LESS(1) General Commands Manual
LESS(1)
1mNAME0m
less - opposite of more
1mSYNOPSIS0m
1mless -?0m
1mless --help0m
1mless -V0m
1mless --version0m
1mless [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]0m
1m[-b 4m22mspace24m1m] [-h 4m22mlines24m1m] [-j
4m22mline24m1m] [-k 4m22mkeyfile24m1m]0m
1m[-{oO} 4m22mlogfile24m1m] [-p 4m22mpattern24m1m] [-P
4m22mprompt24m1m] [-t 4m22mtag24m1m]0m
1m[-T 4m22mtagsfile24m1m] [-x 4m22mtab24m1m,...] [-y
4m22mlines24m1m] [-[z] 4m22mlines24m1m]0m
1m[-# 4m22mshift24m1m] [+[+]4m22mcmd24m1m] [--]
[4m22mfilename24m1m]...0m
(See the OPTIONS section for alternate option syntax with long
option
names.)
1mDESCRIPTION0m
4mLess24m is a program similar to 4mmore24m(1), but which allows
backward move-
ment in the file as well as forward movement. Also, 4mless24m
does not have
to read the entire input file before starting, so with large
input
files it starts up faster than text editors like 4mvi24m(1).
4mLess24m 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 4mmore24m and 4mvi24m. Commands may
be preceded by a
decimal number, called N in the descriptions below. The number is
used
by some commands, as indicated.
1mCOMMANDS0m
In the following descriptions, ^X means control-X. ESC stands for
the
ESCAPE key; for example ESC-v means the two character sequence
"ES-
CAPE", then "v".
h or H Help: display a summary of these commands. If you forget
all
the other commands, remember this one.
SPACE or ^V or f or ^F
Scroll forward N lines, default one window (see option -z
be-
low). If N is more than the screen size, only the final
screen-
ful is displayed. Warning: some systems use ^V as a
special
literalization character.
z Like SPACE, but if N is specified, it becomes the new
window
size.
ESC-SPACE
Like SPACE, but scrolls a full screenful, even if it
reaches
end-of-file in the process.
ENTER or RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines are
dis-
played, even if N is more than the screen size.
d or ^D
Scroll forward N lines, default one half of the screen size.
If
N is specified, it becomes the new default for subsequent d
and
u commands.
b or ^B or ESC-v
Scroll backward N lines, default one window (see option -z
be-
low). If N is more than the screen size, only the final
screen-
ful is displayed.
w Like ESC-v, but if N is specified, it becomes the new
window
size.
y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1. The entire N lines are
dis-
played, even if N is more than the screen size. Warning:
some
systems use ^Y as a special job control character.
u or ^U
Scroll backward N lines, default one half of the screen
size.
If N is specified, it becomes the new default for subsequent
d
and u commands.
J Like j, but continues to scroll beyond the end of the file.
K or Y Like k, but continues to scroll beyond the beginning of
the
file.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default half the
screen
width (see the -# option). If a number N is specified, it
be-
comes the default for future RIGHTARROW and LEFTARROW
commands.
While the text is scrolled, it acts as though the -S
option
(chop lines) were in effect.
ESC-( or LEFTARROW
Scroll horizontally left N characters, default half the
screen
width (see the -# option). If a number N is specified, it
be-
comes the default for future RIGHTARROW and LEFTARROW
commands.
ESC-} or ^RIGHTARROW
Scroll horizontally right to show the end of the longest
dis-
played line.
ESC-{ or ^LEFTARROW
Scroll horizontally left back to the first column.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input. Useful
if
the file is changing while it is being viewed.
F Scroll forward, and keep trying to read when the end of file
is
reached. Normally this command would be used when already
at
the end of the file. It is a way to monitor the tail of a
file
which is growing while it is being viewed. (The behavior
is
similar to the "tail -f" command.)
ESC-F Like F, but as soon as a line is found which matches the
last
search pattern, the terminal bell is rung and forward
scrolling
stops.
g or < or ESC-<
Go to line N in the file, default 1 (beginning of file).
(Warn-
ing: this may be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the file.
(Warn-
ing: this may be slow if N is large, or if N is not
specified
and standard input, rather than a file, is being read.)
ESC-G Same as G, except if no number N is specified and the input
is
standard input, goes to the last line which is
currently
buffered.
p or % Go to a position N percent into the file. N should be
between 0
and 100, and may contain a decimal point.
P Go to the line containing byte offset N in the file.
{ If a left curly bracket appears in the top line displayed on
the
screen, the { command will go to the matching right
curly
bracket. The matching right curly bracket is positioned on
the
bottom line of the screen. If there is more than one left
curly
bracket on the top line, a number N may be used to specify
the
N-th bracket on the line.
} If a right curly bracket appears in the bottom line displayed
on
the screen, the } command will go to the matching left
curly
bracket. The matching left curly bracket is positioned on
the
top line of the screen. If there is more than one right
curly
bracket on the top line, a number N may be used to specify
the
N-th bracket on the line.
( Like {, but applies to parentheses rather than curly
brackets.
) Like }, but applies to parentheses rather than curly
brackets.
[ Like {, but applies to square brackets rather than curly
brack-
ets.
] Like }, but applies to square brackets rather than curly
brack-
ets.
ESC-^F Followed by two characters, acts like {, but uses the two
char-
acters as open and close brackets, respectively. For
example,
"ESC ^F < >" could be used to go forward to the > which
matches
the < in the top displayed line.
ESC-^B Followed by two characters, acts like }, but uses the two
char-
acters as open and close brackets, respectively. For
example,
"ESC ^B < >" could be used to go backward to the < which
matches
the > in the bottom displayed line.
m Followed by any lowercase or uppercase letter, marks the
first
displayed line with that letter. If the status column is
en-
abled via the -J option, the status column shows the
marked
line.
M Acts like m, except the last displayed line is marked
rather
than the first displayed line.
' (Single quote.) Followed by any lowercase or uppercase
letter,
returns to the position which was previously marked with
that
letter. Followed by another single quote, returns to the
posi-
tion at which the last "large" movement command was
executed.
Followed by a ^ or $, jumps to the beginning or end of the
file
respectively. Marks are preserved when a new file is
examined,
so the ' command can be used to switch between input files.
^X^X Same as single quote.
ESC-m Followed by any lowercase or uppercase letter, clears the
mark
identified by that letter.
/pattern
Search forward in the file for the N-th line containing the
pat-
tern. N defaults to 1. The pattern is a regular expression,
as
recognized by the regular expression library supplied by
your
system. The search starts at the first line displayed (but
see
the -a and -j options, which change this).
Certain characters are special if entered at the beginning
of
the pattern; they modify the type of search rather than
become
part of the pattern:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search
reaches
the END of the current file without finding a match,
the
search continues in the next file in the command
line
list.
