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LESS !!!LESS NAME SYNOPSIS DESCRIPTION COMMANDS OPTIONS LINE EDITING KEY BINDINGS INPUT PREPROCESSOR NATIONAL CHARACTER SETS PROMPTS SECURITY ENVIRONMENT VARIABLES SEE ALSO WARNINGS COPYRIGHT AUTHOR ---- !!NAME less - opposite of more !!SYNOPSIS __less -? less --help less -V less --version less [[-[[+]aBcCdeEfFgGiIJmMnNqQrRsSuUVwWX] [[-b__ ''space''__] [[-h__ ''lines''__] [[-j__ ''line''__] [[-k__ ''keyfile''__] [[-{oO}__ ''logfile''__] [[-p__ ''pattern''__] [[-P__ ''prompt''__] [[-t__ ''tag''__] [[-T__ ''tagsfile''__] [[-x__ ''tab''__,...] [[-y__ ''lines''__] [[-[[z]__ ''lines''__] [[+[[+]__''cmd''__] [[--] [[__''filename''__]...__ (See the OPTIONS section for alternate option syntax with long option names.) !!DESCRIPTION ''Less'' is a program similar to ''more'' (1), but which allows backward 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 a caret.) Commands are based on both ''more'' and ''vi.'' Commands may be preceded 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 h or H Help: display a summary of these commands. If you forget all the other commands, remember this one. SPACE or ^V or f or ^F 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. z Like SPACE, but if N is specified, it becomes the new window size. ESC-SPACE Like SPACE, but scrolls a full screenful, even if it reaches end-of-file in the process. 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. 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. 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. w Like ESC-v, but if N is specified, it becomes the new window 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. 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. ESC-) or RIGHTARROW Scroll horizontally right N characters, default half the screen width (see the -# option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW commands. While the text is scrolled, it acts as though the -S option (chop lines) were in effect. ESC-( or LEFTARROW Scroll horizontally left N characters, default half the screen width (see the -# option). If a number N is specified, it becomes the default for future RIGHTARROW and LEFTARROW 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. F Scroll forward, and keep trying to read when the end of file is reached. Normally this command would be used when already at the end of the file. It is a way to monitor the tail of a file which is growing while it is being viewed. (The behavior is similar to the g or Go to line N in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.) G or 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. { If a left curly bracket appears in the top line displayed on the screen, the { command will go to the matching right curly bracket. The matching right curly bracket is positioned on the bottom line of the screen. If there is more than one left curly bracket on the top line, a number N may be used to specify the N-th bracket on the line. } If a right curly bracket appears in the bottom line displayed on the screen, the } command will go to the matching left curly bracket. The matching left curly bracket is positioned on the top line of the screen. If there is more than one right curly bracket on the top line, a number N may be used to specify the N-th bracket on the line. ( Like {, but applies to parentheses rather than curly brackets. ) Like }, but applies to parentheses rather than curly brackets. [[ Like {, but applies to square brackets rather than curly brackets. ] Like }, but applies to square brackets rather than curly brackets. ESC-^F Followed by two characters, acts like {, but uses the two characters as open and close brackets, respectively. For example, ESC-^B Followed by two characters, acts like }, but uses the two characters as open and close brackets, respectively. For example, 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 position at which the last ^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 and -j options, which change this). Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern: ^N or ! Search for lines which do NOT match the pattern. ^E or * Search multiple files. That is, if the search reaches the END of the current file without finding a match, the search continues in the next file in the command line list. ^F or @ Begin the search at the first line of the FIRST file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j options. ^K Highlight any text which matches the pattern on the current screen, but don't move to the first match (KEEP current position). ^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison. ?