less

Display input in "pageable" chunks with search and navagation
(a replacment for more)

More powerful then you thought!

less [-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-b space] [-h lines] [-j line] [-k keyfile] [-{oO} logfile]
[-p pattern] [-P prompt] [-t tag] [-T tagsfile] [-x tab,...]
[-y lines] [-[z] lines] [-# shift] [+[+]cmd] [--] [filename]

Commands may be preceded by n.

In the following descriptions:
^X means control-X.
stands for the ESCAPE key; For example -v means the two character sequence , then "v".

f
SPACE
^V
^F
forward a window (see -z ).
If n is more than the screen size, only the final screenful is displayed.
z forward with n is specified, it becomes the new window size.
␛-SPACE forward screen
RETURN
^N
e
^E
j
^J
next line
d
^D
down half screen .
With n scroll down n lines, and n becomes the default for d and u .
F Scroll forward, and continue displaying as lines are added to the file by another process, (similar to tail -f file .)
b
^B
␛-v
back a window
w Like ␛-v, but if n is specified, it becomes the new window size.
y
^Y
^P
k
^K
Scroll back n lines, default 1. The entire N lines are displayed, even if N is more than the screen size. Warning: some systems use ^Y as a special job control character.
u
^U
up half a screen. With n ,n becomes the new default for d and u .
␛-)
RIGHTARROW
right half a screen (see the -# option).
With n, n becomes the default for RIGHTARROW and LEFTARROW .
While the text is scrolled, it acts as though the -S option (chop lines) were in effect.
␛-(
LEFTARROW
Scroll horizontally left n characters, default half the screen width (see the -# option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW commands.
r
^R
^L
Repaint the screen.
R Repaint the screen, discarding any buffered input. Useful if the file is changing while it is being viewed.
g
<
␛-<
Go to line n in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.)
G
>
␛->
Go to line n in the file, default the end of the file. (Warning: this may be slow if N is large,
if N is not specified and standard input, rather than a file, is being read.)
p
%
Go to a position n percent into the file. N should be between 0 and 100, and may contain a decimal point.
P Go to the line containing byte offset n in the file.
{ If a left curly bracket appears in the top line displayed on the screen, the { command will go to the matching right curly bracket. The matching right curly bracket is positioned on the bottom line of the screen. If there is more than one left curly bracket on the top line, a number n may be used to specify the N-th bracket on the line.
} If a right curly bracket appears in the bottom line displayed on the screen, the } command will go to the matching left curly bracket. The matching left curly bracket is positioned on the top line of the screen. If there is more than one right curly bracket on the top line, a number n may be used to specify the N-th bracket on the line.
( Like {, but applies to parentheses rather than curly brackets.
) Like }, but applies to parentheses rather than curly brackets.
[ Like {, but applies to square brackets rather than curly brackets.
] Like }, but applies to square brackets rather than curly brackets.
␛-^Fxy acts like {, but uses the two characters as open and close brackets, respectively. For example, "␛ ^F < > could be used to go forward to the > which matches the < in the top displayed line.
␛-^B xylike }, but uses the two characters as open and close brackets, respectively. For example, ␛ ^B < > could be used to go backward to the < which matches the > in the bottom displayed line.
mp marks the current position with that letter.
'p
apostrphe
^X^Xp
returns to the position which was previously marked .
Followed by another apostrphe, returns to the position at which the last "large" movement command was executed.
Followed by a ^ jumps to the beginning ; $ end of the file .
Marks are preserved when a new file is examined, so the ' command can be used to switch between input files.
/pattern Search forward in the file for the N-th line containing the pattern. n defaults to 1. The pattern is a regular expression, as recognized by the regular expression library supplied by your system. The search starts at the second line displayed (but see the -a and -j options, which change this). Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern:
^N
!
Search for lines which do NOT match the pattern.
^E
*
Search multiple files. That is, if the search reaches the END of the current file without finding a match, the search continues in the next file in the command line list.
^F
@
Begin the search at the first line of the FIRST file in the command line list, regardless of what is currently displayed on the screen
the settings of the -a
-j options.
