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2.\" Copyright 2018-2021,2023 Thomas E. Dickey *
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30.\" $Id: term.5,v 1.2 2023/10/17 09:52:08 nicm Exp $
31.TH term 5 2023-07-01 "ncurses 6.4" "File formats"
32.ie \n(.g .ds `` \(lq
33.el .ds `` ``
34.ie \n(.g .ds '' \(rq
35.el .ds '' ''
36.de NS
37.ie n .sp
38.el .sp .5
39.ie n .in +4
40.el .in +2
41.nf
42.ft CR \" Courier
43..
44.de NE
45.fi
46.ft R
47.ie n .in -4
48.el .in -2
49..
50.de bP
51.ie n .IP \(bu 4
52.el .IP \(bu 2
53..
54.ds n 5
55.ds d /usr/share/terminfo
56.SH NAME
57term \- format of compiled term file.
58.SH SYNOPSIS
59.B term
60.SH DESCRIPTION
61.SS STORAGE LOCATION
62Compiled terminfo descriptions are placed under the directory \fB\*d\fP.
63Two configurations are supported (when building the \fBncurses\fP libraries):
64.TP 5
65.B directory tree
66A two-level scheme is used to avoid a linear search
67of a huge \s-1UNIX\s+1 system directory: \fB\*d/c/name\fP where
68.I name
69is the name of the terminal, and
70.I c
71is the first character of
72.IR name .
73Thus,
74.I act4
75can be found in the file \fB\*d/a/act4\fP.
76Synonyms for the same terminal are implemented by multiple
77links to the same compiled file.
78.TP 5
79.B hashed database
80Using Berkeley database, two types of records are stored:
81the terminfo data in the same format as stored in a directory tree with
82the terminfo's primary name as a key,
83and records containing only aliases pointing to the primary name.
84.IP
85If built to write hashed databases,
86\fBncurses\fP can still read terminfo databases organized as a directory tree,
87but cannot write entries into the directory tree.
88It can write (or rewrite) entries in the hashed database.
89.IP
90\fBncurses\fP distinguishes the two cases in the TERMINFO and TERMINFO_DIRS
91environment variable by assuming a directory tree for entries that
92correspond to an existing directory,
93and hashed database otherwise.
94.SS LEGACY STORAGE FORMAT
95The format has been chosen so that it will be the same on all hardware.
96An 8 or more bit byte is assumed, but no assumptions about byte ordering
97or sign extension are made.
98.PP
99The compiled file is created with the \fBtic\fP program,
100and read by the routine \fBsetupterm\fP(3).
101The file is divided into six parts:
102.RS 5
103.TP 3
104a) \fIheader\fP,
105.TP 3
106b) \fIterminal names\fP,
107.TP 3
108c) \fIboolean flags\fP,
109.TP 3
110d) \fInumbers\fP,
111.TP 3
112e) \fIstrings\fP, and
113.TP 3
114f) \fIstring table\fP.
115.RE
116.PP
117The \fIheader\fP section begins the file.
118This section contains six short integers in the format
119described below.
120These integers are
121.RS 5
122.TP 5
123(1) the \fImagic number\fP (octal 0432);
124.TP 5
125(2) the size, in bytes, of the \fIterminal names\fP section;
126.TP 5
127(3) the number of bytes in the \fIboolean flags\fP section;
128.TP 5
129(4) the number of short integers in the \fInumbers\fP section;
130.TP 5
131(5) the number of offsets (short integers) in the \fIstrings\fP section;
132.TP 5
133(6) the size, in bytes, of the \fIstring table\fP.
134.RE
135.PP
136The capabilities in the
137\fIboolean flags\fP,
138\fInumbers\fP, and
139\fIstrings\fP
140sections are in the same order as the file <term.h>.
141.PP
142Short integers are signed, in the range \-32768 to 32767.
143They are stored as two 8-bit bytes.
144The first byte contains the least significant 8 bits of the value,
145and the second byte contains the most significant 8 bits.
146(Thus, the value represented is 256*second+first.)
147This format corresponds to the hardware of the \s-1VAX\s+1
148and \s-1PDP\s+1-11 (that is, little-endian machines).
149Machines where this does not correspond to the hardware must read the
150integers as two bytes and compute the little-endian value.
151.PP
152Numbers in a terminal description,
153whether they are entries in the \fInumbers\fP or \fIstrings\fP table,
154are positive integers.
155Boolean flags are treated as positive one-byte integers.
156In each case, those positive integers represent a terminal capability.
157The terminal compiler tic uses negative integers to handle the cases where
158a capability is not available:
159.bP
160If a capability is absent from this terminal,
161tic stores a \-1 in the corresponding table.
162.IP
163The integer value \-1 is represented by two bytes 0377, 0377.
164.br
165Absent boolean values are represented by the byte 0 (false).
