# term 5 2024-06-15 ncurses 6.5 File formats

    term(5)                          File formats                          term(5)

## NAME

           term - compiled terminfo terminal description

## DESCRIPTION

           tic(1) compiles a terminfo terminal type description, and setupterm(3x)
           reads it.  A compiled description may be stored  in  a  file  or  in  a
           database  of, potentially, many such descriptions.  Further, a compiled
           description may be in one of two formats: one similar to that  used  by
           System V,  and  a  newer,  extensible  format  employed  exclusively by
           ncurses.

### Storage Location

           Compiled  terminfo  descriptions  are  placed   under   the   directory
           /usr/share/terminfo.   One  of  two  configurations  is  selected  when
           building the ncurses libraries.

           directory tree
                A two-level scheme is used to avoid a linear search of a huge Unix
                system  directory:  /usr/share/terminfo/c/name  where  name is the
                name of the terminal, and c is the first character of name.  Thus,
                the  compiled  description of terminal type "act4" is found in the
                file /usr/share/terminfo/a/act4.  Synonyms for the  same  terminal
                are implemented by multiple links to the same compiled file.

           hashed database
                Using  the Berkeley database API, two types of records are stored:
                the terminfo data in the same format as that stored in a directory
                tree  with  the terminal's primary type name as a key, and records
                containing only aliases pointing to the primary name.

                If built to write hashed databases, ncurses can still  read  term-
                info  databases  organized  as  a directory tree, but cannot write
                entries into the  directory  tree.   It  can  write  (or  rewrite)
                entries in the hashed database.

                ncurses   distinguishes   the   two  cases  in  the  TERMINFO  and
                TERMINFO_DIRS environment variable by assuming  a  directory  tree
                for entries that correspond to an existing directory, and a hashed
                database otherwise.

### Legacy Storage Format

           The format has been chosen so that it will be the same on all hardware.
           A  byte  of  at  least eight bits' width is assumed, but no assumptions
           about bit ordering or sign extension are made.

           The file is divided into six parts:

                (a) header,

                (b) terminal names,

                (c) Boolean flags,

                (d) numbers,

                (e) strings, and

                (f) a string table.

           The header section begins the file.  This section  contains  six  short
           integers in the format described below.  These integers are

                (1) the magic number
                     (octal 0432);

                (2) the size,
                     in bytes, of the terminal names section;

                (3) the number of bytes in the Boolean flags section;

                (4) the number of short integers in the numbers section;

                (5) the number of offsets
                     (short integers) in the strings section;

                (6) the size,
                     in bytes, of the string table.

           The  capabilities  in  the Boolean flags, numbers, and strings sections
           are in the same order as in the header file term.h.

           Short integers are signed, in the range -32768 to 32767, and stored  in
           little-endian format.

           Numbers  in  a  terminal  description,  whether they are entries in the
           numbers or strings table, are positive  integers.   Boolean  flags  are
           treated  as  positive  one-byte integers.  In each case, those positive
           integers represent a terminal capability.  The  terminal  compiler  tic
           uses  negative  integers  to handle the cases where a capability is not
           available:

           o   If a capability is absent from this terminal, tic stores  a  -1  in
               the corresponding table.

               The integer value -1 is represented by two bytes 0377, 0377.
               Absent Boolean values are represented by the byte 0 (false).

           o   If  a capability has been canceled from this terminal, tic stores a
               -2 in the corresponding table.

               The integer value -2 is represented by two bytes 0377, 0376.
               The Boolean value -2 is represented by the byte 0376.

           o   Other negative values are illegal.

           The terminal names section comes after the  header.   It  contains  the
           first  line  of the terminfo description, listing the various names for
           the terminal, separated by  the  "|"  character.   The  terminal  names
           section is terminated with an ASCII NUL character.

           The  Boolean  flags  section  has  one  byte  for  each  flag.  Boolean
           capabilities are either 1 or 0 (true or false) according to whether the
           terminal supports the given capability or not.

           Between  the  Boolean flags section and the number section, a null byte
           will be inserted, if necessary,  to  ensure  that  the  number  section
           begins  on  an even byte This is a relic of the PDP-11's word-addressed
           architecture, originally designed to avoid traps induced by  addressing
           a  word  on  an odd byte boundary.  All short integers are aligned on a
           short word boundary.

