term 5 2024-01-13 ncurses 6.4 File formats

term(5)                          File formats                          term(5)


       term - compiled terminfo terminal description




Storage Location

       Compiled   terminfo   descriptions   are  placed  under  the  directory
       /usr/share/terminfo.  Two configurations are supported  (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,
            act4  can  be  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 Berkeley database, two types  of  records  are  stored:  the
            terminfo  data  in  the  same format as stored in a directory tree
            with the terminfo's primary name as a key, and records  containing
            only aliases pointing to the primary name.

            If  built  to  write  hashed  databases,  ncurses  can  still read
            terminfo 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  hashed
            database otherwise.

Legacy Storage Format

       The format has been chosen so that it will be the same on all hardware.
       An 8 or more bit  byte  is  assumed,  but  no  assumptions  about  byte
       ordering or sign extension are made.

       The  compiled  file  is  created  with the tic program, and read by the
       routine setupterm(3x).  The file is divided into six parts:

            a) header,

            b) terminal names,

            c) Boolean flags,

            d) numbers,

            e) strings, and

            f) 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 the file <term.h>.

       Short integers are signed, in the range  -32768  to  32767.   They  are
       stored  as  two  8-bit  bytes.   The  first  byte  contains  the  least
       significant 8 bits of the value, and the second byte contains the  most
       significant 8 bits.  (Thus, the value represented is 256*second+first.)
       This format corresponds to the hardware of the VAX and PDP-11 (that is,
       little-endian  machines).   Machines  where this does not correspond to
       the hardware must read the  integers  as  two  bytes  and  compute  the
       little-endian value.

       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

       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

       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  which  are  loaded  at
       runtime.   This  extension  is made possible by using the fact that the
       other implementations stop reading the terminfo  data  when  they  have
       reached  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,  e.g.,  Booleans,  then  numbers and
       finally strings.

       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 which need  more  than  the  predefined
       capabilities.  See user_caps(5) for an overview of the way ncurses uses
       this extended information.

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

Extended Number Format

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

       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.


              compiled terminal description database



       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

       Despite  the  consistent  use  of  little-endian  for  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) which diverged from System V
       terminfo after SVr1, and  have  added  extension  capabilities  to  the
       string  table that (in the binary format) collide with System V and XSI
       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  the  tigetflag  and
       related  functions  described in curs_terminfo(3x) for reading terminal

Mixed-case Terminal Names

       A small number of terminal descriptions  use  uppercase  characters  in
       their  names.   If  the  underlying  filesystem  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.


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




       The  legacy storage format and the extended number format differ by the
       types of numeric capability which they can store (i.e.,  16-bit  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

       o   total  compiled  entries  cannot exceed 32768 bytes in the extended

       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.


       As  an  example,  here  is  a description for the Lear-Siegler ADM-3, a
       popular though rather stupid early terminal:

       adm3a|lsi adm3a,
               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,

       and a hexadecimal dump of the compiled terminal description:

       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                       ........ .


       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, e.g., from pcurses.


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

ncurses 6.4                       2024-01-13                           term(5)