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curs_termcap(3X)					      curs_termcap(3X)

NAME
       PC, UP, BC, ospeed, tgetent, tgetflag, tgetnum, tgetstr,	tgoto, tputs -
       direct curses interface to the terminfo capability database

SYNOPSIS
       #include	<ncurses/curses.h>
       #include	<term.h>

       extern char PC;
       extern char * UP;
       extern char * BC;
       extern short 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));

DESCRIPTION
       These routines are included as a	conversion aid for programs  that  use
       the  termcap  library.	Their parameters are the same and the routines
       are emulated using the terminfo database.  Thus,	they can only be  used
       to  query  the  capabilities  of	entries	for which a terminfo entry has
       been compiled.

   INITIALIZATION
       The tgetent routine loads the entry for name.  It returns:

	  1  on	success,

	  0  if	there is no such entry (or that	it is a	generic	 type,	having
	     too little	information for	curses applications to run), and

	  -1 if	the terminfo database could not	be found.

       This differs from the termcap library in	two ways:

	  o   The  emulation  ignores  the buffer pointer bp.  The termcap li-
	      brary would store	a copy of the terminal description in the area
	      referenced  by this pointer.  However, ncurses stores its	termi-
	      nal descriptions in compiled binary form,	which is not the  same
	      thing.

	  o   There is a difference in return codes.  The termcap library does
	      not check	if the terminal	description is marked with the generic
	      capability,  or  if the terminal description has cursor-address-
	      ing.

   CAPABILITY VALUES
       The tgetflag routine gets the boolean entry for id, or zero  if	it  is
       not available.

       The  tgetnum  routine gets the numeric entry for	id, or -1 if it	is not
       available.

       The tgetstr routine returns the string entry for	id, or zero if	it  is
       not  available.	Use tputs to output the	returned string.  The area pa-
       rameter is used as follows:

	  o   It is assumed to be the address of a pointer to a	buffer managed
	      by the calling application.

	  o   However, ncurses checks to ensure	that area is not NULL, and al-
	      so that the resulting buffer pointer is  not  NULL.   If	either
	      check fails, the area parameter is ignored.

	  o   If  the  checks succeed, ncurses also copies the return value to
	      the buffer pointed to by area, and the area value	will be	updat-
	      ed to point past the null	ending this value.

	  o   The  return  value itself	is an address in the terminal descrip-
	      tion which is loaded into	memory.

       Only the	first two characters of	the id parameter of tgetflag,  tgetnum
       and tgetstr are compared	in lookups.

   FORMATTING CAPABILITIES
       The tgoto routine expands the given capability using the	parameters.

       o   Because  the	 capability may	have padding characters, the output of
	   tgoto should	be passed to tputs rather than some other output func-
	   tion	such as	printf.

       o   While  tgoto	is assumed to be used for the two-parameter cursor po-
	   sitioning capability, termcap applications also use it for  single-
	   parameter capabilities.

	   Doing this shows a quirk in tgoto: most hardware terminals use cur-
	   sor addressing with row first, but the original developers  of  the
	   termcap  interface  chose  to  put the column parameter first.  The
	   tgoto function swaps	the order of parameters.  It  does  this  also
	   for	calls  requiring  only	a single parameter.  In	that case, the
	   first parameter is merely a placeholder.

       o   Normally the	ncurses	library	is compiled with terminfo support.  In
	   that	case, tgoto uses tparm(3X) (a more capable formatter).

	   However,  tparm  is not a termcap feature, and portable termcap ap-
	   plications should not rely upon its availability.

       The tputs routine is described on the  curs_terminfo(3X)	 manual	 page.
       It can retrieve capabilities by either termcap or terminfo name.

   GLOBAL VARIABLES
       The  variables PC, UP and BC are	set by tgetent to the terminfo entry's
       data for	pad_char, cursor_up and	backspace_if_not_bs, respectively.  UP
       is  not used by ncurses.	 PC is used in the tdelay_output function.  BC
       is used in the tgoto emulation.	The variable ospeed is set by  ncurses
       in a system-specific coding to reflect the terminal speed.

RETURN VALUE
       Except  where  explicitly noted,	routines that return an	integer	return
       ERR upon	failure	and OK (SVr4 only specifies "an	 integer  value	 other
       than ERR") upon successful completion.

       Routines	that return pointers return NULL on error.

BUGS
       If  you	call tgetstr to	fetch ca or any	other parameterized string, be
       aware that it will be returned in terminfo notation, not	the older  and
       not-quite-compatible termcap notation.  This will not cause problems if
       all you do with it is call tgoto	or tparm, which	both expand  terminfo-
       style  strings as terminfo.  (The tgoto function, if configured to sup-
       port termcap, will check	if the	string	is  indeed  terminfo-style  by
       looking	for  "%p"  parameters or "$<..>" delays, and invoke a termcap-
       style parser if the string does not appear to be	terminfo).