           The numbers section is similar to  the  Boolean  flags  section.   Each
           capability  takes  up two bytes, and is stored as a little-endian short
           integer.

           The strings section is also similar.  Each capability is  stored  as  a
           short integer.  The capability value is an index into the string table.

           The string table is the last section.  It contains all of the values of
           string capabilities referenced in the strings section.  Each string  is
           null-terminated.  Special characters in ^X or \c notation are stored in
           their interpreted  form,  not  the  printing  representation.   Padding
           information  $<nn>  and  parameter  information %x are stored intact in
           uninterpreted form.

### Extended Storage Format

           The previous section describes the conventional terminfo binary format.
           With  some  minor variations of the offsets (see PORTABILITY), the same
           binary format is used in all modern Unix systems.  Each system  uses  a
           predefined set of Boolean, number or string capabilities.

           The ncurses libraries and applications support extended terminfo binary
           format, allowing users  to  define  capabilities  that  are  loaded  at
           runtime.   This  extension  is made possible by using the fact that the
           other implementations stop reading the terminfo data  when  they  reach
           the  end of the size given in the header.  ncurses checks the size, and
           if it exceeds that due to  the  predefined  data,  continues  to  parse
           according to its own scheme.

           First, it reads the extended header (5 short integers):

                (1)  count of extended Boolean capabilities

                (2)  count of extended numeric capabilities

                (3)  count of extended string capabilities

                (4)  count of the items in extended string table

                (5)  size of the extended string table in bytes

           The  count-  and  size-values for the extended string table include the
           extended capability names as well as extended capability values.

           Using the counts and sizes, ncurses allocates arrays and reads data for
           the extended capabilities in the same order as the header information.

           The  extended  string  table  contains  values for string capabilities.
           After the end of these values, it contains the names for  each  of  the
           extended capabilities in order: Boolean, numeric, and string.

           By  storing  terminal  descriptions  in  this  way,  ncurses is able to
           provide  a  database  useful  with  legacy  applications,  as  well  as
           providing  data  for applications that require more information about a
           terminal type than was anticipated by X/Open Curses.  See  user_caps(5)
           for an overview of the way ncurses uses this extended information.

           Applications  that  manipulate  terminal  data  can use the definitions
           described in term_variables(3x) associating the long  capability  names
           with members of a TERMTYPE structure.

### Extended Number Format

           On  occasion, 16-bit signed integers are not large enough.  ncurses 6.1
           introduced a new format by making a few changes to the legacy format:

           o   a different magic number (octal 01036)

           o   changing the type for the number array from signed 16-bit  integers
               to signed 32-bit integers.

           To   maintain   compatibility,  the  library  presents  the  same  data
           structures to direct users of the TERMTYPE  structure  as  in  previous
           formats.   However,  that  cannot  provide  callers  with  the extended
           numbers.   The  library  uses  a  similar  but  hidden  data  structure
           TERMTYPE2 to provide data for the terminfo functions.

## FILES

           /usr/share/terminfo
                  compiled terminal description database

## PORTABILITY

### setupterm

           Note  that  it  is  possible for setupterm to expect a different set of
           capabilities than  are  actually  present  in  the  file.   Either  the
           database   may   have  been  updated  since  setupterm  was  recompiled
           (resulting in extra unrecognized entries in the file)  or  the  program
           may  have  been  recompiled more recently than the database was updated
           (resulting in missing entries).  The routine setupterm must be prepared
           for  both  possibilities  -  this  is  why  the  numbers  and sizes are
           included.  Also, new capabilities must always be added at  the  end  of
           the lists of Boolean, number, and string capabilities.

### Binary Format

           X/Open  Curses  does  not  specify  a format for the terminfo database.
           System V curses used a directory-tree of binary files, one per terminal
           description.

           Despite  the  consistent use of little-endian numbers and the otherwise
           self-describing format, it is not  wise  to  count  on  portability  of
           binary  terminfo entries between commercial Unix versions.  The problem
           is that there are at least three versions  of  terminfo  (under  HP-UX,
           AIX,  and  OSF/1)  each  of which diverged from System V terminfo after
           SVr1, and added extension capabilities to the string table that (in the
           binary format) collide with System V and X/Open Curses extensions.  See
           terminfo(5) for detailed discussion of  terminfo  source  compatibility
           issues.

