LESS(1) General Commands Manual LESS(1) 1mNAME0m less - opposite of more 1mSYNOPSIS0m 1mless -?0m 1mless --help0m 1mless -V0m 1mless --version0m 1mless [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]0m 1m[-b 4m22mspace24m1m] [-h 4m22mlines24m1m] [-j 4m22mline24m1m] [-k 4m22mkeyfile24m1m]0m 1m[-{oO} 4m22mlogfile24m1m] [-p 4m22mpattern24m1m] [-P 4m22mprompt24m1m] [-t 4m22mtag24m1m]0m 1m[-T 4m22mtagsfile24m1m] [-x 4m22mtab24m1m,...] [-y 4m22mlines24m1m] [-[z] 4m22mlines24m1m]0m 1m[-# 4m22mshift24m1m] [+[+]4m22mcmd24m1m] [--] [4m22mfilename24m1m]...0m (See the OPTIONS section for alternate option syntax with long option names.) 1mDESCRIPTION0m 1mLess 22mis a program similar to 1mmore22m(1), but which allows backward move ment in the file as well as forward movement. Also, 1mless 22mdoes not have to read the entire input file before starting, so with large input files it starts up faster than text editors like 1mvi22m(1). 1mLess 22muses 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 1mmore 22mand 1mvi22m. Commands may be preceded by a decimal number, called N in the descriptions below. The number is used by some commands, as indicated. 1mCOMMANDS0m In the following descriptions, ^X means control-X. ESC stands for the ESCAPE key; for example ESC-v means the two character sequence "ES CAPE", then "v". 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 be low). If N is more than the screen size, only the final screen ful 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. ENTER or RETURN or ^N or e or ^E or j or ^J Scroll forward N lines, default 1. The entire N lines are dis played, 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 be low). If N is more than the screen size, only the final screen ful 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 dis played, 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. J Like j, but continues to scroll beyond the end of the file. K or Y Like k, but continues to scroll beyond the beginning of the file. ESC-) or RIGHTARROW Scroll horizontally right N characters, default half the screen width (see the -# option). If a number N is specified, it be comes 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 be comes the default for future RIGHTARROW and LEFTARROW commands. ESC-} or ^RIGHTARROW Scroll horizontally right to show the end of the longest dis played line. ESC-{ or ^LEFTARROW Scroll horizontally left back to the first column. r or ^R or ^L Repaint the screen. R Repaint the screen, discarding any buffered input. That is, reload the current file. 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 "tail -f" command.) To stop waiting for more data, enter the interrupt character (usually ^C). On systems which support 1mpoll22m(2) you can also use ^X or the character spec ified by the --intr option. If the input is a pipe and the --exit-follow-on-close option is in effect, 1mless 22mwill automati cally stop waiting for data when the input side of the pipe is closed. ESC-F Like F, but as soon as a line is found which matches the last search pattern, the terminal bell is rung and forward scrolling stops. g or < or ESC-< Go to line N in the file, default 1 (beginning of file). (Warn ing: 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. (Warn ing: this may be slow if N is large, or if N is not specified and standard input, rather than a file, is being read.) ESC-G Same as G, except if no number N is specified and the input is standard input, goes to the last line which is currently buffered. p or % Go to a position N percent into the file. N should be between 0 and 100, and may contain a decimal point. P Go to the line containing byte offset N in the file. { 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 bottom 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 brack ets. ] Like }, but applies to square brackets rather than curly brack ets. ESC-^F Followed by two characters, acts like {, but uses the two char acters as open and close brackets, respectively. For example, "ESC ^F < >" could be used to go forward to the > which matches the < in the top displayed line. ESC-^B Followed by two characters, acts like }, but uses the two char acters as open and close brackets, respectively. For example, "ESC ^B < >" could be used to go backward to the < which matches the > in the bottom displayed line. m Followed by any lowercase or uppercase letter, marks the first displayed line with that letter. If the status column is en abled via the -J option, the status column shows the marked line. M Acts like m, except the last displayed line is marked rather than the first displayed line. ' (Single quote.) Followed by any lowercase or uppercase letter, returns to the position which was previously marked with that letter. Followed by another single quote, returns to the posi tion at which the last "large" movement command was executed. Followed by a ^ or $, jumps to the beginning or end of the file respectively. Marks are preserved when a new file is examined, so the ' command can be used to switch between input files. ^X^X Same as single quote. ESC-m Followed by any lowercase or uppercase letter, clears the mark identified by that letter. /pattern Search forward in the file for the N-th line containing the pat tern. N defaults to 1. The pattern is a regular expression, as recognized by the regular expression library supplied by your system. By default, searching is case-sensitive (uppercase and lowercase are considered different); the -i option can be used to change this. The search starts at the first 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 cur rent screen, but don't move to the first match (KEEP cur rent position). ^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison. ^S Followed by a digit N between 1 and 5. Only text which has a non-empty match for the N-th parenthesized SUB- PAT TERN will be considered to match the pattern. (Supported only if 1mless 22mis built with one of the regular expression libraries 1mposix22m, 1mpcre22m, or 1mpcre222m.) Multiple ^S modifiers can be specified, to match more than one sub-pattern. ^W WRAP around the current file. That is, if the search reaches the end of the current file without finding a match, the search continues from the first line of the current file up to the line where it started. If the ^W modifier is set, the ^E modifier is ignored. ?pattern Search backward in the file for the N-th line containing the pattern. The search starts at the last line displayed (but see the -a and -j options, which change this). 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 dis played on the screen or the settings of the -a or -j op tions. ^K As in forward searches. ^R As in forward searches. ^S As in forward searches. ^W WRAP around the current file. That is, if the search reaches the beginning of the current file without finding a match, the search continues from the last line of the current file up to the line where it started. ESC-/pattern Same as "/*". ESC-?pattern Same as "?