^F or @
Begin the search at the first line of the FIRST file
in
the command line list, regardless of what is
currently
displayed on the screen or the settings of the -a or
-j
options.
^K Highlight any text which matches the pattern on the
cur-
rent screen, but don't move to the first match (KEEP
cur-
rent position).
^R Don't interpret regular expression metacharacters;
that
is, do a simple textual comparison.
?pattern
Search backward in the file for the N-th line containing
the
pattern. The search starts at the last line displayed (but
see
the -a and -j options, which change this).
Certain characters are special as in the / command:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search
reaches
the beginning of the current file without
finding a
match, the search continues in the previous file in
the
command line list.
^F or @
Begin the search at the last line of the last file in
the
command line list, regardless of what is currently
dis-
played on the screen or the settings of the -a or -j
op-
tions.
^K As in forward searches.
^R As in forward searches.
ESC-/pattern
Same as "/*".
ESC-?pattern
Same as "?*".
n Repeat previous search, for N-th line containing the last
pat-
tern. If the previous search was modified by ^N, the search
is
made for the N-th line NOT containing the pattern. If the
pre-
vious search was modified by ^E, the search continues in
the
next (or previous) file if not satisfied in the current
file.
If the previous search was modified by ^R, the search is
done
without using regular expressions. There is no effect if
the
previous search was modified by ^F or ^K.
N Repeat previous search, but in the reverse direction.
ESC-n Repeat previous search, but crossing file boundaries. The
ef-
fect is as if the previous search were modified by *.
ESC-N Repeat previous search, but in the reverse direction and
cross-
ing file boundaries.
ESC-u Undo search highlighting. Turn off highlighting of
strings
matching the current search pattern. If highlighting is
already
off because of a previous ESC-u command, turn highlighting
back
on. Any search command will also turn highlighting back
on.
(Highlighting can also be disabled by toggling the -G option;
in
that case search commands do not turn highlighting back on.)
&pattern
Display only lines which match the pattern; lines which do
not
match the pattern are not displayed. If pattern is empty
(if
you type & immediately followed by ENTER), any filtering
is
turned off, and all lines are displayed. While filtering is
in
effect, an ampersand is displayed at the beginning of
the
prompt, as a reminder that some lines in the file may be
hidden.
Certain characters are special as in the / command:
^N or !
Display only lines which do NOT match the pattern.
^R Don't interpret regular expression metacharacters;
that
is, do a simple textual comparison.
:e [filename]
Examine a new file. If the filename is missing, the
"current"
file (see the :n and :p commands below) from the list of
files
in the command line is re-examined. A percent sign (%) in
the
filename is replaced by the name of the current file. A
pound
sign (#) is replaced by the name of the previously
examined
file. However, two consecutive percent signs are simply
re-
placed with a single percent sign. This allows you to enter
a
filename that contains a percent sign in the name.
Similarly,
two consecutive pound signs are replaced with a single
pound
sign. The filename is inserted into the command line list
of
files so that it can be seen by subsequent :n and :p
commands.
If the filename consists of several files, they are all
inserted
into the list of files and the first one is examined. If
the
filename contains one or more spaces, the entire filename
should
be enclosed in double quotes (also see the -" option).
^X^V or E
Same as :e. Warning: some systems use ^V as a special
literal-
ization character. On such systems, you may not be able to
use
^V.
:n Examine the next file (from the list of files given in the
com-
mand line). If a number N is specified, the N-th next file
is
examined.
:p Examine the previous file in the command line list. If a
number
N is specified, the N-th previous file is examined.
:x Examine the first file in the command line list. If a
number N
is specified, the N-th file in the list is examined.
:d Remove the current file from the list of files.
t Go to the next tag, if there were more than one matches for
the
current tag. See the -t option for more details about tags.
T Go to the previous tag, if there were more than one matches
for
the current tag.
= or ^G or :f
Prints some information about the file being viewed,
including
its name and the line number and byte offset of the bottom
line
being displayed. If possible, it also prints the length of
the
file, the number of lines in the file and the percent of
the
file above the last displayed line.
- Followed by one of the command line option letters (see
OPTIONS
below), this will change the setting of that option and
print a
message describing the new setting. If a ^P (CONTROL-P) is
en-
tered immediately after the dash, the setting of the option
is
changed but no message is printed. If the option letter has
a
numeric value (such as -b or -h), or a string value (such as
-P
or -t), a new value may be entered after the option letter.
If
no new value is entered, a message describing the current
set-
ting is printed and nothing is changed.
-- Like the - command, but takes a long option name (see
OPTIONS
below) rather than a single option letter. You must press
ENTER
or RETURN after typing the option name. A ^P immediately
after
the second dash suppresses printing of a message describing
the
new setting, as in the - command.
-+ Followed by one of the command line option letters this will
re-
set the option to its default setting and print a message
de-
scribing the new setting. (The "-+4mX24m" command does
the same
thing as "-+4mX24m" on the command line.) This does
not work for
string-valued options.
--+ Like the -+ command, but takes a long option name rather than
a
single option letter.
-! Followed by one of the command line option letters, this
will
reset the option to the "opposite" of its default setting
and
print a message describing the new setting. This does not
work
for numeric or string-valued options.
--! Like the -! command, but takes a long option name rather than
a
single option letter.
_ (Underscore.) Followed by one of the command line option
let-
ters, this will print a message describing the current
setting
of that option. The setting of the option is not changed.
__ (Double underscore.) Like the _ (underscore) command, but
takes
a long option name rather than a single option letter. You
must
press ENTER or RETURN after typing the option name.
+cmd Causes the specified cmd to be executed each time a new file
is
examined. For example, +G causes 4mless24m to initially
display each
file starting at the end rather than the beginning.
V Prints the version number of 4mless24m being run.
q or Q or :q or :Q or ZZ
Exits 4mless24m.
The following four commands may or may not be valid, depending on
your
particular installation.
v Invokes an editor to edit the current file being viewed.
The
editor is taken from the environment variable VISUAL if
defined,
or EDITOR if VISUAL is not defined, or defaults to "vi" if
nei-
ther VISUAL nor EDITOR is defined. See also the discussion
of
LESSEDIT under the section on PROMPTS below.
! shell-command
Invokes a shell to run the shell-command given. A percent
sign
(%) in the command is replaced by the name of the current
file.
A pound sign (#) is replaced by the name of the previously
exam-
ined file. "!!" repeats the last shell command. "!" with
no
shell command simply invokes a shell. On Unix systems,
the
shell is taken from the environment variable SHELL, or
defaults
to "sh". On MS-DOS and OS/2 systems, the shell is the
normal
command processor.
| <m> shell-command
<m> represents any mark letter. Pipes a section of the
input
file to the given shell command. The section of the file to
be
piped is between the position marked by the letter and the
cur-
rent screen. The entire current screen is included,
regardless
of whether the marked position is before or after the
current
screen. <m> may also be ^ or $ to indicate beginning or end
of
file respectively. If <m> is . or newline, the current
screen
is piped.
s filename
Save the input to a file. This only works if the input is
a
pipe, not an ordinary file.
