# tbl - prepare tables for groff documents - man(1) - [phpMan]

> **TLDR:** Table preprocessor for the groff (GNU Troff) document formatting system.
>
- Process input with tables, saving the output for future typesetting with groff to PostScript:
  `tbl {{path/to/input_file}} > {{path/to/output.roff}}`
- Typeset input with tables to PDF using the [me] macro package:
  `tbl -T {{pdf}} {{path/to/input.tbl}} | groff -{{me}} -T {{pdf}} > {{path/to/output.pdf}}`

*Source: tldr-pages*

---

[_tbl_(1)](https://www.chedong.com/phpMan.php/man/tbl/1/markdown)                                 General Commands Manual                                [_tbl_(1)](https://www.chedong.com/phpMan.php/man/tbl/1/markdown)

## 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)](https://www.chedong.com/phpMan.php/man/groff/1/markdown) document formatting system.  _tbl_ is a
       [_troff_(1)](https://www.chedong.com/phpMan.php/man/troff/1/markdown) preprocessor that translates descriptions of tables embedded in [_roff_(7)](https://www.chedong.com/phpMan.php/man/roff/7/markdown) 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  em‐
       ployed)  must  be  used.   Normally, _tbl_ is not executed directly by the user, but invoked by
       specifying the **-t **option to [_groff_(1)](https://www.chedong.com/phpMan.php/man/groff/1/markdown).  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 head‐
       ings that repeat on subsequent pages (see below).

       (Experienced _roff_ users should observe that _tbl_ is not a _roff_ language interpreter:  the  de‐
       fault 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 is‐
       sues 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_  _defini‐_
       _tions;_  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 influ‐
       ence 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 op‐
       tion  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)  clas‐
              sifier (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)](https://www.chedong.com/phpMan.php/man/eqn/1/markdown) in‐
              put, 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 indenta‐
              tion) 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 hor‐
              izontal  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  se‐
       ries  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 em‐
       boldened 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  be‐
       low, 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  rectangu‐
       lar  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  adja‐
       cent cells in the table.  Except for “**|**”, any classifier can be followed by one or more _modi‐_
       _fiers;_  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  modi‐
       fiers  in  lowercase.  Thus, “**CbCb,LR.**” defines two rows of two columns.  The first row's en‐
       tries 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**-classi‐
              fied  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 col‐
              umn.  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  cor‐
              respond 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 col‐
              umn 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 ta‐
       ble 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  ac‐
       cepted,  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 mod‐
       ifier **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”  be‐
              low).  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 modi‐
              fier 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.  Parenthe‐
              ses are required if the width is to be followed immediately by an explicit column sep‐
              aration (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  rectangular‐
       ization  of  the  table) are discarded with a diagnostic message.  _roff_ control lines are ac‐
       cepted 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,  ad‐
       justed,  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 corre‐
       sponding 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 con‐
       trast 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 hor‐
         izontal 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 **\R_**x_, where _x_ is any _roff_ ordinary or special character, is  re‐
         placed  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  ta‐
       ble  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  di‐
       version)  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)](https://www.chedong.com/phpMan.php/man/eqn/1/markdown).  ([_groff_(1)](https://www.chedong.com/phpMan.php/man/groff/1/markdown) automatically arranges preprocessors in
       the correct order.)  Don't call the **EQ **and **EN **macros within tables; instead,  set  up  delim‐
       iters 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  recog‐
         nized 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  defini‐
       tion.

       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_  uncondition‐
       ally  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     
              ter other than space or newline.  Furthermore, interpret the uninterpreted leader  es‐
              cape 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 di‐
       vert  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.  Oth‐
       erwise, pass the macro call to the enclosing diversion using the transparent line escape  se‐
       quence **\!**; 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)](https://www.chedong.com/phpMan.php/man/grotty/1/markdown); 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 verti‐
       cal 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  over‐
       strike 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 inter‐
       preted only in copy mode.

              .ds a \a
              .TS
              box center tab(;);
              [Lw(2i)](https://www.chedong.com/phpMan.php/man/Lw/2i/markdown)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  de‐
       sired (so that the rule abuts the content), you can introduce “dummy” columns with zero sepa‐
       ration 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
       It can be easier to acquire the language of _tbl_ through examples than formal description, es‐
       pecially 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  descrip‐
       tion.

              .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 re‐
       main 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**
       “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)](https://www.chedong.com/phpMan.php/man/groff/1/markdown), [_troff_(1)](https://www.chedong.com/phpMan.php/man/troff/1/markdown)

groff 1.23.0                                31 March 2024                                     [_tbl_(1)](https://www.chedong.com/phpMan.php/man/tbl/1/markdown)
