• Introduction.
• Input commands.
• Usage.
• Examples.
• Acknowledgments.
• References.
• List of Tbl Command Characters and Words
  

Tbl -- A Program to Format Tables

Tbl is a document formatting preprocessor for troff or nroff which makes even fairly complex tables easy to specify and enter. It is available on the UNIX[[dagger]] [[footnote: [[dagger]] UNIX is a trademark of Bell Laboratories. ]] system and on Honeywell 6000 GCOS. Tables are made up of columns which may be independently centered, right-adjusted, left-adjusted, or aligned by decimal points. Headings may be placed over single columns or groups of columns. A table entry may contain equations, or may consist of several rows of text. Horizontal or vertical lines may be drawn as desired in the table, and any table or element may be enclosed in a box. For example:

1970 Federal Budget Transfers
(in billions of dollars)
State	Taxes	Money	Net
	collected	spent
New York	22.91	21.35	-1.56
New Jersey	8.33	6.96	-1.37
Connecticut	4.12	3.10	-1.02
Maine	0.74	0.67	-0.07
California	22.29	22.42	+0.13
New Mexico	0.70	1.49	+0.79
Georgia	3.30	4.28	+0.98
Mississippi	1.15	2.32	+1.17
Texas	9.33	11.13	+1.80

   text
   .TS
   table
   .TE
   text
   .TS
   table
   .TE
   text
   . . .

   .TS
   options ;
   format .
   data
   .TE

1)

OPTIONS. There may be a single line of options affecting the whole table. If present, this line must follow the .TS line immediately and must contain a list of option names separated by spaces, tabs, or commas, and must be terminated by a semicolon. The allowable options are:

center

-- center the table (default is left-adjust);


expand

-- make the table as wide as the current line length;


box

-- enclose the table in a box;


allbox

-- enclose each item in the table in a box;


doublebox

-- enclose the table in two boxes;


tab (x)

-- use x instead of tab to separate data items.


linesize (n)

-- set lines or rules (e.g. from box) in n point type;


delim (xy)

-- recognize x and y as the eqn delimiters.

The tbl program tries to keep boxed tables on one page by issuing appropriate "need" (.ne) commands. These requests are calculated from the number of lines in the tables, and if there are spacing commands embedded in the input, these requests may be inaccurate; use normal troff procedures, such as keep-release macros, in that case. The user who must have a multi-page boxed table should use macros designed for this purpose, as explained below under 'Usage.'

2)

FORMAT. The format section of the table specifies the layout of the columns. Each line in this section corresponds to one line of the table (except that the last line corresponds to all following lines up to the next .T&, if any -- see below), and each line contains a key-letter for each column of the table. It is good practice to separate the key letters for each column by spaces or tabs. Each key-letter is one of the following:

L or l

to indicate a left-adjusted column entry;


R or r

to indicate a right-adjusted column entry;


C or c

to indicate a centered column entry;


N or n

to indicate a numerical column entry, to be aligned with other numerical entries so that the units digits of numbers line up;


A or a

to indicate an alphabetic subcolumn; all corresponding entries are aligned on the left, and positioned so that the widest is centered within the column (see example on page 12);


S ori s

to indicate a spanned heading, i.e. to indicate that the entry from the previous column continues across this column (not allowed for the first column, obviously); or


^

to indicate a vertically spanned heading, i.e. to indicate that the entry from the previous row continues down through this row. (Not allowed for the first row of the table, obviously).

When numerical alignment is specified, a location for the decimal point is sought. The rightmost dot (.) adjacent to a digit is used as a decimal point; if there is no dot adjoining a digit, the rightmost digit is used as a units digit; if no alignment is indicated, the item is centered in the column. However, the special non-printing character string \& may be used to override unconditionally dots and digits, or to align alphabetic data; this string lines up where a dot normally would, and then disappears from the final output. In the example below, the items shown at the left will be aligned (in a numerical column) as shown on the right:

13	13
4.2	4.2
26.4.12	26.4.12
abc	abc
abc\&	abc
43\&3.22	433.22
749.12	749.12

Note: If numerical data are used in the same column with wider L or r type table entries, the widest number is centered relative to the wider L or r items (L is used instead of l for readability; they have the same meaning as key-letters). Alignment within the numerical items is preserved. This is similar to the behavior of a type data, as explained above. However, alphabetic subcolumns (requested by the a key-letter) are always slightly indented relative to L items; if necessary, the column width is increased to force this. This is not true for n type entries.

Warning: the n and a items should not be used in the same column.