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. Certain characters are special as in the / command: ^N or ! Search for lines which do NOT match the pattern. ^E or * Search multiple files. That is, if the search reaches the beginning of the current file without finding a match, the search continues in the previous file in the command line list. ^F or @ Begin the search at the last line of the last file in the command line list, regardless of what is currently displayed on the screen or the settings of the -a or -j options. ^K As in forward searches. ^R As in forward searches. ESC-/pattern Same as ESC-?pattern Same as n Repeat previous search, for N-th line containing the last pattern. If the previous search was modified by ^N, the search is made for the N-th line NOT containing the pattern. If the previous search was modified by ^E, the search continues in the next (or previous) file if not satisfied in the current file. If the previous search was modified by ^R, the search is done without using regular expressions. There is no effect if the previous search was modified by ^F or ^K. N Repeat previous search, but in the reverse direction. ESC-n Repeat previous search, but crossing file boundaries. The effect is as if the previous search were modified by *. ESC-N Repeat previous search, but in the reverse direction and crossing file boundaries. ESC-u Undo search highlighting. Turn off highlighting of strings matching the current search pattern. If highlighting is already off because of a previous ESC-u command, turn highlighting back on. Any search command will also turn highlighting back on. (Highlighting can also be disabled by toggling the -G option; in that case search commands do not turn highlighting back on.) :e [[filename] Examine a new file. If the filename is missing, the ^X^V or E Same as :e. Warning: some systems use ^V as a special literalization character. On such systems, you may not be able to use ^V. :n Examine the next file (from the list of files given in the command line). If a number N is specified, the N-th next file is examined. :p Examine the previous file in the command line list. If a number N is specified, the N-th previous file is examined. :x Examine the first file in the command line list. If a number N is specified, the N-th file in the list is examined. :d Remove the current file from the list of files. t Go to the next tag, if there were more than one matches for the current tag. See the -t option for more details about tags. T Go to the previous tag, if there were more than one matches for the current tag. = or ^G or :f 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, the number of lines in the file and the percent of the file above the last displayed line. - Followed by one of the command line option letters (see OPTIONS below), this will change the setting of that option and print a message describing the new setting. If a ^P (CONTROL-P) is entered immediately after the dash, the setting of the option is changed but no message is printed. 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. If no new value is entered, a message describing the current setting is printed and nothing is changed. -- Like the - command, but takes a long option name (see OPTIONS below) rather than a single option letter. You must press RETURN after typing the option name. A ^P immediately after the second dash suppresses printing of a message describing the new setting, as in the - command. -+ Followed by one of the command line option letters this will reset the option to its default setting and print a message describing the new setting. (The X'' ''X'' '' --+ Like the -+ command, but takes a long option name rather than a single option letter. -! Followed by one of the command line option letters, this will reset the option to the --! Like the -! command, but takes a long option name rather than a single option letter. _ (Underscore.) Followed by one of the command line option letters, this will print a message describing the current setting of that option. The setting of the option is not changed. __ (Double underscore.) Like the _ (underscore) command, but takes a long option name rather than a single option letter. You must press RETURN after typing the option name. +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 :q or :Q or ZZ Exits ''less.'' The following four 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 VISUAL if defined, or EDITOR if VISUAL is not defined, or defaults to ! 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. A pound sign (#) is replaced by the name of the previously examined file. | s filename Save the input to a file. This only works if the input is a pipe, not an ordinary file. !!OPTIONS Command line options are described below. Most options may be changed while ''less'' is running, via the '' Most options may be given in one of two forms: either a dash followed by a single letter, or two dashes followed by a long option name. A long option name may be abbreviated as long as the abbreviation is unambiguous. For example, --quit-at-eof may be abbreviated --quit, but not --qui, since both --quit-at-eof and --quiet begin with --qui. Some long option names are in uppercase, such as --QUIT-AT-EOF, as distinct from --quit-at-eof. Such option names need only have their first letter capitalized; the remainder of the name may be in either case. For example, --Quit-at-eof is equivalent to --QUIT-AT-EOF. Options are also taken from the environment variable less'' is invoked, you might tell ''csh:'' setenv LESS or if you use ''sh:'' LESS= On MS-DOS, you don't need the quotes, but you should replace any percent signs in the options string by double percent signs. 