groffer breaking Options¶

As soon as one of these options is found on the command line it is executed, printed to standard output, and the running groffer is terminated thereafter. All other arguments are ignored.

-h | --help

Print a helping information with a short explanation of option sto standard output.

-v | --version

Print version information to standard output.

groffer Mode Options¶

The display mode and the viewer programs are determined by these options. If none of these mode and viewer options is specified groffer tries to find a suitable display mode automatically. The default modes are mode pdf, mode ps, mode html, mode x, and mode dvi in X Window with different viewers and mode tty with device latin1 under less on a terminal; other modes are tested if the programs for the main default mode do not exist.

In X Window, many programs create their own window when called. groffer can run these viewers as an independent program in the background. As this does not work in text mode on a terminal (tty) there must be a way to know which viewers are X Window graphical programs. The groffer script has a small set of information on some viewer names. If a viewer argument of the command-line chooses an element that is kept as X Window program in this list it is treated as a viewer that can run in the background. All other, unknown viewer calls are not run in the background.

For each mode, you are free to choose whatever viewer you want. That need not be some graphical viewer suitable for this mode. There is a chance to view the output source; for example, the combination of the options --mode=ps and --ps-viewer=less shows the content of the Postscript output, the source code, with the pager less.

--auto

Equivalent to --mode=auto.

--default

Reset all configuration from previously processed command line options to the default values. This is useful to wipe out all former options of the configuration, in $GROFFER_OPT, and restart option processing using only the rest of the command line.

--default-modes mode1,mode2,...

Set the sequence of modes for auto mode to the comma separated list given in the argument. See --mode for details on modes. Display in the default manner; actually, this means to try the modes x, ps, and tty in this sequence.

--dvi

Equivalent to --mode=dvi.

--dvi-viewer prog

Choose a viewer program for dvi mode. This can be a file name or a program to be searched in $PATH. Known X Window dvi viewers include xdvi(1) and dvilx(1) In each case, arguments can be provided additionally.

--groff

Equivalent to --mode=groff.

--html

Equivalent to --mode=html.

--html-viewer

Choose a web browser program for viewing in html mode. It can be the path name of an executable file or a program in $PATH. In each case, arguments can be provided additionally.

--mode value

Set the display mode. The following mode values are recognized:

--pdf

Equivalent to --mode=pdf.

--pdf-viewer prog

Choose a viewer program for pdf mode. This can be a file name or a program to be searched in $PATH; arguments can be provided additionally.

--ps

Equivalent to --mode=ps.

--ps-viewer prog

Choose a viewer program for ps mode. This can be a file name or a program to be searched in $PATH. Common Postscript viewers inlude gv(1), ghostview(1), and gs(1), In each case, arguments can be provided additionally.

--source

Equivalent --mode=source.

--text

Equivalent to --mode=text.

--to-stdout

The file for the chosen mode is generated and its content is printed to standard output. It will not be displayed in graphical mode.

--tty

Equivalent to --mode=tty.

--tty-viewer prog

Choose a text pager for mode tty. The standard pager is less(1). This option is eqivalent to man option --pager=prog. The option argument can be a file name or a program to be searched in $PATH; arguments can be provided additionally.

--www

Equivalent to --mode=html.

--www-viewer prog

Equivalent to --html-viewer.

--X | --x

Equivalent to --mode=x.

--X-viewer | --x-viewer prog

Choose a viewer program for x mode. Suitable viewer programs are gxditview(1) which is the default and xditview(1). The argument can be any executable file or a program in $PATH; arguments can be provided additionally.

--

Signals the end of option processing; all remaining arguments are interpreted as filespec parameters.

Besides these, groffer accepts all short options that are valid for the groff(1) program. All non-groffer options are sent unmodified via grog to groff. So postprocessors, macro packages, compatibility with classical troff, and much more can be manually specified.

Options related to groff¶

All short options of groffer are compatible with the short options of groff(1). The following of groff options have either an additional special meaning within groffer or make sense for normal usage.

Because of the special outputting behavior of the groff option -Z groffer was designed to be switched into groff mode ; the groffer viewing features are disabled there. The other groff options do not switch the mode, but allow to customize the formatting process.

-a

This generates an ascii approximation of output in the text modes. That could be important when the text pager has problems with control sequences in tty mode.

-m file

Add file as a groff macro file. This is useful in case it cannot be recognized automatically.

-P opt_or_arg

Send the argument opt_or_arg as an option or option argument to the actual groff postprocessor.

