullanılması hatalı görüntülemeye neden olabilir, çünkü boruyla aktarılan verilerin yalnızca en son görüntülenen kısmı bellekte tutulur; önceki veriler kaybolur. Kaybolan karakterler soru işareti olarak gösterilir.
-c or --clear-screen Tam ekran yeniden çizimlerinin en üst satırdan aşağıya doğru boyanmasını sağlar. Varsayılan olarak, tam ekran yeniden çizimleri ekranın altından yukarı kaydırılarak yapılır.
-C or --CLEAR-SCREEN less'in eski sürümleriyle uyumluluk amacıyla -c ile aynıdır.
-d or --dumb -d seçeneği, terminal "dumb" ise (yani ekranı temizleme veya geriye doğru kaydırma gibi bazı önemli yeteneklerden yoksunsa) normalde görüntülenen hata mesajını bastırır. -d seçeneği, less'in dumb bir terminaldeki davranışını başka bir şekilde değiştirmez.
-Dxcolor or --color=xcolor Görüntülenen metnin farklı bölümlerinin rengini değiştirir. x, rengi ayarlanan metin türünü seçen tek bir karakterdir:
B İkili (binary) karakterler.
C Kontrol karakterleri.
E Hatalar ve bilgilendirici mesajlar.
H --header seçeneği aracılığıyla ayarlanan üstbilgi (header) satırları ve sütunları.
M Durum sütunundaki işaret harfleri.
N -N seçeneği aracılığıyla etkinleştirilen satır numaraları.
P İstemler (prompts).
R rscroll karakteri.
S Arama sonuçları.
W -w seçeneği aracılığıyla etkinleştirilen vurgulama.
1-5 Bir arama sonucunda, birinci ila beşinci parantez içindeki alt kalıpla eşleşen metin. Alt kalıp renklendirmesi yalnızca less; posix, pcre veya pcre2 düzenli ifade kitaplıklarından biriyle derlenmişse çalışır.
d Kalın metin.
k Yanıp sönen metin.
s Belirgin (standout) metin.
u Altı çizili metin.
Büyük harfler ve rakamlar yalnızca --use-color seçeneği etkinleştirildiğinde kullanılabilir. Metin rengi hem bir büyük harf hem de bir küçük harfle belirtildiğinde büyük harf önceliklidir. Örneğin, hata mesajları normalde belirgin metin olarak görüntülenir. Dolayısıyla, hem "s" hem de "E" için bir renk verilirse, "E" rengi hata mesajlarına uygulanır ve "s" rengi diğer belirgin metinlere uygulanır. Küçük harfler, geri alma karakterleriyle (backspace) üst üste yazma yoluyla oluşturulan kalın ve altı çizili metinleri (bkz. -U seçeneği) ve içerik dışı metinleri (satır numaraları ve istemler gibi) ifade eder; ancak -R seçeneğiyle ANSI kaçış dizileri kullanılarak biçimlendirilmiş metinleri ifade etmez (ancak Windows ve MS-DOS'taki farklı davranışlar için aşağıdaki nota bakın).
Bir küçük harfin ardından, hem normal biçim değişikliğinin hem de belirtilen rengin kullanılması gerektiğini belirtmek için bir + işareti gelebilir. Örneğin, -Dug altı çizili metni altı çizilmeden yeşil olarak görüntüler; yeşil renk her zamanki altı çizili biçimlendirmenin yerini almıştır. Ancak -Du+g altı çizili metni hem yeşil hem de altı çizili biçimde görüntüler.
color ya 4-bitlik bir renk dizesidir ya da 8-bitlik bir renk dizesidir:
4-bitlik bir renk dizesi bir veya iki karakterden oluşur; burada ilk karakter ön plan rengini ve ikinci karakter arka plan rengini aşağıdaki gibi belirtir:
b Mavi
c Camgöbeği (Cyan)
g Yeşil
k Siyah
m Eflatun (Magenta)
r Kırmızı
w Beyaz
y Sarı
Karşılık gelen büyük harf, rengin daha parlak bir tonunu belirtir. Örneğin, -DNGk satır numaralarını siyah arka plan üzerinde parlak yeşil metin olarak görüntüler ve
-DEbR hata mesajlarını parlak kırmızı arka plan üzerinde mavi metin olarak görüntüler.: Karakterlerden biri "-" ise veya atlanmışsa, ilgili renk normal metninkine ayarlanır.
8-bitlik bir renk dizesi, aralarında nokta bulunan bir veya iki ondalık tam sayıdır; burada ilk tam sayı ön plan rengini ve ikincisi arka plan rengini belirtir. 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). If either integer is a "-" or is omitted, the corresponding color is set to that of normal text.
Bir 4-bitlik veya 8-bitlik renk dizesini, renge ek olarak metin özniteliklerini ayarlamak için aşağıdaki karakterlerden biri veya daha fazlası takip edebilir.
s veya ~ Belirgin (ters video)
u veya _ Altı çizili
d veya * Kalın
l veya & Yanıp sönen
MS-DOS ve Windows'ta --color seçeneği, yukarıda açıklanandan şu yönlerden farklı davranır:
• Renk dizesinin sonundaki kalın (d ve *) ve yanıp sönen (l and &) metin öznitelikleri desteklenmez.
• Küçük harfli renk seçici harfleri, üst üste yazılmış ve içerik dışı metne ek olarak -R ile ANSI kaçış dizileri tarafından biçimlendirilmiş metni ifade eder (ancak bkz. -Da).
• Geçmişe yönelik nedenlerden dolayı, küçük harfli bir renk seçici harfini sayısal bir renk değeri takip ettiğinde, sayı yukarıda açıklandığı gibi bir "CSI 38;5" renk değeri olarak değil, bunun yerine 0 ile 15 (dahil) arasında bir 4-bitlik CHAR_INFO.Attributes değeri olarak yorumlanır (bkz. https://learn.microsoft.com/en-us/windows/console/char-info-str).
Kafa confusion'ını önlemek için, MS-DOS/Windows'ta küçük harfli bir renk seçiciden sonra sayılar yerine eşdeğer harflerin kullanılması önerilir.
• Bir büyük harf renk seçici harfini takip eden sayısal renk değerleri ("CSI 38;5" renk), Windows 10'dan önceki sistemlerde desteklenmez.
• İçerikte renk ayarlamak için yalnızca sınırlı sayıda ANSI kaçış dizisi düzgün çalışır. 4-bitlik renk dizileri çalışır, ancak "CSI 38;5" renk dizileri çalışmaz.
• -Da seçeneği, (1) küçük harfli renk seçici harflerinin ANSI kaçış dizileriyle biçimlendirilmiş metni etkilememesini sağlayarak ve (2) içerikteki "CSI 38;5" renk dizilerinin terminale aktarılarak çalışmasına izin vererek (yalnızca Windows 10 ve sonrasında; daha eski Windows sistemlerinde bu tür diziler, -Da ayarından bağımsız olarak çalışmaz) --color seçeneğinin davranışını MS-DOS/Windows dışı sistemlerdeki davranışına daha benzer hale getirir.