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 value on the command line by beginning the command line option with For options like -P or -D which take a following string, a dollar sign ($) must be used to signal the end of the string. For example, to set two -D options on MS-DOS, you must have a dollar sign between them, like this: LESS= -? or --help This option displays a summary of the commands accepted by ''less'' (the same as the h command). (Depending on how your shell interprets the question mark, it may be necessary to quote the question mark, thus: '' -a or --search-skip-screen Causes searches to start after the last line displayed on the screen, thus skipping all lines displayed on the screen. By default, searches start at the second line on the screen (or after the last found line; see the -j option). -b''n'' or --buffers=''n'' Specifies the amount of buffer space ''less'' will use for each file, in units of kilobytes (1024 bytes). By default 64K of buffer space is used for each file (unless the file is a pipe; see the -B option). The -b option specifies instead that ''n'' kilobytes of buffer space should be used for each file. If ''n'' is -1, buffer space is unlimited; that is, the entire file is read into memory. -B or --auto-buffers By default, when data is read from a pipe, buffers are allocated automatically as needed. If a large amount of data is read from the pipe, this can cause a large amount of memory to be allocated. The -B option disables this automatic allocation of buffers for pipes, so that only 64K (or the amount of space specified by the -b option) is used for the pipe. Warning: use of -B can result in erroneous display, since only the most recently viewed part of the file is kept in memory; any earlier data is lost. -c or --clear-screen Causes full screen repaints to be painted from the top line down. By default, full screen repaints are done by scrolling from the bottom of the screen. -C or --CLEAR-SCREEN The -C option is like -c, but the screen is cleared before it is repainted. -d or --dumb The -d option suppresses the error message normally displayed if the terminal is dumb; that is, lacks some important capability, such as the ability to clear the screen or scroll backward. The -d option does not otherwise change the behavior of ''less'' on a dumb terminal. -D__x__''color'' or --color=__x__''color'' [[MS-DOS only] Sets the color of the text displayed. __x__ is a single character which selects the type of text whose color is being set: n=normal, s=standout, d=bold, u=underlined, k=blink. ''color'' is a pair of numbers separated by a period. The first number selects the foreground color and the second selects the background color of the text. A single number ''N'' is the same as ''N.0''. -e or --quit-at-eof Causes ''less'' to automatically exit the second time it reaches end-of-file. By default, the only way to exit ''less'' is via the '' -E or --QUIT-AT-EOF Causes ''less'' to automatically exit the first time it reaches end-of-file. -f or --force Forces non-regular files to be opened. (A non-regular file is a directory or a device special file.) Also suppresses the warning message when a binary file is opened. By default, ''less'' will refuse to open non-regular files. -F or --quit-if-one-screen Causes ''less'' to automatically exit if the entire file can be displayed on the first screen. -g or --hilite-search Normally, ''less'' will highlight ALL strings which match the last search command. The -g option changes this behavior to highlight only the particular string which was found by the last search command. This can cause ''less'' to run somewhat faster than the default. -G or --HILITE-SEARCH The -G option suppresses all highlighting of strings found by search commands. -h''n'' or ---max-back-scroll=''n'' Specifies a maximum number of lines to scroll backward. If it is necessary to scroll backward more than ''n'' lines, the screen is repainted in a forward direction instead. (If the terminal does not have the ability to scroll backward, -h0 is implied.) -i or --ignore-case Causes searches to ignore case; that is, uppercase and lowercase are considered identical. This option is ignored if any uppercase letters appear in the search pattern; in other words, if a pattern contains uppercase letters, then that search does not ignore case. -I or --IGNORE-CASE Like -i, but searches ignore case even if the pattern contains uppercase letters. -j''n'' or --jump-target=''n'' Specifies a line on the screen where the -J or --status-column Displays a status column at the left edge of the screen. The status column shows the lines that matched the current search. The status column is also used if the -w or -W option is in effect. -k''filename'' or --lesskey-file=''filename'' Causes ''less'' to open