LESS(1)LESS(1)NAME
less - opposite of more
SYNOPSIS
less [-[+]aABcCdeEimMnqQuUsw] [-bN] [-hN] [-xN] [-[z]N]
[-P[mM=]string] [-[lL]logfile] [+cmd]
[-ttag] [filename]...
DESCRIPTION
Less is a program similar to more (1), but which allows backwards
movement in the file as well as forward movement. Also, less does not
have to read the entire input file before starting, so with large input
files it starts up faster than text editors like vi (1). Less uses
termcap (or terminfo on some systems), so it can run on a variety of
terminals. There is even limited support for hardcopy terminals. (On
a hardcopy terminal, lines which should be printed at the top of the
screen are prefixed with an up-arrow.)
Commands are based on both more and vi. Commands may be preceeded by a
decimal number, called N in the descriptions below. The number is used
by some commands, as indicated.
COMMANDS
In the following descriptions, ^X means control-X. ESC stands for the
ESCAPE key; for example ESC-v means the two character sequence
"ESCAPE", then "v".
H Help: display a summary of these commands. If you forget all
the other commands, remember this one.
SPACE or f or ^F or ^V
Scroll forward N lines, default one window (see option -z
below). If N is more than the screen size, only the final
screenful is displayed. Warning: some systems use ^V as a
special literalization character.
b or ^B or ESC-v
Scroll backward N lines, default one window (see option -z
below). If N is more than the screen size, only the final
screenful is displayed.
RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines are
displayed, even if N is more than the screen size.
y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1. The entire N lines are
displayed, even if N is more than the screen size. Warning:
some systems use ^Y as a special job control character.
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.
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.
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.
g or < or ESC-<
Go to line N in the file, default 1 (beginning of file).
(Warning: this may be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the file.
(Warning: this may be slow if N is large, or if N is not
specified and standard input, rather than a file, is being
read.)
p or % Go to a position N percent into the file. N should be between 0
and 100. (This works if standard input is being read, but only
if less has already read to the end of the file. It is always
fast, but not always useful.)
m Followed by any lowercase letter, marks the current position
with that letter.
' (Single quote.) Followed by any lowercase letter, returns to
the position which was previously marked with that letter.
Followed by another single quote, returns to the postion at
which the last "large" movement command was executed. All marks
are lost when a new file is examined.
^X^X Same as single quote.
/pattern
Search forward in the file for the N-th line containing the
pattern. N defaults to 1. The pattern is a regular expression,
as recognized by ed. The search starts at the second line
displayed (but see the -a option, which changes this).
?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.
/!pattern
Like /, but the search is for the N-th line which does NOT
contain the pattern.
?!pattern
Like ?, but the search is for the N-th line which does NOT
contain the pattern.
n Repeat previous search, for N-th line containing the last
pattern (or NOT containing the last pattern, if the previous
search was /! or ?!).
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. If the filename is a pound
sign (#), the previously examined file is re-examined.
^X^V or :e
Same as E. Warning: some systems use ^V as a special
literalization character.
N or :n
Examine the next file (from the list of files given in the
command line). If a number N is specified (not to be confused
with the command N), the N-th next file is examined.
P or :p
Examine the previous file. If a number N is specified, the N-th
previous file is examined.
= or ^G
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 and the percent of the file above the last displayed line.
- Followed by one of the command line option letters (see below),
this will change the setting of that option and print a message
describing the new setting. 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.
_ (Underscore.) Followed by one of the command line option
letters (see below), this will print a message describing the
current setting of that option. The setting of the option is
not changed.
+cmd Causes the specified cmd to be executed each time a new file is
examined. For example, +G causes less to initially display each
file starting at the end rather than the beginning.
V Prints the version number of less being run.
q or :q or ZZ
Exits less.
The following two 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 EDITOR, or
defaults to "vi".
! 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.
"!!" repeats the last shell command. "!" with no shell command
simply invokes a shell. In all cases, the shell is taken from
the environment variable SHELL, or defaults to "sh".
OPTIONS
Command line options are described below. Most options may be changed
while less is running, via the "-" command.
Options are also taken from the environment variable "LESS". For
example, to avoid typing "less -options ..." each time less is invoked,
you might tell csh:
setenv LESS "-options"
or if you use sh:
LESS="-options"; export LESS
The environment variable is parsed before the command line, so command
line options override the LESS environment variable. If an option
appears in the LESS variable, it can be reset to its default on the
command line by beginning the command line option with "-+".
A dollar sign ($) may be used to signal the end of an option string.
This is important only for options like -P which take a following
string.
-a Normally, forward searches start just after the top displayed
line (that is, at the second displayed line). Thus, forward
searches include the currently displayed screen. The -a option
causes forward searches to start just after the bottom line
displayed, thus skipping the currently displayed screen.
-A The -A option causes searches to start at the second SCREEN line
displayed, as opposed to the default which is to start at the
second REAL line displayed. For example, suppose a long real
line occupies the first three screen lines. The default search
will start at the second real line (the fourth screen line),
while the -A option will cause the search to start at the second
screen line (in the midst of the first real line). (This option
is rarely useful.)
-b The -bn option tells less to use a non-standard number of
buffers. Buffers are 1K, and normally 10 buffers are used
(except if data in coming from standard input; see the -B
option). The number n specifies a different number of buffers
to use.