1mOPTIONS0m
Command line options are described below. Most options may be
changed
while 4mless24m is running, via the "-" command.
Most options may be given in one of two forms: either a dash
followed
by a single letter, or two dashes followed by a long option name.
A
long option name may be abbreviated as long as the abbreviation is
un-
ambiguous. For example, --quit-at-eof may be abbreviated --quit,
but
not --qui, since both --quit-at-eof and --quiet begin with --qui.
Some
long option names are in uppercase, such as --QUIT-AT-EOF, as
distinct
from --quit-at-eof. Such option names need only have their first
let-
ter capitalized; the remainder of the name may be in either case.
For
example, --Quit-at-eof is equivalent to --QUIT-AT-EOF.
Options are also taken from the environment variable "LESS". For
exam-
ple, to avoid typing "less -options ..." each time 4mless24m is
invoked, you
might tell 4mcsh24m:
setenv LESS "-options"
or if you use 4msh24m:
LESS="-options"; export LESS
On MS-DOS, you don't need the quotes, but you should replace any
per-
cent signs in the options string by double percent signs.
The environment variable is parsed before the command line, so
command
line options override the LESS environment variable. If an option
ap-
pears in the LESS variable, it can be reset to its default value on
the
command line by beginning the command line option with "-+".
Some options like -k or -D require a string to follow the option
let-
ter. The string for that option is considered to end when a
dollar
sign ($) is found. For example, you can set two -D options on
MS-DOS
like this:
LESS="Dn9.1$Ds4.1"
If the --use-backslash option appears earlier in the options,
then a
dollar sign or backslash may be included literally in an option
string
by preceding it with a backslash. If the --use-backslash option is
not
in effect, then backslashes are not treated specially, and there is
no
way to include a dollar sign in the option string.
-? or --help
This option displays a summary of the commands accepted by
4mless0m
(the same as the h command). (Depending on how your shell
in-
terprets the question mark, it may be necessary to quote
the
question mark, thus: "-?".)
-a or --search-skip-screen
By default, forward searches start at the top of the
displayed
screen and backwards searches start at the bottom of the
dis-
played screen (except for repeated searches invoked by the n
or
N commands, which start after or before the "target" line
re-
spectively; see the -j option for more about the target
line).
The -a option causes forward searches to instead start at
the
bottom of the screen and backward searches to start at the
top
of the screen, thus skipping all lines displayed on the
screen.
-A or --SEARCH-SKIP-SCREEN
Causes all forward searches (not just non-repeated searches)
to
start just after the target line, and all backward searches
to
start just before the target line. Thus, forward searches
will
skip part of the displayed screen (from the first line up to
and
including the target line). Similarly backwards searches
will
skip the displayed screen from the last line up to and
including
the target line. This was the default behavior in less
versions
prior to 441.
-b4mn24m or --buffers=4mn0m
Specifies the amount of buffer space 4mless24m 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 4mn0m
kilobytes of buffer space should be used for each file. If
4mn24m is
-1, buffer space is unlimited; that is, the entire file can
be
read into memory.
-B or --auto-buffers
By default, when data is read from a pipe, buffers are
allocated
automatically as needed. If a large amount of data is read
from
the pipe, this can cause a large amount of memory to be
allo-
cated. The -B option disables this automatic allocation of
buf-
fers for pipes, so that only 64 KB (or the amount of space
spec-
ified by the -b option) is used for the pipe. Warning: use
of
-B can result in erroneous display, since only the most
recently
viewed part of the piped data is kept in memory; any
earlier
data is lost.
-c or --clear-screen
Causes full screen repaints to be painted from the top
line
down. By default, full screen repaints are done by
scrolling
from the bottom of the screen.
-C or --CLEAR-SCREEN
Same as -c, for compatibility with older versions of
4mless24m.
-d or --dumb
The -d option suppresses the error message normally displayed
if
the terminal is dumb; that is, lacks some important
capability,
such as the ability to clear the screen or scroll backward.
The
-d option does not otherwise change the behavior of
4mless24m on a
dumb terminal.
-D1mx4m22mcolor24m or --color=1mx4m22mcolor0m
[MS-DOS only] Sets the color of the text displayed. 1mx
22mis a sin-
gle character which selects the type of text whose color is
be-
ing set: n=normal, s=standout, d=bold, u=underlined,
k=blink.
4mcolor24m 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 4mN24m is
the same as
4mN.M24m, where 4mM24m is the normal background color.
The color may
start or end with 1mu 22mto use underline (with the normal
color, if
by itself), if the system supports it (Windows only).
1mx 22mmay
also be 1ma 22mto toggle strict ANSI sequence rendering
(SGR mode).
-e or --quit-at-eof
Causes 4mless24m to automatically exit the second time
it reaches
end-of-file. By default, the only way to exit 4mless24m is
via the
"q" command.
-E or --QUIT-AT-EOF
Causes 4mless24m to automatically exit the first time it
reaches end-
of-file.
-f or --force
Forces non-regular files to be opened. (A non-regular file
is a
directory or a device special file.) Also suppresses the
warn-
ing message when a binary file is opened. By default,
4mless24m will
refuse to open non-regular files. Note that some operating
sys-
tems will not allow directories to be read, even if -f is
set.
-F or --quit-if-one-screen
Causes 4mless24m to automatically exit if the entire file
can be dis-
played on the first screen.
-g or --hilite-search
Normally, 4mless24m will highlight ALL strings which
match the last
search command. The -g option changes this behavior to
high-
light only the particular string which was found by the
last
search command. This can cause 4mless24m to run somewhat
faster than
the default.
-G or --HILITE-SEARCH
The -G option suppresses all highlighting of strings found
by
search commands.
-h4mn24m or --max-back-scroll=4mn0m
Specifies a maximum number of lines to scroll backward. If
it
is necessary to scroll backward more than 4mn24m lines, the
screen is
repainted in a forward direction instead. (If the terminal
does
not have the ability to scroll backward, -h0 is implied.)
-i or --ignore-case
Causes searches to ignore case; that is, uppercase and
lowercase
are considered identical. This option is ignored if any
upper-
case letters appear in the search pattern; in other words,
if a
pattern contains uppercase letters, then that search does
not
ignore case.
-I or --IGNORE-CASE
Like -i, but searches ignore case even if the pattern
contains
uppercase letters.