^K Highlight any text which matches the pattern on the current screen, but don't move to the first match (KEEP current position).
^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison.
?pattern Search backward in the file for the N-th line containing the pattern. The search starts at the line immediately before the top line displayed.
Certain characters are special as in the / command:
^N
! Search for lines which do NOT match the pattern.
^E
* Search multiple files. That is, if the search reaches the beginning of the current file without finding a match, the search continues in the previous file in the command line list.
^F
@    the search at the last line of the last file in the command line list, regardless of what is currently displayed on the screen
the settings of the -a
-j options.
^K As in forward searches.
^R As in forward searches.
␛-/pattern Same as /*.
␛-?pattern Same as ?*
n Repeat 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
^K.
N Repeat previous search, but in the reverse direction.
␛-n Repeat previous search, but crossing file boundaries. The effect is as if the previous search were modified by *.
␛-N Repeat previous search, but in the reverse direction and crossing file boundaries.
␛-u Undo search highlighting. Turn off highlighting of strings matching the current search pattern. If highlighting is already off because of a previous ␛-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.)
: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
more spaces, the entire filename should be enclosed in double quotes (also see the -" option).
^X^V
E
Same as :e. Warning: some systems use ^V as a special literalization character. On such systems, you may not be able to use ^V.
:n Examine the next file (from the list of files given in the command line). If a number n is specified, the N-th next file is examined.
:p Examine the previous file in the command line list. If a number n is specified, the N-th previous file is examined.
:x Examine the first file in the command line list. If a number n is specified, the N-th file in the list is examined.
:d Remove the current file from the list of files.
t Go to the next tag, if there were more than one matches for the current tag. See the -t option for more details about tags.
T Go to the previous tag, if there were more than one matches for the current tag.
=
^G
:f
Display filename, line number and byte offset of the last line displayed, the length of the file, the number of lines in the file and the percent of the file above the last displayed line.
For example: less.1.html lines 1-35/1060 byte 1587/65878 2% (press RETURN)
-C 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
-h),
a string value (such as -P
-t), a new value may be entered after the option letter. If no new value is entered, a message describing the current setting is printed and nothing is changed.
-- Like the - command, but takes a long option name (see OPTIONS below) rather than a single option letter. You must press RETURN after typing the option name. A ^P 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
string-valued options.
--! Like the -! command, but takes a long option name rather than a single option letter.
_ (Underscore.) Followed by one of the command line option letters, this will print a message describing the current setting of that option. The setting of the option is not changed.
__ (Double underscore.) Like the _ (underscore) command, but takes a long option name rather than a single option letter. You must press RETURN after typing the option name.
+cmd Causes the specified cmd to be executed each time a new file is examined. For example, +G causes less to initially display each file starting at the end rather than the beginning.
V Prints the version number of less being run.
q
Q
:q
:Q
ZZ
Exits less.
The following commands may 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,
EDITOR if VISUAL is not defined,
defaults to "vi" if neither VISUAL nor EDITOR is defined. See also the discussion of LESSEDIT under the section on PROMPTS below.
! shell-command Invokes a shell to run the shell-command given. A percent sign (%) in the command is replaced by the name of the current file. A pound sign (#) is replaced by the name of the previously examined file. "!!" repeats the last shell command. "!" with no shell command simply invokes a shell. On Unix systems, the shell is taken from the environment variable SHELL,
defaults to "sh". On MS-DOS and OS/2 systems, the shell is the normal command processor.
| µ shell-command µ represents any mark letter.
Pipes a section of the input to shell command, from the first line on the current screen and the position marked by the letter.
µ may be ^ or $ to indicate beginning or end of input.
If µ is . or the current screen is piped.
s filename Save the input to a file, only if the input is a pipe, not an ordinary file.