*". n Repeat previous search, for N-th line containing the last pat tern. If the previous search was modified by ^N, the search is made for the N-th line NOT containing the pattern. If the pre vious 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 ef fect is as if the previous search were modified by *. ESC-N Repeat previous search, but in the reverse direction and cross ing 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.) ESC-U Like ESC-u but also clears the saved search pattern. If the status column is enabled via the -J option, this clears all search matches marked in the status column. &pattern Display only lines which match the pattern; lines which do not match the pattern are not displayed. If pattern is empty (if you type & immediately followed by ENTER), any filtering is turned off, and all lines are displayed. While filtering is in effect, an ampersand is displayed at the beginning of the prompt, as a reminder that some lines in the file may be hidden. Multiple & commands may be entered, in which case only lines which match all of the patterns will be displayed. Certain characters are special as in the / command: ^N or ! Display only lines which do NOT match the pattern. ^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison. :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. A percent sign (%) in the filename is replaced by the name of the current file. A pound sign (#) is replaced by the name of the previously examined file. However, two consecutive percent signs are simply re placed with a single percent sign. This allows you to enter a filename that contains a percent sign in the name. Similarly, two consecutive pound signs are replaced with a single pound sign. The filename is inserted into the command line list of files so that it can be seen by subsequent :n and :p commands. If the filename consists of several files, they are all inserted into the list of files and the first one is examined. If the filename contains one or more spaces, the entire filename should be enclosed in double quotes (also see the -" option). ^X^V or E Same as :e. Warning: some systems use ^V as a special literal ization 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 com mand 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 en tered 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 set ting 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 ENTER or 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 re set the option to its default setting and print a message de scribing the new setting. (The "-+4mX24m" command does the same thing as "-+4mX24m" on the command line.) This does not work for string-valued options. --+ 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 "opposite" of its default setting and print a message describing the new setting. This does not work for numeric or string-valued options. --! Like the -! command, but takes a long option name rather than a single option letter. _ (Underscore.) Followed by one of the command line option let ters, 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 ENTER or 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 1mless 22mto initially display each file starting at the end rather than the beginning. V Prints the version number of 1mless 22mbeing run. q or Q or :q or :Q or ZZ Exits 1mless22m. The following six 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 "vi" if nei ther VISUAL nor EDITOR is defined. See also the discussion of LESSEDIT under the section on PROMPTS below. ! 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 exam ined file. "!!" repeats the last shell command. "!" with no shell command simply invokes a shell. On Unix systems, the shell is taken from the environment variable SHELL, or defaults to "sh". On MS-DOS and OS/2 systems, the shell is the normal command processor. # shell-command Similar to the "!" command, except that the command is expanded in the same way as prompt strings. For example, the name of the current file would be given as "%f". | <m> shell-command <m> represents any mark letter. Pipes a section of the input file to the given shell command. The section of the file to be piped is between the position marked by the letter and the cur rent screen. The entire current screen is included, regardless of whether the marked position is before or after the current screen. <m> may also be ^ or $ to indicate beginning or end of file respectively. If <m> is . or newline, the current screen is piped. s filename Save the input to a file. This works only if the input is a pipe, not an ordinary file. ^X When the "Waiting for data" message is displayed, such as while in the F command, pressing ^X will stop 1mless 22mfrom waiting and return to a prompt. This may cause 1mless 22mto think that the file ends at the current position, so it may be necessary to use the R or F command to see more data. The --intr option can be used to specify a different character to use instead of ^X. This command works only on systems that support the 1mpoll22m(2) function. On systems without 1mpoll22m(2), the interrupt character (usually ^C) can be used instead. 1mOPTIONS0m Command line options are described below. Most options may be changed while 1mless 22mis running, via the "-" command. Some 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 un ambiguous. 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 let ter 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". For exam ple, to avoid typing "less -options ..." each time 1mless 22mis invoked, you might tell 1mcsh22m: setenv LESS "-options" or if you use 1msh22m: LESS="-options"; export LESS On MS-DOS, you don't need the quotes, but you should replace any per cent 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 ap pears in the LESS variable, it can be reset to its default value on the command line by beginning the command line option with "-+". Some options like -k or -D require a string to follow the option let ter. The string for that option is considered to end when a dollar sign ($) is found. For example, you can set two -D options like this: LESS="Dn9.1$Ds4.1" If the --use-backslash option appears earlier in the options, then a dollar sign or backslash may be included literally in an option string by preceding it with a backslash. If the --use-backslash option is not in effect, then backslashes are not treated specially, and there is no way to include a dollar sign in the option string. -? or --help This option displays a summary of the commands accepted by 1mless0m (the same as the h command). (Depending on how your shell in terprets the question mark, it may be necessary to quote the question mark, thus: "-?".) -a or --search-skip-screen By default, forward searches start at the top of the displayed screen and backwards searches start at the bottom of the dis played screen (except for repeated searches invoked by the n or N commands, which start after or before the "target" line re spectively; see the -j option for more about the target line). The -a option causes forward searches to instead start at the bottom of the screen and backward searches to start at the top of the screen, thus skipping all lines displayed on the screen. -A or --SEARCH-SKIP-SCREEN Causes all forward searches (not just non-repeated searches) to start just after the target line, and all backward searches to start just before the target line. Thus, forward searches will skip part of the displayed screen (from the first line up to and including the target line). Similarly backwards searches will skip the displayed screen from the last line up to and including the target line. This was the default behavior in less versions prior to 441. -b4mn24m or --buffers=4mn0m Specifies the amount of buffer space 1mless 22mwill use for each file, in units of kilobytes (1024 bytes). By default 64 KB of buffer space is used for each file (unless the file is a pipe; see the -B option). The -b option specifies instead that 4mn0m kilobytes of buffer space should be used for each file. If 4mn24m is -1, buffer space is unlimited; that is, the entire file can be 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 allo cated. The -B option disables this automatic allocation of buf fers for pipes, so that only 64 KB (or the amount of space spec ified 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 piped data is kept in memory; any earlier data is lost. Lost characters are displayed as question marks. -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 Same as -c, for compatibility with older versions of 1mless22m. -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 1mless 22mon a dumb terminal. -D1mx4m22mcolor24m or --color=1mx4m22mcolor0m Changes the color of different parts of the displayed text. 1mx0m is a single character which selects the type of text whose color is being set: B Binary characters. C Control characters. E Errors and informational messages. H Header lines and columns, set via the --header option. M Mark letters in the status column. N Line numbers enabled via the -N option. P Prompts. R The rscroll character. S Search results. 