-T | --device devname

This option determines groff's output device. The most important devices are the text output devices for referring to the different character sets, such as ascii, utf8, latin1, and others. Each of these arguments switches groffer into a text mode using this device, to mode tty if the actual mode is not a text mode. The following devname arguments are mapped to the corresponding groffer --mode=devname option: dvi, html, and ps. All X* arguments are mapped to mode x. Each other devname argument switches to mode groff using this device.

-X

is equivalent to groff -X. It displays the groff intermediate output with gxditview. As the quality is relatively bad this option is deprecated; use --X instead because the x mode uses an X* device for a better display.

-Z | --intermediate-output | --ditroff

Switch into groff mode and format the input with the groff intermediate output without postprocessing; see groff_out(5). This is equivalent to option --ditroff of man, which can be used as well.

All other groff options are supported by groffer, but they are just transparently transferred to groff without any intervention. The options that are not explicitly handled by groffer are transparently passed to groff. Therefore these transparent options are not documented here, but in groff(1). Due to the automatism in groffer, none of these groff options should be needed, except for advanced usage.

Options for man pages¶

--apropos

Start the apropos(1) command or facility of man(1) for searching the filespec arguments within all man page descriptions. Each filespec argument is taken for search as it is; section specific parts are not handled, such that 7 groff searches for the two arguments 7 and groff, with a large result; for the filespec groff.7 nothing will be found. The language locale is handled only when the called programs do support this; the GNU apropos and man -k do not. The display differs from the apropos program by the following concepts:

--apropos-data

Show only the apropos descriptions for data documents, these are the man(7) sections 4, 5, and 7. Direct section declarations are ignored, wildcards are accepted.

--apropos-devel

Show only the apropos descriptions for development documents, these are the man(7) sections 2, 3, and 9. Direct section declarations are ignored, wildcards are accepted.

--apropos-progs

Show only the apropos descriptions for documents on programs, these are the man(7) sections 1, 6, and 8. Direct section declarations are ignored, wildcards are accepted.

--whatis

For each filespec argument search all man pages and display their description — or say that it is not a man page. This is written from anew, so it differs from man's whatis output by the following concepts

The following options were added to groffer for choosing whether the file name arguments are interpreted as names for local files or as a search pattern for man pages. The default is looking up for local files.

--man

Check the non-option command line arguments (filespecs) first on being man pages, then whether they represent an existing file. By default, a filespec is first tested whether it is an existing file.

--no-man | --local-file

Do not check for man pages. --local-file is the corresponding man option.

--no-special

Disable former calls of --all, --apropos*, and --whatis.

Long options taken over from GNU man¶

The long options of groffer were synchronized with the long options of GNU man. All long options of GNU man are recognized, but not all of these options are important to groffer, so most of them are just ignored. These ignored man options are --catman, --troff, and --update.

In the following, the man options that have a special meaning for groffer are documented.

If your system has GNU man installed the full set of long and short options of the GNU man program can be passed via the environment variable $MANOPT; see man(1).

--all

In searching man pages, retrieve all suitable documents instead of only one.

-7 | --ascii

In text modes, display ASCII translation of special characters for critical environment. This is equivalent to groff -mtty_char; see groff_tmac(5).

--ditroff

Produce groff intermediate output. This is equivalent to groffer -Z.

--extension suffix

Restrict man page search to file names that have suffix appended to their section element. For example, in the file name /usr/share/man/man3/terminfo.3ncurses.gz the man page extension is ncurses.

--locale language

Set the language for man pages. This has the same effect, but overwrites $LANG

--location

Print the location of the retrieved files to standard error.

--no-location

Do not display the location of retrieved files; this resets a former call to --location. This was added by groffer.

--manpath

Use the specified search path for retrieving man pages instead of the program defaults. If the argument is set to the empty string "" the search for man page is disabled.

--pager

Set the pager program in tty mode; default is less. This is equivalent to --tty-viewer.

--sections

Restrict searching for man pages to the given sections, a colon-separated list.

--systems

Search for man pages for the given operating systems; the argument systems is a comma-separated list.

--where

Eqivalent to --location.

X Window Toolkit Options¶

The following long options were adapted from the corresponding X Window Toolkit options. groffer will pass them to the actual viewer program if it is an X Window program. Otherwise these options are ignored.

Unfortunately these options use the old style of a single minus for long options. For groffer that was changed to the standard with using a double minus for long options, for example, groffer uses the option --font for the X Window option -font.