OPTIONS

Change the way less operates.
Most may be changed while running, using -.

Most may be given as a dash followed by a single letter, or
two dashes followed by a long option name. which may be abbreviated as long as it is unambiguous. For example, --quit-at-eof may be abbreviated --quit. Long option names in uppercase, such as --QUIT-AT-EOF, are distinct from --quit-at-eof. need only have their first letter capitalized; For example: --Quit-at-eof

Options are also taken from $LESS .

 LESS="-options"; export LESS
On MS-windows, omit quotes, replace embedded percent signs by double percent signs.

$LESS is parsed before the command line, which will override the environment variable.
An option in $LESS , can be reset to its default value by beginning the command line option with -+

Options like -P -D take a string which must be terminaled with $
For example, to set two -D options on MS-DOS, use a dollar sign to terminate the string, like this:

LESS="-Dn9.1$-Ds4.1"

-F
--quit-if-one-screen
exit if the entire file can be displayed on the first screen.
-g
--hilite-search
Highlight only the string which was found by the last search command.
-G
--HILITE-SEARCH
Suppresses highlighting of strings found by search
-i
--ignore-case
Causes searches to ignore case. If uppercase letters are in the search pattern that search does not ignore case.
-I
--IGNORE-CASE
even if the pattern contains uppercase letters.
-xn[ ,…
--tabs=n[,…
Sets tabs . With one, tabs are set at multiples of n. The default is 8.
With multiple values separated by commas are specified, tabs are set at those positions, and then continue with the same spacing as the last two. For example, -x9,17 will set tabs at positions 9, 17, 25, 33, etc.
-a
--search-skip-screen
Searches start after the last line on the screen, ignoring lines on the screen.
By default, searches start at the second line (or after the last found line; see the -j option).
-c
--clear-screen
-C
--CLEAR-SCREEN
Causes full screen repaints are done from the top line down. By default, full screen repaints are done by scrolling from the bottom of the screen.
-d
--dumb
suppresses the error if the terminal is dumb; i.e., lacks some capability, such as the ability to clear the screen
scroll backward.
-Dxcolor
--color=xcolor
[MS-DOS only] Sets the color of the text displayed. x is a single character which selects the type of text whose color is being set: n=normal, s=standout, d=bold, u=underlined, k=blink. color is a pair of numbers separated by a period. The first number selects the foreground color and the second selects the background color of the text. A single number n is the same as N.0.
-f
--force
Forces non-regular files to be opened. (a directory or a device special file.)
Suppresses the warning when a non text file is opened.
-jn
--jump-target=n
Line on the screen where the "target" line ( the line specified by any command to search for a pattern, jump to a line number, jump to a file percentage jump to a tag) is to be positioned.
A number, the top line is 1, the next is 2, ….
A negative number relative to the bottom< of the screen: -1, the second to the bottom is -2, ….
A decimal fraction of the height of the screen for example .5 is in the middle of the screen, .3 is three tenths down from the first line, …. the line number is recalculated whenever the terminal window is resized.

If any form of -j is used, forward searches begin at the line immediately after the target line, and backward searches begin at the target line. For example, -j4 the target line is the fourth line on the screen, so forward searches begin at the fifth line on the screen.

-J
--status-column
Displays a status column at the left edge of the screen, which shows the lines that matched the current search.
The status column is also used if -w or -W is in effect.
-kfilename
--lesskey-file=filename
open and interpret the file as a lesskey file. Multiple -k options may be specified. If the $LESSKEY $LESSKEY_SYSTEM> is set,
if a lesskey file is found in a standard place (see KEY BINDINGS), it is also used as a lesskey file.
-K
--quit-on-intr
Causes less to exit immediately when an interrupt character (usually ^C) is typed. Normally, an interrupt character causes less to stop whatever it is doing and return to its command prompt. Note that use of this option makes it impossible to return to the command prompt from the "F" command.
-L
--no-lessopen
Ignore the LESSOPEN environment variable (see the INPUT PREPROCESSOR section below). This option can be set from within less, but it will apply only to files opened subsequently, not to the file which is currently open.
-m
--long-prompt
Causes less to prompt verbosely (like more), with the percent into the file. By default, less prompts with a colon.
-M
--LONG-PROMPT
prompt even more verbosely
-n
--line-numbers
>isplay byte position in the file. The default (show line numbers) line number are displayed in the verbose prompt as n-m/total p%. Also in the = command. The v command will pass the current line number to the editor (see also the discussion of LESSEDIT in PROMPTS
-N
--LINE-NUMBERS
displaye line numbers
-ofilename
--log-file=filename
When the input file is a pipe, copy input to the file as it is being viewed.
Confirm before overwriting file
-Ofilename
--LOG-FILE=filename
Like -o overwrites an existing file

Without a log file -o and -O can be used from within less to specify a log file. Without a file name, they report the name of the log file.
The s is equivalent to -o from within less.

