Compiled terminfo descriptions are placed under the directory
@TERMINFO@. Two configurations are supported (when building the
A two-level scheme is used to avoid a linear search of a huge
UNIX system directory: @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 @TERMINFO@/a/act4. Synonyms for
the same terminal are implemented by multiple links to the same
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
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: the
header, terminal names, boolean flags, numbers, strings, and string
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 names section;
(3) the number of bytes in the boolean section;
(4) the number of short integers in the numbers section;
(5) the number of offsets (short integers) in the strings
(6) the size, in bytes, of the string table.
Short integers are stored in 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.) The value -1 is represented by the
two bytes 0377, 0377; other negative values are illegal. This value
generally means that the corresponding capability is missing from
this terminal. Note that 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.
The terminal names section comes next. It contains the first line of
the terminfo description, listing the various names for the terminal,
separated by the “|” character. The section is terminated with an
ASCII NUL character.
The boolean flags have one byte for each flag. This byte is either 0
or 1 as the flag is present or absent. The capabilities are in the
same order as the file <term.h>.
Between the boolean 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 in to avoid IOT 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 flags section. Each capability
takes up two bytes, and is stored as a little-endian short integer.
If the value represented is -1, the capability is taken to be
The strings section is also similar. Each capability is stored as a
short integer, in the format above. A value of -1 means the
capability is missing. Otherwise, the value is taken as an offset
from the beginning of the string table. 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.
The final section is the string table. It contains all the values of
string capabilities referenced in the string section. Each string is
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
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) size of the extended string table in bytes.
(5) last offset of the extended string table in bytes.
Using the counts and sizes, ncurses allocates arrays and reads data
for the extended capabilities in the same order as the header
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
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 has been 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.
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 page is part of the ncurses (new curses) project. Information
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