See X(1), X(7), and the documentation on the X Window Toolkit options for more details on these options and their arguments.

--background color

Set the background color of the viewer window.

--bd pixels

This is equivalent to --bordercolor.

--bg color

This is equivalent to --background.

--bw pixels

This is equivalent to --borderwidth.

--bordercolor pixels

Specifies the color of the border surrounding the viewer window.

--borderwidth pixels

Specifies the width in pixels of the border surrounding the viewer window.

--display X-display

Set the X Window display on which the viewer program shall be started, see the X Window documentation for the syntax of the argument.

--foreground color

Set the foreground color of the viewer window.

--fg color

This is equivalent to -foreground.

--fn font_name

This is equivalent to --font.

--font font_name

Set the font used by the viewer window. The argument is an X Window font name.

--ft font_name

This is equivalent to --font.

--geometry size_pos

Set the geometry of the display window, that means its size and its starting position. See X(7) for the syntax of the argument.

--resolution value

Set X Window resolution in dpi (dots per inch) in some viewer programs. The only supported dpi values are 75 and 100. Actually, the default resolution for groffer is set to 75 dpi. The resolution also sets the default device in mode x.

--rv

Reverse foreground and background color of the viewer window.

--title

Set the title for the viewer window.

--xrm

Set X Window resource.

Options for Development¶

--debug

Enable seven debugging informations. The temporary files are kept and not deleted, the name of the temporary directory and the shell name for groffer2.sh are printed, the displayed file names are printed, the parameters are printed at several steps of development, and a function stack is output with function error_user() as well. Neither the function call stack at the opening and closing of each function call nor the landmark information to determine how far the program is running are printed. These seem to be the most useful parts among all debugging options.

--debug-all

Enable all nine debugging informations including the function call stack and the landmark information.

--debug-filenames

Print the names of the files and man pages that are displayed by groffer.

--debug-func

Enable the basic debugging information for checking the functions on the beginning and end of each call. The options --debug-stacks and --debug-user enable this option automatically. This option is important for the development, but it decreases the speed of groffer by large amounts.

--debug-keep

Enable two debugging informations, the printing of the name of the temporary directory and the keeping of the temporary files.

--debug-lm

Enable one debugging information, the landmark information.

--debug-params

Enable one debugging information, the parameters at several steps.

--debug-shell

Enable one debugging information, the shell name for groffer2.sh.

--debug-stacks

Enable one debugging information, the function call stack.

--debug-tmpdir

Enable one debugging information, the name of the temporary directory.

--debug-user

Enable one debugging information, the function stack with error_user().

--do-nothing

This is like --version, but without the output; no viewer is started. This makes only sense in development.

--print=text

Just print the argument to standard error. This is good for parameter check.

--shell shell_program

Specify the shell under which the groffer2.sh script should be run. This option overwrites the automatic shell determination of the program. If the argument shell_program is empty a former shell option and the automatic shell determination is cancelled and the default shell is restored. Some shells run considerably faster than the standard shell.

-V

This is an advanced option for debugging only. Instead of displaying the formatted input, a lot of groffer specific information is printed to standard output:

Other useful debugging options are the groff option -Z and --mode=groff.

Filespec Arguments¶

A filespec parameter is an argument that is not an option or option argument. In groffer, filespec parameters are a file name or a template for searching man pages. These input sources are collected and composed into a single output file such as groff does.

The strange POSIX behavior to regard all arguments behind the first non-option argument as filespec arguments is ignored. The GNU behavior to recognize options even when mixed with filespec arguments is used througout. But, as usual, the double minus argument -- ends the option handling and interprets all following arguments as filespec arguments; so the POSIX behavior can be easily adopted.

The options have a special handling of filespec arguments. Each argument is taken as a search scheme of its own. Also a regexp (regular expression) can be used in the filespec. For example, groffer --apropos '^gro.f$' searches groff in the man page name, while groffer --apropos groff searches groff somewhere in the name or description of the man pages.

All other parts of groffer, such as the normal display or the output with have a different scheme for filespecs. No regular expressions are used for the arguments. The filespec arguments are handled by the following scheme.

It is necessary to know that on each system the man pages are sorted according to their content into several sections. The classical man sections have a single-character name, either a digit from 1 to 9 or one of the characters n or o.

This can optionally be followed by a string, the so-called extension. The extension allows to store several man pages with the same name in the same section. But the extension is only rarely used, usually it is omitted. Then the extensions are searched automatically by alphabet.

In the following, we use the name section_extension for a word that consists of a single character section name or a section character that is followed by an extension. Each filespec parameter can have one of the following forms in decreasing sequence.

•

No filespec parameters means that groffer waits for standard input. The minus option - always stands for standard input; it can occur several times. If you want to look up a man page called - use the argument man:-.

•

Next a filespec is tested whether it is the path name of an existing file. Otherwise it is assumed to be a searching pattern for a man page.

•

man:name(section_extension), man:name.section_extension, name(section_extension), or name.section_extension search the man page name in man section and possibly extension of section_extension.

•

Now man:name searches for a man page in the lowest man section that has a document called name.

•

section_extension name is a pattern of 2 arguments that originates from a strange argument parsing of the man program. Again, this searches the man page name with section_extension, a combination of a section character optionally followed by an extension.

•

We are left with the argument name which is not an existing file. So this searches for the man page called name in the lowest man section that has a document for this name.

Several file name arguments can be supplied. They are mixed by groff into a single document. Note that the set of option arguments must fit to all of these file arguments. So they should have at least the same style of the groff language.

Graphical Display Modes¶

The graphical display modes work mostly in the X Window environment (or similar implementations within other windowing environments). The environment variable $DISPLAY and the option --display are used for specifying the X Window display to be used. If this environment variable is empty groffer assumes that no X Window is running and changes to a text mode. You can change this automatic behavior by the option --default-modes.

Known viewers for the graphical display modes and their standard X Window viewer progams are

•

in a PDF viewer (pdf mode),

•

in a web browser (html or www mode).

•

in a Postscript viewer (ps mode),

•

X Window roff viewers such as gxditview(1) or xditview(1) (in x mode),

•

in a dvi viewer program (dvi mode),

The pdf mode has a major advantage — it is the only graphical diplay mode that allows to search for text within the viewer; this can be a really important feature. Unfortunately, it takes some time to transform the input into the PDF format, so it was not chosen as the major mode.

These graphical viewers can be customized by options of the X Window Toolkit. But the groffer options use a leading double minus instead of the single minus used by the X Window Toolkit.

Text modes¶

There are two modes for text output, mode text for plain output without a pager and mode tty for a text output on a text terminal using some pager program.

If the variable $DISPLAY is not set or empty, groffer assumes that it should use tty mode.

In the actual implementation, the groff output device latin1 is chosen for text modes. This can be changed by specifying option -T or --device.

The pager to be used can be specified by one of the options --pager and --tty-viewer, or by the environment variable $PAGER. If all of this is not used the less(1) program with the option -r for correctly displaying control sequences is used as the default pager.

Special Modes for Debugging and Development¶

These modes use the groffer file determination and decompression. This is combined into a single input file that is fed directly into groff with different strategy without the groffer viewing facilities. These modes are regarded as advanced, they are useful for debugging and development purposes.

The source mode with option --source just displays the decompressed input.

Otion --to-stdout does not display in a graphical mode. It just generates the file for the chosen mode and then prints its content to standard output.

The groff mode passes the input to groff using only some suitable options provided to groffer. This enables the user to save the generated output into a file or pipe it into another program.

In groff mode, the option -Z disables post-processing, thus producing the groff intermediate output. In this mode, the input is formatted, but not postprocessed; see groff_out(5) for details.

All groff short options are supported by groffer.

Search Algoritm¶

Let us now assume that a man page should be searched. The groffer program provides a search facility for man pages. All long options, all environment variables, and most of the functionality of the GNU man(1) program were implemented. The search algorithm shall determine which file is displayed for a given man page. The process can be modified by options and environment variables.

The only man action that is omitted in groffer are the preformatted man pages, also called cat pages. With the excellent performance of the actual computers, the preformatted man pages aren't necessary any longer. Additionally, groffer is a roff program; it wants to read roff source files and format them itself.

The algorithm for retrieving the file for a man page needs first a set of directories. This set starts with the so-called man path that is modified later on by adding names of operating system and language. This arising set is used for adding the section directories which contain the man page files.

The man path is a list of directories that are separated by colon. It is generated by the following methods.

•

The environment variable $MANPATH can be set.

•

It can be read from the arguments of the environment variable $MANOPT.

•

The man path can be manually specified by using the option --manpath. An empty argument disables the man page searching.

•

When no man path was set the manpath(1) program is tried to determine one.

•

If this does not work a reasonable default path from $PATH is determined.

We now have a starting set of directories. The first way to change this set is by adding names of operating systems. This assumes that man pages for several operating systems are installed. This is not always true. The names of such operating systems can be provided by 3 methods.

•

The environment variable $SYSTEM has the lowest precedence.

•

This can be overridden by an option in $MANOPT.

•

This again is overridden by the command line option --systems.

Several names of operating systems can be given by appending their names, separated by a comma.

The man path is changed by appending each system name as subdirectory at the end of each directory of the set. No directory of the man path set is kept. But if no system name is specified the man path is left unchanged.

After this, the actual set of directories can be changed by language information. This assumes that there exist man pages in different languages. The wanted language can be chosen by several methods.

•

Enviroment variable $LANG.

•

This is overridden by $LC_MESSAGES.

•

This is overridden by $LC_ALL.

•

This can be overridden by providing an option in $MANOPT.

•

All these environment variables are overridden by the command line option --locale.

The default language can be specified by specifying one of the pseudo-language parameters C or POSIX. This is like deleting a formerly given language information. The man pages in the default language are usually in English.

Of course, the language name is determined by man. In GNU man, it is specified in the POSIX 1003.1 based format:

<language>[_<territory>[.<character-set>[,<version>]]],

but the two-letter code in <language> is sufficient for most purposes. If for a complicated language formulation no man pages are found groffer searches the country part consisting of these first two characters as well.

The actual directory set is copied thrice. The language name is appended as subdirectory to each directory in the first copy of the actual directory set (this is only done when a language information is given). Then the 2-letter abbreviation of the language name is appended as subdirectories to the second copy of the directory set (this is only done when the given language name has more than 2 letters). The third copy of the directory set is kept unchanged (if no language information is given this is the kept directory set). These maximally 3 copies are appended to get the new directory set.

We now have a complete set of directories to work with. In each of these directories, the man files are separated in sections. The name of a section is represented by a single character, a digit between 1 and 9, or the character o or n, in this order.

For each available section, a subdirectory man<section> exists containing all man files for this section, where <section> is a single character as described before. Each man file in a section directory has the form man<section>/<name>.<section>[<extension>][.<compression>], where <extension> and <compression> are optional. <name> is the name of the man page that is also specified as filespec argument on the command line.

The extension is an addition to the section. This postfix acts like a subsection. An extension occurs only in the file name, not in name of the section subdirectory. It can be specified on the command line.

On the other hand, the compression is just an information on how the file is compressed. This is not important for the user, such that it cannot be specified on the command line.

There are 4 methods to specify a section on the command line:

•

Environment variable $MANSECT

•

Command line option --sections

•

Appendix to the name argument in the form <name>.<section>

•

Preargument before the name argument in the form <section> <name>

It is also possible to specify several sections by appending the single characters separated by colons. One can imagine that this means to restrict the man page search to only some sections. The multiple sections are only possible for $MANSECT and --sections.

If no section is specified all sections are searched one after the other in the given order, starting with section 1, until a suitable file is found.

There are 4 methods to specify an extension on the command line. But it is not necessary to provide the whole extension name, some abbreviation is good enough in most cases.

•

Environment variable $EXTENSION

•

Command line option --extension

•

Appendix to the <name>.<section> argument in the form <name>.<section><extension>

•

Preargument before the name argument in the form <section><extension> <name>

For further details on man page searching, see man(1).

Examples of man files¶

/usr/share/man/man1/groff.1

This is an uncompressed file for the man page groff in section 1. It can be called by

].groffer:Shell_cmd.prompt_text " "groffer groff" No section is specified here, so all sections should be searched, but as section 1 is searched first this file will be found first. The file name is composed of the following components. /usr/share/man must be part of the man path; the subdirectory man1/ and the part .1 stand for the section; groff is the name of the man page.

/usr/local/share/man/man7/groff.7.gz

The file name is composed of the following components. /usr/local/share/man must be part of the man path; the subdirectory man7/ and the part .7 stand for the section; groff is the name of the man page; the final part .gz stands for a compression with gzip(1). As the section is not the first one it must be specified as well. This can be done by one of the following commands.