and interpret the named file as a ''lesskey'' (1) file. Multiple -k options may be specified. If the LESSKEY or LESSKEY_SYSTEM environment variable is set, or if a lesskey file is found in a standard place (see KEY BINDINGS), it is also used as a ''lesskey'' file. -m or --long-prompt Causes ''less'' to prompt verbosely (like ''more''), with the percent into the file. By default, ''less'' prompts with a colon. -M or --LONG-PROMPT Causes ''less'' to prompt even more verbosely than ''more.'' -n or --line-numbers 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 option 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 (see also the discussion of LESSEDIT in PROMPTS below). -N or --LINE-NUMBERS Causes a line number to be displayed at the beginning of each line in the display. -o''filename'' or --log-file=''filename'' Causes ''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. -O''filename'' or --LOG-FILE=''filename'' The -O option is like -o, but it will overwrite an existing file without asking for confirmation. If no log file has been specified, the -o and -O 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. The ''less.'' -p''pattern'' or --pattern=''pattern'' The -p option on the command line is equivalent to specifying +/''pattern''; that is, it tells ''less'' to start at the first occurrence of ''pattern'' in the file. -P''prompt'' or --prompt=''prompt'' Provides a way to tailor the three prompt styles to your own preference. This option would normally be put in the LESS environment variable, rather than being typed 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. -Ps followed by a string changes the default (short) prompt to that string. -Pm changes the medium (-m) prompt. -PM changes the long (-M) prompt. -Ph changes the prompt for the help screen. -P= changes the message printed by the = command. -Pw changes the message printed while waiting for data (in the F command). All prompt strings consist of a sequence of letters and special escape sequences. See the section on PROMPTS for more details. -q or --quiet or --silent Causes moderately -Q or --QUIET or --SILENT Causes totally -r or --raw-control-chars Causes less'' cannot keep track of the actual appearance of the screen (since this depends on how the screen responds to each type of control character). Thus, various display problems may result, such as long lines being split in the wrong place. -R or --RAW-CONTROL-CHARS Like -r, but tries to keep track of the screen appearance where possible. This works only if the input consists of normal text and possibly some ANSI ESC [[ ... m where the less'' think that characters other than '' -s or --squeeze-blank-lines Causes consecutive blank lines to be squeezed into a single blank line. This is useful when viewing ''nroff'' output. -S or --chop-long-lines Causes lines longer than the screen width to be chopped rather than folded. That is, the remainder of a long line is simply discarded. The default is to fold long lines; that is, display the remainder on the next line. -t''tag'' or --tag=''tag'' The -t option, followed immediately by a TAG, will edit the file containing that tag. For this to work, tag information must be available; for example, there may be a file in the current directory called ctags'' (1) or an equivalent command. If the environment variable LESSGLOBALTAGS is set, it is taken to be the name of a command compatible with ''global'' (1), and that command is executed to find the tag. (See http://www.gnu.org/software/global/global.html). The -t option may also be specified from within ''less'' (using the - command) as a way of examining a new file. The command ''less.'' -T''tagsfile'' or --tag-file=''tagsfile'' Specifies a tags file to be used instead of -u or --underline-special Causes backspaces and carriage returns to be treated as printable characters; that is, they are sent to the terminal when they appear in the input. -U or --UNDERLINE-SPECIAL Causes backspaces, tabs and carriage returns to be treated as control characters; that is, they are handled as specified by the -r option. By default, 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 preceding character. Carriage returns immediately followed by a newline are deleted. other carriage returns are handled as specified by the -r option. Text which is overstruck or underlined can be searched for if neither -u nor -U is in effect. -V or --version Displays the version number of ''less.'' -w or --hilite-unread Temporarily highlights the first -W or --HILITE-UNREAD Like -w, but temporarily highlights the first new line after any forward movement command larger than one line. -x''n'',... or --tabs=''n'',... Sets tab stops. If only one ''n'' is specified, tab stops are set at multiples of ''n''. If multiple values separated by commas are specified, tab stops are set at those positions, and then continue with the same spacing as the last two. For example, ''-x9,17'' will set tabs at positions 9, 17, 25, 33, etc. The default for ''n'' is 8. -X or --no-init Disables sending the