-j4mn24m or --jump-target=4mn0m
Specifies a line on the screen where the "target" line is to
be
positioned. The target line is the line specified by any
com-
mand to search for a pattern, jump to a line number, jump to
a
file percentage or jump to a tag. The screen line may be
speci-
fied by a number: the top line on the screen is 1, the next
is
2, and so on. The number may be negative to specify a line
rel-
ative to the bottom of the screen: the bottom line on the
screen
is -1, the second to the bottom is -2, and so on.
Alternately,
the screen line may be specified as a fraction of the height
of
the screen, starting with a decimal point: .5 is in the
middle
of the screen, .3 is three tenths down from the first line,
and
so on. If the line is specified as a fraction, the actual
line
number is recalculated if the terminal window is resized,
so
that the target line remains at the specified fraction of
the
screen height. If any form of the -j option is used,
repeated
forward searches (invoked with "n" or "N") begin at the line
im-
mediately after the target line, and repeated backward
searches
begin at the target line, unless changed by -a or -A. For
exam-
ple, if "-j4" is used, the target line is the fourth line on
the
screen, so forward searches begin at the fifth line on
the
screen. However nonrepeated searches (invoked with "/" or
"?")
always begin at the start or end of the current screen
respec-
tively.
-J or --status-column
Displays a status column at the left edge of the screen.
The
status column shows the lines that matched the current
search,
and any lines that are marked (via the m or M command).
The
status column is also used if the -w or -W option is in
effect.
-k4mfilename24m or --lesskey-file=4mfilename0m
Causes 4mless24m to open and interpret the named file as a
4mlesskey24m(1)
file. Multiple -k options may be specified. If the LESSKEY
or
LESSKEY_SYSTEM environment variable is set, or if a lesskey
file
is found in a standard place (see KEY BINDINGS), it is also
used
as a 4mlesskey24m file.
-K or --quit-on-intr
Causes 4mless24m to exit immediately (with status 2) when
an inter-
rupt character (usually ^C) is typed. Normally, an
interrupt
character causes 4mless24m to stop whatever it is doing and
return to
its command prompt. Note that use of this option makes it
im-
possible to return to the command prompt from the "F"
command.
-L or --no-lessopen
Ignore the LESSOPEN environment variable (see the INPUT
PRE-
PROCESSOR section below). This option can be set from
within
4mless24m, but it will apply only to files opened
subsequently, not
to the file which is currently open.
-m or --long-prompt
Causes 4mless24m to prompt verbosely (like 4mmore24m),
with the percent
into the file. By default, 4mless24m prompts with a colon.
-M or --LONG-PROMPT
Causes 4mless24m to prompt even more verbosely than
4mmore24m.
-n or --line-numbers
Suppresses line numbers. The default (to use line numbers)
may
cause 4mless24m to run more slowly in some cases,
especially with a
very large input file. Suppressing line numbers with the -n
op-
tion will avoid this problem. Using line numbers means:
the
line number will be displayed in the verbose prompt and in
the =
command, and the v command will pass the current line number
to
the editor (see also the discussion of LESSEDIT in PROMPTS
be-
low).
-N or --LINE-NUMBERS
Causes a line number to be displayed at the beginning of
each
line in the display.
-o4mfilename24m or --log-file=4mfilename0m
Causes 4mless24m to copy its input to the named file as
it is being
viewed. This applies only when the input file is a pipe, not
an
ordinary file. If the file already exists, 4mless24m
will ask for
confirmation before overwriting it.
-O4mfilename24m or --LOG-FILE=4mfilename0m
The -O option is like -o, but it will overwrite an existing
file
without asking for confirmation.
If no log file has been specified, the -o and -O options can
be
used from within 4mless24m to specify a log file.
Without a file
name, they will simply report the name of the log file. The
"s"
command is equivalent to specifying -o from within
4mless24m.
-p4mpattern24m or --pattern=4mpattern0m
The -p option on the command line is equivalent to
specifying
+/4mpattern24m; that is, it tells 4mless24m to start at
the first occur-
rence of 4mpattern24m in the file.
-P4mprompt24m or --prompt=4mprompt0m
Provides a way to tailor the three prompt styles to your
own
preference. This option would normally be put in the LESS
envi-
ronment variable, rather than being typed in with each
4mless24m com-
mand. Such an option must either be the last option in the
LESS
variable, or be terminated by a dollar sign.
-Ps followed by a string changes the default (short) prompt
to
that string.
-Pm changes the medium (-m) prompt.
-PM changes the long (-M) prompt.
-Ph changes the prompt for the help screen.
-P= changes the message printed by the = command.
-Pw changes the message printed while waiting for data (in
the
F command).
All prompt strings consist of a sequence of letters and
special
escape sequences. See the section on PROMPTS for more
details.
-q or --quiet or --silent
Causes moderately "quiet" operation: the terminal bell is
not
rung if an attempt is made to scroll past the end of the file
or
before the beginning of the file. If the terminal has a
"visual
bell", it is used instead. The bell will be rung on
certain
other errors, such as typing an invalid character. The
default
is to ring the terminal bell in all such cases.
-Q or --QUIET or --SILENT
Causes totally "quiet" operation: the terminal bell is
never
rung. If the terminal has a "visual bell", it is used in
all
cases where the terminal bell would have been rung.
-r or --raw-control-chars
Causes "raw" control characters to be displayed. The default
is
to display control characters using the caret notation; for
ex-
ample, a control-A (octal 001) is displayed as "^A".
Warning:
when the -r option is used, 4mless24m cannot keep track of
the actual
appearance of the screen (since this depends on how the
screen
responds to each type of control character). Thus, various
dis-
play problems may result, such as long lines being split in
the
wrong place.
-R or --RAW-CONTROL-CHARS
Like -r, but only ANSI "color" escape sequences are output
in
"raw" form. Unlike -r, the screen appearance is maintained
cor-
rectly in most cases. ANSI "color" escape sequences are
se-
quences of the form:
ESC [ ... m
where the "..." is zero or more color specification
characters
For the purpose of keeping track of screen appearance,
ANSI
color escape sequences are assumed to not move the cursor.
You
can make 4mless24m 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 4mless24m think that
characters
other than the standard ones may appear between the ESC and
the
m by setting the environment variable LESSANSIMIDCHARS to
the
list of characters which can appear.
-s or --squeeze-blank-lines
Causes consecutive blank lines to be squeezed into a
single
blank line. This is useful when viewing 4mnroff24m output.
-S or --chop-long-lines
Causes lines longer than the screen width to be chopped
(trun-
cated) rather than wrapped. That is, the portion of a long
line
that does not fit in the screen width is not displayed until
you
press RIGHT-ARROW. The default is to wrap long lines; that
is,
display the remainder on the next line.