-e or --quit-at-eof less'in dosya sonuna (EOF) ikinci kez ulaştığında otomatik olarak çıkmasını sağlar. Varsayılan olarak less'ten çıkmanın tek yolu "q" komutudur.
-E or --QUIT-AT-EOF less'in dosya sonuna ilk kez ulaştığında otomatik olarak çıkmasını sağlar.
-f or --force Normal olmayan dosyaların açılmasını zorlar. (Normal olmayan bir dosya, bir dizin veya bir özel aygıt dosyasıdır.) Ayrıca ikili (binary) bir dosya açıldığında verilen uyarı mesajını da bastırır. Varsayılan olarak less, normal olmayan dosyaları açmayı refus eder. Bazı işletim sistemlerinin, -f ayarlanmış olsa bile dizinlerin okunmasına izin vermeyeceğini unutmayın.
-F or --quit-if-one-screen Dosyanın tamamı ilk ekranda görüntülenebiliyorsa less'in otomatik olarak çıkmasını sağlar.
-g or --hilite-search Normalde less, son arama komutuyla eşleşen TÜM dizeleri vurgular. -g seçeneği bu davranışı, yalnızca son arama komutuyla bulunan belirli dizeyi vurgulayacak şekilde değiştirir. Bu, less'in varsayılana göre biraz daha hızlı çalışmasını sağlayabilir.
-G or --HILITE-SEARCH -G seçeneği, arama komutları tarafından bulunan dizelerin tüm vurgulanmasını bastırır.
-hn or --max-back-scroll=n Geriye doğru kaydırılacak maksimum satır sayısını belirtir. Geriye doğru n satırdan fazla kaydırmak gerekirse, ekran bunun yerine ileriye doğru yeniden çizilir. (Terminal geriye doğru kaydırma yeteneğine sahip değilse, -h0 varsayılır.)
-i or --ignore-case Aramaların harf büyüklüğünü yoksaymasını sağlar; yani büyük harf ve küçük harf aynı kabul edilir. Arama kalıbında herhangi bir büyük harf görünürse bu seçenek yoksayılır; başka bir deyişle, bir kalıp büyük harf içeriyorsa, o arama harf büyüklüğünü yoksaymaz.
-I or --IGNORE-CASE -i gibidir, ancak kalıp büyük harf içerse bile aramalar harf büyüklüğünü yoksayar.
-jn or --jump-target=n Ekranda "hedef" satırın konumlandırılacağı bir satır belirtir. Hedef satır; bir kalıbı aramak, bir satır numarasına atlamak, bir dosya yüzdesine atlamak veya bir etikete (tag) atlamak için herhangi bir komut tarafından belirtilen satırdır. Ekran satırı bir sayı ile belirtilebilir: ekrandaki en üst satır 1, bir sonraki 2 vb. Ekranın altına göreli bir satır belirtmek için sayı negatif olabilir: ekrandaki en alt sat -1, alttan ikinci satır -2 vb.
Alternatif olarak ekran satırı, bir ondalık nokta ile başlayarak ekran yüksekliğinin bir oranı olarak belirtilebilir: .5 ekranın ortasıdır, .3 ilk satırdan aşağıya doğru onda üçüdür vb. Satır bir oran olarak belirtilirse, terminal penceresi yeniden boyutlandırıldığında gerçek satır sayısı yeniden hesaplanır. --header seçeneği kullanılıyorsa ve -j tarafından belirtilen hedef satır üstbilgi tarafından kapatılacaksa, hedef satır üstbilgiden sonraki ilk satıra taşınır. --header seçeneği etkinken, -S seçeneği yoksayılır ve ekran genişliğinden uzun olan satırlar kesilir.
Herhangi bir -j seçeneği biçimi kullanılırsa, yinelenen ileriye doğru aramalar ("n" veya "N" ile çağrılan), -a veya -A ile değiştirilmedikçe hedef satırın hemen arkasındaki satırdan başlar ve yinelenen geriye doğru aramalar hedef satırdan başlar. Örneğin, "-j4" kullanılırsa, hedef satır ekrandaki dördüncü satırdır, dolayısıyla ileriye doğru aramalar ekrandaki beşinci satırdan başlar. Ancak yinelenmeyen aramalar ("/" veya "?" ile çağrılan) her zaman sırasıyla mevcut ekranın başından veya sonundan başlar.
-J or --status-column Ekranın sol kenarında bir durum sütunu görüntüler. Durum sütunda görüntülenen karakter şunlardan biri olabilir:
Satır -S seçeneğiyle kesilmiştir ve ekranın sağ kenarının ötesinde kesilen metin, mevcut arama için bir eşleşme içermektedir.
< Satır yatay olarak kaydırılmıştır ve ekranın sol tarafının ötesine kayan metin, mevcut arama için bir eşleşme içermektedir.
= Satır hem kesilmiş hem de kaydırılmıştır ve ekranın her iki tarafının ötesinde de eşleşmeler vardır.
Satırın görünür kısmında eşleşmeler vardır, ancak sağında veya solunda yoktur.
a-z, A-Z Satır, m komutu aracılığıyla ilgili harfle işaretlenmiştir.
-kfilename or --lesskey-file=filename less'in belirtilen dosyayı bir lesskey(1) ikili (binary) dosyası olarak açmasını ve yorumlamasını sağlar. Birden fazla -k seçeneği belirtilebilir. LESSKEY veya LESSKEY_SYSTEM çevre değişkeni ayarlanmışsa veya standart bir yerde bir lesskey dosyası bulunursa (bkz. TUŞ BAĞLANTILARI), o da bir lesskey dosyası olarak kullanılır. Aşağıdaki "--lesskey-content" altındaki uyarıya dikkat edin.
--lesskey-src=filename less'in belirtilen dosyayı bir lesskey(1) kaynak dosyası olarak açmasını ve yorumlamasını sağlar. LESSKEYIN veya LESSKEYIN_SYSTEM çevre değişkeni ayarlanmışsa veya standart bir yerde bir lesskey kaynak dosyası bulunursa (bkz. TUŞ BAĞLANTILARI), o da bir lesskey kaynak dosyası olarak kullanılır. Sürüm 582'den önce, less'in kullanabilmesi için bir lesskey kaynak dosyasını lesskey ikili dosyasına dönüştürmek üzere lesskey programının çalıştırılması gerekiyordu. less'in daha yeni sürümleri, lesskey kaynak dosyasını doğrudan okur ve kaynak dosya mevcutsa ikili dosyayı yoksayar. Aşağıdaki "--lesskey-content" altındaki uyarıya dikkat edin.