-ppattern
--pattern=pattern
Equivalent to specifying +/pattern; that is, start at the first occurrence of pattern
-Pprompt
--prompt=prompt
Normally the last option in $LESS
: -Ps followed by a string changes the default (short) prompt to that string.
-Pm medium (-m) prompt. -PM changes the long (-M) prompt. -Ph prompt for the help screen.
-P= message printed by the = command.
-Pw message printed while waiting for data (in the F command).
All prompt strings consist of a sequence of letters and special escape sequences. See the section on PROMPTS for more details.
-q
--quiet
--silent
Causes moderately "quiet" operation: "visual bell" is used if an attempt is made to scroll past the end of the file before the beginning of the file. . The bell will be rung on certain other errors, such as typing an invalid character. The default is to ring the terminal bell in all such cases.
-Q
--QUIET
--SILENT
bell is never rung.
-r
--raw-control-chars
Causes "raw" control characters to be displayed. The default is to display control characters using the caret notation; for example, a control-A (octal 001) is displayed as "^A". Warning: when the -r option is used, less cannot keep track of the actual appearance of the screen (since this depends on how the screen responds to each type of control character). Thus, various display problems may result, such as long lines being split in the wrong place.
-R
--RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences are output in "raw" form. Unlike -r, the screen appearance is maintained correctly in most cases. ANSI "color" escape sequences are sequences of the form:
                   ␛ [ ... m
where the "..." is zero
more color specification characters For the purpose of keeping track of screen appearance, ANSI color escape sequences are assumed to not move the cursor. You can make less think that characters other than "m" can end ANSI color escape sequences by setting the environment variable LESSANSIENDCHARS to the list of characters which can end a color escape sequence. And you can make less think that characters other than the standard ones may appear between the ␛ and the m by setting the environment variable LESSAN SIMIDCHARS to the list of characters which can appear.
-s
--squeeze-blank-lines
Causes consecutive blank lines to be squeezed into a single blank line. This is useful when viewing nroff output.
-S
--chop-long-lines
Causes lines longer than the screen width to be chopped rather than folded. That is, the portion of a long line that does not fit in the screen width is not shown. The default is to fold long lines; that is, display the remainder on the next line.
-ttag
--tag=tag
The -t option, followed immediately by a TAG, will edit the file containing that tag. For this to work, tag information must be available; for example, there may be a file in the current directory called "tags", which was previously built by ctags (1)
an equivalent command. If the environment variable LESSGLOBALTAGS is set, it is taken to be the name of a command compatible with global (1), and that command is executed to find the tag. (See http://www.gnu.org/software/global/global.html). The -t option may also be specified from within less (using the - command) as a way of examining a new file. The command ":t" is equivalent to specifying -t from within less.
-Ttagsfile
--tag-file=tagsfile
Specifies a tags file to be used instead of "tags".
-u
--underline-special
Causes backspaces and carriage returns to be treated as printable characters; that is, they are sent to the terminal when they appear in the input.
-U
--UNDERLINE-SPECIAL
Causes backspaces, tabs and carriage returns to be treated as control characters; that is, they are handled as specified by the -r option. By default, if neither -u nor -U is given, backspaces which appear adjacent to an underscore character are treated specially: the underlined text is displayed using the terminal's hardware underlining capability. Also, backspaces which appear between two identical characters are treated specially: the overstruck text is printed using the terminal's hardware boldface capability. Other backspaces are deleted, along with the preceding character. Carriage returns immediately followed by a newline are deleted. other carriage returns are handled as specified by the -r option. Text which is overstruck
underlined can be searched for if neither -u nor -U is in effect.
-w
--hilite-unread
Temporarily highlights the first "new" line after a forward movement of a full page. The first "new" line is the line immediately following the line previously at the bottom of the screen. Also highlights the target line after a g
p command. The highlight is removed at the next command which causes movement. The entire line is highlighted, unless the -J option is in effect, in which case only the status column is highlighted.
-W
--HILITE-UNREAD
Like -w, but temporarily highlights the first new line after any forward movement command larger than one line.
-X
--no-init
Disables sending the termcap initialization and deinitialization strings to the terminal. This is sometimes desirable if the deinitialization string does something unnecessary, like clearing the screen.
-yn
--max-forw-scroll=n
maximum number of lines to scroll forward if needed the screen is repainted instead.
-c -C option may be used to repaint from the top of the screen if desired. By default, any forward movement causes scrolling.
-hn
--max-back-scroll=n
Maximum lines to scroll backward.
\-?
--help
summary of the commands
-V
--version
Displays the version number of less.
-[z]n
--window=n
Sets the default scrolling window size to n lines. The default is a` screenful.
z and w can also be used to change the window size.
The z" may be omitted .
If negative, indicates n lines oless than the current size. For example, if the screen is 24 lines, -z-4 sets the scrolling window to 20 lines. If the screen is resized to 40 lines, the scrolling window automatically changes to 36 lines.
-"c[c]
--quotes=c[c]
Sets filename quoting character for refering to names containing spaces or quotes.
For two characters, sets the open quote to the first character, and the close quote to the second character. Filenames containing a space should be preceded by the open quote character and followed by the close quote character.
-~
--tilde
lines after end of file to be displayed as blank lines.
-#
--shift
the default number of positions to scroll horizontally in the RIGHTARROW and LEFTARROW commands.
If zero, the default number of positions is half of the screen width.
--no-keypad Disables sending the keypad initialization and deinitialization strings
--follow-name if the file is renamed while an F command is executing, less will continue to display the contents of the original file despite its name change.
with --follow-name is specified, during an F command less will periodically attempt to reopen the file by name. If the reopen succeeds and the file is a different file from the original (which means that a new file has been created with the same name as the original (now renamed) file), less will display the contents of the new file.
-- -- ends options, filenames follow. Useful when viewing a file which begins with "-" or "+".
+
  • +G starts at the end of the file .
  • +/xyz start at the first occurrence of "xyz" .
  • +n starts at line n. (see "g" ).
  • ++ the initial command applies to every file being viewed, not just the first one.
The + command may also be used to set (or change) an initial command for every file.
-bn
--buffers=n
Size of buffer for each file, in kilobytes (1024 bytes).
By default 64K (unless the file is a pipe; see -B ).
If n is -1, buffer space is unlimited; that is, the entire file will be read into memory.
-B
--auto-buffers
Disables automatic allocation of buffers for pipes.
Warning: -B can result in erroneous display, since only the most recently viewed part of the piped data is kept in memory; any earlier data is lost.
h
H
Help: display a summary

