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.TH LESS l
.SH NAME
less \- opposite of more
.SH SYNOPSIS
.B "less [-cdepstwmMqQuU] [-h\fIN\fB] [-b[fp]\fIN\fB] [-x\fIN\fB] [-[z]\fIN\fB]"
.br
.B "     [-P[mM]\fIstring\fB] [-l\fIlogfile\fB] [+\fIcmd\fB]  [\fIfilename\fB]..."
.SH DESCRIPTION
.I Less
is a program similar to 
.I more
(1), but which allows backwards movement
in the file as well as forward movement.
Also,
.I 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
.I vi
(1).
.I Less
uses termcap, 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.)
.PP
Commands are based on both
.I more
and
.I vi.
Commands may be preceeded by a decimal number, 
called N in the descriptions below.
The number is used by some commands, as indicated.

.SH COMMANDS
In the following descriptions, ^X means control-X.
.IP h
Help: display a summary of these commands.
If you forget all the other commands, remember this one.
.PP
.IP SPACE
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.
.PP
.IP "f or ^F"
Same as SPACE.
.PP
.IP "b or ^B"
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.
.PP
.IP RETURN
Scroll forward N lines, default 1.
The entire N lines are displayed, even if N is more than the screen size.
.PP
.IP "e or ^E"
Same as RETURN.
.PP
.IP "j or ^J"
Also the same as RETURN.
.PP
.IP "y or ^Y"
Scroll backward N lines, default 1.
The entire N lines are displayed, even if N is more than the screen size.
.IP "k or ^K"
Same as y.
.PP
.IP "d or ^D"
Scroll forward N lines, default 10.
If N is specified, it becomes the new default for 
subsequent d and u commands.
.PP
.IP "u or ^U"
Scroll backward N lines, default 10.
If N is specified, it becomes the new default for 
subsequent d and u commands.
.PP
.IP "r or ^R or ^L"
Repaint the screen.
.PP
.IP R
Repaint the screen, discarding any buffered input.
Useful if the file is changing while it is being viewed.
.PP
.IP g
Go to line N in the file, default 1 (beginning of file).
(Warning: this may be slow if N is large.)
.PP
.IP G
Go to line N in the file, default the end of the file.
(Warning: this may be slow if standard input, 
rather than a file, is being read.)
.PP
.IP p
Go to a position N percent into the file.
N should be between 0 and 100.
(This is possible if standard input is being read,
but only if
.I less
has already read to the end of the file.
It is always fast, but not always useful.)
.PP
.IP %
Same as p.
.PP
.IP m
Followed by any lowercase letter, 
marks the current position with that letter.
.PP
.IP "'"
(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.
.PP
.IP /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
.I ed.
The search starts at the second line displayed
(but see the \-t option, which changes this).
.PP
.IP ?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.
.PP
.IP n
Repeat previous search, for N-th line containing the last pattern.
.PP
.IP 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.
.PP
.IP 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.
.PP
.IP P
Examine the previous file.
If a number N is specified, the N-th previous file is examined.
.PP
.IP "= or ^G"
Prints some information about the file being viewed,
including its name
and the 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.
.PP
.IP \-
Followed by one of the command line option letters (see below),
this will toggle the setting of that option
and print a message describing the new setting.
.PP
.IP +cmd
Causes the specified cmd to be executed each time a new file is examined.
For example, +G causes 
.I less
to initially display each file starting at the end 
rather than the beginning.
.PP
.IP V
Prints the version number of 
.I less 
being run.
.PP
.IP q
Exits
.I less.
.PP
The following 
two 
commands may or may not be valid, depending on your particular installation.
.PP
.IP v
Invokes an editor to edit the current file being viewed.
The editor is taken from the environment variable EDITOR,
or defaults to "vi".
.PP
.IP "! shell-command"
Invokes a shell to run the shell-command given.
.PP
.SH OPTIONS
Command line options are described below.
Most options may be changed while
.I less 
is running, via the "\-" command.
.PP
Options are also taken from the environment variable "LESS".
For example, if you like 
more-style prompting, to avoid typing "less \-m ..." each time 
.I less 
is invoked, you might tell 
.I csh:
.sp
setenv LESS m
.sp
or if you use 
.I sh:
.sp
LESS=m; export LESS
.sp
The environment variable is parsed before the command line,
so command line options override the LESS environment variable.
A dollar sign ($) may be used to signal the end of an option string.
This is important only for options like \-P which take a
following string.
.IP \-s
The \-s option causes
consecutive blank lines to be squeezed into a single blank line.