--lesskey-content=text less'in belirtilen metni bir lesskey(1) kaynak dosyasının içeriği olarak yorumlamasını sağlar. Metin içinde lesskey satırları, her zamanki gibi yeni satırlarla veya noktalı virgüllerle ayrılabilir. Değişmez (literal) bir noktalı virgül, bir ters eğik çizgi ve ardından bir noktalı virgül ile temsil edilebilir.
Uyarı: Başlangıçta erken kullanılan LESS, LESSSECURE, LESSCHARSET ve diğerleri gibi belirli çevre değişkenleri, bir komut satırı seçeneği (--lesskey, --lesskey-src veya --lesskey-content) tarafından belirtilen bir dosyada ayarlanamaz. Çevre değişkenlerini ayarlamak için bir lesskey dosyası kullanırken varsayılan lesskey dosyasını kullanmak veya dosyayı bir komut satırı seçeneği kullanmak yerine LESSKEYIN veya LESS_CONTENT çevre değişkenlerini kullanarak belirtmek daha güvenlidir.
-K or --quit-on-intr Bir kesme (interrupt) karakteri (genellikle ^C) yazıldığında less'in hemen (durum 2 ile) çıkmasını sağlar. Normalde, bir kesme karakteri less'in yaptığı işi durdurmasına ve komut istemine geri dönmesine neden olur. Bu seçeneğin kullanılmasının, "F" komutundan komut istemine geri dönmeyi imkansız hale getirdiğini unutmayın.
-L or --no-lessopen LESSOPEN çevre değişkenini yoksayar (aşağıdaki GİRDİ ÖNİŞLEMCİSİ bölümüne bakın). Bu seçenek less içinden ayarlanabilir, ancak şu anda açık olan dosyaya değil, yalnızca daha sonra açılan dosyalara uygulanır.
-m or --long-prompt less'in dosyaya olan yüzdeyi de göstererek ayrıntılı bir şekilde (more(1) gibi) istem vermesini sağlar. Varsayılan olarak less iki nokta üst üste ile istem verir.
-M or --LONG-PROMPT less'in more(1)'dan bile daha ayrıntılı istem vermesini sağlar.
-n or --line-numbers Satır numaralarını bastırır. Varsayılan durum (satır numaralarının kullanılması), özellikle çok büyük bir girdi dosyasında less'in bazı durumlarda daha yavaş çalışmasına neden olabilir. -n seçeneğiyle satır numaralarının bastırılması bu sorunu önleyecektir. Satır numaralarının kullanılması şu anlama gelir: Satır numarası ayrıntılı istemde ve = komutunda görüntülenecektir ve v komutu geçerli satır numarasını düzenleyiciye iletecektir (ayrıca aşağıdaki İSTEMLER bölümünde LESSEDIT tartışmasına bakın).
-N or --LINE-NUMBERS Ekranda her satırın başında bir satır numarasının görüntülenmesini sağlar.
-ofilename or --log-file=filename less'in görüntülenirken girdisini belirtilen dosyaya kopyalamasını sağlar. Bu yalnızca girdi dosyası bir boru (pipe) olduğunda geçerlidir, sıradan bir dosya olduğunda geçerli değildir. Dosya zaten mevcutsa less, üzerine yazmadan önce onay isteyecektir.
-Ofilename or --LOG-FILE=filename -O seçeneği -o gibidir, ancak onay istemeden mevcut bir dosyanın üzerine yazacaktır.
Herhangi bir günlük dosyası belirtilmemişse, less içinden bir günlük dosyası belirtmek için -o ve -O seçenekleri kullanılabilir. Bir dosya adı olmadan, yalnızca günlük dosyasının adını bildiriler. "s" komutu, less içinden -o belirtmeye eşdeğerdir.
-ppattern or --pattern=pattern Komut satırındaki -p seçeneği, +/pattern belirtmeye eşdeğerdir; yani less'e dosyadaki pattern'in ilk geçtiği yerden başlamasını söyler.
-Pprompt or --prompt=prompt Üç istem stilini kendi tercihinize göre uyarlamanın bir yolunu sunar. Bu seçenek normalde her less komutuyla yazılmak yerine LESS çevre değişkenine yerleştirilir. Böyle bir seçenek ya LESS değişkenindeki son seçenek olmalı ya da bir dolar işareti ile sonlandırılmalıdır. -Ps ve ardından bir dize, varsayılan (kısa) istemi o dizeye değiştirir. -Pm orta (-m) istemi değiştirir. -PM uzun (-M) istemi değiştirir. -Ph yardım ekranı istemini değiştirir. -P=, = komutu tarafından yazdırılan mesajı değiştirir. -Pw, veri beklerken ("F" komutunda) yazdırılan mesajı değiştirir.
Tüm istem dizileri, bir dizi harf ve özel kaçış dizilerinden oluşur. Daha fazla ayrıntı için İSTEMLER bölümüne bakın.
-q or --quiet or --silent Kısmen "sessiz" çalışmayı sağlar: Dosyanın sonundan sonrasına veya başlangıcından öncesine kaydırma girişimi yapıldığında terminal zili çalmaz. Terminalin "görsel zili" (visual bell) varsa, bunun yerine o kullanılır. Geçersiz bir karakter yazmak gibi diğer bazı hatalarda zil çalacaktır. Varsayılan davranış, bu tür tüm durumlarda terminal zilini çalmaktır.
-Q or --QUIET or --SILENT Tamamen "sessiz" çalışmayı sağlar: Terminal zili asla çalmaz. Terminalin "görsel zili" varsa, terminal zilinin çalacağı tüm durumlarda o kullanılır.
-r or --raw-control-chars "Ham" (raw) kontrol karakterlerinin görüntülenmesini sağlar. Varsayılan davranış, kontrol karakterlerini şapka (caret) gösterimini kullanarak görüntülemektir; örneğin, bir kontrol-A (oktal 001), "^A" olarak görüntülenir (-U seçeneği altında açıklanan bazı istisnalarla birlikte). Uyarı: -r seçeneği kullanıldığında, less ekranın gerçek görünümünü takip edemez (çünkü bu, ekranın her bir kontrol karakteri türüne nasıl yanıt verdiğine bağlıdır). Bu nedenle, uzun satırların yanlış yerde bölünmesi gibi çeşitli görüntüleme sorunları ortaya çıkabilir.
-r SEÇENEĞİNİN KULLANILMASI ÖNERİLMEZ.
-R or --RAW-CONTROL-CHARS -r gibidir, ancak yalnızca ANSI "renk" kaçış dizileri ve OSC 8 köprü (hyperlink) dizileri "ham" biçimde çıktı olarak verilir. -r'nin aksine, dosyada bu tür kaçış dizilerinden başka kaçış dizisi bulunmadığı sürece ekran görünümü doğru bir şekilde korunur. Renk kaçış dizileri yalnızca renk bir satır içinde değiştirildiğinde desteklenir, satırlar arasında desteklenmez. Başka bir deyişle, önceki satırlardaki kaçış dizilerinden bağımsız olarak her satırın başlangıcının normal (renksiz) olduğu varsayılır. Ekran görünümünü takip etmek amacıyla bu kaçış dizilerinin imleci hareket ettirmediği varsayılır.