LINE EDITING

When entering command line at the bottom of the screen (for example, a filename for the :e command,
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 ␛ do not work in some MS-DOS and Windows systems because ␛ is the line erase character.) Any of these special keys may be entered literally by preceding it with the "literal" character, either ^V
^A. A backslash itself may also be entered literally by entering two backslashes. LEFTARROW [ ␛-h ] Move the cursor one space to the left. RIGHTARROW [ ␛-l ] Move the cursor one space to the right. ^LEFTARROW [ ␛-b
␛-LEFTARROW ] (That is, CONTROL and LEFTARROW simultaneously.) Move the cursor one word to the left. ^RIGHTARROW [ ␛-w
␛-RIGHTARROW ] (That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right. HOME [ ␛-0 ] Move the cursor to the beginning of the line. END [ ␛-$ ] Move the cursor to the end of the line. BACKSPACE Delete the character to the left of the cursor,
cancel the command if the command line is empty. DELETE
[ ␛-x ] Delete the character under the cursor. ^BACKSPACE [ ␛-BACKSPACE ] (That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor. ^DELETE [ ␛-X
␛-DELETE ] (That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor. UPARROW [ ␛-k ] Retrieve the previous command line. DOWNARROW [ ␛-j ] Retrieve the next command line. TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match is entered into the command line. Repeated TABs will cycle thru the other matching filenames. If the completed filename is a directory, a "/" is appended to the filename. (On MS-DOS systems, a "\" is appended.) The environment variable LESSSEPARATOR can be used to specify a different character to append to a directory name. BACKTAB [ ␛-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)
␛ (MS-DOS) Delete the entire command line,
cancel the command if the command line is empty. If you have changed your line-kill character in Unix to something other than ^U, that character is used instead of ^U. KEY BINDINGS You may define your own less commands by using the program lesskey (1) to create a lesskey file. This file specifies a set of command keys and an action associated with each key. You may also use lesskey to change the line-editing keys (see LINE EDITING), and to set environment variables. If the environment variable LESSKEY is set, less uses that as the name of the lesskey file. Otherwise, less looks in a standard place for the lesskey file: On Unix systems, less looks for a lesskey file called "$HOME/.less". On MS-DOS and Windows systems, less looks for a lesskey file called "$HOME/_less", and if it is not found there, then looks for a lesskey file called "_less" in any directory specified in the PATH environment variable. On OS/2 systems, less looks for a lesskey file called "$HOME/less.ini", and if it is not found, then looks for a lesskey file called "less.ini" in any directory specified in the INIT environment variable, and if it not found there, then looks for a lesskey file called "less.ini" in any directory specified in the PATH environment variable. See the lesskey manual page for more details. A system-wide lesskey file may also be set up to provide key bindings. If a key is defined in both a local lesskey file and in the system-wide file, key bindings in the local file take precedence over those in the system-wide file. If the environment variable LESSKEY_SYSTEM is set, less uses that as the name of the system-wide lesskey file. Otherwise, less looks in a standard place for the system-wide lesskey file: On Unix systems, the system-wide lesskey file is /usr/local/etc/sysless. (However, if less was built with a different sysconf directory than /usr/local/etc, that directory is where the sysless file is found.) On MS-DOS and Windows systems, the system-wide lesskey file is c:\_sysless. On OS/2 systems, the system-wide lesskey file is c:\sysless.ini. INPUT PREPROCESSOR You may define an "input preprocessor" for less. Before less opens a file, it first gives your input preprocessor a chance to modify the way the contents of the file are displayed. An input preprocessor is simply an executable program (or shell script), which writes the contents of the file to a different file, called the replacement file. The contents of the replacement file are then displayed in place of the contents of the original file. However, it will appear to the user as if the original file is opened; that is, less will display the original filename as the name of the current file. An input preprocessor receives one command line argument, the original filename, as entered by the user. It should create the replacement file, and when finished, print the name of the replacement file to its standard output. If the input preprocessor does not output a replacement filename, less uses the original file, as normal. The input preprocessor is not called when viewing standard input. To set up an input preprocessor, set the LESSOPEN environment variable to a command line which will invoke your input preprocessor. This command line should include one occurrence of the string "%s", which will be replaced by