-t4mtag24m or --tag=4mtag0m
The -t option, followed immediately by a TAG, will edit the
file
containing that tag. For this to work, tag information must
be
available; for example, there may be a file in the current
di-
rectory called "tags", which was previously built by
4mctags24m(1) or
an equivalent command. If the environment variable
LESSGLOBALT-
AGS is set, it is taken to be the name of a command
compatible
with 4mglobal24m(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 4mless24m (using
the - com-
mand) as a way of examining a new file. The command ":t"
is
equivalent to specifying -t from within 4mless24m.
-T4mtagsfile24m or --tag-file=4mtagsfile0m
Specifies a tags file to be used instead of "tags".
-u or --underline-special
Causes backspaces and carriage returns to be treated as
print-
able characters; that is, they are sent to the terminal
when
they appear in the input.
-U or --UNDERLINE-SPECIAL
Causes backspaces, tabs, carriage returns and "formatting
char-
acters" (as defined by Unicode) to be treated as control
charac-
ters; that is, they are handled as specified by the -r
option.
By default, if neither -u nor -U is given, backspaces which
ap-
pear adjacent to an underscore character are treated
specially:
the underlined text is displayed using the terminal's
hardware
underlining capability. Also, backspaces which appear
between
two identical characters are treated specially: the
overstruck
text is printed using the terminal's hardware boldface
capabil-
ity. Other backspaces are deleted, along with the
preceding
character. Carriage returns immediately followed by a
newline
are deleted. Other carriage returns are handled as specified
by
the -r option. Text which is overstruck or underlined can
be
searched for if neither -u nor -U is in effect.
-V or --version
Displays the version number of 4mless24m.
-w or --hilite-unread
Temporarily highlights the first "new" line after a
forward
movement of a full page. The first "new" line is the line
imme-
diately following the line previously at the bottom of
the
screen. Also highlights the target line after a g or p
command.
The highlight is removed at the next command which causes
move-
ment. The entire line is highlighted, unless the -J option
is
in effect, in which case only the status column is
highlighted.
-W or --HILITE-UNREAD
Like -w, but temporarily highlights the first new line after
any
forward movement command larger than one line.
-x4mn24m,... or --tabs=4mn24m,...
Sets tab stops. If only one 4mn24m is specified, tab
stops are set
at multiples of 4mn24m. If multiple values separated by
commas are
specified, tab stops are set at those positions, and then
con-
tinue with the same spacing as the last two. For
example,
4m-x9,1724m will set tabs at positions 9, 17, 25, 33,
etc. The de-
fault for 4mn24m is 8.
-X or --no-init
Disables sending the termcap initialization and
deinitialization
strings to the terminal. This is sometimes desirable if
the
deinitialization string does something unnecessary, like
clear-
ing the screen.
-y4mn24m or --max-forw-scroll=4mn0m
Specifies a maximum number of lines to scroll forward. If it
is
necessary to scroll forward more than 4mn24m lines, the
screen is re-
painted instead. The -c or -C option may be used to
repaint
from the top of the screen if desired. By default, any
forward
movement causes scrolling.
-z4mn24m or --window=4mn24m or -4mn0m
Changes the default scrolling window size to 4mn24m
lines. The de-
fault is one screenful. The z and w commands can also be
used
to change the window size. The "z" may be omitted for
compati-
bility with some versions of 4mmore24m. If the number
4mn24m is negative,
it indicates 4mn24m lines less than the current screen
size. For ex-
ample, if the screen is 24 lines, 4m-z-424m sets the
scrolling window
to 20 lines. If the screen is resized to 40 lines,
the
scrolling window automatically changes to 36 lines.
-"4mcc24m or --quotes=4mcc0m
Changes the filename quoting character. This may be
necessary
if you are trying to name a file which contains both spaces
and
quote characters. Followed by a single character, this
changes
the quote character to that character. Filenames
containing a
space should then be surrounded by that character rather than
by
double quotes. Followed by two characters, changes the
open
quote to the first character, and the close quote to the
second
character. Filenames containing a space should then be
preceded
by the open quote character and followed by the close
quote
character. Note that even after the quote characters
are
changed, this option remains -" (a dash followed by a
double
quote).
-~ or --tilde
Normally lines after end of file are displayed as a single
tilde
(~). This option causes lines after end of file to be
displayed
as blank lines.
-# or --shift
Specifies the default number of positions to scroll
horizontally
in the RIGHTARROW and LEFTARROW commands. If the number
speci-
fied is zero, it sets the default number of positions to
one
half of the screen width. Alternately, the number may be
speci-
fied as a fraction of the width of the screen, starting
with a
decimal point: .5 is half of the screen width, .3 is
three
tenths of the screen width, and so on. If the number is
speci-
fied as a fraction, the actual number of scroll positions is
re-
calculated if the terminal window is resized, so that the
actual
scroll remains at the specified fraction of the screen width.
--follow-name
Normally, if the input file is renamed while an F command is
ex-
ecuting, 4mless24m will continue to display the contents of
the orig-
inal file despite its name change. If --follow-name is
speci-
fied, during an F command 4mless24m will periodically
attempt to re-
open the file by name. If the reopen succeeds and the file
is a
different file from the original (which means that a new
file
has been created with the same name as the original (now
re-
named) file), 4mless24m will display the contents of that
new file.
--mouse
Enables mouse input: scrolling the mouse wheel down moves
for-
ward in the file, scrolling the mouse wheel up moves
backwards
in the file, and clicking the mouse sets the "#" mark to
the
line where the mouse is clicked. The number of lines to
scroll
when the wheel is moved can be set by the --wheel-lines
option.
Mouse input works only on terminals which support X11 mouse
re-
porting, and on the Windows version of 4mless24m.
--MOUSE
Like --mouse, except the direction scrolled on mouse wheel
move-
ment is reversed.
--no-keypad
Disables sending the keypad initialization and
deinitialization
strings to the terminal. This is sometimes useful if the
keypad
strings make the numeric keypad behave in an undesirable
manner.
--no-histdups
This option changes the behavior so that if a search string
or
file name is typed in, and the same string is already in
the
history list, the existing copy is removed from the history
list
before the new one is added. Thus, a given string will
appear
only once in the history list. Normally, a string may
appear
multiple times.
--rscroll
This option changes the character used to mark truncated
lines.
It may begin with a two-character attribute indicator like
LESS-
BINFMT does. If there is no attribute indicator, standout
is
used. If set to "-", truncated lines are not marked.
--save-marks
Save marks in the history file, so marks are retained
across
different invocations of 4mless24m.
--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.
--wheel-lines=4mn0m
Set the number of lines to scroll when the mouse wheel
is
scrolled and the --mouse or --MOUSE option is in effect.
The
default is 1 line.
-- A command line argument of "--" marks the end of option
argu-
ments. Any arguments following this are interpreted as
file-
names. This can be useful when viewing a file whose name
begins
with a "-" or "+".