OSC 8 köprüleri aşağıdaki biçimdeki dizilerdir:
ESC ] 8 ; ... \7
Sonlandırma dizisi bir BEL karakteri (\7) veya iki karakterli "ESC " dizisi olabilir.
ANSI renk kaçış dizileri aşağıdaki biçimdeki dizilerdir:
ESC [ ... m
buradaki "...", sıfır veya daha fazla renk belirtim karakteridir. LESSANSIENDCHARS çevre değişkenini, bir renk kaçış dizisini sonlandırabilecek karakterlerin listesine ayarlayarak less'in "m" dışındaki karakterlerin ANSI renk kaçış dizilerini sonlandırabileceğini düşünmesini sağlayabilirsiniz. Ve LESSANSIMIDCHARS çevre değişkenini, görünebilecek karakterlerin listesine ayarlayarak less'in ESC ile m arasında standart olanlar dışındaki karakterlerin görünebileceğini düşünmesini sağlayabilirsiniz.
-s or --squeeze-blank-lines Ardışık boş satırların tek bir boş satıra sıkıştırılmasını sağlar. Bu, nroff çıktısını görüntülerken yararlıdır.
-S or --chop-long-lines Ekran genişliğinden uzun satırların kaydırılması (wrap) yerine kesilmesini (kırpılmasını) sağlar. Yani, uzun bir satırın ekran genişliğine sığmayan kısmı siz SAĞ OK tuşuna basana kadar görüntülenmez. Varsayılan davranış uzun satırları kaydırmaktır; yani geri kalanını bir sonraki satırda görüntülemektir. Ayrıca --wordwrap seçeneğine bakın.
-ttag or --tag=tag Hemen ardından bir ETIKET (TAG) gelen -t seçeneği, o etiketi içeren dosyayı düzenleyecektir. Bunun çalışabilmesi için etiket bilgilerinin mevcut olması gerekir; örneğin geçerli dizinde daha önce ctags(1) veya eşdeğer bir komut tarafından oluşturulmuş "tags" adlı bir dosya bulunabilir. LESSGLOBALTAGS çevre değişkeni ayarlanmışsa, bunun global(1) ile uyumlu bir komutun adı olduğu kabul edilir ve etiketi bulmak için o komut yürütülür. (Bkz. http://www.gnu.org/software/global/global.html). -t seçeneği, yeni bir dosyayı incelemenin bir yolu olarak less içinden de (- komutu kullanılarak) belirtilebilir. ":t" komutu, less içinden -t belirtmeye eşdeğerdir.
-Ttagsfile or --tag-file=tagsfile "tags" yerine kullanılacak bir etiketler (tags) dosyası belirtir.
-u or --underline-special Geri alma (backspace) ve satır başı (carriage return) karakterlerinin yazdırılabilir karakterler olarak ele alınmasını sağlar; yani girdide göründüklerinde terminale gönderilirler.
-U or --UNDERLINE-SPECIAL Geri alma (backspace), sekme (tab), satır başı (carriage return) ve "biçimlendirme karakterlerinin" (Unicode tarafından tanımlandığı gibi) kontrol karakterleri olarak ele alınmasını sağlar; yani -r seçeneğiyle belirtildiği gibi işlenirler.
Varsayılan olarak, -u veya -U verilmemişse, bir alt çizgi karakterinin yanında görünen geri alma karakterleri özel olarak işlenir: Altı çizili metin, terminalin donanımsal alt çizgi yeteneği kullanılarak görüntülenir. Ayrıca, iki özdeş karakter arasında görünen geri alma karakterleri özel olarak işlenir: Üst üste yazılmış metin, terminalin donanımsal kalın yazı yeteneği kullanılarak yazdırılır. Diğer geri alma karakterleri, önündeki karakterle birlikte silinir. Hemen ardından yeni satır karakteri gelen satır başı karakterleri silinir. Diğer satır başı karakterleri -r seçeneğiyle belirtildiği gibi işlenir. Bayt Sırası İşareti (Byte Order Mark) gibi Unicode biçimlendirme karakterleri terminale gönderilir. Ne -u ne de -U etkin değilse üst üste yazılmış veya altı çizili metinler aranabilir.
Ayrıca --proc-backspace, --proc-tab ve --proc-return seçeneklerine bakın.
-V or --version less'in sürüm numarasını görüntüler.
-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. If the --status-line option is in effect, the entire line (the width of the screen) is highlighted. Otherwise, only the text in the line is highlighted, unless the -J option is in effect, in which case only the status column is highlighted.
-W or --HILITE-UNREAD -w gibidir, ancak bir satırdan büyük herhangi bir ileri hareket komutundan sonraki ilk yeni satırı geçici olarak vurgular.
-xn,... or --tabs=n,... Sekme duraklarını (tab stops) ayarlar. Yalnızca bir n belirtilirse, sekme durakları n'nin katlarında ayarlanır. Virgülle ayrılmış birden fazla değer belirtilirse, sekme durakları bu konumlarda ayarlanır ve ardından son ikisiyle aynı aralıklarla devam eder. Örneğin, "-x9,17" sekmeleri 9, 17, 25, 33 vb. konumlarda ayarlayacaktır. n için varsayılan değer 8'dir.
-X or --no-init Termcap başlatma (initialization) ve sonlandırma (deinitialization) dizilerinin terminale gönderilmesini devre dışı bırakır. Sonlandırma dizisinin ekranı temizlemek gibi gereksiz bir şey yapması durumunda bu bazen istenir.
-yn or --max-forw-scroll=n İleriye doğru kaydırılacak maksimum satır sayısını belirtir. İleriye doğru n satırdan fazla kaydırmak gerekirse, ekran bunun yerine yeniden çizilir. İstenirse ekranın üstünden yeniden çizmek için -c veya -C seçeneği kullanılabilir. Varsayılan olarak, herhangi bir ileri hareket kaydırmaya neden olur.
-zn or --window=n or -n Varsayılan kaydırma penceresi boyutunu n satıra değiştirir. Varsayılan değer bir ekran dolusudur. Pencere boyutunu değiştirmek için z ve w komutları da kullanılabilir. "z" harfi, more(1)'un bazı sürümleriyle uyumluluk için atlanabilir. n sayısı negatifse, geçerli ekran boyutundan n satır daha azını belirtir. Örneğin, ekran 24 satır ise, -z-4 kaydırma penceresini 20 satıra ayarlar. Ekran 40 satır olarak yeniden boyutlandırılırsa, kaydırma penceresi otomatik olarak 36 satıra değişir.