the filename when the input preprocessor command is invoked. When less closes a file opened in such a way, it will call another program, called the input postprocessor, which may perform any desired clean-up action (such as deleting the replacement file created by LESSOPEN). This program receives two command line arguments, the original filename as entered by the user, and the name of the replacement file. To set up an input postprocessor, set the LESSCLOSE environment variable to a command line which will invoke your input post processor. It may include two occurrences of the string "%s"; the first is replaced with the original name of the file and the second with the name of the replacement file, which was output by LESSOPEN. For example, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let less view them directly: lessopen.sh: #! /bin/sh case "$1" in *.Z) uncompress - if [ -s /tmp/less.$$ ]; then echo /tmp/less.$$ else rm -f /tmp/less.$$ fi ;; esac lessclose.sh: #! /bin/sh rm $2 To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on. It is also possible to set up an input preprocessor to pipe the file data directly to less, rather than putting the data into a replacement file. This avoids the need to decompress the entire file before starting to view it. An input preprocessor that works this way is called an input pipe. An input pipe, instead of writing the name of a replacement file on its standard output, writes the entire contents of the replacement file on its standard output. If the input pipe does not write any characters on its standard output, then there is no replacement file and less uses the original file, as normal. To use an input pipe, make the first character in the LESSOPEN environment variable a vertical bar (|) to signify that the input preprocessor is an input pipe. For example, 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 ;; esac To use this script, put it where it can be executed and set LESSOPEN="|lesspipe.sh %s". 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 "-". 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
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 1251). In rare cases, it may be desired to tailor less to use a character set other than the ones definable by LESSCHARSET. In this case, the 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"
"utf8" is found in the LC_ALL, LC_TYPE
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
LC_CTYPE environment variables. Finally, if the setlocale interface is also not available, the default character set is latin1. Control and binary characters are displayed in standout (reverse video). Each such character is displayed in caret notation if possible (e.g. ^A for control-A). Caret notation is used only if inverting the 0100 bit results in a normal printable character. Otherwise, the 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<%X>". The default if no LESSBINFMT is specified is "*s<%02X>". Warning: the result of expanding the character via LESSBINFMT must be less than 31 characters. When the character set is utf-8, the LESSUTFBINFMT environment variable acts similarly to LESSBINFMT but it applies to Unicode code points that were successfully decoded but are unsuitable for display (e.g., unassigned code points). Its default value is "<U+%04lX>". Note that LESSUTFBINFMT and LESSBINFMT share their display attribute setting ("*x") so specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so its setting, if any, will have priority. Problematic octets in a UTF-8 file (octets of a truncated sequence, octets of a complete but non-shortest form sequence, illegal octets, and stray trailing octets) are displayed individually using LESSBINFMT so as to facilitate diagnostic of how the UTF-8 file is ill-formed. PROMPTS The -P option allows you to tailor the prompt to your preference. The string given to the -P option replaces the specified prompt string. Certain characters in the string are interpreted specially. The prompt mechanism is rather complicated to provide flexibility, but the ordinary user need not understand the details of constructing personalized prompt strings. A percent sign followed by a single character is expanded according to what the following character is: %bX Replaced by the byte offset into the current input file. The b is followed by a single character (shown as X above) which specifies the line whose byte offset is to be used. If the character is a "t", the byte offset of the top line in the display is used, an "m" means use the middle line, a "b" means use the bottom line, a "B" means use the line just after the bottom line, and a "j" means use the "target" line, as specified by the -j option. %B Replaced by the size of the current input file. %c Replaced by the column number of the text appearing in the first column of the screen. %dX Replaced by the page number of a line in the input file. The line to be used is determined by the X, as with the %b option. %D Replaced by the number of pages in the input file,
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,