       Because terminfo	conventions for	representing padding in	 string	 capa-
       bilities	 differ	 from  termcap's,  tputs("50");	will put out a literal
       "50" rather than	busy-waiting for 50 milliseconds.  Cope	with it.

       Note that termcap has nothing analogous to terminfo's sgr string.   One
       consequence  of	this  is that termcap applications assume me (terminfo
       sgr0) does not reset the	alternate character set.  This	implementation
       checks for, and modifies	the data shown to the termcap interface	to ac-
       commodate termcap's limitation in this respect.

PORTABILITY
   Standards
       These functions are provided for	supporting  legacy  applications,  and
       should not be used in new programs:

       o   The XSI Curses standard, Issue 4 describes these functions.	Howev-
	   er, they are	marked TO BE WITHDRAWN and may be  removed  in	future
	   versions.

       o   X/Open Curses, Issue	5 (December 2007) marked the termcap interface
	   (along with vwprintw	and vwscanw) as	withdrawn.

       Neither the XSI Curses standard nor the SVr4 man	pages  documented  the
       return  values  of tgetent correctly, though all	three were in fact re-
       turned ever since SVr1.	In particular, an omission in the  XSI	Curses
       documentation  has  been	misinterpreted to mean that tgetent returns OK
       or ERR.	Because	the purpose of these functions is to provide  compati-
       bility  with the	termcap	library, that is a defect in XCurses, Issue 4,
       Version 2 rather	than in	ncurses.

   Compatibility with BSD Termcap
       External	variables are provided for support of certain termcap applica-
       tions.  However,	termcap	applications' use of those variables is	poorly
       documented, e.g., not distinguishing between input and output.  In par-
       ticular,	 some  applications  are reported to declare and/or modify os-
       peed.

       The comment that	only the first two characters of the id	parameter  are
       used escapes many application developers.  The original BSD 4.2 termcap
       library (and historical relics thereof) did not require a trailing null
       NUL  on	the  parameter	name  passed to	tgetstr, tgetnum and tgetflag.
       Some applications assume	that the termcap interface  does  not  require
       the trailing NUL	for the	parameter name.	 Taking	into account these is-
       sues:

       o   As a	special	case,  tgetflag	 matched  against  a  single-character
	   identifier  provided	 that  was at the end of the terminal descrip-
	   tion.  You should not rely upon this	behavior in portable programs.
	   This	 implementation	disallows matches against single-character ca-
	   pability names.

       o   This	implementation disallows  matches  by  the  termcap  interface
	   against extended capability names which are longer than two charac-
	   ters.

       The BSD termcap function	tgetent	returns	the text of a termcap entry in
       the  buffer  passed  as an argument.  This library (like	other terminfo
       implementations)	does not store terminal	descriptions as	text.  It sets
       the buffer contents to a	null-terminated	string.

   Other Compatibility
       This  library includes a	termcap.h header, for compatibility with other
       implementations.	 But the header	is rarely used because the  other  im-
       plementations are not strictly compatible.

       The original BSD	termcap	(through 4.3BSD) had no	header file which gave
       function	prototypes, because that was a feature of ANSI C.  BSD termcap
       was  written  several  years before C was standardized.	However, there
       were two	different termcap.h header files in the	BSD sources:

       o   One was used	internally by the jove editor in 2BSD through  4.4BSD.
	   It defined global symbols for the termcap variables which it	used.

       o   The	other  appeared	in 4.4BSD Lite Release 2 (mid-1993) as part of
	   libedit (also known as the editline library).  The CSRG source his-
	   tory	 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 vari-
	   ables.

       The header file from libedit was	added to NetBSD's termcap  library  in
       mid-1994.

       Meanwhile,  GNU	termcap	 was under development,	starting in 1990.  The
       first release (termcap 1.0) in 1991 included a termcap.h	 header.   The
       second  release	(termcap 1.1) in September 1992	modified the header to
       use const for the function prototypes in	the header where one would ex-
       pect  the parameters to be read-only.  This was a difference versus the
       original	BSD termcap.  The prototype for	tputs also  differed,  but  in
       that instance, it was libedit which differed from BSD termcap.

       A copy of GNU termcap 1.3 was bundled with bash in mid-1993, to support
       the readline library.

       A termcap.h file	was provided in	ncurses	1.8.1 (November	 1993).	  That
       reflected influence by emacs (rather than jove) and GNU termcap:

       o   it provided declarations for	a few global symbols used by emacs

       o   it provided function	prototypes (using const).

       o   a prototype for tparam (a GNU termcap feature) was provided.

       Later (in mid-1996) the tparam function was removed from	ncurses.  As a
       result, there are differences between any of the	four  implementations,
       which  must  be	taken into account by programs which can work with all
       termcap library interfaces.

SEE ALSO
       curses(3X), terminfo(5),	term_variables(3X), putc(3).

       https://invisible-island.net/ncurses/tctest.html

							      curs_termcap(3X)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | BUGS | PORTABILITY | SEE ALSO

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