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$Id: curs_termcap.3x,v 1.85 2024/04/20 19:13:12 tom Exp $
#include <curses.h> #include <term.h>char PC; char * UP; char * BC; @NCURSES_OSPEED@ ospeed;
int tgetent(char *bp, const char *name); int tgetflag(const char *id); int tgetnum(const char *id); char *tgetstr(const char *id, char **area); char *tgoto(const char *cap, int col, int row); int tputs(const char *str, int affcnt, int (*putc)(int));
5 \" "-1" + 2n + adjust for PDF 1 on success,
0 if there is no such entry (or if the matching entry describes a generic terminal, having too little information for curses applications to run), and
-1 if the \%term\%info database could not be found.
This implementation differs from those of historical termcap libraries.
.bP \%ncurses ignores the buffer pointer bp, as do other termcap implementations conforming to portions of X/Open Curses now withdrawn. The BSD termcap library would store a copy of the terminal type description in the area referenced by this pointer. \%term\%info stores terminal type descriptions in compiled form, which is not the same thing. .bP The meanings of the return values differ. The BSD termcap library does not check whether the terminal type description includes the \%generic ( gn ) capability, nor whether the terminal type description supports an addressable cursor, a property essential for any curses implementation to operate.
\%tgetnum obtains the numeric entry for id, or -1 if it is not available.
\%tgetstr returns the string entry for id, or NULL if it is not available. Use \%tputs to output the string returned. The area parameter is used as follows.
.bP It is assumed to be the address of a pointer to a buffer managed by the calling application. .bP However, \%ncurses checks to ensure that area is not NULL , and also that the resulting buffer pointer is not NULL . If either check fails, area is ignored. .bP If the checks succeed, \%ncurses also copies the return value to the buffer pointed to by area, and the library updates area to point past the null character terminating this value. .bP The return value itself is an address in the terminal type description loaded into memory.
\%tputs is described in \%curs_terminfo(3X). It can retrieve capabilities by either termcap or \%term\%info code.
By contrast, \%term\%info allocates memory. It uses \%setupterm(3X) to obtain the data used by \%tgetent and the functions that retrieve capability values. One could use
.EX del_curterm(cur_term);
An application that uses only the termcap functions, not the higher level \%curses API, could release the memory using \%del_curterm(3X), because the pool is freed using other functions; see \%curs_memleaks(3X).
\%tgoto returns NULL on error. Error conditions include: .bP uninitialized state (\%tgetent was not called successfully), .bP cap being a null pointer, .bP cap referring to a canceled capability, .bP cap being a capability with string-valued parameters (a \%term\%info-only feature), and .bP cap being a capability with more than two parameters.
See \%curs_terminfo(3X) regarding \%tputs.
Neither X/Open Curses nor the SVr4 man pages documented the return values of \%tgetent correctly, though all three shown here were in fact returned ever since SVr1. In particular, an omission in the X/Open Curses specification has been misinterpreted to mean that \%tgetent returns OK or ERR. Because the purpose of these functions is to provide compatibility with the termcap library, that is a defect in X/Open Curses, Issue 4, Version 2 rather than in \%ncurses.
The constraint that only the first two characters of the id
parameter are used escapes many application developers.
The BSD termcap library did not require a trailing null character
on the capability identifier passed to \%tgetstr,
\%tgetnum,
and
\%tgetflag.
See <https://minnie.tuhs.org/cgi-bin/utree.pl?file=2BSD/src/\
termlib/termcap.c>.
Some applications thus assume that the termcap interface does not
require the trailing null character for the capability identifier.
.bP
\%ncurses disallows matches by the termcap interface against extended
capability names that are longer than two characters;
see \%user_caps(5).
The BSD termcap function \%tgetent returns the text of a termcap entry in the buffer passed as an argument. This library, like other \%term\%info implementations, does not store terminal type descriptions as text. It sets the buffer contents to a null-terminated string.
for much BSD release history.
Bill Joy originated a forerunner of termcap called \*(``ttycap\*('', dated September 1977, and released in 1BSD (March 1978). https://minnie.tuhs.org/cgi-bin/utree.pl?file=1BSD/s7/ttycap.c
https://minnie.tuhs.org/cgi-bin/utree.pl?file=1BSD/man7/ttycap.7
It used many of the same function names as the later termcap, such as \%tgetent, \%tgetflag, \%tgetnum, and \%tgetstr.