-"cc or --quotes=cc Dosya adı tırnak karakterini değiştirir. Hem boşluk hem de tırnak karakterleri içeren bir dosyayı adlandırmaya çalışıyorsanız bu gerekli olabilir. Tek bir karakter takip ederse, tırnak karakterini o karaktere değiştirir. Bu durumda boşluk içeren dosya adları çift tırnak yerine bu karakterle çevrelenmelidir. İki karakter takip ederse, açılış tırnağını ilk karaktere ve kapanış tırnağını ikinci karaktere değiştirir. Boşluk içeren dosya adlarının önüne açılış tırnağı karakteri ve arkasına kapanış tırnağı karakteri getirilmelidir. Tırnak karakterleri değiştirildikten sonra bile bu seçeneğin -" (bir tire ve ardından bir çift tırnak) olarak kaldığını unutmayın.
-~ or --tilde Normalde dosya sonundan sonraki satırlar tek bir tilde (~) olarak görüntülenir. Bu seçenek, dosya sonundan sonraki satırların boş satırlar olarak görüntülenmesini sağlar.
-# or --shift RIGHTARROW ve LEFTARROW komutlarında yatay olarak kaydırılacak varsayılan konum sayısını belirtir. Belirtilen sayı sıfır ise, varsayılan konum sayısını ekran genişliğinin yarısına ayarlar. Alternatif olarak, sayı bir ondalık nokta ile başlayarak ekran genişliğinin bir oranı olarak belirtilebilir: .5 ekran genişliğinin yarısıdır, .3 ekran genişliğinin onda üçüdür vb. Sayı bir oran olarak belirtilirse, terminal penceresi yeniden boyutlandırıldığında gerçek kaydırma konumu sayısı yeniden hesaplanır.
--exit-follow-on-close Bir boru (pipe) üzerinde "F" komutu kullanılırken, borunun girdi tarafı kapatıldığında less daha fazla veri beklemeyi otomatik olarak durduracaktır.
--file-size --file-size belirtilirse, less dosyayı açtıktan hemen sonra dosyanın boyutunu belirleyecektir. Ardından "=" komutu dosyadaki satır sayısını görüntüleyecektir. Normalde bu yapılmaz, çünkü girdi dosyası rastgele erişimli değilse (bir boru gibi) ve büyükse yavaş olabilir.
--follow-name Normalde, bir F komutu yürütülürken girdi dosyası yeniden adlandırılırsa less, ad değişikliğine rağmen orijinal dosyanın içeriğini görüntülemeye devam edecektir. --follow-name belirtilirse, bir F komutu sırasında less periyodik olarak dosyayı adıyla yeniden açmaya çalışacaktır. Yeniden açma başarılı olursa ve dosya orijinalinden farklı bir dosyaysa (yani orijinal [şimdi adı değiştirilmiş] dosya ile aynı adla yeni bir dosya oluşturulmuş demektir), less o yeni dosyanın içeriğini görüntüleyecektir.
--header=L,C,N Ekranda görüntülenen üstbilgi (header) satır ve sütunlarının sayısını ayarlar. Üstbilgi satır sayısı L olarak ayarlanır. L 0 ise, üstbilgi satırları devre dışı bırakılır. L boşsa veya eksikse, üstbilgi satırlarının sayısı değişmez. Üstbilgi sütunlarının sayısı C olarak ayarlanır. C 0 ise, üstbilgi sütunları devre dışı bırakılır. C boşsa veya eksikse, üstbilgi sütunlarının sayısı değişmez. İlk üstbilgi satırı, dosyadaki N. satır numarasına ayarlanır. N boşsa veya eksikse, ekranın ilk satırında o anda görüntülenen satırın oranı (eğer --header komutu less içinden verilmişse) veya 1 (eğer --header seçeneği komut satırından verilmişse) olarak kabul edilir. Özel "--header=-" biçimi üstbilgi satırlarını ve üstbilgi sütunlarını devre dışı bırakır ve "--header=0,0" ile eşdeğerdir.
L sıfırdan farklı olduğunda, ekranın üstündeki ilk L satır, dosyanın hangi bölümünün görüntülendiğine bakılmaksızın, N satırından başlayan dosyanın L satırıyla değiştirilir. Üstbilgi satırları görüntülendiğinde, üstbilgi satırından önceki herhangi bir dosya içeriği görüntülenemez. C sıfırdan farklı olduğunda, her satırın başında görüntülenen ilk C karakter, satırın geri kalanı yatay olarak kaydırılsa bile satırın ilk C karakteriyle değiştirilir.
--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.
--intr=c Use the character c instead of ^X to interrupt a read when the "Waiting for data" message is displayed. c must be an ASCII character; that is, one with a value between 1 and 127 inclusive. A caret followed by a single character can be used to specify a control character.
--line-num-width=n Sets the minimum width of the line number field when the -N option is in effect to n characters. The default is 7.
--match-shift=n When -S is in effect, if a search match is not visible because it is shifted to the left or right of the currently visible screen, the text will horizontally shift to ensure that the search match is visible. This option selects the column in which the first character of the search match will be placed after the shift. In other words, there will be n characters visible to the left of the search match.
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.
--modelines=n Before displaying a file, less will read the first n lines to try to find a vim- compatible modeline. If n is zero, less does not try to find modelines. By using a modeline, the file itself can specify the tab stops that should be used when viewing it.
A modeline contains, anywhere in the line, a program name ("vi", "vim", "ex", or "less"), followed by a colon, possibly followed by the word "set", and finally followed by zero or more option settings. If the word "set" is used, option settings are separated by spaces, and end at the first colon. If the word "set" is not used, option settings may be separated by either spaces or colons. The word "set" is required if the program name is "less" but optional if any of the other three names are used. If any option setting is of the form "tabstop=n" or "ts=n", then tab stops are automatically set as if --tabs=n had been given. See the --tabs description for acceptable values of n.
--mouse Enables mouse input: scrolling the mouse wheel down moves forward in the file, scrolling the mouse wheel up moves backwards in the file, left-click sets the "#" mark to the line where the mouse is clicked, and right-click (or any other) returns to the "#" mark position. If a left-click is performed with the mouse cursor on an OSC 8 hyperlink, the hyperlink is selected as if by the ^O^N command. If a left-click is performed with the mouse cursor on an OSC 8 hyperlink which is already selected, the hyperlink is opened as if by the ^O^O command. 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 reporting, and on the Windows version of less.
--MOUSE Like --mouse, except the direction scrolled on mouse wheel movement 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.
--no-number-headers Header lines (defined via the --header option) are not assigned line numbers. Line number 1 is assigned to the first line after any header lines.
--no-search-header-lines Searches do not include header lines, but still include header columns.
--no-search-header-columns Searches do not include header columns, but still include header lines.
--no-search-headers Searches do not include header lines or header columns.
--no-vbell Disables the terminal's visual bell.