           This  implementation  is by default compatible with the binary terminfo
           format used by Solaris curses, except in a few less-used details  where
           it  was  found that the latter did not match X/Open Curses.  The format
           used by the other Unix versions can be matched by building ncurses with
           different configuration options.

### Magic Codes

           The  magic  number  in a binary terminfo file is the first 16 bits (two
           bytes).  Besides making it more reliable for the library to check  that
           a  file  is  terminfo,  utilities such as file(1) also use that to tell
           what the file-format is.  System V defined more than one magic  number,
           with 0433, 0435 as screen-dumps (see scr_dump(5)).  This implementation
           uses 01036 as a continuation of that sequence,  but  with  a  different
           high-order byte to avoid confusion.

       The TERMTYPE Structure
           Direct  access  to  the  TERMTYPE  structure  is  provided  for  legacy
           applications.   Portable  applications  should  use  tigetflag(3x)  and
           related functions to read terminal capabilities.

### Mixed-case Terminal Names

           A  small  number  of  terminal descriptions use uppercase characters in
           their names.  If the underlying  file  system  ignores  the  difference
           between   uppercase   and  lowercase,  ncurses  represents  the  "first
           character" of the terminal name used as the  intermediate  level  of  a
           directory tree in (two-character) hexadecimal form.

### Limits

           ncurses stores compiled terminal descriptions in three related formats,
           described in the subsections

           o   Legacy Storage Format, and

           o   Extended Storage Format, and

           o   Extended Number Format.

           The legacy storage format and the extended number format differ by  the
           types  of  numeric  capability  that  they  can store (for example, 16-
           versus 32-bit integers).  The extended  storage  format  introduced  by
           ncurses 5.0 adds data to either of these formats.

           Some limitations apply:

           o   total  compiled  entries  cannot  exceed  4096  bytes in the legacy
               format.

           o   total compiled entries cannot exceed 32768 bytes  in  the  extended
               format.

           o   the name field cannot exceed 128 bytes.

           Compiled  entries  are  limited to 32768 bytes because offsets into the
           strings table use two-byte integers.   The  legacy  format  could  have
           supported  32768-byte  entries,  but  was  limited  to a virtual memory
           page's 4096 bytes.

## EXAMPLES

           Here is a terminfo description of the  Lear-Siegler  ADM-3,  a  popular
           though rather stupid early terminal.

           adm3a|lsi adm3a,
                   am,
                   cols#80, lines#24,
                   bel=^G, clear=\032$<1>, cr=^M, cub1=^H, cud1=^J,
                   cuf1=^L, cup=\E=%p1%{32}%+%c%p2%{32}%+%c, cuu1=^K,
                   home=^^, ind=^J,

           A  hexadecimal  dump  of  its  compiled terminal description (in legacy
           format) follows.

           0000  1a 01 10 00 02 00 03 00  82 00 31 00 61 64 6d 33  ........ ..1.adm3
           0010  61 7c 6c 73 69 20 61 64  6d 33 61 00 00 01 50 00  a|lsi ad m3a...P.
           0020  ff ff 18 00 ff ff 00 00  02 00 ff ff ff ff 04 00  ........ ........
           0030  ff ff ff ff ff ff ff ff  0a 00 25 00 27 00 ff ff  ........ ..%.'...
           0040  29 00 ff ff ff ff 2b 00  ff ff 2d 00 ff ff ff ff  ).....+. ..-.....
           0050  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0060  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0070  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0080  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0090  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00a0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00b0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00c0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00d0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00e0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           00f0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0100  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0110  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  ........ ........
           0120  ff ff ff ff ff ff 2f 00  07 00 0d 00 1a 24 3c 31  ....../. .....$<1
           0130  3e 00 1b 3d 25 70 31 25  7b 33 32 7d 25 2b 25 63  >..=%p1% {32}%+%c
           0140  25 70 32 25 7b 33 32 7d  25 2b 25 63 00 0a 00 1e  %p2%{32} %+%c....
           0150  00 08 00 0c 00 0b 00 0a  00                       ........ .

## AUTHORS

           Thomas E. Dickey
           extended terminfo format for ncurses 5.0
           hashed database support for ncurses 5.6
           extended number support for ncurses 6.1

           Eric S. Raymond
           documented legacy terminfo format (that used by pcurses).

## SEE ALSO

           curses(3x), curs_terminfo(3x), terminfo(5), user_caps(5)

    ncurses 6.5                       2024-06-15                           term(5)