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. %i Replaced by the index of the current file in the list of input files. %lX Replaced by the line number of a line in the input file. The line to be used is determined by the X, as with the %b option. %L Replaced by the line number of the last line in the input file. %m Replaced by the total number of input files. %pX Replaced by the percent into the current input file, based on byte offsets. The line used is determined by the X as with the %b option. %PX Replaced by the percent into the current input file, based on line numbers. The line used is determined by the X as with the %b option. %s Same as %B. %t Causes any trailing spaces to be removed. Usually used at the end of the string, but may appear anywhere. %x Replaced by the name of the next input file in the list. If any item is unknown (for example, the file size if input is a pipe), a question mark is printed instead. The format of the prompt string can be changed depending on certain conditions. A question mark followed by a single character acts like an "IF": depending on the following character, a condition is evaluated. If the condition is true, any characters following the question mark and condition character, up to a period, are included in the prompt. If the condition is false, such characters are not included. A colon appearing between the question mark and the period can be used to establish an "ELSE": any characters between the colon and the period are included in the string if and only if the IF condition is false. Condition characters (which follow a question mark) may be: ?a True if any characters have been included in the prompt so far. ?bX True if the byte offset of the specified line is known. ?B True if the size of current input file is known. ?c True if the text is horizontally shifted (%c is not zero). ?dX True if the page number of the specified line is known. ?e True if at end-of-file. ?f True if there is an input filename (that is, if input is not a pipe). ?lX True if the line number of the specified line is known. ?L True if the line number of the last line in the file is known. ?m True if there is more than one input file. ?n True if this is the first prompt in a new input file. ?pX True if the percent into the current input file, based on byte offsets, of the specified line is known. ?PX True if the percent into the current input file, based on line numbers, of the specified line is known. ?s Same as "?B". ?x True if there is a next input file (that is, if the current input file is not the last one). Any characters other than the special ones (question mark, colon, period, percent, and backslash) become literally part of the prompt. Any of the special characters may be included in the prompt literally by preceding it with a backslash. Some examples: ?f%f:Standard input. This prompt prints the filename, if known; otherwise the string "Standard input". ?f%f .?ltLine %lt:?pt%pt\%:?btByte %bt:-... This prompt would print the filename, if known. The filename is followed by the line number, if known, otherwise the percent if known, otherwise the byte offset if known. Otherwise, a dash is printed. Notice how each question mark has a matching period, and how the % after the %pt is included literally by escaping it with a backslash. ?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x..%t This prints the filename if this is the first prompt in a file, followed by the "file n of N" message if there is more than one input file. Then, if we are at end-of-file, the string "(END)" is printed followed by the name of the next file, if there is one. Finally, any trailing spaces are truncated. This is the default prompt. For reference, here are the defaults for the other two prompts (-m and -M respectively). Each is broken into two lines here for readability only. ?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x.: ?pB%pB\%:byte %bB?s/%s...%t ?f%f .?n?m(file %i of %m) ..?ltlines %lt-%lb?L/%L. : byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t And here is the default message produced by the = command: ?f%f .?m(file %i of %m) .?ltlines %lt-%lb?L/%L. . byte %bB?s/%s. ?e(END) :?pB%pB\%..%t The prompt expansion features are also used for another purpose: if an environment variable LESSEDIT is defined, it is used as the command to be executed when the v command is invoked. The LESSEDIT string is expanded in the same way as the prompt strings. The default value for LESSEDIT is: %E ?lm+%lm. %f Note that this expands to the editor name, followed by a + and the line number, followed by the file name. If your editor does not accept the "+linenumber" syntax,
has other differences in invocation syntax, the LESSEDIT variable can be changed to modify this default. SECURITY When the environment variable LESSSECURE is set to 1, less runs in a "secure" mode. This means these features are disabled: ! the shell command | the pipe command :e the examine command. v the editing command s -o log files -k use of lesskey files -t use of tags files metacharacters in filenames, such as * filename completion (TAB, ^L) Less can also be compiled to be permanently in "secure" mode.

