Ubuntu Manpage: tbl - prepare tables for groff documents

Name

       tbl - prepare tables for groff documents

Synopsis

       tbl [-C] [file ...]

       tbl --help

       tbl -v
       tbl --version

Description

The GNU implementation of tbl is part of the groff(1) document formatting system. tbl is a troff(1)
preprocessor that translates descriptions of tables embedded in roff(7) input files into the language
understood by troff. It copies the contents of each file to the standard output stream, except that
lines between .TS and .TE are interpreted as table descriptions. While GNU tbl's input syntax is highly
compatible with AT&T tbl, the output GNU tbl produces cannot be processed by AT&T troff; GNU troff (or a
troff implementing any GNU extensions employed) must be used. Normally, tbl is not executed directly by
the user, but invoked by specifying the -t option to groff(1). If no file operands are given on the
command line, or if file is “-”, tbl reads the standard input stream.

Overview
tbl expects to find table descriptions between input lines that begin with .TS (table start) and .TE
(table end). Each such table region encloses one or more table descriptions. Within a table region,
table descriptions beyond the first must each be preceded by an input line beginning with .T&. This
mechanism does not start a new table region; all table descriptions are treated as part of their .TS/.TE
enclosure, even if they are boxed or have column headings that repeat on subsequent pages (see below).

(Experienced roff users should observe that tbl is not a roff language interpreter: the default control
character must be used, and no spaces or tabs are permitted between the control character and the macro
name. These tbl input tokens remain as-is in the output, where they become ordinary macro calls. Macro
packages often define TS, T&, and TE macros to handle issues of table placement on the page. tbl
produces groff code to define these macros as empty if their definitions do not exist when the formatter
encounters a table region.)

Each table region may begin with region options, and must contain one or more table definitions; each
table definition contains a format specification followed by one or more input lines (rows) of entries.
These entries comprise the table data.

Region options
The line immediately following the .TS token may specify region options, keywords that influence the
interpretation or rendering of the region as a whole or all table entries within it indiscriminately.
They must be separated by commas, spaces, or tabs. Those that require a parenthesized argument permit
spaces and tabs between the option's name and the opening parenthesis. Options accumulate and cannot be
unset within a region once declared; if an option that takes a parameter is repeated, the last occurrence
controls. If present, the set of region options must be terminated with a semicolon (;).

Any of the allbox, box, doublebox, frame, and doubleframe region options makes a table “boxed” for the
purpose of later discussion.

allbox Enclose each table entry in a box; implies box.

box Enclose the entire table region in a box. As a GNU extension, the alternative option name frame
is also recognized.

center Center the table region with respect to the current indentation and line length; the default is to
left-align it. As a GNU extension, the alternative option name centre is also recognized.

decimalpoint(c)
Recognize character c as the decimal separator in columns using the N (numeric) classifier (see
subsection “Column classifiers” below). This is a GNU extension.

delim(xy)
Recognize characters x and y as start and end delimiters, respectively, for eqn(1) input, and
ignore input between them. x and y need not be distinct.

doublebox
Enclose the entire table region in a double box; implies box. As a GNU extension, the alternative
option name doubleframe is also recognized.

expand Spread the table horizontally to fill the available space (line length minus indentation) by
increasing column separation. Ordinarily, a table is made only as wide as necessary to
accommodate the widths of its entries and its column separations (whether specified or default).
When expand applies to a table that exceeds the available horizontal space, column separation is
reduced as far as necessary (even to zero). tbl produces groff input that issues a diagnostic if
such compression occurs. The column modifier x (see below) overrides this option.

linesize(n)
Draw lines or rules (e.g., from box) with a thickness of n points. The default is the current
type size when the region begins. This option is ignored on terminal devices.

nokeep Don't use roff diversions to manage page breaks. Normally, tbl employs them to avoid breaking a
page within a table row. This usage can sometimes interact badly with macro packages' own use of
diversions—when footnotes, for example, are employed. This is a GNU extension.

nospaces
Ignore leading and trailing spaces in table entries. This is a GNU extension.

nowarn Suppress diagnostic messages produced at document formatting time when the line or page lengths
are inadequate to contain a table row. This is a GNU extension.

tab(c) Use the character c instead of a tab to separate entries in a row of table data.