--proc-backspace If set, backspaces are handled as if neither the -u option nor the -U option were set. That is, a backspace adjacent to an underscore causes text to be displayed in underline mode, and a backspace between identical characters cause text to be displayed in boldface mode. This option overrides the -u and -U options, so that display of backspaces can be controlled separate from tabs and carriage returns. If not set, backspace display is controlled by the -u and -U options.
--PROC-BACKSPACE If set, backspaces are handled as if the -U option were set; that is backspaces are treated as control characters.
--proc-return If set, carriage returns are handled as if neither the -u option nor the -U option were set. That is, a carriage return immediately before a newline is deleted. This option overrides the -u and -U options, so that display of carriage returns can be controlled separate from that of backspaces and tabs. If not set, carriage return display is controlled by the -u and -U options.
--PROC-RETURN If set, carriage returns are handled as if the -U option were set; that is carriage returns are treated as control characters.
--proc-tab If set, tabs are handled as if the -U option were not set. That is, tabs are expanded to spaces. This option overrides the -U option, so that display of tabs can be controlled separate from that of backspaces and carriage returns. If not set, tab display is controlled by the -U options.
--PROC-TAB If set, tabs are handled as if the -U option were set; that is tabs are treated as control characters.
--redraw-on-quit When quitting, after sending the terminal deinitialization string, redraws the entire last screen. On terminals whose terminal deinitialization string causes the terminal to switch from an alternate screen, this makes the last screenful of the current file remain visible after less has quit.
--rscroll=c This option changes the character used to mark truncated lines. It may begin with a two-character attribute indicator like LESSBINFMT does. If there is no attribute indicator, standout is used. If set to "-", truncated lines are not marked.
--save-marks Save marks in the history file, so marks are retained across different invocations of less.
--search-options=... Sets default search modifiers. The value is a string of one or more of the characters E, F, K, N, R or W. Setting any of these has the same effect as typing that control character at the beginning of every search pattern. For example, setting --search- options=W is the same as typing ^W at the beginning of every pattern. The value may also contain a digit between 1 and 5, which has the same effect as typing ^S followed by that digit at the beginning of every search pattern. The value "-" disables all default search modifiers.
--show-preproc-errors If a preprocessor produces data, then exits with a non-zero exit code, less will display a warning.
--status-col-width=n Sets the width of the status column when the -J option is in effect. The default is 2 characters.
--status-line If a line is marked, the entire line (rather than just the status column) is highlighted. Also lines highlighted due to the -w option will have the entire line highlighted. If --use-color is set, the line is colored rather than highlighted.
--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 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 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.
--wordwrap When the -S option is not in use, wrap each line at a space or tab if possible, so that a word is not split between two lines. The default is to wrap at any character.
--: 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, +
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 cursor one word to the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ] (That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right.
HOME [ ESC-0 ] Move the cursor to the beginning of the line.
END [ ESC-$ ] Move the cursor to the end of the line.
BACKSPACE Delete the character to the left of the cursor, or cancel the command if the command line is empty.
DELETE or [ ESC-x ] Delete the character under the cursor.
^BACKSPACE [ ESC-BACKSPACE ] (That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor.
^DELETE [ ESC-X or ESC-DELETE ] (That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor.
UPARROW [ ESC-k ] Retrieve the previous command line. If you first enter some text and then press UPARROW, it will retrieve the previous command which begins with that text.
DOWNARROW [ ESC-j ] Retrieve the next command line. If you first enter some text and then press DOWNARROW, it will retrieve the next command which begins with that text.
TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match is entered into the command line. Repeated TABs will cycle thru the other matching filenames. If the completed filename is a directory, a "/" is appended to the filename. (On MS-DOS and Windows 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 and Windows) 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.
^G Delete the entire command line and return to the main prompt.
Key Bindings
You may define your own less commands by creating a lesskey source file. This file specifies a set of command keys and an action associated with each key. You may also change the line- editing keys (see LINE EDITING), and set environment variables used by less. See the lesskey(1) manual page for details about the file format.
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/.config/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.
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 system-wide lesskey file: On Unix systems, the system-wide lesskey file is /usr/local/etc/syslesskey. (However, if less was built with a different sysconf directory than /usr/local/etc, that directory is where the sysless file is found.) On MS-DOS and Windows systems, the system-wide lesskey file is c:_syslesskey. On OS/2 systems, the system-wide lesskey file is c:\syslesskey.ini.
Previous versions of less (before v582) used lesskey files with a binary format, 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 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 "$1" in *.Z) TEMPFILE=$(mktemp) uncompress -c $1 >$TEMPFILE 2>/dev/null if [ -s $TEMPFILE ]; then echo $TEMPFILE else rm -f $TEMPFILE fi ;; esac
lessclose.sh: #! /bin/sh rm $2
To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on.
It is also possible to set up an input preprocessor to pipe the file data directly to less, rather than putting the data into a replacement file. This avoids the need to decompress the entire file before starting to view it. An input preprocessor that works this way is called an input pipe. An input pipe, instead of writing the name of a replacement file on its standard output, writes the entire contents of the replacement file on its standard output. If the input pipe does not write any characters on its standard output, then there is no replacement file and less uses the original file, as normal. To use an input pipe, make the first character in the LESSOPEN environment variable a vertical bar (|) to signify that the input preprocessor is an input pipe. As with non-pipe input preprocessors, the command string must contain one occurrence of %s, which is replaced with the filename of the input file.
For example, on many Unix systems, this script will work like the previous example scripts:
lesspipe.sh: #! /bin/sh case "$1" in *.Z) uncompress -c $1 2>/dev/null ;; *) exit 1 ;; esac exit $?
To use this script, put it where it can be executed and set LESSOPEN="|lesspipe.sh %s".
Note that a preprocessor cannot output an empty file, since that is interpreted as meaning there is no replacement, and the original file is used. To avoid this, if LESSOPEN starts with two vertical bars, the exit status of the script determines the behavior when the output is empty. If the output is empty and the exit status is zero, the empty output is considered to be replacement text. If the output is empty and the exit status is nonzero, the original file is used. For compatibility with previous versions of less, if LESSOPEN starts with only one vertical bar, the exit status of the preprocessor is ignored.
When an input pipe is used, a LESSCLOSE postprocessor can be used, but it is usually not necessary since there is no replacement file to clean up. In this case, the replacement file name passed to the LESSCLOSE postprocessor is "-".
For compatibility with previous versions of less, the input preprocessor or pipe is not used if less is viewing standard input. However, if the first character of LESSOPEN is a dash (-), the input preprocessor is used on standard input as well as other files. In this case, the dash is not considered to be part of the preprocessor command. If standard input is being viewed, the input preprocessor is passed a file name consisting of a single dash. Similarly, if the first two characters of LESSOPEN are vertical bar and dash (|-) or two vertical bars and a dash (||-), the input pipe is used on standard input as well as other files. Again, in this case the dash is not considered to be part of the input pipe command.
