LESS(1-SysV) RISC/os Reference Manual LESS(1-SysV)
NAME
less - file browser
SYNOPSIS
less [-cdepstwmMqQuU] [-hN] [-b[fp]N] [-xN] [-[z]N] [-
P[mM]string] [-llogfile]
[+cmd] [filename]...
DESCRIPTION
less is a program similar to more(1). 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, so it can run on a variety of
terminals. There is even limited support for hardcopy ter-
minals. (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 pre-
ceeded 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.
h Help: display a summary of these commands. If you for-
get all the other commands, remember this one.
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.
f or ^F
Same as SPACE.
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.
RETURN
Scroll forward N lines, default 1. The entire N lines
are displayed, even if N is more than the screen size.
e or ^E
Same as RETURN.
j or ^J
Also the same as RETURN.
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y or ^Y
Scroll backward N lines, default 1. The entire N lines
are displayed, even if N is more than the screen size.
k or ^K
Same as y.
d or ^D
Scroll forward N lines, default 10. If N is specified,
it becomes the new default for subsequent d and u com-
mands.
u or ^U
Scroll backward N lines, default 10. If N is speci-
fied, 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 Go to line N in the file, default 1 (beginning of
file). (Warning: this may be slow if N is large.)
G Go to line N in the file, default the end of the file.
(Warning: this may be slow if standard input, rather
than a file, is being read.)
p Go to a position N percent into the file. N should be
between 0 and 100. (This is possible 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.)
% Same as p.
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" move-
ment command was executed. All marks are lost when a
new file is examined.
/pattern
Search forward in the file for the N-th line containing
the pattern. N defaults to 1. The pattern is a
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regular expression, as recognized by ed. The search
starts at the second line displayed (but see the -t
option, which changes this).
?pattern
Search backward in the file for the N-th line contain-
ing the pattern. The search starts at the line immedi-
ately before the top line displayed.
n Repeat previous search, for N-th line containing the
last pattern.
E 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.
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 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 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 toggle the setting of that option and
print a message describing the new setting.
+cmd Causes the specified cmd to be executed each time a new
file is examined. For example, +G causes less to ini-
tially display each file starting at the end rather
than the beginning.
V Prints the version number of less being run.
q Exits less.
The following two commands may or may not be valid, depend-
ing on your particular installation.
v Invokes an editor to edit the current file being
viewed. The editor is taken from the environment vari-
able EDITOR, or defaults to "vi".
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! shell-command
Invokes a shell to run the shell-command given.
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, if you like more-style prompting, to avoid typ-
ing "less -m ..." each time less is invoked, you might tell
csh:
setenv LESS m
or if you use sh:
LESS=m; export LESS
The environment variable is parsed before the command line,
so command line options override the LESS environment vari-
able. A dollar sign ($) may be used to signal the end of an
option string. This is important only for options like -P
which take a following string.
-s The -s option causes consecutive blank lines to be
squeezed into a single blank line. This is useful when
viewing nroff output.
-t Normally, forward searches start just after the top
displayed line (that is, at the second displayed line).
Thus forward searches include the currently displayed
screen. The -t option causes forward searches to start
just after the bottom line displayed, thus skipping the
currently displayed screen.
-m Normally, less prompts with a colon. The -m option
causes less to prompt verbosely (like more), with the
percent into the file.
-M The -M option causes less to prompt even more verbosely
than more.
-P The -P option provides a way to tailor the three prompt
styles to your own preference. You would normally put
this option in your LESS environment variable, rather
than type it in with each less command. Such an option
must either be the last option in the LESS variable, or
be terminated by a dollar sign. -P followed by a
string changes the default (short) prompt to that
string. -Pm changes the medium (-m) prompt to the
string, and -PM changes the long (-M) prompt. The
string consists of a sequence of letters which are
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replaced with certain predefined strings, as follows:
F file name
f file name, only once
O file n of n
o file n of n, only once
b byte offset
p percent into file
P percent if known, else byte offset
Angle brackets, < and >, may be used to surround a
literal string to be included in the prompt. The
defaults are "fo" for the short prompt, "foP" for the
medium prompt, and "Fobp" for the long prompt.
Example: Setting your LESS variable to "PmFOP$PMFObp"
would change the medium and long prompts to always
include the file name and "file n of n" message.
Another example: Setting your LESS variable to "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").
-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.
-e Normally the only way to exit less is via the "q" com-
mand. The -e option tells less to automatically exit
the second time it reaches end-of-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 spe-
cially: the underlined text is displayed using the
terminal's hardware underlining capability. Also,
backspaces which appear between two identical
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characters are treated specially: the overstruck text
is printed using the terminal's hardware boldface capa-
bility. 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.
-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 oth-
erwise change the behavior of the program on a dumb
terminal).
-p Normally, less will repaint the screen by scrolling
from the bottom of the screen. If the -p option is
set, when less needs to change the entire display, it
will clear the screen and paint from the top line down.
-h Normally, less will scroll backwards when backwards
movement is necessary. The -h option specifies a max-
imum 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 back-
wards, -h0 is implied.)
-[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. If n 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 more.
-x The -xn option sets tab stops every n positions. The
default for n is 8.
-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.
-b The -bn option tells 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 n speci-
fies a different number of buffers to use. The -b may
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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.
-c Normally, when data is read by 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 less to skip this checking,
causing an imperceptible speed improvement. (However,
if the data is not "clean", unpredicatable results may
occur.)
+ 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.
ERRORS
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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