Table format specification
The table format specification is mandatory: it determines the number of columns in the table and directs
how the entries within it are to be typeset. The format specification is a series of column descriptors.
Each descriptor encodes a classifier followed by zero or more modifiers. Classifiers are letters
(recognized case-insensitively) or punctuation symbols; modifiers consist of or begin with letters or
numerals. Spaces, tabs, newlines, and commas separate descriptors. Newlines and commas are special;
they apply the descriptors following them to a subsequent row of the table. (This enables column
headings to be centered or emboldened while the table entries for the data are not, for instance.) We
term the resulting group of column descriptors a row definition. Within a row definition, separation
between column descriptors (by spaces or tabs) is often optional; only some modifiers, described below,
make separation necessary.

Each column descriptor begins with a mandatory classifier, a character that selects from one of several
arrangements. Some determine the positioning of table entries within a rectangular cell: centered, left-
aligned, numeric (aligned to a configurable decimal separator), and so on. Others perform special
operations like drawing lines or spanning entries from adjacent cells in the table. Except for “|”, any
classifier can be followed by one or more modifiers; some of these accept an argument, which in GNU tbl
can be parenthesized. Modifiers select fonts, set the type size, and perform other tasks described
below.

The format specification can occupy multiple input lines, but must conclude with a dot “.” followed by a
newline. Each row definition is applied in turn to one row of the table. The last row definition is
applied to rows of table data in excess of the row definitions.

For clarity in this document's examples, we shall write classifiers in uppercase and modifiers in
lowercase. Thus, “CbCb,LR.” defines two rows of two columns. The first row's entries are centered and
boldfaced; the second and any further rows' first and second columns are left- and right-aligned,
respectively.

The row definition with the most column descriptors determines the number of columns in the table; any
row definition with fewer is implicitly extended on the right-hand side with L classifiers as many times
as necessary to make the table rectangular.

Column classifiers
The L, R, and C classifiers are the easiest to understand and use.

A, a Center longest entry in this column, left-align remaining entries in the column with respect to
the centered entry, then indent all entries by one en. Such “alphabetic” entries (hence the name
of the classifier) can be used in the same column as L-classified entries, as in “LL,AR.”. The A
entries are often termed “sub-columns” due to their indentation.

C, c Center entry within the column.

L, l Left-align entry within the column.

N, n Numerically align entry in the column. tbl aligns columns of numbers vertically at the units
place. If multiple decimal separators are adjacent to a digit, it uses the rightmost one for
vertical alignment. If there is no decimal separator, the rightmost digit is used for vertical
alignment; otherwise, tbl centers the entry within the column. The roff dummy character \& in an
entry marks the glyph preceding it (if any) as the units place; if multiple instances occur in the
data, the leftmost is used for alignment.

If N-classified entries share a column with L or R entries, tbl centers the widest N entry with
respect to the widest L or R entry, preserving the alignment of N entries with respect to each
other.

The appearance of eqn equations within N-classified columns can be troublesome due to the
foregoing textual scan for a decimal separator. Use the delim region option to make tbl ignore
the data within eqn delimiters for that purpose.

R, r Right-align entry within the column.

S, s Span previous entry on the left into this column.

^ Span entry in the same column from the previous row into this row.

_, - Replace table entry with a horizontal rule. An empty table entry is expected to correspond to
this classifier; if data are found there, tbl issues a diagnostic message.

= Replace table entry with a double horizontal rule. An empty table entry is expected to correspond
to this classifier; if data are found there, tbl issues a diagnostic message.

| Place a vertical rule (line) on the corresponding row of the table (if two of these are adjacent,
a double vertical rule). This classifier does not contribute to the column count and no table
entries correspond to it. A | to the left of the first column descriptor or to the right of the
last one produces a vertical rule at the edge of the table; these are redundant (and ignored) in
boxed tables.

To change the table format within a tbl region, use the .T& token at the start of a line. It is followed
by a format specification and table data, but not region options. The quantity of columns in a new table
format thus introduced cannot increase relative to the previous table format; in that case, you must end
the table region and start another. If that will not serve because the region uses box options or the
columns align in an undesirable manner, you must design the initial table format specification to include
the maximum quantity of columns required, and use the S horizontal spanning classifier where necessary to
achieve the desired columnar alignment.

Attempting to horizontally span in the first column or vertically span on the first row is an error.
Non-rectangular span areas are also not supported.