1-5 The text in a search result which matches the first through fifth parenthesized sub-pattern. Sub- pattern coloring works only if 1mless 22mis built with one of the reg ular expression libraries 1mposix22m, 1mpcre22m, or 1mpcre222m. W The highlight enabled via the -w option. d Bold text. k Blinking text. s Standout text. u Underlined text. The uppercase letters and digits can be used only when the --use-color option is enabled. When text color is specified by both an uppercase letter and a lowercase letter, the uppercase letter takes precedence. For example, error messages are nor mally displayed as standout text. So if both "s" and "E" are given a color, the "E" color applies to error messages, and the "s" color applies to other standout text. The "d" and "u" let ters refer to bold and underline text formed by overstriking with backspaces (see the -U option), not to text using ANSI es cape sequences with the -R option. A lowercase letter may be followed by a + to indicate that the normal format change and the specified color should both be used. For example, -Dug displays underlined text as green with out underlining; the green color has replaced the usual under line formatting. But -Du+g displays underlined text as both green and in underlined format. 4mcolor24m is either a 4-bit color string or an 8-bit color string: A 4-bit color string is zero, one or two characters, where the first character specifies the foreground color and the second specifies the background color as follows: b Blue c Cyan g Green k Black m Magenta r Red w White y Yellow The corresponding uppercase letter denotes a brighter shade of the color. For example, -DNGk displays line numbers as bright green text on a black background, and -DEbR displays error mes sages as blue text on a bright red background. If either char acter is a "-" or is omitted, the corresponding color is set to that of normal text. An 8-bit color string is one or two decimal integers separated by a dot, where the first integer specifies the foreground color and the second specifies the background color. Each integer is a value between 0 and 255 inclusive which selects a "CSI 38;5" color value (see https://en.wikipedia.org/wiki/ANSI_escape_code#SGR) If either integer is a "-" or is omitted, the corresponding color is set to that of normal text. On MS-DOS versions of 1mless22m, 8-bit color is not supported; instead, decimal values are interpreted as 4-bit CHAR_INFO.Attributes values (see https://docs.microsoft.com/en-us/windows/console/char-info- str). On MS-DOS only, the -Da option may be used to specify strict parsing of ANSI color (SGR) sequences when the -R option is used. Without this option, sequences that change text at tributes (bold, underline, etc.) may clear the text color. -e or --quit-at-eof Causes 1mless 22mto automatically exit the second time it reaches end-of-file. By default, the only way to exit 1mless 22mis via the "q" command. -E or --QUIT-AT-EOF Causes 1mless 22mto 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 warn ing message when a binary file is opened. By default, 1mless 22mwill refuse to open non-regular files. Note that some operating sys tems will not allow directories to be read, even if -f is set. -F or --quit-if-one-screen Causes 1mless 22mto automatically exit if the entire file can be dis played on the first screen. -g or --hilite-search Normally, 1mless 22mwill highlight ALL strings which match the last search command. The -g option changes this behavior to high light only the particular string which was found by the last search command. This can cause 1mless 22mto run somewhat faster than the default. -G or --HILITE-SEARCH The -G option suppresses all highlighting of strings found by search commands. -h4mn24m or --max-back-scroll=4mn0m Specifies a maximum number of lines to scroll backward. If it is necessary to scroll backward more than 4mn24m 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 upper case 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. -j4mn24m or --jump-target=4mn0m Specifies a line on the screen where the "target" line is to be positioned. The target line is the line specified by any com mand to search for a pattern, jump to a line number, jump to a file percentage or jump to a tag. The screen line may be speci fied by a number: the top line on the screen is 1, the next is 2, and so on. The number may be negative to specify a line rel ative to the bottom of the screen: the bottom line on the screen is -1, the second to the bottom is -2, and so on. Alternately, the screen line may be specified as a fraction of the height of the screen, starting with a decimal point: .5 is in the middle of the screen, .3 is three tenths down from the first line, and so on. If the line is specified as a fraction, the actual line number is recalculated if the terminal window is resized. If any form of the -j option is used, repeated forward searches (invoked with "n" or "N") begin at the line immediately after the target line, and repeated backward searches begin at the target line, unless changed by -a or -A. For example, if "-j4" is used, the target line is the fourth line on the screen, so forward searches begin at the fifth line on the screen. However nonrepeated searches (invoked with "/" or "?") always begin at the start or end of the current screen respectively. -J or --status-column Displays a status column at the left edge of the screen. The character displayed in the status column may be one of: > The line is chopped with the -S option, and the text that is chopped off beyond the right edge of the screen con tains a match for the current search. < The line is horizontally shifted, and the text that is shifted beyond the left side of the screen contains a match for the current search. = The line is both chopped and shifted, and there are matches beyond both sides of the screen. * There are matches in the visible part of the line but none to the right or left of it. a-z, A-Z The line has been marked with the corresponding letter via the m command. -k4mfilename24m or --lesskey-file=4mfilename0m Causes 1mless 22mto open and interpret the named file as a 1mlesskey22m(1) binary 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 1mlesskey 22mfile. --lesskey-src=4mfilename0m Causes 1mless 22mto open and interpret the named file as a 1mlesskey22m(1) source file. If the LESSKEYIN or LESSKEYIN_SYSTEM environment variable is set, or if a lesskey source file is found in a stan dard place (see KEY BINDINGS), it is also used as a 4mlesskey0m 4msource24m file. Prior to version 582, the 1mlesskey 22mprogram needed to be run to convert a 4mlesskey24m 4msource24m file to a 4mlesskey24m 4mbinary0m file for 1mless 22mto use. Newer versions of 1mless 22mread the 4mlesskey0m 4msource24m file directly and ignore the binary file if the source file exists. -K or --quit-on-intr Causes 1mless 22mto exit immediately (with status 2) when an inter rupt character (usually ^C) is typed. Normally, an interrupt character causes 1mless 22mto stop whatever it is doing and return to its command prompt. Note that use of this option makes it im possible to return to the command prompt from the "F" command. -L or --no-lessopen Ignore the LESSOPEN environment variable (see the INPUT PRE PROCESSOR section below). This option can be set from within 1mless22m, but it will apply only to files opened subsequently, not to the file which is currently open. -m or --long-prompt Causes 1mless 22mto prompt verbosely (like 1mmore22m(1)), with the percent into the file. By default, 1mless 22mprompts with a colon. -M or --LONG-PROMPT Causes 1mless 22mto prompt even more verbosely than 1mmore22m(1). -n or --line-numbers Suppresses line numbers. The default (to use line numbers) may cause 1mless 22mto run more slowly in some cases, especially with a very large input file. Suppressing line numbers with the -n op tion 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 be low). -N or --LINE-NUMBERS Causes a line number to be displayed at the beginning of each line in the display. -o4mfilename24m or --log-file=4mfilename0m Causes 1mless 22mto 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, 1mless 22mwill ask for confirmation before overwriting it. -O4mfilename24m or --LOG-FILE=4mfilename0m 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 1mless 22mto specify a log file. Without a file name, they will simply report the name of the log file. The "s" command is equivalent to specifying -o from within 1mless22m. -p4mpattern24m or --pattern=4mpattern0m The -p option on the command line is equivalent to specifying +/4mpattern24m; that is, it tells 1mless 22mto start at the first occur rence of 4mpattern24m in the file. -P4mprompt24m or --prompt=4mprompt0m Provides a way to tailor the three prompt styles to your own preference. This option would normally be put in the LESS envi ronment variable, rather than being typed in with each 1mless 22mcom mand. 