# term 5 2024-01-13 ncurses 6.4 File formats

    term(5)                          File formats                          term(5)

## NAME

           term - compiled terminfo terminal description

## SYNOPSIS

           term

## 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
           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  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
           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  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
           capabilities.

### 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.

### Limits

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

           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 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
               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

           As  an  example,  here  is  a description for 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,

           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                       ........ .

## 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, e.g., from pcurses.

## SEE ALSO

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

    ncurses 6.4                       2024-01-13                           term(5)