Column modifiers
Any number of modifiers can follow a column classifier. Arguments to modifiers, where accepted, are
case-sensitive. If the same modifier is applied to a column specifier more than once, or if conflicting
modifiers are applied, only the last occurrence has effect. The modifier x is mutually exclusive with e
and w, but e is not mutually exclusive with w; if these are used in combination, x unsets both e and w,
while either e or w overrides x.

b, B Typeset entry in boldface, abbreviating f(B).

d, D Align a vertically spanned table entry to the bottom (“down”), instead of the center, of its
range. This is a GNU extension.

e, E Equalize the widths of columns with this modifier. The column with the largest width controls.
This modifier sets the default line length used in a text block.

f, F Select the typeface for the table entry. This modifier must be followed by a font or style name
(one or two characters not starting with a digit), font mounting position (a single digit), or a
name or mounting position of any length in parentheses. The last form is a GNU extension. (The
parameter corresponds to that accepted by the troff ft request.) A one-character argument not in
parentheses must be separated by one or more spaces or tabs from what follows.

i, I Typeset entry in an oblique or italic face, abbreviating f(I).

m, M Call a groff macro before typesetting a text block (see subsection “Text blocks” below). This is
a GNU extension. This modifier must be followed by a macro name of one or two characters or a
name of any length in parentheses. A one-character macro name not in parentheses must be
separated by one or more spaces or tabs from what follows. The named macro must be defined before
the table region containing this column modifier is encountered. The macro should contain only
simple groff requests to change text formatting, like adjustment or hyphenation. The macro is
called after the column modifiers b, f, i, p, and v take effect; it can thus override other column
modifiers.

p, P Set the type size for the table entry. This modifier must be followed by an integer n with an
optional leading sign. If unsigned, the type size is set to n scaled points. Otherwise, the type
size is incremented or decremented per the sign by n scaled points. The use of a signed multi-
digit number is a GNU extension. (The parameter corresponds to that accepted by the troff ps
request.) If a type size modifier is followed by a column separation modifier (see below), they
must be separated by at least one space or tab.

t, T Align a vertically spanned table entry to the top, instead of the center, of its range.

u, U Move the column up one half-line, “staggering” the rows. This is a GNU extension.

v, V Set the vertical spacing to be used in a text block. This modifier must be followed by an
integer n with an optional leading sign. If unsigned, the vertical spacing is set to n points.
Otherwise, the vertical spacing is incremented or decremented per the sign by n points. The use
of a signed multi-digit number is a GNU extension. (This parameter corresponds to that accepted
by the troff vs request.) If a vertical spacing modifier is followed by a column separation
modifier (see below), they must be separated by at least one space or tab.

w, W Set the column's minimum width. This modifier must be followed by a number, which is either a
unitless integer, or a roff horizontal measurement in parentheses. Parentheses are required if
the width is to be followed immediately by an explicit column separation (alternatively, follow
the width with one or more spaces or tabs). If no unit is specified, ens are assumed. This
modifier sets the default line length used in a text block.

x, X Expand the column. After computing the column widths, distribute any remaining line length evenly
over all columns bearing this modifier. Applying the x modifier to more than one column is a GNU
extension. This modifier sets the default line length used in a text block.

z, Z Ignore the table entries corresponding to this column for width calculation purposes; that is,
compute the column's width using only the information in its descriptor.

n A numeric suffix on a column descriptor sets the separation distance (in ens) from the succeeding
column; the default separation is 3n. This separation is proportionally multiplied if the expand
region option is in effect; in the case of tables wider than the output line length, this
separation might be zero. A negative separation cannot be specified. A separation amount after
the last column in a row is nonsensical and provokes a diagnostic from tbl.

Table data
The table data come after the format specification. Each input line corresponds to a table row, except
that a backslash at the end of a line of table data continues an entry on the next input line. (Text
blocks, discussed below, also spread table entries across multiple input lines.) Table entries within a
row are separated in the input by a tab character by default; see the tab region option above. Excess
entries in a row of table data (those that have no corresponding column descriptor, not even an implicit
one arising from rectangularization of the table) are discarded with a diagnostic message. roff control
lines are accepted between rows of table data and within text blocks. If you wish to visibly mark an
empty table entry in the document source, populate it with the \& roff dummy character. The table data
are interrupted by a line consisting of the .T& input token, and conclude with the line .TE.