National Character Sets
There are three types of characters in the input file:
normal characters can be displayed directly to the screen.
control characters should not be displayed directly, but are expected to be found in ordinary text files (such as backspace and tab).
binary characters should not be displayed directly and are not expected to be found in text files.
A "character set" is simply a description of which characters are to be considered normal, control, and binary. 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 multi-byte characters.
windows Selects a character set appropriate for Microsoft Windows (cp 1252).
In rare cases, it may be desired to tailor less to use a character set other than the ones definable by LESSCHARSET. In this case, the environment variable LESSCHARDEF can be used to define a character set. It should be set to a string where each 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 number 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 binary, 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 interface, less will use setlocale to determine the character set. setlocale is controlled by setting the LANG or LC_CTYPE environment variables.
Finally, if the setlocale interface is also not available, the default character set is utf-8.
Control and binary characters are displayed in standout (reverse video). Each such character is displayed in caret notation if possible (e.g. ^A for control-A). Caret notation is used only if inverting the 0100 bit results in a normal printable character. Otherwise, the character is displayed as a hex number in angle brackets. This format can be changed by setting the LESSBINFMT environment variable. LESSBINFMT may begin with a "*" and one character to select the display attribute: "*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout, and "n" is normal. If LESSBINFMT does not begin with a "", normal attribute is assumed. The remainder of LESSBINFMT is a string which may include one printf-style escape sequence (a % followed by x, X, o, d, etc.). For example, if LESSBINFMT is "*u[%x]", binary characters are displayed in underlined hexadecimal surrounded by brackets. The default if no LESSBINFMT is specified is "*s<%02X>". Warning: the result of expanding the character via LESSBINFMT must be less than 31 characters.
When the character set is utf-8, the LESSUTFBINFMT environment variable acts similarly to LESSBINFMT but it applies to Unicode code points that were successfully decoded but are unsuitable for display (e.g., unassigned code points). Its default value is "<U+%04lX>". Note that LESSUTFBINFMT and LESSBINFMT share their display attribute setting ("*x") so specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so its setting, if any, will have priority. Problematic octets in a UTF-8 file (octets of a truncated sequence, octets of a complete but non-shortest form sequence, 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.
When the character set is utf-8, in rare cases it may be desirable to override the Unicode definition of the type of certain characters. For example, characters in a Private Use Area are normally treated as control characters, but if you are using a custom font with printable characters in that range, it may be desirable to tell less to treat such characters as printable. This can be done by setting the LESSUTFCHARDEF environment variable to a comma- separated list of character type definitions. Each character type definition consists of either one hexadecimal codepoint or a pair of codepoints separated by a dash, followed by a colon and a type character. Each hexadecimal codepoint may optionally be preceded by a "U" or "U+". If a pair of codepoints is given, the type is set for all characters inclusively between the two values. If there are multiple comma-separated codepoint values, they must be in ascending numerical order. The type character may be one of:
p A normal printable character.
w A wide (2-space) printable character.
b A binary (non-printable) character.
c A composing (zero width) character.
For example, setting LESSUTFCHARDEF to
E000-F8FF:p,F0000-FFFFD:p,100000-10FFFD:p
would make all Private Use Area characters be treated as printable.
Prompts
The -P option allows you to tailor the prompt to your preference. The string given to the -P option replaces the specified prompt string. Certain characters in the string are interpreted specially. The prompt mechanism is rather complicated to provide flexibility, but the ordinary user need not understand the details of constructing personalized prompt strings.
A percent sign followed by a single character is expanded according to what the following character is. (References to the input file size below refer to the preprocessed size, if an input preprocessor is being used.)
%bX Replaced by the byte offset into the current input file. The b is followed by a single character (shown as X above) which specifies the line whose byte offset is to be used. If the character is a "t", the byte offset of the top line in the display is used, an "m" means use the middle line, a "b" means use the bottom line, a "B" means use the line just after the bottom line, and a "j" means use the "target" line, as specified by the -j option.
%B Replaced by the size of the current input file.
%c Replaced by the column number of the text appearing in the first column of the screen.
%dX Replaced by the page number of a line in the input file. The line to be used is determined by the X, as with the %b option.
%D Replaced by the number of pages in the input file, or equivalently, the page number of the last line in the input file.
%E Replaced by the name of the editor (from the VISUAL environment variable, or 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.
%o Replaced by the URI of the currently selected OSC 8 hyperlink, or a question mark if no hyperlink is selected. This is used by OSC 8 handlers as explained in the ^O^O command description.
%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 evaluated. If the condition is true, any characters following the question mark and condition character, up to a period, are included in the prompt. If the condition is false, such characters are not included. A colon appearing between the question mark and the period can be used to establish an "ELSE": any characters between the colon and the period are included in the string if and only if the IF condition is false. Condition characters (which follow a question mark) may be:
?a True if any characters have been included in the prompt so far.
?bX True if the byte offset of the specified line is known.
?B True if the size of current input file is known.
?c True if the text is horizontally shifted (%c is not zero).
?dX True if the page number of the specified line is known.
?e True if at end-of-file.
?f True if there is an input filename (that is, if input is not a pipe).
?lX True if the line number of the specified line is known.
?L True if the line number of the last line in the file is known.
?m True if there is more than one input file.
?n True if this is the first prompt in a new input file.
?pX True if the percent into the current input file, based on byte offsets, of the specified line is known.
?PX True if the percent into the current input file, based on line numbers, of the specified line is known.
?s Same as "?B".
?x True if there is a next input file (that is, if the current input file is not the last one).
Any characters other than the special ones (question mark, colon, period, percent, and backslash) become literally part of the prompt. Any of the special characters may be included in the prompt literally by preceding it with a backslash.
Some examples:
?f%f:Standard input.
This prompt prints the filename, if known; otherwise the string "Standard input".
?f%f .?ltLine %lt:?pt%pt%:?btByte %bt:-...
This prompt would print the filename, if known. The filename is followed by the line number, if known, otherwise the percent if known, otherwise the byte offset if known. Otherwise, a dash is printed. Notice how each question mark has a matching period, and how the % after the %pt is included literally by escaping it with a backslash.
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next: %x..%t
This prints the filename if this is the first prompt in a file, followed by the "file N of N" message if there is more than one input file. Then, if we are at end-of-file, the string "(END)" is printed followed by the name of the next file, if there is one. Finally, any trailing spaces are truncated. This is the default prompt. For reference, here are the defaults for the other two prompts (-m and -M respectively). Each is broken into two lines here for readability only.