For readability, the key-letters describing each column should be separated by spaces. The end of the format section is indicated by a period. The layout of the key-letters in the format section resembles the layout of the actual data in the table. Thus a simple format might appear as:
c s s
l n n .
which specifies a table of three columns. The first line of the table contains a heading centered across all three columns; each remaining line contains a left-adjusted item in the first column followed by two columns of numerical data. A sample table in this format might be:

Overall title
Item-a	34.22	9.1
Item-b	12.65	.02
Items: c,d,e	23	5.8
Total	69.87	14.92

There are some additional features of the key-letter system:

Horizontal lines

-- A key-letter may be replaced by '_' (underscore) to indicate a horizontal line in place of the corresponding column entry, or by '=' to indicate a double horizontal line. If an adjacent column contains a horizontal line, or if there are vertical lines adjoining this column, this horizontal line is extended to meet the nearby lines. If any data entry is provided for this column, it is ignored and a warning message is printed.


Vertical lines

-- A vertical bar may be placed between column key-letters. This will cause a vertical line between the corresponding columns of the table. A vertical bar to the left of the first key-letter or to the right of the last one produces a line at the edge of the table. If two vertical bars appear between key-letters, a double vertical line is drawn.


Space between columns

-- A number may follow the key-letter. This indicates the amount of separation between this column and the next column. The number normally specifies the separation in ens (one en is about the width of the letter 'n').* * More precisely, an en is a number of points (1 point = 1/72 inch) equal to half the current type size. If the "expand" option is used, then these numbers are multiplied by a constant such that the table is as wide as the current line length. The default column separation number is 3. If the separation is changed the worst case (largest space requested) governs.


Vertical spanning

-- Normally, vertically spanned items extending over several rows of the table are centered in their vertical range. If a key-letter is followed by t or T, any corresponding vertically spanned item will begin at the top line of its range.


Font changes

-- A key-letter may be followed by a string containing a font name or number preceded by the letter f or F. This indicates that the corresponding column should be in a different font from the default font (usually Roman). All font names are one or two letters; a one-letter font name should be separated from whatever follows by a space or tab. The single letters B, b, I, and i are shorter synonyms for fB and fI. Font change commands given with the table entries override these specifications.


Point size changes

-- A key-letter may be followed by the letter p or P and a number to indicate the point size of the corresponding table entries. The number may be a signed digit, in which case it is taken as an increment or decrement from the current point size. If both a point size and a column separation value are given, one or more blanks must separate them.


Vertical spacing changes

-- A key-letter may be followed by the letter v or V and a number to indicate the vertical line spacing to be used within a multi-line corresponding table entry. The number may be a signed digit, in which case it is taken as an increment or decrement from the current vertical spacing. A column separation value must be separated by blanks or some other specification from a vertical spacing request. This request has no effect unless the corresponding table entry is a text block (see below).


Column width indication

-- A key-letter may be followed by the letter w or W and a width value in parentheses. This width is used as a minimum column width. If the largest element in the column is not as wide as the width value given after the w, the largest element is assumed to be that wide. If the largest element in the column is wider than the specified value, its width is used. The width is also used as a default line length for included text blocks. Normal troff units can be used to scale the width value; if none are used, the default is ens. If the width specification is a unitless integer the parentheses may be omitted. If the width value is changed in a column, the last one given controls.


Equal width columns

-- A key-letter may be followed by the letter e or E to indicate equal width columns. All columns whose key-letters are followed by e or E are made the same width. This permits the user to get a group of regularly spaced columns.


Note:

The order of the above features is immaterial; they need not be separated by spaces, except as indicated above to avoid ambiguities involving point size and font changes. Thus a numerical column entry in italic font and 12 point type with a minimum width of 2.5 inches and separated by 6 ens from the next column could be specified as
np12w(2.5i)fI 6


Alternative notation

-- Instead of listing the format of successive lines of a table on consecutive lines of the format section, successive line formats may be given on the same line, separated by commas, so that the format for the example above might have been written:
c s s, l n n .


Default

-- Column descriptors missing from the end of a format line are assumed to be L. The longest line in the format section, however, defines the number of columns in the table; extra columns in the data are ignored silently.

3)

DATA. The data for the table are typed after the format. Normally, each table line is typed as one line of data. Very long input lines can be broken: any line whose last character is \ is combined with the following line (and the \ vanishes). The data for different columns (the table entries) are separated by tabs, or by whatever character has been specified in the option tabs option. There are a few special cases:

Troff commands within tables

-- An input line beginning with a '.' followed by anything but a number is assumed to be a command to troff and is passed through unchanged, retaining its position in the table. So, for example, space within a table may be produced by ".sp" commands in the data.