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 "quiet" operation: the terminal bell is not rung if an attempt is made to scroll past the end of the file or before the beginning of the file. If the terminal has a "visual bell", it is used instead. The bell will be rung on certain other errors, such as typing an invalid character. The default is to ring the terminal bell in all such cases. -Q or --QUIET or --SILENT Causes totally "quiet" operation: the terminal bell is never rung. If the terminal has a "visual bell", it is used in all cases where the terminal bell would have been rung. -r or --raw-control-chars Causes "raw" control characters to be displayed. The default is to display control characters using the caret notation; for ex ample, a control-A (octal 001) is displayed as "^A" (with some exceptions as described under the -U option). Warning: when the -r option is used, 1mless 22mcannot keep track of the actual appear ance of the screen (since this depends on how the screen re sponds to each type of control character). Thus, various dis play problems may result, such as long lines being split in the wrong place. USE OF THE -r OPTION IS NOT RECOMMENDED. -R or --RAW-CONTROL-CHARS Like -r, but only ANSI "color" escape sequences and OSC 8 hyper link sequences are output in "raw" form. Unlike -r, the screen appearance is maintained correctly, provided that there are no escape sequences in the file other than these types of escape sequences. Color escape sequences are only supported when the color is changed within one line, not across lines. In other words, the beginning of each line is assumed to be normal (non- colored), regardless of any escape sequences in previous lines. For the purpose of keeping track of screen appearance, these es cape sequences are assumed to not move the cursor. OSC 8 hyperlinks are sequences of the form: ESC ] 8 ; ... 7 The terminating sequence may be either a BEL character (7) or the two-character sequence "ESC ANSI color escape sequences are sequences of the form: ESC [ ... m where the "..." is zero or more color specification characters. You can make 1mless 22mthink that characters other than "m" can end ANSI color escape sequences by setting the environment variable LESSANSIENDCHARS to the list of characters which can end a color escape sequence. And you can make 1mless 22mthink that characters other than the standard ones may appear between the ESC and the m by setting the environment variable LESSANSIMIDCHARS to the list of characters which can appear. -s or --squeeze-blank-lines Causes consecutive blank lines to be squeezed into a single blank line. This is useful when viewing 1mnroff 22moutput. -S or --chop-long-lines Causes lines longer than the screen width to be chopped (trun cated) rather than wrapped. That is, the portion of a long line that does not fit in the screen width is not displayed until you press RIGHT-ARROW. The default is to wrap long lines; that is, display the remainder on the next line. See also the -- wordwrap option. -t4mtag24m or --tag=4mtag0m 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 di rectory called "tags", which was previously built by 1mctags22m(1) or an equivalent command. If the environment variable LESSGLOBALT AGS is set, it is taken to be the name of a command compatible with 1mglobal22m(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 1mless 22m(using the - com mand) as a way of examining a new file. The command ":t" is equivalent to specifying -t from within 1mless22m. -T4mtagsfile24m or --tag-file=4mtagsfile0m Specifies a tags file to be used instead of "tags". -u or --underline-special Causes backspaces and carriage returns to be treated as print able characters; that is, they are sent to the terminal when they appear in the input. -U or --UNDERLINE-SPECIAL Causes backspaces, tabs, carriage returns and "formatting char acters" (as defined by Unicode) to be treated as control charac ters; that is, they are handled as specified by the -r option. By default, if neither -u nor -U is given, backspaces which ap pear 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 capabili ty. 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. Unicode formatting characters, such as the Byte Order Mark, are sent to the terminal. Text which is overstruck or underlined can be searched for if neither -u nor -U is in ef fect. See also the --proc-backspace, --proc-tab, and --proc-return op tions. -V or --version Displays the version number of 1mless22m. -w or --hilite-unread Temporarily highlights the first "new" line after a forward movement of a full page. The first "new" line is the line imme diately following the line previously at the bottom of the screen. Also highlights the target line after a g or p command. The highlight is removed at the next command which causes move ment. If the --status-line option is in effect, the entire line (the width of the screen) is highlighted. Otherwise, only the text in the line is highlighted, unless the -J option is in ef fect, in which case only the status column is highlighted. -W or --HILITE-UNREAD Like -w, but temporarily highlights the first new line after any forward movement command larger than one line. -x4mn24m,... or --tabs=4mn24m,... Sets tab stops. If only one 4mn24m is specified, tab stops are set at multiples of 4mn24m. If multiple values separated by commas are specified, tab stops are set at those positions, and then con tinue with the same spacing as the last two. For example, "-x9,17" will set tabs at positions 9, 17, 25, 33, etc. The de fault for 4mn24m 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 clear ing the screen. -y4mn24m or --max-forw-scroll=4mn0m Specifies a maximum number of lines to scroll forward. If it is necessary to scroll forward more than 4mn24m lines, the screen is re painted 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. -z4mn24m or --window=4mn24m or -4mn0m Changes the default scrolling window size to 4mn24m lines. The de fault is one screenful. The z and w commands can also be used to change the window size. The "z" may be omitted for compati bility with some versions of 1mmore22m(1). If the number 4mn24m is nega tive, it indicates 4mn24m lines less than the current screen size. For example, if the screen is 24 lines, 4m-z-424m sets the scrolling window to 20 lines. If the screen is resized to 40 lines, the scrolling window automatically changes to 36 lines. -"4mcc24m or --quotes=4mcc0m 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 -" (a dash followed by a double quote). -~ 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 speci fied is zero, it sets the default number of positions to one half of the screen width. Alternately, the number may be speci fied as a fraction of the width of the screen, starting with a decimal