NAME

less − opposite of more

SYNOPSIS

less [-dstwcCeEmMqQuU] [-hN] [-b[fp]N] [-xN] [-[z]N]
     [-P[mM]string] [-[lL]logfile] [+cmd]  [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 terminfo(5), 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. 

HHelp: display a summary of these commands.  If you forget 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.

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 commands.

u or ^U
Scroll backward N lines, default 10. If N is specified, it becomes the new default for subsequent d and u commands.

r or ^R or ^L
Repaint the screen.

RRepaint the screen, discarding any buffered input.  Useful if the file is changing while it is being viewed. 

gGo to line N in the file, default 1 (beginning of file).  (Warning: this may be slow if N is large.) 

GGo 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.) 

pGo 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. 

mFollowed 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. 

/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 −t 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.

nRepeat 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. If the filename is a pound sign (#), the previously examined file is re-examined.

NExamine 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. 

PExamine 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. 

+cmdCauses 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. 

VPrints the version number of less being run. 

qExits less. 

The following two commands may or may not be valid, depending on your particular installation. 

vInvokes an editor to edit the current file being viewed.  The editor is taken from the environment variable EDITOR, or defaults to "emacs". 

! 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.

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 typing "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 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.

-bThe -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 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. 

−cNormally, 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. 

−CThe -C option is like -c, but the screen is cleared before it is repainted. 

−dNormally, 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). 

−eNormally 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. 

−EThe −E flag causes less to exit the first time it reaches end-of-file. 

−hNormally, 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.) 

−lThe −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. 

−LThe −L option is like −l, but it will overwrite an existing file without asking for confirmation. 

−mNormally, less prompts with a colon.  The −m option causes less to prompt verbosely (like more), with the percent into the file. 

−MThe −M option causes less to prompt even more verbosely than more. 

−PThe −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:
Ffile name
ffile name, only once
Ofile n of n
ofile n of n, only once
bbyte offset
ppercent into file
Ppercent 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").

−qNormally, 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. 

−QEven 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. 

−sThe −s option causes consecutive blank lines to be squeezed into a single blank line.  This is useful when viewing nroff output. 

−tNormally, 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. 

−uIf 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. 

−UIf 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.

−wNormally, less uses a tilde character to represent lines past the end of the file.  The −w option causes blank lines to be used instead. 

-xThe -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.  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. 

+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. 
 

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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