Ordinarily, a table entry is typeset rigidly. It is not filled, broken, hyphenated, adjusted, or
populated with additional inter-sentence space. tbl instructs the formatter to measure each table entry
as it occurs in the input, updating the width required by its corresponding column. If the z modifier
applies to the column, this measurement is ignored; if w applies and its argument is larger than this
width, that argument is used instead. In contrast to conventional roff input (within a paragraph, say),
changes to text formatting, such as font selection or vertical spacing, do not persist between entries.

Several forms of table entry are interpreted specially.

• If a table row contains only an underscore or equals sign (_ or =), a single or double horizontal rule
(line), respectively, is drawn across the table at that point.

• A table entry containing only _ or = on an otherwise populated row is replaced by a single or double
horizontal rule, respectively, joining its neighbors.

• Prefixing a lone underscore or equals sign with a backslash also has meaning. If a table entry
consists only of \_ or \= on an otherwise populated row, it is replaced by a single or double
horizontal rule, respectively, that does not (quite) join its neighbors.

• A table entry consisting of \Rx, where x is any roff ordinary or special character, is replaced by
enough repetitions of the glyph corresponding to x to fill the column, albeit without joining its
neighbors.

• On any row but the first, a table entry of \^ causes the entry above it to span down into the current
one.

On occasion, these special tokens may be required as literal table data. To use either _ or = literally
and alone in an entry, prefix or suffix it with the roff dummy character \&. To express \_, \=, or \R,
use a roff escape sequence to interpolate the backslash (\e or \[rs]). A reliable way to emplace the \^
glyph sequence within a table entry is to use a pair of groff special character escape sequences
(\[rs]\[ha]).

Rows of table entries can be interleaved with groff control lines; these do not count as table data. On
such lines the default control character (.) must be used (and not changed); the no-break control
character is not recognized. To start the first table entry in a row with a dot, precede it with the
roff dummy character \&.

Text blocks
An ordinary table entry's contents can make a column, and therefore the table, excessively wide; the
table then exceeds the line length of the page, and becomes ugly or is exposed to truncation by the
output device. When a table entry requires more conventional typesetting, breaking across more than one
output line (and thereby increasing the height of its row), it can be placed within a text block.

tbl interprets a table entry beginning with “T{” at the end of an input line not as table data, but as a
token starting a text block. Similarly, “T}” at the start of an input line ends a text block; it must
also end the table entry. Text block tokens can share an input line with other table data (preceding T{
and following T}). Input lines between these tokens are formatted in a diversion by troff. Text blocks
cannot be nested. Multiple text blocks can occur in a table row.

Text blocks are formatted as was the text prior to the table, modified by applicable column descriptors.
Specifically, the classifiers A, C, L, N, R, and S determine a text block's alignment within its cell,
but not its adjustment. Add na or ad requests to the beginning of a text block to alter its adjustment
distinctly from other text in the document. As with other table entries, when a text block ends, any
alterations to formatting parameters are discarded. They do not affect subsequent table entries, not
even other text blocks.

If w or x modifiers are not specified for all columns of a text block's span, the default length of the
text block (more precisely, the line length used to process the text block diversion) is computed as
L×C/(N+1), where L is the current line length, C the number of columns spanned by the text block, and N
the number of columns in the table. If necessary, you can also control a text block's width by including
an ll (line length) request in it prior to any text to be formatted. Because a diversion is used to
format the text block, its height and width are subsequently available in the registers dn and dl,
respectively.

roff interface
The register TW stores the width of the table region in basic units; it can't be used within the region
itself, but is defined before the .TE token is output so that a groff macro named TE can make use of it.
T. is a Boolean-valued register indicating whether the bottom of the table is being processed. The #T
register marks the top of the table. Avoid using these names for any other purpose.

tbl also defines a macro T# to produce the bottom and side lines of a boxed table. While tbl itself
arranges for the output to include a call of this macro at the end of such a table, it can also be used
by macro packages to create boxes for multi-page tables by calling it from a page footer macro that is
itself called by a trap planted near the bottom of the page. See section “Limitations” below for more on
multi-page tables.

GNU tbl internally employs register, string, macro, and diversion names beginning with the numeral 3. A
document to be preprocessed with GNU tbl should not use any such identifiers.

Interaction with eqn
tbl should always be called before eqn(1). (groff(1) automatically arranges preprocessors in the correct
order.) Don't call the EQ and EN macros within tables; instead, set up delimiters in your eqn input and
use the delim region option so that tbl will recognize them.