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next: %x.: ?pB%pB%:byte %bB?s/%s...%t
?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%lb?L/%L. : byte %bB?s/%s. .?e(END) ?x- Next: %x.:?pB%pB%..%t
And here is the default message produced by the = command:
?f%f .?m(%T %i of %m) .?ltlines %lt-%lb?L/%L. . byte %bB?s/%s. ?e(END) :?pB%pB%..%t
The prompt expansion features are also used for another purpose: if an environment variable LESSEDIT is defined, it is used as the command to be executed when the v command is invoked. The LESSEDIT string is expanded in the same way as the prompt strings. The default value for LESSEDIT is:
%E ?lm+%lm. %g
Note that this expands to the editor name, followed by a + and the line number, followed by the shell-escaped file name. If your editor does not accept the "+linenumber" syntax, or has other differences in invocation syntax, the LESSEDIT variable can be changed to modify this default.
Security
When the environment variable LESSSECURE is set to 1, less runs in a "secure" mode. In this mode, these features are disabled:
edit the edit command (v)
examine the examine command (:e)
glob metacharacters such as * in filenames, and filename completion (TAB, ^L)
history history file
lesskey use of lesskey files (-k and --lesskey-src)
lessopen input preprocessor (LESSOPEN environment variable)
logfile log files (s and -o)
osc8 opening OSC 8 links (^O^O)
pipe the pipe command (|)
shell the shell and pshell commands (! and #)
stop stopping less via a SIGSTOP signal
tags use of tags files (-t)
The LESSSECURE_ALLOW environment variable can be set to a comma-separated list of names of features which are selectively enabled when LESSSECURE is set. Each feature name is the first word in each line in the above list. A feature name may be abbreviated as long as the abbreviation is unambiguous. For example, if LESSSECURE=1 and LESSSECURE_ALLOW=hist,edit were set, all of the above features would be disabled except for history files and the edit command.
Less can also be compiled to be permanently in "secure" mode. In that case, the LESSSECURE and LESSSECURE_ALLOW variables are ignored.
Compatibility With More
If the environment variable LESS_IS_MORE is set to 1, or if the program is invoked via a file link named "more", less behaves (mostly) in conformance with the POSIX more(1) command specification. In this mode, less behaves differently in these ways:
The -e option works differently. If the -e option is not set, less behaves as if the -e option were set. If the -e option is set, less behaves as if the -E option were set.
The -m option works differently. If the -m option is not set, the medium prompt is used, and it is prefixed with the string "--More--". If the -m option is set, the short prompt is used.
The -n option acts like the -z option. The normal behavior of the -n option is 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 defined in more than one place, variables defined in a local lesskey file take precedence over variables defined in the system environment, which take precedence over variables defined in the system-wide lesskey file.
COLUMNS Sets the number of columns on the screen. Takes precedence over the number of columns specified by the TERM variable. (But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD, the window system's idea of the screen size takes precedence over the LINES and COLUMNS environment variables.)
EDITOR The name of the editor (used for the v command).
HOME Name of the user's home directory (used to find a lesskey file on Unix and OS/2 systems).
HOMEDRIVE, HOMEPATH Concatenation of the HOMEDRIVE and HOMEPATH environment variables is the name of the user's home directory if the HOME variable is not set (only in the 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 discussion under PROMPTS.
LESSGLOBALTAGS Name of the command used by the -t option to find global tags. Normally should be set to "global" if your system has the global(1) command. If not set, global tags are not used.
LESSHISTFILE Name of the history file used to remember search commands and shell commands between invocations of less. If set to "-" or "/dev/null", a history file is not used. The default depends on the operating system, but is usually:
Linux and Unix "$XDG_STATE_HOME/lesshst" or "$HOME/.local/state/lesshst" or "$XDG_DATA_HOME/lesshst" or "$HOME/.lesshst".
Windows and MS-DOS "$HOME/_lesshst".
OS/2 "$HOME/lesshst.ini" or "$INIT/lesshst.ini".
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 "$LESSKEYIN" exists.)
LESSKEY_CONTENT The value is parsed as if it were the parameter of a --lesskey-content option.
LESSKEYIN_SYSTEM Name of the default system-wide lesskey source file.
LESSKEY_SYSTEM Name of the default system-wide lesskey binary file. (Not used if "$LESSKEYIN_SYSTEM" exists.)
LESSMETACHARS List of characters which are considered "metacharacters" by the shell.
LESSMETAESCAPE Prefix which less will add before each metacharacter in a command sent to the shell. If LESSMETAESCAPE is an empty string, commands containing 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.
LESSSECURE_ALLOW Enables individual features which are normally disabled by LESSSECURE. See discussion under SECURITY.
LESSSEPARATOR String to be appended to a directory name in filename completion.
LESSUTFBINFMT Format for displaying non-printable Unicode code points.
LESSUTFCHARDEF Overrides the type of specified Unicode characters.
LESS_COLUMNS Sets the number of columns on the screen. Unlike COLUMNS, takes precedence over the system's idea of the screen size, so it can be used to make less use less than the full screen width. If set to a negative number, sets the number of columns used to this much less than the actual screen width.
LESS_LINES Sets the number of lines on the screen. Unlike LINES, takes precedence over the system's idea of the screen size, so it can be used to make less use less than the full screen height. If set to a negative number, sets the number of lines used to this much less than the actual screen height. When set, less repaints the entire screen on every movement command, so scrolling may be slower.
LESS_DATA_DELAY Duration (in milliseconds) after starting to read data from the input, after which the "Waiting for data" message will be displayed. The default is 4000 (4 seconds).
LESS_IS_MORE Emulate the more(1) command.
LESS_OSC8_xxx Where "xxx" is a URI scheme such as "http" or "file", sets an OSC 8 handler for opening OSC 8 links containing a URI with that scheme.
LESS_OSC8_ANY Sets an OSC 8 handler for opening OSC 8 links for which there is no specific LESS_OSC8_xxx handler set for the "xxx" scheme.
LESS_TERMCAP_xx Where "xx" is any two characters, overrides the definition of the termcap "xx" capability for the terminal.
LESS_UNSUPPORT A space-separated list of command line options. These options will be ignored (with no error message) if they appear on the command line or in the LESS environment variable. Options listed in LESS_UNSUPPORT can still be changed by the - and -- commands. Each option in LESS_UNSUPPORT is a dash followed by a single character option letter, or two dashes followed by a long option name.
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, Windows, 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).
XDG_CONFIG_HOME Possible location of the lesskey file; see the KEY BINDINGS section.
XDG_DATA_HOME Possible location of the history file; see the description of the LESSHISTFILE environment variable.
XDG_STATE_HOME Possible location of the history file; see the description of the LESSHISTFILE environment variable.
Copyright
Copyright (C) 1984-2024 Mark Nudelman
less is part of the GNU project and is free software. You can redistribute it and/or modify it under the terms of either (1) the GNU General Public License as published by the Free Software Foundation; or (2) the Less License. See the file README in the less distribution for more details regarding redistribution. You should have 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 FITNESS 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 668: 06 Oct 2024 LESS(1)