Compatibility with more

Allows backward as well as forward movement.
Uses termcap (terminfo), so it can run on a variety of terminals. Limited support for hardcopy terminals, lines which should be printed at the top of the screen are prefixed with a caret.

If $LESS_IS_MORE is set to 1, or` if invoked via a link named "more", less behaves (mostly) in conformance with the POSIX "more" -e If not set, if the -E option were set.
If set, as if the -e and -F options were set.

-m not set, the medium prompt is used, and it is prefixed with the string "--More--".
If set, the short prompt is used.

-n acts like -z .

The parameter to -p is taken to be a less command rather than a search pattern.

$LESS is ignored, $MORE is used

ENVIRONMENT VARIABLES Environment variables may also be specified in lesskey which takes precedence. which take precedence over variables defined in the system-wide lesskey $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
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 ␛ 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. $LESSHISTFILE Name of the history file used to remember search commands and shell commands between invocations of less. If set to "-"
"/dev/null", a history file is not used. The default is "$HOME/.lesshst" on Unix systems, "$HOME/_lesshst" on DOS and Windows systems,
"$HOME/lesshst.ini"
"$INIT/lesshst.ini" on OS/2 systems. $LESSHISTSIZE The maximum number of commands to save in the history file. The default is 100. $LESSKEY Name of the default lesskey(1) file. $LESSKEY_SYSTEM Name of the default system-wide lesskey(1) file. $LESSMETACHARS List of characters which are considered "metacharacters" by the shell. $LESSMETAESCAPE Prefix which less will add before each metacharacter in a command sent to the shell. If LESSMETA␛APE is an empty string, commands containing metacharacters will not be passed to the shell. $LESSOPEN Command line to invoke the (optional) input-preprocessor. $LESSSECURE Runs less in "secure" mode. See discussion under SECURITY. $LESSSEPARATOR String to be appended to a directory name in filename completion. $LESSUTFBINFMT Format for displaying non-printable Unicode code points. $LESS_IS_MORE Emulate the more (1) command. $LINES Sets the number of lines on the screen. Takes precedence over the number of lines specified by the TERM variable. (But if you have a windowing system which supports TIOCGWINSZ
WIOCGETD, the window system's idea of the screen size takes precedence over the LINES and COLUMNS environment variables.) $PATH User's search path (used to find a lesskey file on MS-DOS and OS/2 systems). $SHELL The shell used to execute the ! command, as well as to expand filenames. $TERM The type of terminal on which less is being run. $VISUAL The name of the editor (used for the v command).

SEE

lesskey

help from less

COPYRIGHT Copyright (C) 1984-2007 Mark Nudelman AUTHOR Mark Nudelman Version 418: 02 Jan 2008