+ If a command line option begins with 1m+22m, the remainder
of that
option is taken to be an initial command to 4mless24m.
For example,
+G tells 4mless24m to start at the end of the file rather
than the
beginning, and +/xyz tells it to start at the first
occurrence
of "xyz" in the file. As a special case, +<number> acts
like
+<number>g; that is, it starts the display at the specified
line
number (however, see the caveat under the "g" command
above).
If the option starts with ++, the initial command applies to
ev-
ery file being viewed, not just the first one. The +
command
described previously may also be used to set (or change) an
ini-
tial command for every file.
1mLINE EDITING0m
When entering command line at the bottom of the screen (for example,
a
filename for the :e command, or the pattern for a search command),
cer-
tain keys can be used to manipulate the command line. Most
commands
have an alternate form in [ brackets ] which can be used if a key
does
not exist on a particular keyboard. (Note that the forms
beginning
with ESC do not work in some MS-DOS and Windows systems because ESC
is
the line erase character.) Any of these special keys may be
entered
literally by preceding it with the "literal" character, either ^V
or
^A. A backslash itself may also be entered literally by entering
two
backslashes.
LEFTARROW [ ESC-h ]
Move the cursor one space to the left.
RIGHTARROW [ ESC-l ]
Move the cursor one space to the right.
^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.) Move the
cur-
sor one word to the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.) Move the
cur-
sor one word to the right.
HOME [ ESC-0 ]
Move the cursor to the beginning of the line.
END [ ESC-$ ]
Move the cursor to the end of the line.
BACKSPACE
Delete the character to the left of the cursor, or cancel
the
command if the command line is empty.
DELETE or [ ESC-x ]
Delete the character under the cursor.
^BACKSPACE [ ESC-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.) Delete
the
word to the left of the cursor.
^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.) Delete the
word
under the cursor.
UPARROW [ ESC-k ]
Retrieve the previous command line. If you first enter
some
text and then press UPARROW, it will retrieve the previous
com-
mand which begins with that text.
DOWNARROW [ ESC-j ]
Retrieve the next command line. If you first enter some
text
and then press DOWNARROW, it will retrieve the next
command
which begins with that text.
TAB Complete the partial filename to the left of the cursor. If
it
matches more than one filename, the first match is entered
into
the command line. Repeated TABs will cycle thru the
other
matching filenames. If the completed filename is a
directory, a
"/" is appended to the filename. (On MS-DOS systems, a "
appended.) The environment variable LESSSEPARATOR can be
used
to specify a different character to append to a directory
name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the
matching
filenames.
^L Complete the partial filename to the left of the cursor. If
it
matches more than one filename, all matches are entered into
the
command line (if they fit).
^U (Unix and OS/2) or ESC (MS-DOS)
Delete the entire command line, or cancel the command if
the
command line is empty. If you have changed your line-kill
char-
acter in Unix to something other than ^U, that character is
used
instead of ^U.
^G Delete the entire command line and return to the main prompt.
1mKEY BINDINGS0m
You may define your own 4mless24m commands by using the program
4mlesskey24m(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
4mlesskey24m to
change the line-editing keys (see LINE EDITING), and to set
environment
variables. If the environment variable LESSKEY is set, 4mless24m
uses that
as the name of the lesskey file. Otherwise, 4mless24m looks in
a standard
place for the lesskey file: On Unix systems, 4mless24m looks for
a lesskey
file called "$HOME/.less". On MS-DOS and Windows systems,
4mless24m looks
for a lesskey file called "$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, 4mless24m
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 4mlesskey24m manual page
for more de-
tails.
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,
4mless24m uses that as the name of the system-wide lesskey file.
Otherwise,
4mless24m 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 4mless24m 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:_sys-
less. On OS/2 systems, the system-wide lesskey file is c:sless.ini.
1mINPUT PREPROCESSOR0m
You may define an "input preprocessor" for 4mless24m. Before
4mless24m opens a
file, it first gives your input preprocessor a chance to modify the
way
the contents of the file are displayed. An input preprocessor is
sim-
ply an executable program (or shell script), which writes the
contents
of the file to a different file, called the replacement file. The
con-
tents of the replacement file are then displayed in place of the
con-
tents of the original file. However, it will appear to the user as
if
the original file is opened; that is, 4mless24m will display
the original
filename as the name of the current file.
An input preprocessor receives one command line argument, the
original
filename, as entered by the user. It should create the
replacement
file, and when finished, print the name of the replacement file to
its
standard output. If the input preprocessor does not output a
replace-
ment filename, 4mless24m uses the original file, as normal. The
input pre-
processor is not called when viewing standard input. To set up an
in-
put preprocessor, set the LESSOPEN environment variable to a
command
line which will invoke your input preprocessor. This command
line
should include one occurrence of the string "%s", which will be
re-
placed by the filename when the input preprocessor command is
invoked.
When 4mless24m closes a file opened in such a way, it will call
another pro-
gram, called the input postprocessor, which may perform any
desired
clean-up action (such as deleting the replacement file created
by
LESSOPEN). This program receives two command line arguments, the
orig-
inal filename as entered by the user, and the name of the
replacement
file. To set up an input postprocessor, set the LESSCLOSE
environment
variable to a command line which will invoke your input
postprocessor.
It may include two occurrences of the string "%s"; the first is
re-
placed with the original name of the file and the second with the
name
of the replacement file, which was output by LESSOPEN.
For example, on many Unix systems, these two scripts will allow you
to
keep files in compressed format, but still let 4mless24m 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 4mless24m, rather than putting the data into a
replacement
file. This avoids the need to decompress the entire file before
start-
ing to view it. An input preprocessor that works this way is called
an
input pipe. An input pipe, instead of writing the name of a
replace-
ment file on its standard output, writes the entire contents of the
re-
placement file on its standard output. If the input pipe does
not
write any characters on its standard output, then there is no
replace-
ment file and 4mless24m uses the original file, as normal. To use
an input
pipe, make the first character in the LESSOPEN environment
variable a
vertical bar (|) to signify that the input preprocessor is an
input
pipe. As with non-pipe input preprocessors, the command string
must
contain one occurrence of %s, which is replaced with the filename
of
the input file.
For example, on many Unix systems, this script will work like the
pre-
vious example scripts:
lesspipe.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -c $1 2>/dev/null
;;
*) exit 1
;;
esac
exit $?
To use this script, put it where it can be executed and
set
LESSOPEN="|lesspipe.sh %s".
Note that a preprocessor cannot output an empty file, since that is
in-
terpreted as meaning there is no replacement, and the original file
is
used. To avoid this, if LESSOPEN starts with two vertical bars,
the
exit status of the script becomes meaningful. If the exit status
is
zero, the output is considered to be replacement text, even if it
is
empty. If the exit status is nonzero, any output is ignored and
the
original file is used. For compatibility with previous versions
of
4mless24m, 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 4mless24m, the input
preproces-
sor or pipe is not used if 4mless24m is viewing standard input.