point: .5 is half of the screen width, .3 is three tenths of the screen width, and so on. If the number is speci fied as a fraction, the actual number of scroll positions is re calculated if the terminal window is resized. --exit-follow-on-close When using the "F" command on a pipe, 1mless 22mwill automatically stop waiting for more data when the input side of the pipe is closed. --file-size If --file-size is specified, 1mless 22mwill determine the size of the file immediately after opening the file. Then the "=" command will display the number of lines in the file. Normally this is not done, because it can be slow if the input file is non- seek able (such as a pipe) and is large. --follow-name Normally, if the input file is renamed while an F command is ex ecuting, 1mless 22mwill continue to display the contents of the orig inal file despite its name change. If --follow-name is speci fied, during an F command 1mless 22mwill periodically attempt to re open the file by name. If the reopen succeeds and the file is a different file from the original (which means that a new file has been created with the same name as the original (now re named) file), 1mless 22mwill display the contents of that new file. --header=4mN[,M]0m Sets the number of header lines and columns displayed on the screen. The value may be of the form "N,M" where N and M are integers, to set the header lines to N and the header columns to M, or it may be a single integer "N" which sets the header lines to N and the header columns to zero, or it may be ",M" which sets the header columns to M and the header lines to zero. When N is nonzero, the first N lines at the top of the screen are re placed with the first N lines of the file, regardless of what part of the file are being viewed. When M is nonzero, the char acters displayed at the beginning of each line are replaced with the first M characters of the line, even if the rest of the line is scrolled horizontally. If either N or M is zero, 1mless 22mstops displaying header lines or columns, respectively. (Note that it may be necessary to change the setting of the -j option to en sure that the target line is not obscured by the header line(s).) --incsearch Subsequent search commands will be "incremental"; that is, 1mless0m will advance to the next line containing the search pattern as each character of the pattern is typed in. --intr=4mc0m Use the character 4mc24m instead of ^X to interrupt a read when the "Waiting for data" message is displayed. 4mc24m must be an ASCII character; that is, one with a value between 1 and 127 inclu sive. A caret followed by a single character can be used to specify a control character. --line-num-width=4mn0m Sets the minimum width of the line number field when the -N op tion is in effect to 4mn24m characters. The default is 7. --modelines=4mn0m Before displaying a file, 1mless 22mwill read the first 4mn24m lines to try to find a vim-compatible 4mmodeline24m. If 4mn24m is zero, 1mless 22mdoes not try to find modelines. By using a modeline, the file itself can specify the tab stops that should be used when viewing it. A modeline contains, anywhere in the line, a program name ("vi", "vim", "ex", or "less"), followed by a colon, possibly followed by the word "set", and finally followed by zero or more option settings. If the word "set" is used, option settings are sepa rated by spaces, and end at the first colon. If the word "set" is not used, option settings may be separated by either spaces or colons. The word "set" is required if the program name is "less" but optional if any of the other three names are used. If any option setting is of the form "tabstop=4mn24m" or "ts=4mn24m", then tab stops are automatically set as if --tabs=4mn24m had been given. See the --tabs description for acceptable values of 4mn24m. --mouse Enables mouse input: scrolling the mouse wheel down moves for ward in the file, scrolling the mouse wheel up moves backwards in the file, and clicking the mouse sets the "#" mark to the line where the mouse is clicked. The number of lines to scroll when the wheel is moved can be set by the --wheel-lines option. Mouse input works only on terminals which support X11 mouse re porting, and on the Windows version of 1mless22m. --MOUSE Like --mouse, except the direction scrolled on mouse wheel move ment is reversed. --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. --no-histdups This option changes the behavior so that if a search string or file name is typed in, and the same string is already in the history list, the existing copy is removed from the history list before the new one is added. Thus, a given string will appear only once in the history list. Normally, a string may appear multiple times. --no-number-headers Header lines (defined via the --header option) are not assigned line numbers. Line number 1 is assigned to the first line after any header lines. --no-search-headers Searches do not include header lines or header columns. --no-vbell Disables the terminal's visual bell. --proc-backspace If set, backspaces are handled as if neither the -u option nor the -U option were set. That is, a backspace adjacent to an un derscore causes text to be displayed in underline mode, and a backspace between identical characters cause text to be dis played in boldface mode. This option overrides the -u and -U options, so that display of backspaces can be controlled sepa rate from tabs and carriage returns. If not set, backspace dis play is controlled by the -u and -U options. --PROC-BACKSPACE If set, backspaces are handled as if the -U option were set; that is backspaces are treated as control characters. --proc-return If set, carriage returns are handled as if neither the -u option nor the -U option were set. That is, a carriage return immedi ately before a newline is deleted. This option overrides the -u and -U options, so that display of carriage returns can be con trolled separate from that of backspaces and tabs. If not set, carriage return display is controlled by the -u and -U options. --PROC-RETURN If set, carriage returns are handled as if the -U option were set; that is carriage returns are treated as control characters. --proc-tab If set, tabs are handled as if the -U option were not set. That is, tabs are expanded to spaces. This option overrides the -U option, so that display of tabs can be controlled separate from that of backspaces and carriage returns. If not set, tab dis play is controlled by the -U options. --PROC-TAB If set, tabs are handled as if the -U option were set; that is tabs are treated as control characters. --redraw-on-quit When quitting, after sending the terminal deinitialization string, redraws the entire last screen. On terminals whose ter minal deinitialization string causes the terminal to switch from an alternate screen, this makes the last screenful of the cur rent file remain visible after 1mless 22mhas quit. --rscroll=4mc0m This option changes the character used to mark truncated lines. It may begin with a two-character attribute indicator like LESS BINFMT does. If there is no attribute indicator, standout is used. If set to "-", truncated lines are not marked. --save-marks Save marks in the history file, so marks are retained across different invocations of 1mless22m. --search-options=4m...0m Sets default search modifiers. The value is a string of one or more of the characters E, F, K, N, R or W. Setting any of these has the same effect as typing that control character at the be ginning of every search pattern. For example, setting -- search- options=W is the same as typing ^W at the beginning of every pattern. The value may also contain a digit between 1 and 5, which has the same effect as typing ^S followed by that digit at the beginning of every search pattern. The value "-" disables all default search modifiers. --show-preproc-errors If a preprocessor produces data, then exits with a non-zero exit code, 1mless 22mwill display a warning. --status-col-width=4mn0m