GNU tbl enhancements
In addition to extensions noted above, GNU tbl removes constraints endured by users of AT&T tbl.

• Region options can be specified in any lettercase.

• There is no limit on the number of columns in a table, regardless of their classification, nor any
limit on the number of text blocks.

• All table rows are considered when deciding column widths, not just those occurring in the first 200
input lines of a region. Similarly, table continuation (.T&) tokens are recognized outside a region's
first 200 input lines.

• Numeric and alphabetic entries may appear in the same column.

• Numeric and alphabetic entries may span horizontally.

Using GNU tbl within macros
You can embed a table region inside a macro definition. However, since tbl writes its own macro
definitions at the beginning of each table region, it is necessary to call end macros instead of ending
macro definitions with “..”. Additionally, the escape character must be disabled.

Not all tbl features can be exercised from such macros because tbl is a roff preprocessor: it sees the
input earlier than troff does. For example, vertically aligning decimal separators fails if the numbers
containing them occur as macro or string parameters; the alignment is performed by tbl itself, which sees
only \$1, \$2, and so on, and therefore can't recognize a decimal separator that only appears later when
troff interpolates a macro or string definition.

Using tbl macros within conditional input (that is, contingent upon an if, ie, el, or while request) can
result in misleading line numbers in subsequent diagnostics. tbl unconditionally injects its output into
the source document, but the conditional branch containing it may not be taken, and if it is not, the lf
requests that tbl injects to restore the source line number cannot take effect. Consider copying the
input line counter register c. and restoring its value at a convenient location after applicable
arithmetic.

Options

       --help displays a usage message, while -v and --version show version information; all exit afterward.

       -C     Enable AT&T compatibility mode: recognize .TS and .TE even when followed by a character other than
              space or newline.  Furthermore, interpret the uninterpreted leader escape sequence \a.

Limitations

Multi-page tables, if boxed and/or if you want their column headings repeated after page breaks, require
support at the time the document is formatted. A convention for such support has arisen in macro
packages such as ms, mm, and me. To use it, follow the .TS token with a space and then “H”; this will be
interpreted by the formatter as a TS macro call with an H argument. Then, within the table data, call
the TH macro; this informs the macro package where the headings end. If your table has no such heading
rows, or you do not desire their repetition, call TH immediately after the table format specification.
If a multi-page table is boxed or has repeating column headings, do not enclose it with keep/release
macros, or divert it in any other way. Further, the bp request will not cause a page break in a “TS H”
table. Define a macro to wrap bp: invoke it normally if there is no current diversion. Otherwise, pass
the macro call to the enclosing diversion using the transparent line escape sequence \!; this will
“bubble up” the page break to the output device. See section “Examples” below for a demonstration.

Double horizontal rules are not supported by grotty(1); single rules are used instead. grotty also
ignores half-line motions, so the u column modifier has no effect. On terminal devices (“nroff mode”),
horizontal rules and box borders occupy a full vee of space; this amount is doubled for doublebox tables.
Tables using these features thus require more vertical space in nroff mode than in troff mode: write ne
requests accordingly. Vertical rules between columns are drawn in the space between columns in nroff
mode; using double vertical rules and/or reducing the column separation below the default can make them
ugly or overstrike them with table data.

A text block within a table must be able to fit on one page.

Using \a to put leaders in table entries does not work in GNU tbl, except in compatibility mode. This is
correct behavior: \a is an uninterpreted leader. You can still use the roff leader character (Control+A)
or define a string to use \a as it was designed: to be interpreted only in copy mode.

.ds a \a
.TS
box center tab(;);
Lw(2i)0 L.
Population\*a;6,327,119
.TE

┌──────────────────────────────┐
│Population..........6,327,119 │
└──────────────────────────────┘
A leading and/or trailing | in a format specification, such as “|LCR|.”, produces an en space between the
vertical rules and the content of the adjacent columns. If no such space is desired (so that the rule
abuts the content), you can introduce “dummy” columns with zero separation and empty corresponding table
entries before and/or after.

.TS
center tab(#);
R0|L C R0|L.
_
#levulose#glucose#dextrose#
_
.TE

These dummy columns have zero width and are therefore invisible; unfortunately they usually don't work as
intended on terminal devices.

Examples