This is useful when viewing
.I nroff
output.
.IP \-t
Normally, forward searches start just after
the top displayed line (that is, at the second displayed line).
Thus forward searches include the currently displayed screen.
The \-t option causes forward searches to start 
just after the bottom line displayed,
thus skipping the currently displayed screen.
.IP \-m
Normally,
.I less
prompts with a colon.
The \-m option causes 
.I less
to prompt verbosely (like 
.I more),
with the percent into the file.
.IP \-M
The \-M option causes 
.I less
to prompt even more verbosely than 
.I more.
.IP \-P
The \-P option provides a way to tailor the three prompt
styles to your own preference.
You would normally put this option in your LESS environment
variable, rather than type it in with each less command.
Such an option must either be the last option in the LESS variable,
or be terminated by a dollar sign.
\-P followed by a string changes the default (short) prompt to that string.
\-Pm changes the medium (\-m) prompt to the string, and
\-PM changes the long (\-M) prompt.
The string consists of a sequence of letters which are replaced
with certain predefined strings, as follows:
.br
	F	file name
.br
	f	file name, only once
.br
	O	file n of n
.br
	o	file n of n, only once
.br
	b	byte offset
.br
	p	percent into file
.br
	P	percent if known, else byte offset
.br
Angle brackets, < and >, may be used to surround a
literal string to be included in the prompt.
The defaults are "fo" for the short prompt,
"foP" for the medium prompt, and
"Fobp" for the long prompt.
.br
Example: Setting your LESS variable to "PmFOP$PMFObp"
would change the medium and long prompts to always 
include the file name and "file n of n" message.
.br
Another example: Setting your LESS variable to 
.br
"mPm<--Less-->FoPe"
would change the medium prompt to the string "--Less--" followed
by the file name and percent into the file.
It also selects the medium
prompt as the default prompt (because of the first "m").
.IP \-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
.I less
not to ring the bell at such times.
If the terminal has a "visual bell", it is used instead.
.IP \-Q
Even if \-q is given, 
.I less 
will ring the bell on certain other errors,
such as typing an invalid character.
The \-Q option tells
.I 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.
.IP \-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.
.IP \-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.
.IP \-U
If the \-U option is given,
backspaces are printed as the two character sequence "^H".
.sp
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.
.IP \-w
Normally,
.I less
uses a tilde character to represent lines past the end of the file.
The \-w option causes blank lines to be used instead.
.IP \-d
Normally,
.I 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).
.IP \-p
Normally, 
.I less 
will repaint the screen by scrolling from the bottom of the screen.
If the \-p option is set, when
.I less 
needs to change the entire display, it will clear the screen
and paint from the top line down.
.IP \-h
Normally,
.I 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.)
.IP \-[z]
When given a backwards or forwards window command,
.I less
will by
default scroll backwards or forwards one screenful of lines. 
The \-z\fIn\fR option changes the default scrolling window size 
to \fIn\fR lines.
If \fIn\fR is greater than the screen size, 
the scrolling window size will be set to one screenful.  
Note that the "z" is optional for compatibility with
.I more.
.IP -x
The -x\fIn\fR option sets tab stops every \fIn\fR positions.
The default for \fIn\fR is 8.
.IP -l
The -l option, followed immediately by a filename,
will cause 
.I 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.
.IP -b
The -b\fIn\fR option tells
.I less
to use a non-standard buffer size.
There are two standard (default) buffer sizes,
one is used when a file is being read and the other
when a pipe (standard input) is being read.
The current defaults are 5 buffers for files and 12 for pipes.
(Buffers are 1024 bytes.)
The number \fIn\fR specifies a different number of buffers to use.
The -b may be followed by "f", in which case only 
the file default is changed, or by "p" in which case only the 
pipe default is changed.  Otherwise, both are changed.
.IP -c
Normally, when data is read by
.I less,
it is scanned to ensure that bit 7 (the high order bit) is turned off in
each byte read, and to ensure that there are no null (zero) bytes in
the data (null bytes are turned into "@" characters).
If the data is known to be "clean",
the -c option will tell 
.I less
to skip this checking, causing an imperceptible speed improvement.
(However, if the data is not "clean", unpredicatable results may occur.)
.IP +
If a command line option begins with \fB+\fR,
the remainder of that option is taken to be an initial command to
.I less.
For example, +G tells
.I 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 \fB++\fR, 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.

.SH BUGS
When used on standard input (rather than a file), you can move
backwards only a finite amount, corresponding to that portion
of the file which is still buffered.
The -b option may be used to expand the buffer space.
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