Sets the width of the status column when the -J option is in ef fect. The default is 2 characters. --status-line If a line is marked, the entire line (rather than just the sta tus column) is highlighted. Also lines highlighted due to the -w option will have the entire line highlighted. If --use- color is set, the line is colored rather than highlighted. --use-backslash This option changes the interpretations of options which follow this one. After the --use-backslash option, any backslash in an option string is removed and the following character is taken literally. This allows a dollar sign to be included in option strings. --use-color Enables colored text in various places. The -D option can be used to change the colors. Colored text works only if the ter minal supports ANSI color escape sequences (as defined in EC MA-48 SGR; see https://www.ecma-international.org/publications-and- standards/standards/ecma-48). --wheel-lines=4mn0m Set the number of lines to scroll when the mouse wheel is scrolled and the --mouse or --MOUSE option is in effect. The default is 1 line. --wordwrap When the -S option is not in use, wrap each line at a space or tab if possible, so that a word is not split between two lines. The default is to wrap at any character. -- A command line argument of "--" marks the end of option argu ments. Any arguments following this are interpreted as file names. This can be useful when viewing a file whose name begins with a "-" or "+". + If a command line option begins with 1m+22m, the remainder of that option is taken to be an initial command to 1mless22m. For example, +G tells 1mless 22mto start at the end of the file rather than the beginning, and +/xyz tells it to start at the first occurrence 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 ev ery file being viewed, not just the first one. The + command described previously may also be used to set (or change) an ini tial command for every file. 1mLINE EDITING0m When entering a 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. (Note that the forms beginning with ESC do not work in some MS-DOS and Windows systems because ESC is the line erase character.) Any of these special keys may be entered literally by preceding it with the "literal" character, either ^V or ^A. A backslash itself may also be entered literally by entering two backslashes. 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 cur sor one word to the left. ^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ] (That is, CONTROL and RIGHTARROW simultaneously.) Move the cur sor 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. If you first enter some text and then press UPARROW, it will retrieve the previous com mand which begins with that text. DOWNARROW [ ESC-j ] Retrieve the next command line. If you first enter some text and then press DOWNARROW, it will retrieve the next command which begins with that text. 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 "/" is appended to the filename. (On MS-DOS systems, a " appended.) The environment variable LESSSEPARATOR can be used to specify a different character to append to a directory name. 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 char acter in Unix to something other than ^U, that character is used instead of ^U. ^G Delete the entire command line and return to the main prompt. 1mKEY BINDINGS0m You may define your own 1mless 22mcommands by creating a lesskey source file. This file specifies a set of command keys and an action associ ated with each key. You may also change the line-editing keys (see LINE EDITING), and set environment variables used by 1mless22m. See the 1mlesskey22m(1) manual page for details about the file format. If the environment variable LESSKEYIN is set, 1mless 22muses that as the name of the lesskey source file. Otherwise, 1mless 22mlooks in a standard place for the lesskey source file: On Unix systems, 1mless 22mlooks for a lesskey file called "$XDG_CONFIG_HOME/lesskey" or "$HOME/.con fig/lesskey" or "$HOME/.lesskey". On MS-DOS and Windows systems, 1mless0m looks for a lesskey file called "$HOME/_lesskey", and if it is not found there, then looks for a lesskey file called "_lesskey" in any di rectory specified in the PATH environment variable. On OS/2 systems, 1mless 22mlooks for a lesskey file called "$HOME/lesskey.ini", and if it is not found, then looks for a lesskey file called "lesskey.ini" in any directory specified in the INIT environment variable, and if it not found there, then looks for a lesskey file called "lesskey.ini" in any directory specified in the PATH environment variable. A system-wide lesskey source 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 LESSKEYIN_SYSTEM is set, 1mless 22muses that as the name of the system-wide lesskey file. Otherwise, 1mless 22mlooks in a standard place for the sys tem-wide lesskey file: On Unix systems, the system-wide lesskey file is /usr/local/etc/syslesskey. (However, if 1mless 22mwas built with a differ ent 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:_syslesskey. On OS/2 systems, the system- wide lesskey file is c:slesskey.ini. Previous versions of 1mless 22m(before v582) used lesskey files with a bina ry format, produced by the 1mlesskey 22mprogram. It is no longer necessary to use the 1mlesskey 22mprogram. 1mINPUT PREPROCESSOR0m You may define an "input preprocessor" for 1mless22m. Before 1mless 22mopens 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 sim ply an executable program (or shell script), which writes the contents of the file to a different file, called the replacement file. The con tents of the replacement file are then displayed in place of the con tents of the original file. However, it will appear to the user as if the original file is opened; that is, 1mless 22mwill 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 replace ment filename, 1mless 22muses the original file, as normal. The input pre processor is not called when viewing standard input. To set up an in put 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 "%s", which will be re placed by the filename when the input preprocessor command is invoked. When 1mless 22mcloses a file opened in such a way, it will call another pro gram, 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 orig inal 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 "%s"; the first is re placed with the original name of the file and the second with the name of the replacement file, which was output by LESSOPEN. For example, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let 1mless 22mview them directly: lessopen.sh: #! /bin/sh case "$1" in *.Z) TEMPFILE=$(mktemp) uncompress -c $1 >$TEMPFILE 2>/dev/null if [ -s $TEMPFILE ]; then echo $TEMPFILE else rm -f $TEMPFILE fi ;; esac lessclose.sh: #! /bin/sh rm $2 To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files, and so on. It is also possible to set up an input preprocessor to pipe the file data directly to 1mless22m, rather than putting the data into a replacement file. This avoids the need to decompress the entire file before start ing 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 replace ment file on its standard output, writes the entire contents of the re placement file on its standard output. If the input pipe does not write any characters on its standard output, then there is no replace ment file and 1mless 22muses 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. As with non-pipe input preprocessors, the command string must contain one occurrence of %s, which is replaced with the filename of the input file. For example, on many Unix systems, this script will work like the pre vious example scripts: lesspipe.sh: #! /bin/sh case "$1" in *.Z) uncompress -c $1 2>/dev/null ;; *) exit 1 ;; esac exit $? To use this script, put it where it can be executed and set LESSOPEN="|lesspipe.sh %s". Note that a preprocessor cannot output an empty file, since that is in terpreted as meaning there is no