termcap initialization and deinitialization strings to the terminal. This is sometimes desirable if the deinitialization string does something unnecessary, like clearing the screen. --no-keypad Disables sending the keypad initialization and deinitialization strings to the terminal. This is sometimes useful if the keypad strings make the numeric keypad behave in an undesirable manner. -y''n'' or --max-forw-scroll=''n'' Specifies a maximum number of lines to scroll forward. If it is necessary to scroll forward more than ''n'' lines, the screen is repainted instead. The -c or -C option may be used to repaint from the top of the screen if desired. By default, any forward movement causes scrolling. -[[z]''n'' or --window=''n'' Changes the default scrolling window size to ''n'' lines. The default is one screenful. The z and w commands can also be used to change the window size. The ''more.'' If the number ''n'' is negative, it indicates ''n'' lines less than the current screen size. For example, if the screen is 24 lines, ''-z-4'' sets the scrolling window to 20 lines. If the screen is resized to 40 lines, the scrolling window automatically changes to 36 lines. -cc'' or --quotes=''cc'' Changes the filename quoting character. This may be necessary if you are trying to name a file which contains both spaces and quote characters. Followed by a single character, this changes the quote character to that character. Filenames containing a space should then be surrounded by that character rather than by double quotes. Followed by two characters, changes the open quote to the first character, and the close quote to the second character. Filenames containing a space should then be preceded by the open quote character and followed by the close quote character. Note that even after the quote characters are changed, this option remains - -~ or --tilde Normally lines after end of file are displayed as a single tilde (~). This option causes lines after end of file to be displayed as blank lines. -# or --shift Specifies the default number of positions to scroll horizontally in the RIGHTARROW and LEFTARROW commands. If the number specified is zero, it sets the default number of positions to one half of the screen width. -- A command line argument of + 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 occurrence of '' !!LINE EDITING When entering command line at the bottom of the screen (for example, a filename for the :e command, or the pattern for a search command), certain keys can be used to manipulate the command line. Most commands have an alternate form in [[ brackets ] which can be used if a key does not exist on a particular keyboard. (The bracketed forms do not work in the MS-DOS version.) Any of these special keys may be entered literally by preceding it with the LEFTARROW [[ ESC-h ] Move the cursor one space to the left. RIGHTARROW [[ ESC-l ] Move the cursor one space to the right. ^LEFTARROW [[ ESC-b or ESC-LEFTARROW ] (That is, CONTROL and LEFTARROW simultaneously.) Move the cursor one word to the left. ^RIGHTARROW [[ ESC-w or ESC-RIGHTARROW ] (That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right. HOME [[ ESC-0 ] Move the cursor to the beginning of the line. END [[ ESC-$ ] Move the cursor to the end of the line. BACKSPACE Delete the character to the left of the cursor, or cancel the command if the command line is empty. DELETE or [[ ESC-x ] Delete the character under the cursor. ^BACKSPACE [[ ESC-BACKSPACE ] (That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor. ^DELETE [[ ESC-X or ESC-DELETE ] (That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor. UPARROW [[ ESC-k ] Retrieve the previous command line. DOWNARROW [[ ESC-j ] Retrieve the next command line. TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match is entered into the command line. Repeated TABs will cycle thru the other matching filenames. If the completed filename is a directory, a BACKTAB [[ ESC-TAB ] Like, TAB, but cycles in the reverse direction thru the matching filenames. ^L Complete the partial filename to the left of the cursor. If it matches more than one filename, all matches are entered into the command line (if they fit). ^U (Unix and OS/2) or ESC (MS-DOS) Delete the entire command line, or cancel the command if the command line is empty. If you have changed your line-kill character in Unix to something other than ^U, that character is used instead of ^U. !!KEY BINDINGS You may define your own ''less'' commands by using the program ''lesskey'' (1) to create a lesskey file. This file specifies a set of command keys and an action associated with each key. You may also use ''lesskey'' to change the line-editing keys (see LINE EDITING), and to set environment variables. If the environment variable LESSKEY is set, ''less'' uses that as the name of the lesskey file. Otherwise, ''less'' looks in a standard place for the lesskey file: On Unix systems, ''less'' looks for a lesskey file called ''less'' looks for a lesskey file called ''less'' looks for a lesskey file called ''lesskey'' manual page for more details. A system-wide lesskey file may also be set up to provide key bindings. If a key is defined in both a local lesskey file and in the system-wide file, key bindings in the local file take precedence over those in the system-wide file. If the environment variable LESSKEY_SYSTEM is set, ''less'' uses that as the name of the system-wide lesskey file. Otherwise, ''less'' looks in a standard place for the system-wide lesskey file: On Unix systems, the system-wide lesskey file is /usr/local/etc/sysless. (However, if ''less'' was built with a different sysconf directory than /usr/local/etc, that directory is where the sysless file is found.) On MS-DOS and Windows systems, the system-wide lesskey file is c:_sysless. On OS/2 systems, the system-wide lesskey file is c:sysless.ini. !!INPUT PREPROCESSOR You may define an less.'' Before ''less'' opens a file, it first gives your input preprocessor a chance to modify the way the contents of the file are displayed. An input preprocessor is simply an executable program (or shell script), which writes the contents of the file to a different file, called the replacement file. The contents of the replacement file are then displayed in place of the contents of the original file. However, it will appear to the user as if the original file is opened; that is, ''less'' will display the original filename as the name of the current file. An input preprocessor receives one command line argument, the original filename, as entered by the user. It should create the replacement file, and when finished, print the name of the replacement file to its standard output. If the input preprocessor does not output a replacement filename, ''less'' uses the original file, as normal. The input preprocessor is not called when viewing standard input. To set up an input preprocessor, set the LESSOPEN environment variable to a command line which will invoke your input preprocessor. This command line should include one occurrence of the string '' When ''less'' closes a file opened in such a way, it will call another program, called the input postprocessor, which may perform any desired clean-up action (such as deleting the replacement file created by LESSOPEN). This program receives two command line arguments, the original filename as entered by the user, and the name of the replacement file. To set up an input postprocessor, set the LESSCLOSE environment variable to a command line which will invoke your input postprocessor. It may include two occurrences of the string '' For example, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let ''less'' view them directly: lessopen.sh: #! /bin/sh case *.Z) uncompress -c $1 if [[ -s /tmp/less.$$ ]; then echo /tmp/less.$$ else rm -f /tmp/less.$$ fi ;; esac lessclose.sh: #! /bin/sh rm $2 To use these scripts, put them both where they can be executed and set LESSOPEN= It is also possible to set up an input preprocessor to pipe the file data directly to ''less,'' rather than putting the data into a replacement file. This avoids the need to decompress the entire file before starting to view it. An input preprocessor that works this way is called an input pipe. An input pipe, instead of writing the name of a replacement file on its standard output, writes the entire contents of the replacement file on its standard output. If the input pipe does not write any characters on its standard output, then there is no replacement file and ''less'' uses the original file, as normal. To use an input pipe, make the first character in the LESSOPEN environment variable a vertical bar (|) to signify that the input preprocessor is an input pipe. For example, on many Unix systems, this script will work like the previous example scripts: lesspipe.sh: #! /bin/sh case *.Z) uncompress -c $1 2 ;; esac To use this script, put it where it can be executed and set LESSOPEN= !!NATIONAL CHARACTER SETS There are three types of characters in the input file: normal characters can be displayed directly to the screen. control characters should not be displayed directly, but are expected to be found in ordinary text files (such as backspace and tab). binary characters should not be displayed directly and are not expected to be found in text files. A ascii BS, TAB, NL, CR, and formfeed are control characters, all chars with values between 32 and 126 are normal, and all others are binary. iso8859 Selects an ISO 8859 character set. This is the same as ASCII, except characters between 160 and 255 are treated as normal characters. latin1 Same as iso8859. latin9 Same as iso8859. dos Selects a character set appropriate for MS-DOS. ebcdic Selects an EBCDIC character set. IBM-1047 Selects an EBCDIC character set used by OS/390 Unix Services. This is the EBCDIC analogue of latin1. You get similar results by setting either LESSCHARSET=IBM-1047 or LC_CTYPE=en_US in your environment. koi8-r Selects a Russian character set. next Selects a character set appropriate for NeXT computers. utf-8 Selects the UTF-8 encoding of the ISO 10646 character set. In special cases, it may be desired to tailor ''less'' to use a character set other than the ones definable by LESSCHARSET. In this case, the environment variable LESSCHARDEF can be used to define a character set. It should be set to a string where each character in the string represents one character in the character set. The character '' This table shows the value of LESSCHARDEF which is equivalent to each of the possible values for LESSCHARSET: ascii 8bcccbcc18b95.b dos 8bcccbcc12bc5b95.b. ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b 9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b. IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc 191.b iso8859 8bcccbcc18b95.33b. koi8-r 8bcccbcc18b95.b128. latin1 8bcccbcc18b95.33b. next 8bcccbcc18b95.bb125.bb If neither LESSCHARSET nor LESSCHARDEF is set, but the string If that string is not found, but your system supports the ''setlocale'' interface, ''less'' will use setlocale to determine the character set. setlocale is controlled by setting the LANG or LC_CTYPE environment variables. Finally, if the ''setlocale'' interface is also not available, the default character set is latin1. Control and binary characters are displayed in standout (reverse video). Each such character is displayed in caret notation if possible (e.g. ^A for control-A). Caret notation is used only if inverting the 0100 bit results in a normal printable character. Otherwise, the character is displayed as a hex number in angle brackets. This format can be changed by setting the LESSBINFMT environment variable. LESSBINFMT may begin with a !!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: %b''X'' 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 '' %B Replaced by the size of the current input file. %c Replaced by the column number of the text appearing in the first column of the screen. %d''X'' Replaced by the page number of a line in the input file. The line to be used is determined by the ''X'', as with the %b option. %D Replaced by the number of pages in the input file, or equivalently, the page number of the last line in the input file. %E Replaced by the name of the editor (from the VISUAL environment variable, or the EDITOR environment variable if VISUAL is not defined). See the discussion of the LESSEDIT feature below. %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. %l''X'' 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. %L Replaced by the line number of the last line in the input file. %m Replaced by the total number of input files. %p''X'' Replaced by the percent into the current input file, based on byte offsets. The line used is determined by the ''X'' as with the %b option. %P''X'' Replaced by the percent into the current input file, based on line numbers. The line used is determined by the ''X'' as with the %b option. %s Same as %B. %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 ?a True if any characters have been included in the prompt so far. ?b''X'' True if the byte offset of the specified line is known. ?B True if the size of current input file is known. ?c True if the text is horizontally shifted (%c is not zero). ?d''X'' True if the page number 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). ?l''X'' True if the line number of the specified line is known. ?L True if the line number of the last line in the file 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. ?p''X'' True if the percent into the current input file, based on byte offsets, of the specified line is known. ?P''X'' True if the percent into the current input file, based on line numbers, of the specified line is known. ?s Same as ?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 preceding it with a backslash. Some examples: ?f%f:Standard input. This prompt prints the filename, if known; otherwise the string ?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 ?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) ..?ltlines %lt-%lb?L/%L. : 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) .?ltlines %lt-%lb?L/%L. . byte %bB?s/%s. ?e(END) :?pB%pB%..%t The prompt expansion features are also used for another purpose: if an environment variable LESSEDIT is defined, it is used as the command to be executed when the v command is invoked. The LESSEDIT string is expanded in the same way as the prompt strings. The default value for LESSEDIT is: %E ?lm+%lm. %f Note that this expands to the editor name, followed by a + and the line number, followed by the file name. If your editor does not accept the !!SECURITY When the environment variable LESSSECURE is set to 1, ''less'' runs in a '' ! the shell command | the pipe command :e the examine command. v the editing command s -o log files -k use of lesskey files -t use of tags files metacharacters in filenames, such as * filename completion (TAB, ^L) Less can also be compiled to be permanently in !!ENVIRONMENT VARIABLES Environment variables may be specified either in the system environment as usual, or in a ''lesskey'' (1) file. If environment variables are