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Text File | 1985-11-20 | 12.6 KB | 293 lines

LESS - opposite of more less [-cdepstwmMqQuU] [-hn] [-b[fp]n] [-xn] [+cmd] [name(s)] LESS is a program similar to MORE, but which allows backwards movement in the file as well as forward movement. Also, LESS does not have to read the entire input file before starting, so with large input files it starts up fas- ter than text editors like vix. Commands are based on both more and vi. Commands may be preceeded by a decimal number, called N in the descrip- tions below. The number is used by some commands, as indi- cated. As of this posting, LESS works a) from the desktop and b) in the Mark Williams shell. It hasn't been tested with the Breckmeyer or any other shells. All references to environment variables in the rest of this doc refer to Msh environment variables. Shell escapes and invocations of the editor also work only in the Msh. h Help: display a summary of these commands. If you for- get all the other commands, remember this one. SPACEScroll forward N lines, default one screen. If N is more than the screen size, only one screenful is displayed. f Same as SPACE. b Scroll backward N lines, default one screen. If N is more than the screen size, only one screenful is displayed. RETURNScroll forward N lines, default 1. If N is more than the screen size, the entire N lines are displayed. e Same as RETURN. j Also the same as RETURN. y Scroll backward N lines, default 1. If N is more than the screen size, the entire N lines are displayed. k Same as y. d Scroll forward N lines, default 10. If N is specified, it becomes the new default for all d and u commands. u Scroll backward N lines, default 10. If N is speci- fied, it becomes the new default for all d and u com- mands. r Repaint the screen. R Repaint the screen, discarding any buffered input. Useful if the file is changing while it is being viewed. g Go to line N in the file, default 1 (beginning of file). (Warning: this may be slow if N is large.) G Go to line N in the file, default the end of the file. (Warning: this may be slow if standard input, rather than a file, is being read.) p Go to a position N percent into the file. N should be between 0 and 100. (This is possible if standard input is being read, but only if LESS has already read to the end of the file. It is always fast, but not always useful.) % Same as p. m Followed by any lowercase letter, marks the current position with that letter. ' Followed by any lowercase letter, returns to the posi- tion which was previously marked with that letter. All marks are lost when a new file is examined. /pattern Search forward in the file for the N-th occurence of the pattern. N defaults to 1. The pattern is a regu- lar expression (well, it works most of the time..). The search starts at the second line displayed (but see the -t option, which changes this). ?pattern Search backward in the file for the N-th occurence of the pattern. The search starts at the line immediately before the top line displayed. n Repeat previous search, for N-th occurence of the last pattern. E Examine a new file. If the filename is missing, the "current" file (see the N and P commands below) from the list of files in the command line is re-examined. N Examine the next file (from the list of files given in the command line). If a number N is specified (not to be confused with the command N), the N-th next file is examined. P Examine the previous file. If a number N is specified, the N-th previous file is examined. = Prints the name of the file being viewed and the byte offset of the bottom line being displayed. If possi- ble, it also prints the length of the file and the per- cent of the file above the last displayed line. - Followed by one of the command line option letters (see below), this will toggle the setting of that option and print a message describing the new setting. V Prints the version number of LESS being run. q Exits LESS. The following two commands at present work only with the 'msh' of Mark Willaims C (when LESS is run from the desktop, a 'Shell not found' message is printed out. A fix for non-shell environments is in the offing). v Invokes an editor to edit the current file being viewed. The editor is taken from the environment vari- able EDITOR, or defaults to "vi". ! shell-command Invokes a shell to run the shell-command given. Command line options are described below. Options are also taken from the environment variable "LESS". (The environ- ment variable is parsed before the command line, so command line options override the LESS environment variable. Options may be changed while LESS is running via the "-" command.) For example, if you like more-style prompting, to avoid typing "less -pm ..." each time LESS is invoked, you might tell Msh (the Mark Williams shell): setenv LESS=-pm -s The -s flag causes consecutive blank lines to be squeezed into a single blank line. This is useful when viewing nroff output. -t Normally, forward searches start just after the top displayed line (that is, at the second displayed line). Thus forward searches include the currently displayed screen. The -t command line option causes forward searches to start just after the bottom line displayed, thus skipping the currently displayed screen. -m The -m command line option causes LESS to prompt less verbosely like more, printing the file name and percent into the file, or just with a colon. -M The -M command line option causes LESS to prompt even more verbosely than more (this is the default). -q Normally, if an attempt is made to scroll past the end of the file or before the beginning of the file, the terminal bell is rung to indicate this fact. The -q command line option tells LESS not to ring the bell at such times. If the terminal has a "visual bell", it is used instead. -Q Even if -q is given, LESS will ring the bell on certain other errors, such as typing an invalid character. The -Q command line option tells LESS to be quiet all the time. -e Normally the only way to exit LESS is via the "q" com- mand. The -e command line option tells LESS to automatically exit the second time it reaches end-of- file. -u If the -u command line option is given, backspaces are treated as printable characters; that is, they are sent to the terminal when they appear in the input. -U If the -U command line option is given, backspaces are printed as the two character sequence "^H". If neither -u nor -U is given, backspaces which appear adjacent to an underscore character are treated specially: the underlined text is displayed using the terminal's hardware underlining capability. -w Normally, LESS uses a tilde character to represent lines past the end of the file. The -w option causes blank lines to be used instead. -p Normally, LESS will repaint the screen by scrolling from the bottom of the screen. If the -p flag is set, when LESS needs to change the entire display, it will clear the screen and paint from the top line down. -h Normally, LESS will scroll backwards when backwards movement is necessary. The -h option specifies a max- imum number of lines to scroll backwards. If it is necessary to move backwards more than this many lines, the screen is repainted in a forward direction. -x The -xn command line option sets tab stops every n positions. The default for n is 8. -b The -bn command line option tells LESS to use a non- standard buffer size. There are two standard (default) buffer sizes, one is used when a file is being read and the other when a pipe (standard input) is being read. The current defaults are 5 buffers for files and 12 for pipes. (Buffers are 1024 bytes.) The number n speci- fies a different number of buffers to use. The -b may be followed by "f", in which case only the file default is changed, or by "p" in which case only the pipe default is changed. Otherwise, both are changed. -c Normally, when data is read by LESS, it is scanned to ensure that bit 7 (the high order bit) is turned off in each byte read, and to ensure that there are no null (zero) bytes in the data (null bytes are turned into "@" characters). If the data is known to be "clean", the -c command line option will tell LESS to skip this checking, causing an imperceptible speed improvement. (However, if the data is not "clean", unpredicatable results may occur.) + If a command line option begins with +, the remainder of that option is taken to be an initial command to LESS. For example, +G tells LESS to start at the end of the file rather than the beginning, and +/xyz tells it to start at the first occurence of "xyz" in the file. As a special case, +<number> acts like +<number>g; that is, it starts the display at the specified line number (however, see the caveat under the "g" command above). If the option starts with ++, the initial command applies to every file being viewed, not just the first one. When used on standard input (rather than a file), you can move backwards only a finite amount, corresponding to that portion of the file which is still buffered. Bugs: The program has problems when it is fed input as standard input, say from a pipe. eg. the following line (in Msh) will eventually cause something to bomb: $ cat foo | less əəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəəə