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groff_font - format of groff device and font description files
The groff font format is roughly a superset of the ditroff font format.
The font files for device name are stored in a directory devname.
There are two types of file: a device description file called DESC and
for each font F a font file called F. These are text files; unlike the
ditroff font format, there is no associated binary format.
DESC file format
The DESC file can contain the following types of line as shown below.
Later entries in the file override previous values.
This line and everything following in the file are ignored. It
is allowed for the sake of backwards compatibility.
The default font family is fam.
fonts n F1 F2 F3...Fn
Fonts F1...Fn will be mounted in the font positions m+1,...,m+n
where m is the number of styles. This command may extend over
more than one line. A font name of 0 will cause no font to be
mounted on the corresponding font position.
hor n The horizontal resolution is n machine units.
Needed for grohtml only. It specifies the program to generate
PNG images from PostScript input. Under GNU/Linux this is usu-
ally gs but under other systems (notably cygwin) it might be set
to another name.
The physical vertical dimension of the output medium in machine
units. This isn't used by troff itself but by output devices.
Deprecated. Use papersize instead.
Select a paper size. Valid values for string are the ISO paper
types A0-A7, B0-B7, C0-C7, D0-D7, DL, and the US paper types
letter, legal, tabloid, ledger, statement, executive, com10, and
monarch. Case is not significant for string if it holds prede-
fined paper types. Alternatively, string can be a file name
(e.g. `/etc/papersize'); if the file can be opened, groff reads
the first line and tests for the above paper sizes. Finally,
string can be a custom paper size in the format length,width (no
spaces before and after the comma). Both length and width must
have a unit appended; valid values are `i' for inches, `c' for
centimeters, `p' for points, and `P' for picas. Example:
12c,235p. An argument which starts with a digit is always
treated as a custom paper format. papersize sets both the ver-
tical and horizontal dimension of the output medium.
More than one argument can be specified; groff scans from left
to right and uses the first valid paper specification.
The physical horizontal dimension of the output medium in
machine units. Deprecated. Use papersize instead. This isn't
used by troff itself but by output devices.
Make troff tell the driver the source file name being processed.
This is achieved by another tcommand: F filename.
Use program as the postprocessor.
Call program as a preprocessor.
Use program as the spooler program for printing. If omitted,
the -l and -L options of groff are ignored.
res n There are n machine units per inch.
sizes s1 s2...sn 0
This means that the device has fonts at s1, s2,...sn scaled
points. The list of sizes must be terminated by a 0. Each si
can also be a range of sizes m-n. The list can extend over more
than one line.
The scale factor for pointsizes. By default this has a value of
1. One scaled point is equal to one point/n. The arguments to
the unitwidth and sizes commands are given in scaled points.
styles S1 S2...Sm
The first m font positions will be associated with styles
This means that the postprocessor can handle the t and u output
Quantities in the font files are given in machine units for
fonts whose point size is n scaled points.
Make the font handling module always return unscaled character
widths. Needed for the grohtml device.
This command indicates that troff should encode named characters
inside special commands.
vert n The vertical resolution is n machine units.
The res, unitwidth, fonts, and sizes lines are compulsory. Not all
commands in the DESC file are used by troff itself; some of the key-
words (or even additional ones) are used by postprocessors to store
arbitrary information about the device.
Here a list of obsolete keywords which are recognized by groff but com-
pletely ignored: spare1, spare2, biggestfont.
Font file format
A font file has two sections. The first section is a sequence of lines
each containing a sequence of blank delimited words; the first word in
the line is a key, and subsequent words give a value for that key.
ligatures lig1 lig2...lign 
Characters lig1, lig2, ..., lign are ligatures; possible liga-
tures are ff, fi, fl, ffi and ffl. For backwards compatibility,
the list of ligatures may be terminated with a 0. The list of
ligatures may not extend over more than one line.
name F The name of the font is F.
The characters of the font have a slant of n degrees. (Positive
The normal width of a space is n.
The font is special; this means that when a character is
requested that is not present in the current font, it will be
searched for in any special fonts that are mounted.
Other commands are ignored by troff but may be used by postprocessors
to store arbitrary information about the font in the font file.
The first section can contain comments which start with the # character
and extend to the end of a line.
The second section contains one or two subsections. It must contain a
charset subsection and it may also contain a kernpairs subsection.
These subsections can appear in any order. Each subsection starts with
a word on a line by itself.
The word charset starts the charset subsection. The charset line is
followed by a sequence of lines. Each line gives information for one
character. A line comprises a number of fields separated by blanks or
tabs. The format is
name metrics type code [entity_name] [-- comment]
name identifies the character: if name is a single character c then it
corresponds to the groff input character c; if it is of the form \c
where c is a single character, then it corresponds to the special char-
acter \[c]; otherwise it corresponds to the groff input character
\[name]. If it is exactly two characters xx it can be entered as \(xx.
Note that single-letter special characters can't be accessed as \c; the
only exception is `\-' which is identical to `\[-]'. The name --- is
special and indicates that the character is unnamed; such characters
can only be used by means of the \N escape sequence in troff.
Groff supports eight-bit characters; however some utilities have diffi-
culties with eight-bit characters. For this reason, there is a conven-
tion that the name charn is equivalent to the single character whose
code is n. For example, char163 would be equivalent to the character
with code 163 which is the pounds sterling sign in ISO Latin-1.
The type field gives the character type:
1 means the character has a descender, for example, p;
2 means the character has an ascender, for example, b;
3 means the character has both an ascender and a descender, for
The code field gives the code which the postprocessor uses to print the
character. The character can also be input to groff using this code by
means of the \N escape sequence. The code can be any integer. If it
starts with a 0 it will be interpreted as octal; if it starts with 0x
or 0X it will be intepreted as hexadecimal. Note, however, that the \N
escape sequence only accepts a decimal integer.
The entity_name field gives an ascii string identifying the glyph which
the postprocessor uses to print the character. This field is optional
and has been introduced so that the html device driver can encode its
character set. For example, the character `\[Po]' is represented as
`£' in html 4.0.
Anything on the line after the encoding field resp. after `--' will be
The metrics field has the form (in one line; it is broken here for the
sake of readability):
There must not be any spaces between these subfields. Missing sub-
fields are assumed to be 0. The subfields are all decimal integers.
Since there is no associated binary format, these values are not
required to fit into a variable of type char as they are in ditroff.
The width subfields gives the width of the character. The height sub-
field gives the height of the character (upwards is positive); if a
character does not extend above the baseline, it should be given a zero
height, rather than a negative height. The depth subfield gives the
depth of the character, that is, the distance below the lowest point
below the baseline to which the character extends (downwards is posi-
tive); if a character does not extend below above the baseline, it
should be given a zero depth, rather than a negative depth. The
italic-correction subfield gives the amount of space that should be
added after the character when it is immediately to be followed by a
character from a roman font. The left-italic-correction subfield gives
the amount of space that should be added before the character when it
is immediately to be preceded by a character from a roman font. The
subscript-correction gives the amount of space that should be added
after a character before adding a subscript. This should be less than
the italic correction.
A line in the charset section can also have the format
This indicates that name is just another name for the character men-
tioned in the preceding line.
The word kernpairs starts the kernpairs section. This contains a
sequence of lines of the form:
c1 c2 n
This means that when character c1 appears next to character c2 the
space between them should be increased by n. Most entries in kernpairs
section will have a negative value for n.
Device description file for device name.
Font file for font F of device name.
Groff Version 1.19.2 September 4, 2005 GROFF_FONT(5)