replacement, and the original file is used. To avoid this, if LESSOPEN starts with two vertical bars, the exit status of the script determines the behavior when the output is empty. If the output is empty and the exit status is zero, the empty output is considered to be replacement text. If the output is empty and the exit status is nonzero, the original file is used. For compat ibility with previous versions of 1mless22m, if LESSOPEN starts with only one vertical bar, the exit status of the preprocessor is ignored. When an input pipe is used, a LESSCLOSE postprocessor can be used, but it is usually not necessary since there is no replacement file to clean up. In this case, the replacement file name passed to the LESSCLOSE postprocessor is "-". For compatibility with previous versions of 1mless22m, the input preproces sor or pipe is not used if 1mless 22mis viewing standard input. However, if the first character of LESSOPEN is a dash (-), the input preprocessor is used on standard input as well as other files. In this case, the dash is not considered to be part of the preprocessor command. If standard input is being viewed, the input preprocessor is passed a file name consisting of a single dash. Similarly, if the first two charac ters of LESSOPEN are vertical bar and dash (|-) or two vertical bars and a dash (||-), the input pipe is used on standard input as well as other files. Again, in this case the dash is not considered to be part of the input pipe command. 1mNATIONAL CHARACTER SETS0m 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 "character set" is simply a description of which characters are to be considered normal, control, and binary. The LESSCHARSET environment variable may be used to select a character set. Possible values for LESSCHARSET are: 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. UTF-8 is special in that it supports multi-byte characters in the input file. It is the only character set that supports mul ti-byte characters. windows Selects a character set appropriate for Microsoft Windows (cp 1251). In rare cases, it may be desired to tailor 1mless 22mto use a character set other than the ones definable by LESSCHARSET. In this case, the envi ronment 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 "." is used for a normal character, "c" for control, and "b" for binary. A decimal num ber may be used for repetition. For example, "bccc4b." would mean character 0 is binary, 1, 2 and 3 are control, 4, 5, 6 and 7 are bina ry, and 8 is normal. All characters after the last are taken to be the same as the last, so characters 9 through 255 would be normal. (This is an example, and does not necessarily represent any real character set.) 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 any of the strings "UTF-8", "UTF8", "utf-8" or "utf8" is found in the LC_ALL, LC_CTYPE or LANG environment variables, then the default character set is utf-8. If that string is not found, but your system supports the 1msetlocale 22min terface, 1mless 22mwill use setlocale to determine the character set. set locale is controlled by setting the LANG or LC_CTYPE environment vari ables. Finally, if the 4msetlocale24m 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 char acter 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 "*" and one character to select the display attribute: "*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout, and "*n" is normal. If LESSBINFMT does not begin with a "*", normal attribute is assumed. The remainder of LESSBINFMT is a string which may include one printf-style escape sequence (a % followed by x, X, o, d, etc.). For example, if LESSBINFMT is "*u[%x]", binary characters are displayed in underlined hexadecimal surrounded by brackets. The default if no LESSBINFMT is specified is "*s<%02X>". Warning: the re sult of expanding the character via LESSBINFMT must be less than 31 characters. When the character set is utf-8, the LESSUTFBINFMT environment variable acts similarly to LESSBINFMT but it applies to Unicode code points that were successfully decoded but are unsuitable for display (e.g., unas signed code points). Its default value is "<U+%04lX>". Note that LESSUTFBINFMT and LESSBINFMT share their display attribute setting ("*x") so specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so its setting, if any, will have priority. Problematic octets in a UTF-8 file (octets of a truncated sequence, octets of a complete but non-shortest form sequence, invalid octets, and stray trailing octets) are displayed individually using LESSBINFMT so as to facilitate diagnostic of how the UTF-8 file is ill-formed. When the character set is utf-8, in rare cases it may be desirable to override the Unicode definition of the type of certain characters. For example, characters in a Private Use Area are normally treated as con trol characters, but if you are using a custom font with printable characters in that range, it may be desirable to tell 1mless 22mto treat such characters as printable. This can be done by setting the LESSUT FCHARDEF environment variable to a comma-separated list of 4mcharacter0m 4mtype24m definitions. Each character type definition consists of either one hexadecimal codepoint or a pair of codepoints separated by a dash, followed by a colon and a type character. Each hexadecimal codepoint may optionally be preceded by a "U" or "U+". If a pair of codepoints is given, the type is set for all characters inclusively between the two values. If there are multiple comma-separated codepoint values, they must be in ascending numerical order. The type character may be one of: p A normal printable character. w A wide (2-space) printable character. b A binary (non-printable) character. c A composing (zero width) character. For example, setting LESSUTFCHARDEF to E000-F8FF:p,F0000-FFFFD:p,100000-10FFFD:p would make all Private Use Area characters be treated as printable. 1mPROMPTS0m 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 ordi nary 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. (References to the input file size below refer to the preprocessed size, if an input preprocessor is being used.) %b4mX24m Replaced by the byte offset into the current input file. The b is followed by a single character (shown as 4mX24m above) which spec ifies the line whose byte offset is to be used. If the charac ter 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 bot tom line, a "B" means use the line just after the bottom line, and a "j" means use the "target" line, as specified by the -j option. %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. %d4mX24m Replaced by the page number of a line in the input file. The line to be used is determined by the 4mX24m, as with the %b option. %D Replaced by the number of pages in the input file, or equiva lently, 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. %F Replaced by the last component of the name of the current input file. %g Replaced by the shell-escaped name of the current input file. This is useful when the expanded string will be used in a shell command, such as in LESSEDIT. %i Replaced by the index of the current file in the list of input files. %l4mX24m Replaced by the line number of a line in the input file. The line to be used is determined by the 4mX24m, 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. %p4mX24m Replaced by the percent into the current input file, based on byte offsets. The line used is determined by the 4mX24m as with the %b option. %P4mX24m Replaced by the percent into the current input file, based on line numbers. The line used is determined by the 4mX24m 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. %T Normally expands to the word "file". However if viewing files via a tags list using the -t option, it expands to the word "tag". %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 evaluat ed. 