tbl(1) — Linux manual page

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tbl(1)                   General Commands Manual                   tbl(1)

Name         top

       tbl - prepare tables for groff documents

Synopsis         top

       tbl [-C] [file ...]

       tbl --help

       tbl -v
       tbl --version

Description         top

       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         top

       --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         top

       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         top

       It can be easier to acquire the language of tbl through examples
       than formal description, especially at first.

              .TS
              box center tab(#);
              Cb Cb
              L L.
              Ability#Application
              Strength#crushes a tomato
              Dexterity#dodges a thrown tomato
              Constitution#eats a month-old tomato without becoming ill
              Intelligence#knows that a tomato is a fruit
              Wisdom#chooses \f[I]not\f[] to put tomato in a fruit salad
              Charisma#sells obligate carnivores tomato-based fruit salads
              .TE

     ┌────────────────────────────────────────────────────────────────────┐
     │   Ability                          Application                     │
     │ Strength       crushes a tomato                                    │
     │ Dexterity      dodges a thrown tomato                              │
     │ Constitution   eats a month-old tomato without becoming ill        │
     │ Intelligence   knows that a tomato is a fruit                      │
     │ Wisdom         chooses not to put tomato in a fruit salad          │
     │ Charisma       sells obligate carnivores tomato-based fruit salads │
     └────────────────────────────────────────────────────────────────────┘

       The A and N column classifiers can be easier to grasp in visual
       rendering than in description.

              .TS
              center tab(;);
              CbS,LN,AN.
              Daily energy intake (in MJ)
              Macronutrients
              .\" assume 3 significant figures of precision
              Carbohydrates;4.5
              Fats;2.25
              Protein;3
              .T&
              LN,AN.
              Mineral
              Pu-239;14.6
              _
              .T&
              LN.
              Total;\[ti]24.4
              .TE

                              Daily energy intake (in MJ)
                              Macronutrients
                                Carbohydrates       4.5
                                Fats                2.25
                                Protein             3
                              Mineral
                                Pu-239             14.6
                              ────────────────────────────
                              Total               ~24.4

       Next, we'll lightly adapt a compact presentation of spanning,
       vertical alignment, and zero-width column modifiers from the
       mandoc reference for its tbl interpreter.  It rewards close study.

              .TS
              box center tab(:);
              Lz  S | Rt
              Ld| Cb| ^
              ^ | Rz  S.
              left:r
              l:center:
              :right
              .TE

                                  ┌────────────┬───┐
                                  │ le│ft       │ r │
                                  │   │ center │   │
                                  │ l │      right │
                                  └───┴────────────┘

       Row staggering is not visually achievable on terminal devices, but
       a table using it can remain comprehensible nonetheless.

              .TS
              center tab(|);
              Cf(BI) Cf(BI) Cf(B), C C Cu.
              n|n\f[B]\[tmu]\f[]n|difference
              1|1
              2|4|3
              3|9|5
              4|16|7
              5|25|9
              6|36|11
              .TE

                                 n   n×n   difference
                                 1    1
                                 2    4        3
                                 3    9        5
                                 4   16        7
                                 5   25        9
                                 6   36        11

       Some tbl features cannot be illustrated in the limited environment
       of a portable man page.

       We can define a macro outside of a tbl region that we can call
       from within it to cause a page break inside a multi-page boxed
       table.  You can choose a different name; be sure to change both
       occurrences of “BP”.

              .de BP
              .  ie '\\n(.z'' .bp \\$1
              .  el \!.BP \\$1
              ..

See also         top

       “Tbl—A Program to Format Tables”, by M. E. Lesk, 1976 (revised 16
       January 1979), AT&T Bell Laboratories Computing Science Technical
       Report No. 49.

       The spanning example above was taken from mandoc's man page for
       its tbl implementation ⟨https://man.openbsd.org/tbl.7⟩.

       groff(1), troff(1)

COLOPHON         top

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groff 1.23.0                   2 July 2023                         tbl(1)

Pages that refer to this page: col(1)colcrt(1)