-B Normally, when data is coming from standard input, buffers are
allocated automatically as needed, to avoid loss of data. The
-B option disables this feature, so that only the default number
of buffers are used. If more data is read than will fit in the
buffers, the oldest data is discarded.
-c Normally, less will repaint the screen by scrolling from the
bottom of the screen. If the -c option is set, when less needs
to change the entire display, it will paint from the top line
down.
-C The -C option is like -c, but the screen is cleared before it is
repainted.
-d Normally, less will complain if the terminal is dumb; that is,
lacks some important capability, such as the ability to clear
the screen or scroll backwards. The -d option suppresses this
complaint (but does not otherwise change the behavior of the
program on a dumb terminal).
-e Normally the only way to exit less is via the "q" command. The
-e option tells less to automatically exit the second time it
reaches end-of-file.
-E The -E flag causes less to exit the first time it reaches end-
of-file.
-h Normally, less will scroll backwards when backwards movement is
necessary. The -h option specifies a maximum number of lines to
scroll backwards. If it is necessary to move backwards more
than this many lines, the screen is repainted in a forward
direction. (If the terminal does not have the ability to scroll
backwards, -h0 is implied.)
-i The -i option causes searches to ignore case; that is, uppercase
and lowercase are considered identical. Also, text which is
overstruck or underlined can be searched for.
-l The -l option, followed immediately by a filename, will cause
less to copy its input to the named file as it is being viewed.
This applies only when the input file is a pipe, not an ordinary
file. If the file already exists, less will ask for
confirmation before overwriting it.
-L The -L option is like -l, but it will overwrite an existing file
without asking for confirmation.
If no log file has been specified, the -l and -L options can be
used from within less to specify a log file. Without a file
name, they will simply report the name of the log file.
-m Normally, less prompts with a colon. The -m option causes less
to prompt verbosely (like more), with the percent into the file.
-M The -M option causes less to prompt even more verbosely than
more.
-n The -n flag suppresses line numbers. The default (to use line
numbers) may cause less to run more slowly in some cases,
especially with a very large input file. Suppressing line
numbers with the -n flag 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.
-P The -P option provides a way to tailor the three prompt styles
to your own preference. You would normally put this option in
your LESS environment variable, rather than type it in with each
less command. Such an option must either be the last option in
the LESS variable, or be terminated by a dollar sign. -P
followed by a string changes the default (short) prompt to that
string. -Pm changes the medium (-m) prompt to the string, and
-PM changes the long (-M) prompt. Also, -P= changes the message
printed by the = command to the given string. All prompt
strings consist of a sequence of letters and special escape
sequences. See the section on PROMPTS for more details.
-q Normally, if an attempt is made to scroll past the end of the
file or before the beginning of the file, the terminal bell is
rung to indicate this fact. The -q option tells less not to
ring the bell at such times. If the terminal has a "visual
bell", it is used instead.
-Q Even if -q is given, less will ring the bell on certain other
errors, such as typing an invalid character. The -Q option
tells less to be quiet all the time; that is, never ring the
terminal bell. If the terminal has a "visual bell", it is used
instead.
-s The -s option causes consecutive blank lines to be squeezed into
a single blank line. This is useful when viewing nroff output.
-t The -t option, followed immediately by a TAG, will edit the file
containing that tag. For this to work, there must be a file
called "tags" in the current directory, which was previously
built by the ctags (1) command. This option may also be
specified from within less (using the - command) as a way of
examining a new file.
-u If the -u option is given, backspaces are treated as printable
characters; that is, they are sent to the terminal when they
appear in the input.
-U If the -U option is given, backspaces are printed as the two
character sequence "^H".
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 preceeding character.
-w Normally, less uses a tilde character to represent lines past
the end of the file. The -w option causes blank lines to be
used instead.
-x The -xn option sets tab stops every n positions. The default
for n is 8.
-[z] When given a backwards or forwards window command, less will by
default scroll backwards or forwards one screenful of lines.
The -zn option changes the default scrolling window size to n
lines. Note that the "z" is optional for compatibility with
more.
+ If a command line option begins with +, the remainder of that
option is taken to be an initial command to less. For example,
+G tells less to start at the end of the file rather than the
beginning, and +/xyz tells it to start at the first occurence of
"xyz" in the file. As a special case, +<number> acts like
+<number>g; that is, it starts the display at the specified line
number (however, see the caveat under the "g" command above).
If the option starts with ++, the initial command applies to
every file being viewed, not just the first one. The + command
described previously may also be used to set (or change) an
initial command for every file.
KEY BINDINGS
You may define your own less commands by using the program lesskey (1)
to create a file called ".less" in your home directory. This file
specifies a set of command keys and an action associated with each key.
See the lesskey manual page for more details.
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, and a "B" means use the line just after the
bottom line.
%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.
%m Replaced by the total number of input files.
%pX Replaced by the percent into the current input file. The line
used is determined by the X as with the %b option.
%s Replaced by the size of the current input file.
%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.
?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.
?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 of the specified
line is known.
?s True if the size of current input file is known.
?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 preceeding 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) ..?ltline %lt :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) .?ltline %lt .
byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
SEE ALSOlesskey(1)WARNINGS
The = command and prompts (unless changed by -P) report the line number
of the line at the top of the screen, but the byte and percent of the
line at the bottom of the screen.
LESS(1)