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. ?b4mX24m 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). ?d4mX24m 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). ?l4mX24m 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. ?p4mX24m True if the percent into the current input file, based on byte offsets, of the specified line is known. ?P4mX24m True if the percent into the current input file, based on line numbers, of the specified line is known. ?s Same as "?B". ?x True if there is a next input file (that is, if the current in put file is not the last one). Any characters other than the special ones (question mark, colon, peri od, 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 "Stan dard input". ?f%f .?ltLine %lt:?pt%pt:?btByte %bt:-... This prompt would print the filename, if known. The filename is fol lowed by the line number, if known, otherwise the percent if known, otherwise the byte offset if known. Otherwise, a dash is printed. No tice how each question mark has a matching period, and how the % after the %pt is included literally by escaping it with a backslash. %x..%t"; ?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next This prints the filename if this is the first prompt in a file, fol lowed 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 refer ence, here are the defaults for the other two prompts (-m and -M re spectively). Each is broken into two lines here for readability only. %x.: ?n?f%f .?pB%pB:byte %bB?s/%s...%t ?x- Next ?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%l%x.:?pB%pB..%t byte %bB?s/%s. .?e(END) ?x- Next And here is the default message produced by the = command: ?f%f .?m(%T %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 ex panded in the same way as the prompt strings. The default value for LESSEDIT is: %E ?lm+%lm. %g Note that this expands to the editor name, followed by a + and the line number, followed by the shell-escaped file name. If your editor does not accept the "+linenumber" syntax, or has other differences in invo cation syntax, the LESSEDIT variable can be changed to modify this de fault. 1mSECURITY0m When the environment variable LESSSECURE is set to 1, 1mless 22mruns in a "secure" mode. This means these features are disabled: ! the shell command # the pshell 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) history file Less can also be compiled to be permanently in "secure" mode. 1mCOMPATIBILITY WITH MORE0m If the environment variable LESS_IS_MORE is set to 1, or if the program is invoked via a file link named "more", 1mless 22mbehaves (mostly) in con formance with the POSIX 1mmore22m(1) command specification. In this mode, less behaves differently in these ways: The -e option works differently. If the -e option is not set, 1mless 22mbe haves as if the -e option were set. If the -e option is set, 1mless 22mbe haves as if the -E option were set. The -m option works differently. If the -m option is not set, the medium prompt is used, and it is prefixed with the string "-- More--". If the -m option is set, the short prompt is used. The -n option acts like the -z option. The normal behavior of the -n option is unavailable in this mode. The parameter to the -p option is taken to be a 1mless 22mcommand rather than a search pattern. The LESS environment variable is ignored, and the MORE environment variable is used in its place. 1mENVIRONMENT VARIABLES0m Environment variables may be specified either in the system environment as usual, or in a 1mlesskey22m(1) file. If environment variables are de fined 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 vari ables is the name of the user's home directory if the HOME vari able 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 1mless 22mautomatically. LESSANSIENDCHARS Characters which may end an ANSI color escape sequence (default "m"). LESSANSIMIDCHARS Characters which may appear between the ESC character and the end character in an ANSI color escape sequence (default "0123456789:;[?!"'#%()*+ ". 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 "lessecho"). The lessecho program is needed to expand metacharacters, such as * and ?, in filenames on Unix systems. LESSEDIT Editor prototype string (used for the v command). See discus sion under PROMPTS. LESSGLOBALTAGS Name of the command used by the -t option to find global tags. Normally should be set to "global" if your system has the 1mglob0m 1mal22m(1) command. If not set, global tags are not used. LESSHISTFILE Name of the history file used to remember search commands and shell commands between invocations of 1mless22m. If set to "-" or "/dev/null", a history file is not used. The default depends on the operating system, but is usually: Linux and Unix "$XDG_STATE_HOME/lesshst" or "$HOME/.local/state/lesshst" or "$XDG_DATA_HOME/lesshst" or "$HOME/.lesshst". Windows and MS-DOS "$HOME/_lesshst". OS/2 "$HOME/lesshst.ini" or "$INIT/lesshst.ini". LESSHISTSIZE The maximum number of commands to save in the history file. The default is 100. LESSKEYIN Name of the default 4mlesskey24m 4msource24m file. LESSKEY Name of the default 4mlesskey24m 4mbinary24m file. (Not used if "$LESSKEYIN" exists.) LESSKEYIN_SYSTEM Name of the default system-wide 4mlesskey24m 4msource24m file. LESSKEY_SYSTEM Name of the default system-wide 4mlesskey24m 4mbinary24m file. (Not used if "$LESSKEYIN_SYSTEM" exists.) LESSMETACHARS List of characters which are considered "metacharacters" by the shell. LESSMETAESCAPE Prefix which less will add before each metacharacter in a com mand 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 "secure" mode. See discussion under SECURITY. LESSSEPARATOR String to be appended to a directory name in filename comple tion. LESSUTFBINFMT Format for displaying non-printable Unicode code points. LESSUTFCHARDEF Overrides the type of specified Unicode characters. LESS_COLUMNS Sets the number of columns on the screen. Unlike COLUMNS, takes precedence over the system's idea of the screen size, so it can be used to make 1mless 22muse less than the full screen width. If set to a negative number, sets the number of columns used to this much less than the actual screen width. LESS_LINES Sets the number of lines on the screen. Unlike LINES, takes precedence over the system's idea of the screen size, so it can be used to make 1mless 22muse less than the full screen height. If set to a negative number, sets the number of lines used to this much less than the actual screen height. When set, 1mless 22mre paints the entire screen on every movement command, so scrolling may be slower. LESS_DATA_DELAY Duration (in milliseconds) after starting to read data from the input, after which the "Waiting for data" message will be dis played. The default is 4000 (4 seconds). LESS_IS_MORE Emulate the 1mmore22m(1) command. LESS_TERMCAP_xx Where "xx" is any two characters, overrides the definition of the termcap "xx" capability for the terminal. 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.) MORE Options which are passed to 1mless 22mautomatically when running in 1mmore22m-compatible mode. 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 1mless 22mis being run. VISUAL The name of the editor (used for the v command). XDG_CONFIG_HOME Possible location of the 1mlesskey 22mfile; see the KEY BINDINGS sec tion. XDG_DATA_HOME Possible location of the history file; see the description of the LESSHISTFILE environment variable. XDG_STATE_HOME Possible location of the history file; see the description of the LESSHISTFILE environment variable. 1mSEE ALSO0m 1mlesskey22m(1), 1mlessecho22m(1) 1mCOPYRIGHT0m Copyright (C) 1984-2023 Mark Nudelman less is part of the GNU project and is free software. You can redis tribute it and/or modify it under the terms of either (1) the GNU Gen eral 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 FIT NESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. 1mAUTHOR0m Mark Nudelman Report bugs at https://github.com/gwsw/less/issues. For more information, see the less homepage at https://greenwoodsoftware.com/less Version 643: 20 Jul 2023 LESS(1)