However, if
the first character of LESSOPEN is a dash (-), the input
preprocessor
is used on standard input as well as other files. In this case,
the
dash is not considered to be part of the preprocessor command.
If
standard input is being viewed, the input preprocessor is passed a
file
name consisting of a single dash. Similarly, if the first two
charac-
ters of LESSOPEN are vertical bar and dash (|-) or two vertical
bars
and a dash (||-), the input pipe is used on standard input as well
as
other files. Again, in this case the dash is not considered to be
part
of the input pipe command.
1mNATIONAL CHARACTER SETS0m
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
1251).
In rare cases, it may be desired to tailor 4mless24m to use a
character set
other than the ones definable by LESSCHARSET. In this case, the
envi-
ronment variable LESSCHARDEF can be used to define a character set.
It
should be set to a string where each character in the string
represents
one character in the character set. The character "." is used for
a
normal character, "c" for control, and "b" for binary. A decimal
num-
ber may be used for repetition. For example, "bccc4b." would
mean
character 0 is binary, 1, 2 and 3 are control, 4, 5, 6 and 7 are
bi-
nary, 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
char-
acter 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
4msetlocale24m in-
terface, 4mless24m will use setlocale to determine the character
set. set-
locale is controlled by setting the LANG or LC_CTYPE environment
vari-
ables.
Finally, if the 4msetlocale24m interface is also not available,
the default
character set is latin1.
Control and binary characters are displayed in standout
(reverse
video). Each such character is displayed in caret notation if
possible
(e.g. ^A for control-A). Caret notation is used only if inverting
the
0100 bit results in a normal printable character. Otherwise, the
char-
acter is displayed as a hex number in angle brackets. This format
can
be changed by setting the LESSBINFMT environment variable.
LESSBINFMT
may begin with a "*" and one character to select the display
attribute:
"*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is
standout,
and "*n" is normal. If LESSBINFMT does not begin with a "*",
normal
attribute is assumed. The remainder of LESSBINFMT is a string
which
may include one printf-style escape sequence (a % followed by x, X,
o,
d, etc.). For example, if LESSBINFMT is "*u[%x]", binary
characters
are displayed in underlined hexadecimal surrounded by brackets.
The
default if no LESSBINFMT is specified is "*s<%02X>". Warning: the
re-
sult of expanding the character via LESSBINFMT must be less than
31
characters.
When the character set is utf-8, the LESSUTFBINFMT environment
variable
acts similarly to LESSBINFMT but it applies to Unicode code points
that
were successfully decoded but are unsuitable for display (e.g.,
unas-
signed code points). Its default value is "<U+%04lX>". Note
that
LESSUTFBINFMT and LESSBINFMT share their display attribute
setting
("*x") so specifying one will affect both; LESSUTFBINFMT is read
after
LESSBINFMT so its setting, if any, will have priority.
Problematic
octets in a UTF-8 file (octets of a truncated sequence, octets of
a
complete but non-shortest form sequence, invalid octets, and
stray
trailing octets) are displayed individually using LESSBINFMT so as
to
facilitate diagnostic of how the UTF-8 file is ill-formed.
1mPROMPTS0m
The -P option allows you to tailor the prompt to your preference.
The
string given to the -P option replaces the specified prompt
string.
Certain characters in the string are interpreted specially. The
prompt
mechanism is rather complicated to provide flexibility, but the
ordi-
nary user need not understand the details of constructing
personalized
prompt strings.
A percent sign followed by a single character is expanded according
to
what the following character is:
%b4mX24m Replaced by the byte offset into the current input
file. The b
is followed by a single character (shown as 4mX24m above)
which spec-
ifies the line whose byte offset is to be used. If the
charac-
ter is a "t", the byte offset of the top line in the display
is
used, an "m" means use the middle line, a "b" means use the
bot-
tom line, a "B" means use the line just after the bottom
line,
and a "j" means use the "target" line, as specified by the
-j
option.
%B Replaced by the size of the current input file.
%c Replaced by the column number of the text appearing in the
first
column of the screen.
%d4mX24m Replaced by the page number of a line in the input
file. The
line to be used is determined by the 4mX24m, as with the %b
option.
%D Replaced by the number of pages in the input file, or
equiva-
lently, the page number of the last line in the input file.
%E Replaced by the name of the editor (from the VISUAL
environment
variable, or the EDITOR environment variable if VISUAL is
not
defined). See the discussion of the LESSEDIT feature below.
%f Replaced by the name of the current input file.
%F Replaced by the last component of the name of the current
input
file.
%g Replaced by the shell-escaped name of the current input
file.
This is useful when the expanded string will be used in a
shell
command, such as in LESSEDIT.
%i Replaced by the index of the current file in the list of
input
files.
%l4mX24m Replaced by the line number of a line in the input
file. The
line to be used is determined by the 4mX24m, 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.
%p4mX24m Replaced by the percent into the current input file,
based on
byte offsets. The line used is determined by the 4mX24m
as with the
%b option.
%P4mX24m Replaced by the percent into the current input file,
based on
line numbers. The line used is determined by the 4mX24m
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
evalu-
ated. 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.
?b4mX24m 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).
?d4mX24m 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).
?l4mX24m 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.
?p4mX24m True if the percent into the current input file, based
on byte
offsets, of the specified line is known.
?P4mX24m True if the percent into the current input file,
based on line
numbers, of the specified line is known.
?s Same as "?B".
?x True if there is a next input file (that is, if the current
in-
put file is not the last one).
Any characters other than the special ones (question mark, colon,
pe-
riod, percent, and backslash) become literally part of the prompt.
Any
of the special characters may be included in the prompt literally
by
preceding it with a backslash.
Some examples:
?f%f:Standard input.
This prompt prints the filename, if known; otherwise the string
"Stan-
dard input".
?f%f .?ltLine %lt:?pt%pt:?btByte %bt:-...
This prompt would print the filename, if known. The filename is
fol-
lowed by the line number, if known, otherwise the percent if
known,
otherwise the byte offset if known. Otherwise, a dash is printed.
No-
tice how each question mark has a matching period, and how the %
after
the %pt is included literally by escaping it with a backslash.
%x..%t";
?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next
This prints the filename if this is the first prompt in a file,
fol-
lowed by the "file N of N" message if there is more than one
input
file. Then, if we are at end-of-file, the string "(END)" is
printed
followed by the name of the next file, if there is one. Finally,
any
trailing spaces are truncated. This is the default prompt. For
refer-
ence, here are the defaults for the other two prompts (-m and -M
re-
spectively). Each is broken into two lines here for readability
only.