defined in more than one place, variables defined in a local lesskey file take precedence over variables defined in the system environment, which take precedence over variables defined in the system-wide lesskey file. COLUMNS Sets the number of columns on the screen. Takes precedence over the number of columns specified by the TERM variable. (But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD, the window system's idea of the screen size takes precedence over the LINES and COLUMNS environment variables.) EDITOR The name of the editor (used for the v command). HOME Name of the user's home directory (used to find a lesskey file on Unix and OS/2 systems). HOMEDRIVE, HOMEPATH Concatenation of the HOMEDRIVE and HOMEPATH environment variables is the name of the user's home directory if the HOME variable is not set (only in the Windows version). INIT Name of the user's init directory (used to find a lesskey file on OS/2 systems). LANG Language for determining the character set. LC_CTYPE Language for determining the character set. LESS Options which are passed to ''less'' automatically. LESSANSIENDCHARS Characters which are assumed to end an ANSI color escape sequence (default LESSBINFMT Format for displaying non-printable, non-control characters. LESSCHARDEF Defines a character set. LESSCHARSET Selects a predefined character set. LESSCLOSE Command line to invoke the (optional) input-postprocessor. LESSECHO Name of the lessecho program (default LESSEDIT Editor prototype string (used for the v command). See discussion under PROMPTS. LESSGLOBALTAGS Name of the command used by the -t option to find global tags. Normally should be set to global'' (1) command. If not set, global tags are not used. LESSKEY Name of the default lesskey(1) file. LESSKEY_SYSTEM Name of the default system-wide lesskey(1) file. LESSMETACHARS List of characters which are considered LESSMETAESCAPE Prefix which less will add before each metacharacter in a command sent to the shell. If LESSMETAESCAPE is an empty string, commands containing metacharacters will not be passed to the shell. LESSOPEN Command line to invoke the (optional) input-preprocessor. LESSSECURE Runs less in LESSSEPARATOR String to be appended to a directory name in filename completion. LINES Sets the number of lines on the screen. Takes precedence over the number of lines specified by the TERM variable. (But if you have a windowing system which supports TIOCGWINSZ or WIOCGETD, the window system's idea of the screen size takes precedence over the LINES and COLUMNS environment variables.) PATH User's search path (used to find a lesskey file on MS-DOS and OS/2 systems). SHELL The shell used to execute the ! command, as well as to expand filenames. TERM The type of terminal on which ''less'' is being run. VISUAL The name of the editor (used for the v command). !!SEE ALSO lesskey(1) !!WARNINGS The = command and prompts (unless changed by -P) report the line numbers of the lines at the top and bottom of the screen, but the byte and percent of the line after the one at the bottom of the screen. If the :e command is used to name more than one file, and one of the named files has been viewed previously, the new files may be entered into the list in an unexpected order. On certain older terminals (the so-called In certain cases, when search highlighting is enabled and a search pattern begins with a ^, more text than the matching string may be highlighted. (This problem does not occur when less is compiled to use the POSIX regular expression package.) When viewing text containing ANSI color escape sequences using the -R option, searching will not find text containing an embedded escape sequence. Also, search highlighting may change the color of some of the text which follows the highlighted text. On some systems, ''setlocale'' claims that ASCII characters 0 thru 31 are control characters rather than binary characters. This causes ''less'' to treat some binary files as ordinary, non-binary files. To workaround this problem, set the environment variable LESSCHARSET to '' See http://www.greenwoodsoftware.com/less for the latest list of known bugs in this version of less. !!COPYRIGHT Copyright (C) 2001 Mark Nudelman less is part of the GNU project and is free software. You can redistribute it and/or modify it under the terms of either (1) the GNU General Public License as published by the Free Software Foundation; or (2) the Less License. See the file README in the less distribution for more details regarding redistribution. You should have received a copy of the GNU General Public License along with the source for less; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA. You should also have received a copy of the Less License; see the file LICENSE. less is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. !!AUTHOR Mark Nudelman Send bug reports or comments to the above address or to bug-less@gnu.org. For more information, see the less homepage at http://www.greenwoodsoftware.com/less. ----
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