166.bP
167If a capability has been canceled from this terminal,
168tic stores a \-2 in the corresponding table.
169.IP
170The integer value \-2 is represented by two bytes 0377, 0376.
171.br
172The boolean value \-2 is represented by the byte 0376.
173.br
174.bP
175Other negative values are illegal.
176.PP
177The \fIterminal names\fP section comes after the \fIheader\fP.
178It contains the first line of the terminfo description,
179listing the various names for the terminal,
180separated by the \*(``|\*('' character.
181The \fIterminal names\fP section is terminated
182with an \s-1ASCII NUL\s+1 character.
183.PP
184The \fIboolean flags\fP section has one byte for each flag.
185Boolean capabilities are either 1 or 0 (true or false)
186according to whether the terminal supports the given capability or not.
187.PP
188Between the \fIboolean flags\fP section and the \fInumber\fP section,
189a null byte will be inserted, if necessary,
190to ensure that the \fInumber\fP section begins on an even byte
191This is a relic of the PDP\-11's word-addressed architecture,
192originally designed to avoid traps induced
193by addressing a word on an odd byte boundary.
194All short integers are aligned on a short word boundary.
195.PP
196The \fInumbers\fP section is similar to the \fIboolean flags\fP section.
197Each capability takes up two bytes,
198and is stored as a little-endian short integer.
199.PP
200The \fIstrings\fP section is also similar.
201Each capability is stored as a short integer.
202The capability value is an index into the \fIstring table\fP.
203.PP
204The \fIstring table\fP is the last section.
205It contains all of the values of string capabilities referenced in
206the \fIstrings\fP section.
207Each string is null-terminated.
208Special characters in ^X or \ec notation are stored in their
209interpreted form, not the printing representation.
210Padding information $<nn> and parameter information %x are
211stored intact in uninterpreted form.
212.SS EXTENDED STORAGE FORMAT
213The previous section describes the conventional terminfo binary format.
214With some minor variations of the offsets (see PORTABILITY),
215the same binary format is used in all modern UNIX systems.
216Each system uses a predefined set of boolean, number or string capabilities.
217.PP
218The \fBncurses\fP libraries and applications support
219extended terminfo binary format,
220allowing users to define capabilities which are loaded at runtime.
221This
222extension is made possible by using the fact that the other implementations
223stop reading the terminfo data when they have reached the end of the size given
224in the header.
225\fBncurses\fP checks the size,
226and if it exceeds that due to the predefined data,
227continues to parse according to its own scheme.
228.PP
229First, it reads the extended header (5 short integers):
230.RS 5
231.TP 5
232(1)
233count of extended boolean capabilities
234.TP 5
235(2)
236count of extended numeric capabilities
237.TP 5
238(3)
239count of extended string capabilities
240.TP 5
241(4)
242count of the items in extended string table
243.TP 5
244(5)
245size of the extended string table in bytes
246.RE
247.PP
248The count- and size-values for the extended string table
249include the extended capability \fInames\fP as well as
250extended capability \fIvalues\fP.
251.PP
252Using the counts and sizes, \fBncurses\fP allocates arrays and reads data
253for the extended capabilities in the same order as the header information.
254.PP
255The extended string table contains values for string capabilities.
256After the end of these values, it contains the names for each of
257the extended capabilities in order, e.g., booleans, then numbers and
258finally strings.
259.PP
260Applications which manipulate terminal data can use the definitions
261described in \fBterm_variables\fP(3) which associate the long capability
262names with members of a \fBTERMTYPE\fP structure.
263.
264.SS EXTENDED NUMBER FORMAT
265On occasion, 16-bit signed integers are not large enough.
266With \fBncurses\fP 6.1, a new format was introduced by making a few changes
267to the legacy format:
268.bP
269a different magic number (octal 01036)
270.bP
271changing the type for the \fInumber\fP array from signed 16-bit integers
272to signed 32-bit integers.
273.PP
274To maintain compatibility, the library presents the same data structures
275to direct users of the \fBTERMTYPE\fP structure as in previous formats.
276However, that cannot provide callers with the extended numbers.
277The library uses a similar but hidden data structure \fBTERMTYPE2\fP
278to provide data for the terminfo functions.
279.SH PORTABILITY
280.SS setupterm
281Note that it is possible for
282.B setupterm
283to expect a different set of capabilities
284than are actually present in the file.
285Either the database may have been updated since
286.B setupterm
287was recompiled
288(resulting in extra unrecognized entries in the file)
289or the program may have been recompiled more recently
290than the database was updated
291(resulting in missing entries).
292The routine
293.B setupterm
294must be prepared for both possibilities \-
295this is why the numbers and sizes are included.
296Also, new capabilities must always be added at the end of the lists
297of boolean, number, and string capabilities.
298.SS Binary format
299X/Open Curses does not specify a format for the terminfo database.