%x.:
?n?f%f .?pB%pB:byte %bB?s/%s...%t ?x- Next
?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%l%x.:?pB%pB..%t
byte %bB?s/%s. .?e(END) ?x- Next
And here is the default message produced by the = command:
?f%f .?m(%T %i of %m) .?ltlines %lt-%lb?L/%L. .
byte %bB?s/%s. ?e(END) :?pB%pB..%t
The prompt expansion features are also used for another purpose: if
an
environment variable LESSEDIT is defined, it is used as the command
to
be executed when the v command is invoked. The LESSEDIT string is
ex-
panded in the same way as the prompt strings. The default value
for
LESSEDIT is:
%E ?lm+%lm. %g
Note that this expands to the editor name, followed by a + and the
line
number, followed by the shell-escaped file name. If your editor
does
not accept the "+linenumber" syntax, or has other differences in
invo-
cation syntax, the LESSEDIT variable can be changed to modify this
de-
fault.
1mSECURITY0m
When the environment variable LESSSECURE is set to 1, 4mless24m
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.
1mCOMPATIBILITY WITH MORE0m
If the environment variable LESS_IS_MORE is set to 1, or if the
program
is invoked via a file link named "more", 4mless24m behaves
(mostly) in con-
formance with the POSIX "more" command specification. In this
mode,
less behaves differently in these ways:
The -e option works differently. If the -e option is not set,
4mless24m be-
haves as if the -e option were set. If the -e option is set,
4mless24m be-
haves as if the -E option were set.
The -m option works differently. If the -m option is not set,
the
medium prompt is used, and it is prefixed with the string "--
More--".
If the -m option is set, the short prompt is used.
The -n option acts like the -z option. The normal behavior of the
-n
option is unavailable in this mode.
The parameter to the -p option is taken to be a 4mless24m
command rather
than a search pattern.
The LESS environment variable is ignored, and the MORE
environment
variable is used in its place.
1mENVIRONMENT VARIABLES0m
Environment variables may be specified either in the system
environment
as usual, or in a 4mlesskey24m(1) file. If environment
variables are de-
fined in more than one place, variables defined in a local lesskey
file
take precedence over variables defined in the system environment,
which
take precedence over variables defined in the system-wide lesskey
file.
COLUMNS
Sets the number of columns on the screen. Takes precedence
over
the number of columns specified by the TERM variable. (But
if
you have a windowing system which supports TIOCGWINSZ
or
WIOCGETD, the window system's idea of the screen size
takes
precedence over the LINES and COLUMNS environment variables.)
EDITOR The name of the editor (used for the v command).
HOME Name of the user's home directory (used to find a lesskey
file
on Unix and OS/2 systems).
HOMEDRIVE, HOMEPATH
Concatenation of the HOMEDRIVE and HOMEPATH environment
vari-
ables is the name of the user's home directory if the HOME
vari-
able is not set (only in the Windows version).
INIT Name of the user's init directory (used to find a lesskey
file
on OS/2 systems).
LANG Language for determining the character set.
LC_CTYPE
Language for determining the character set.
LESS Options which are passed to 4mless24m automatically.
LESSANSIENDCHARS
Characters which may end an ANSI color escape sequence
(default
"m").
LESSANSIMIDCHARS
Characters which may appear between the ESC character and
the
end character in an ANSI color escape sequence
(default
"0123456789:;[?!"'#%()*+ ".
LESSBINFMT
Format for displaying non-printable, non-control characters.
LESSCHARDEF
Defines a character set.
LESSCHARSET
Selects a predefined character set.
LESSCLOSE
Command line to invoke the (optional) input-postprocessor.
LESSECHO
Name of the lessecho program (default "lessecho"). The
lessecho
program is needed to expand metacharacters, such as * and ?,
in
filenames on Unix systems.
LESSEDIT
Editor prototype string (used for the v command). See
discus-
sion under PROMPTS.
LESSGLOBALTAGS
Name of the command used by the -t option to find global
tags.
Normally should be set to "global" if your system has
the
4mglobal24m(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 4mless24m. If set
to "-" or
"/dev/null", a history file is not used. The default
is
"$HOME/.lesshst" on Unix systems, "$HOME/_lesshst" on DOS
and
Windows systems, or "$HOME/lesshst.ini" or
"$INIT/lesshst.ini"
on OS/2 systems.
LESSHISTSIZE
The maximum number of commands to save in the history file.
The
default is 100.
LESSKEY
Name of the default 4mlesskey24m(1) file.
LESSKEY_SYSTEM
Name of the default system-wide 4mlesskey24m(1) file.
LESSMETACHARS
List of characters which are considered "metacharacters" by
the
shell.
LESSMETAESCAPE
Prefix which less will add before each metacharacter in a
com-
mand sent to the shell. If LESSMETAESCAPE is an empty
string,
commands containing metacharacters will not be passed to
the
shell.
LESSOPEN
Command line to invoke the (optional) input-preprocessor.
LESSSECURE
Runs less in "secure" mode. See discussion under SECURITY.
LESSSEPARATOR
String to be appended to a directory name in filename
comple-
tion.
LESSUTFBINFMT
Format for displaying non-printable Unicode code points.
LESS_IS_MORE
Emulate the 4mmore24m(1) command.
LINES Sets the number of lines on the screen. Takes precedence
over
the number of lines specified by the TERM variable. (But if
you
have a windowing system which supports TIOCGWINSZ or
WIOCGETD,
the window system's idea of the screen size takes
precedence
over the LINES and COLUMNS environment variables.)
MORE Options which are passed to 4mless24m automatically when
running in
4mmore24m compatible mode.
PATH User's search path (used to find a lesskey file on MS-DOS
and
OS/2 systems).
SHELL The shell used to execute the ! command, as well as to
expand
filenames.
TERM The type of terminal on which 4mless24m is being run.
VISUAL The name of the editor (used for the v command).
1mSEE ALSO0m
1mlesskey22m(1)
1mCOPYRIGHT0m
Copyright (C) 1984-2020 Mark Nudelman
less is part of the GNU project and is free software. You can
redis-
tribute it and/or modify it under the terms of either (1) the GNU
Gen-
eral Public License as published by the Free Software Foundation;
or
(2) the Less License. See the file README in the less distribution
for
more details regarding redistribution. You should have received a
copy
of the GNU General Public License along with the source for less;
see
the file COPYING. If not, write to the Free Software Foundation,
59
Temple Place, Suite 330, Boston, MA 02111-1307, USA. You should
also
have received a copy of the Less License; see the file LICENSE.
less is distributed in the hope that it will be useful, but WITHOUT
ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FIT-
NESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for
more details.
1mAUTHOR0m
Mark Nudelman
Report bugs at https://github.com/gwsw/less/issues.
For more information, see the less homepage at
http://www.greenwoodsoftware.com/less.
Version 563: 13 Jun 2020
LESS(1)