Full width horizontal lines

-- An input line containing only the character $fat "_" $ (underscore) or = (equal sign) is taken to be a single or double line, respectively, extending the full width of the table.


Single column horizontal lines

-- An input table entry containing only the character $fat "_" $ or = is taken to be a single or double line extending the full width of the column. Such lines are extended to meet horizontal or vertical lines adjoining this column. To obtain these characters explicitly in a column, either precede them by \& or follow them by a space before the usual tab or newline.


Short horizontal lines

-- An input table entry containing only the string $fat "\_"$ is taken to be a single line as wide as the contents of the column. It is not extended to meet adjoining lines.


Vertically spanned items

-- An input table entry containing only the character string \^ indicates that the table entry immediately above spans downward over this row. It is equivalent to a table format key-letter of '^'.


Text blocks

-- In order to include a block of text as a table entry, precede it by $fat roman "T{" $ and follow it by $fat roman "T}" $. Thus the sequence
. . . $fat roman "T{"$
block of
text
$fat roman "T}"$ . . .
is the way to enter, as a single entry in the table, something that cannot conveniently be typed as a simple string between tabs. Note that the $fat roman "T}" $ end delimiter must begin a line; additional columns of data may follow after a tab on the same line. See the example on page 11 for an illustration of included text blocks in a table. If more than twenty or thirty text blocks are used in a table, various limits in the troff program are likely to be exceeded, producing diagnostics such as 'too many string/macro names' or 'too many number registers.'





Text blocks are pulled out from the table, processed separately by troff, and replaced in the table as a solid block. If no line length is specified in the block of text itself, or in the table format, the default is to use $ L times C / (N+1) $ where L is the current line length, C is the number of table columns spanned by the text, and N is the total number of columns in the table. The other parameters (point size, font, etc.) used in setting the block of text are those in effect at the beginning of the table (including the effect of the ".TS" macro) and any table format specifications of size, spacing and font, using the p, v and f modifiers to the column key-letters. Commands within the text block itself are also recognized, of course. However, troff commands within the table data but not within the text block do not affect that block.
delim off
f1fP


Warnings:

-- Although any number of lines may be present in a table, only the first 200 lines are used in calculating the widths of the various columns. A multi-page table, of course, may be arranged as several single-page tables if this proves to be a problem. Other difficulties with formatting may arise because, in the calculation of column widths all table entries are assumed to be in the font and size being used when the ".TS" command was encountered, except for font and size changes indicated (a) in the table format section and (b) within the table data (as in the entry \s+3\fIdata\fP\s0). Therefore, although arbitrary troff requests may be sprinkled in a table, care must be taken to avoid confusing the width calculations; use requests such as '.ps' with care.

4)

ADDITIONAL COMMAND LINES. If the format of a table must be changed after many similar lines, as with sub-headings or summarizations, the ".T&" (table continue) command can be used to change column parameters. The outline of such a table input is:

   .TS
   options ;
   format .
   data
   . . .
   .T&
   format .
   data
   .T&
   format .
   data
   .TE

as in the examples on pages 10 and 13. Using this procedure, each table line can be close to its corresponding format line.
Warning: it is not possible to change the number of columns, the space between columns, the global options such as box, or the selection of columns to be made equal width.

   tbl input-file | troff

   tbl file-1 file-2 . . . | eqn | troff -ms

Acknowledgments.

[1]

J. F. Ossanna, NROFF/TROFF User's Manual, Computing Science Technical Report No. 54, Bell Laboratories, 1976.

[2]

K. Thompson and D. M. Ritchie, "The UNIX Time-Sharing System," Comm. ACM. 17, pp. 365-75 (1974).

[3]

B. W. Kernighan and L. L. Cherry, "A System for Typesetting Mathematics," Comm. ACM. 18, pp. 151-57 (1975).

[4]

M. E. Lesk, Typing Documents on UNIX, Bell Laboratories internal memorandum.

[5]

M. E. Lesk and B. W. Kernighan, Computer Typesetting of Technical Journals on UNIX, Computing Science Technical Report No. 44, Bell Laboratories, July 1976.

[6]

J. R. Mashey and D. W. Smith, PWB/MM -- Programmer's Workbench Memorandum Macros, Bell Laboratories memorandum.

delim $$
gfont roman
f1fP