A clear descendant,
the termlib library,
https://minnie.tuhs.org/cgi-bin/utree.pl?file=2BSD/src/termlib/
followed in 2BSD
(May 1979),
adding \%tgoto and \%tputs.
The former applied at that time only to cursor positioning capabilities,
https://minnie.tuhs.org/cgi-bin/utree.pl?file=2BSD/bin/etc/termcap
thus the overly specific name.
Little changed in 3BSD
(late 1979)
except the addition of test programs and a \%termlib man page,
which documented the API shown in section \*(``SYNOPSIS\*('' above.
https://minnie.tuhs.org/cgi-bin/utree.pl?file=3BSD/usr/src/lib/\
libtermlib/
https://minnie.tuhs.org/cgi-bin/utree.pl?file=3BSD/usr/man/man3/\
termlib.3
4BSD
(November 1980)
renamed termlib to termcap
...except in the source tree...
https://minnie.tuhs.org/cgi-bin/utree.pl?file=4BSD/usr/src/lib/\
libtermlib/makefile
and added another test program.
The library remained much the same though 4.3BSD
(June 1986).
4.4BSD-Lite
(June 1994)
refactored it,
Observe the `tncktc()`, `tnamatch()`, `tskip()`, and `tdecode()`
entry points disappearing from termcap.c.
leaving the API unchanged.
Function prototypes were a feature of ANSI C (1989).
The library long antedated the standard and thus provided no header file
declaring them.
Nevertheless,
the BSD sources included two different \%termcap.h header files
over time.
.bP
One was used internally by jove(1) from 4.3BSD onward.
2BSD became a branch retaining support for non-virtual memory
systems (such as the PDP-11) whereas most BSD development focused on
the VAX and other VM-enabled systems starting with 3BSD.
This man page previously located a termcap.h in 2BSD, but that may
be confusion arising from its backport to 2.9BSD (and still present
in surviving sources for 2.11BSD, the "end of the line" for that
branch's development).
Observe the copyright notice in
https://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD/usr/contrib/\
jove/Makefile
--much too late for 2BSD (1979).
It declared global symbols for the termcap variables that it used.
.bP
The other appeared in 4.4BSD-Lite Release 2
(June 1995)
as part of libedit
(also known as the \%edit\%line library).
CSRG source history shows that this was added in mid-1992.
The libedit header file was used internally as a convenience for
compiling the \%edit\%line library.
It declared function prototypes,
but no global variables.
This header file was added to NetBSD's termcap library in
mid-1994.
Meanwhile, GNU termcap began development in 1990. Its first release (1.0) in 1991 included a \%termcap.h header. Its second (1.1) in September 1992 modified the header to use const for the function prototypes in the header where one would expect the parameters to be read-only. BSD termcap did not. The prototype for \%tputs also differed, but in that instance, it was libedit that differed from BSD termcap.
GNU termcap 1.3 was bundled with bash(1) in mid-1993 to support the \%readline(3) library.
\%ncurses 1.8.1 (November 1993) provided a \%termcap.h file. It reflected influence from GNU termcap and emacs(1) (rather than jove(1)), providing the following interface: .bP global symbols used by emacs, .bP const-qualified function prototypes, and .bP a prototype for tparam, a GNU termcap feature.
Later (in mid-1996) the \%tparam function was removed from \%ncurses. Any two of the four implementations thus differ, and programs that intend to work with all termcap library interfaces must account for that fact.
Because \%term\%info's syntax for padding in string capabilities differs from termcap's, users can be surprised.
termcap has nothing analogous to \%term\%info's \%set_attributes ( sgr ) capability. One consequence is that termcap applications assume that \*(`` me \*('' (equivalent to \%term\%info's \%exit_attribute_mode ( sgr0 ) capability) does not reset the alternate character set. \%ncurses checks for, and modifies the data shared with, the termcap interface to accommodate the latter's limitation in this respect.
https://invisible-island.net/ncurses/tctest.html