300UNIX System V curses used a directory-tree of binary files,
301one per terminal description.
302.PP
303Despite the consistent use of little-endian for numbers and the otherwise
304self-describing format, it is not wise to count on portability of binary
305terminfo entries between commercial UNIX versions.
306The problem is that there
307are at least three versions of terminfo (under HP\-UX, AIX, and OSF/1) which
308diverged from System V terminfo after SVr1, and have added extension
309capabilities to the string table that (in the binary format) collide with
310System V and XSI Curses extensions.
311See \fBterminfo\fP(\*n) for detailed
312discussion of terminfo source compatibility issues.
313.PP
314This implementation is by default compatible with the binary
315terminfo format used by Solaris curses,
316except in a few less-used details
317where it was found that the latter did not match X/Open Curses.
318The format used by the other Unix versions
319can be matched by building ncurses
320with different configuration options.
321.SS Magic codes
322The magic number in a binary terminfo file is the first 16-bits (two bytes).
323Besides making it more reliable for the library to check that a file
324is terminfo,
325utilities such as \fBfile\fP(1) also use that to tell what the file-format is.
326System V defined more than one magic number,
327with 0433, 0435 as screen-dumps (see \fBscr_dump\fP(5)).
328This implementation uses 01036 as a continuation of that sequence,
329but with a different high-order byte to avoid confusion.
330.SS The TERMTYPE structure
331Direct access to the \fBTERMTYPE\fP structure is provided for legacy
332applications.
333Portable applications should use the \fBtigetflag\fP and related functions
334described in \fBterminfo\fP(3) for reading terminal capabilities.
335.SS Mixed-case terminal names
336A small number of terminal descriptions use uppercase characters in
337their names.
338If the underlying filesystem ignores the difference between
339uppercase and lowercase,
340\fBncurses\fP represents the \*(``first character\*(''
341of the terminal name used as
342the intermediate level of a directory tree in (two-character) hexadecimal form.
343.SH EXAMPLE
344As an example, here is a description for the Lear-Siegler
345ADM\-3, a popular though rather stupid early terminal:
346.NS
347adm3a|lsi adm3a,
348 am,
349 cols#80, lines#24,
350 bel=^G, clear=\032$<1>, cr=^M, cub1=^H, cud1=^J,
351 cuf1=^L, cup=\\E=%p1%{32}%+%c%p2%{32}%+%c, cuu1=^K,
352 home=^^, ind=^J,
353.NE
354.PP
355and a hexadecimal dump of the compiled terminal description:
356.NS
357.ft CW
358\s-20000 1a 01 10 00 02 00 03 00 82 00 31 00 61 64 6d 33 ........ ..1.adm3
3590010 61 7c 6c 73 69 20 61 64 6d 33 61 00 00 01 50 00 a|lsi ad m3a...P.
3600020 ff ff 18 00 ff ff 00 00 02 00 ff ff ff ff 04 00 ........ ........
3610030 ff ff ff ff ff ff ff ff 0a 00 25 00 27 00 ff ff ........ ..%.'...
3620040 29 00 ff ff ff ff 2b 00 ff ff 2d 00 ff ff ff ff ).....+. ..-.....
3630050 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3640060 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3650070 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3660080 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3670090 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
36800a0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
36900b0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
37000c0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
37100d0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
37200e0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
37300f0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3740100 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3750110 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ........ ........
3760120 ff ff ff ff ff ff 2f 00 07 00 0d 00 1a 24 3c 31 ....../. .....$<1
3770130 3e 00 1b 3d 25 70 31 25 7b 33 32 7d 25 2b 25 63 >..=%p1% {32}%+%c
3780140 25 70 32 25 7b 33 32 7d 25 2b 25 63 00 0a 00 1e %p2%{32} %+%c....
3790150 00 08 00 0c 00 0b 00 0a 00 ........ .\s+2
380.ft R
381.NE
382.sp
383.SH LIMITS
384Some limitations:
385.bP
386total compiled entries cannot exceed 4096 bytes in the legacy format.
387.bP
388total compiled entries cannot exceed 32768 bytes in the extended format.
389.bP
390the name field cannot exceed 128 bytes.
391.PP
392Compiled entries are limited to 32768 bytes because offsets into the
393\fIstrings table\fP use two-byte integers.
394The legacy format could have supported 32768-byte entries,
395but was limited a virtual memory page's 4096 bytes.
396.SH FILES
397\*d/*/* compiled terminal capability database
398.SH SEE ALSO
399\fBcurses\fP(3), \fBterminfo\fP(\*n).
400.SH AUTHORS
401Thomas E. Dickey
402.br
403extended terminfo format for ncurses 5.0
404.br
405hashed database support for ncurses 5.6
406.br
407extended number support for ncurses 6.1
408.sp
409Eric S. Raymond
410.br
411documented legacy terminfo format, e.g., from \fIpcurses\fP.