





     NAME
          less - opposite of more

     SYNOPSIS

     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



     Page 1                                          (printed 7/19/88)









               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



     Page 2                                          (printed 7/19/88)









               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),



     Page 3                                          (printed 7/19/88)









               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 "-+".



     Page 4                                          (printed 7/19/88)









          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.



     Page 5                                          (printed 7/19/88)









          -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



     Page 6                                          (printed 7/19/88)









               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



     Page 7                                          (printed 7/19/88)









               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



     Page 8                                          (printed 7/19/88)









               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).




     Page 9                                          (printed 7/19/88)









          ?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 ..



     Page 10                                         (printed 7/19/88)









               ?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 ALSO
          lesskey(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.







































     Page 11                                         (printed 7/19/88)