].groffer:Shell_cmd.prompt_text " "groffer groff.7"

].groffer:Shell_cmd.prompt_text " "groffer 7 groff"

].groffer:Shell_cmd.prompt_text " "groffer --sections=7 groff"

/usr/local/man/man1/ctags.1emacs21.bz2

Here /usr/local/man must be in man path; the subdirectory man1/ and the file name part .1 stand for section 1; the name of the man page is ctags; the section has an extension emacs21; and the file is compressed as .bz2 with bzip2(1). The file can be viewed with one of the following commands

].groffer:Shell_cmd.prompt_text " "groffer ctags.1e"

].groffer:Shell_cmd.prompt_text " "groffer 1e ctags"

].groffer:Shell_cmd.prompt_text " "groffer --extension=e --sections=1 ctags" where e works as an abbreviation for the extension emacs21.

/usr/man/linux/de/man7/man.7.Z

The directory /usr/man is now part of the man path; then there is a subdirectory for an operating system name linux/; next comes a subdirectory de/ for the German language; the section names man7 and .7 are known so far; man is the name of the man page; and .Z signifies the compression that can be handled by gzip(1). We want now show how to provide several values for some options. That is possible for sections and operating system names. So we use as sections 5 and 7 and as system names linux and aix. The command is then

].groffer:Shell_cmd.prompt_text " "groffer --locale=de --sections=5:7 --systems=linux,aix man"

].groffer:Shell_cmd.prompt_text " "LANG=de MANSECT=5:7 SYSTEM=linux,aix groffer man"

Native groffer Variables¶

$GROFFER_OPT

Store options for a run of groffer. The options specified in this variable are overridden by the options given on the command line. The content of this variable is run through the shell builtin `eval'; so arguments containing white-space or special shell characters should be quoted. Do not forget to export this variable, otherwise it does not exist during the run of groffer.

System Variables¶

The groffer program is a shell script that is run through /bin/sh, which can be internally linked to programs like bash(1). The corresponding system environment is automatically effective. The following variables have a special meaning for groffer.

$DISPLAY

If this variable is set this indicates that the X Window system is running. Testing this variable decides on whether graphical or text output is generated. This variable should not be changed by the user carelessly, but it can be used to start the graphical groffer on a remote X Window terminal. For example, depending on your system, groffer can be started on the second monitor by the command

].groffer:Shell_cmd.prompt_text " "DISPLAY=:0.1 groffer " "what.ever" "&"

$LC_ALL

$LC_MESSAGES

$LANG

If one of these variables is set (in the above sequence), its content is interpreted as the locale, the language to be used, especially when retrieving IR man pages . A locale name is typically of the form language[_territory[.codeset[@modifier]]], where language is an ISO 639 language code, territory is an ISO 3166 country code, and codeset is a character set or encoding identifier like ISO-8859-1 or UTF-8; see setlocale(3). The locale values C and POSIX stand for the default, i.e. the man page directories without a language prefix. This is the same behavior as when all 3 variables are unset.

$PAGER

This variable can be used to set the pager for the tty output. For example, to disable the use of a pager completely set this variable to the cat(1) program

].groffer:Shell_cmd.prompt_text " "PAGER=cat groffer " "anything"

$PATH

All programs within the groffer shell script are called without a fixed path. Thus this environment variable determines the set of programs used within the run of groffer.

Groff Variables¶

The groffer program internally calls groff, so all environment variables documented in groff(1) are internally used within groffer as well. The following variable has a direct meaning for the groffer program.

$GROFF_TMPDIR

If the value of this variable is an existing, writable directory, groffer uses it for storing its temporary files, just as groff does.

Man Variables¶

Parts of the functionality of the man program were implemented in groffer; support for all environment variables documented in man(1) was added to groffer, but the meaning was slightly modified due to the different approach in groffer; but the user interface is the same. The man environment variables can be overwritten by options provided with $MANOPT, which in turn is overwritten by the command line.

$EXTENSION

Restrict the search for man pages to files having this extension. This is overridden by option --extension; see there for details.

$MANOPT

This variable contains options as a preset for man(1). As not all of these are relevant for groffer only the essential parts of its value are extracted. The options specified in this variable overwrite the values of the other environment variables that are specific to man. All options specified in this variable are overridden by the options given on the command line.

$MANPATH

If set, this variable contains the directories in which the man page trees are stored. This is overridden by option --manpath.

$MANSECT

If this is a colon separated list of section names, the search for man pages is restricted to those manual sections in that order. This is overridden by option --sections.

$SYSTEM

If this is set to a comma separated list of names these are interpreted as man page trees for different operating systems. This variable can be overwritten by option --systems; see there for details.

The environment variable $MANROFFSEQ is ignored by groffer because the necessary preprocessors are determined automatically.