- These routines are included as a conversion aid for pro-
- grams 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 capa-
- bilities of entries for which a terminfo entry has been
- compiled.
-
- The tgetent routine loads the entry for name. It returns
- 1 on success, 0 if there is no such entry, and -1 if the
- terminfo database could not be found. The emulation
- ignores the buffer pointer bp.
-
- 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 return value will also be copied to
- the buffer pointed to by area, and the area value will be
- updated to point past the null ending this value.
-
- Only the first two characters of the id parameter of tget-
- flag, tgetnum and tgetstr are compared in lookups.
-
- The tgoto routine instantiates the parameters into the
- given capability. The output from this routine is to be
- passed to tputs.
-
- The tputs routine is described on the curs_terminfo(3x)
- manual page. It can retrieve capabilities by either term-
- cap or terminfo name.
-
- The variables PC, UP and BC are set by tgetent to the ter-
- minfo 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 ter-
- minal speed.
+
+ These routines are included as a conversion aid for programs that use
+ the termcap library. Their parameters are the same, but 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.
-
-
RETURN VALUE
- Except where explicitly noted, routines that return an
- integer return ERR upon failure and OK (SVr4 only speci-
- fies "an integer value other than ERR") upon successful
- completion.
+
+ 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.
+
+
+
+ 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.
+
+
+
+ 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(3).
+
+ 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 an internal version of tparm(3x) (a more ca-
+ pable formatter).
+
+ With terminfo support, tgoto is able to use some of the terminfo
+ features, but not all. In particular, it allows only numeric pa-
+ rameters; tparm supports string parameters.
+
+ 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.
+
+
+
+ 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.
+
+
+
+ The termcap functions provide no means for freeing memory, because
+ legacy termcap implementations used only the buffer areas provided by
+ the caller via tgetent and tgetstr. Those buffers are unused in ter-
+ minfo.
+
+ On the other hand, terminfo allocates memory. It uses setupterm to re-
+ trieve the data used by tgetent and the functions which return capabil-
+ ity values such as tgetstr. One could use
+
+ del_curterm(cur_term);
+
+
+ to free this memory, but there is an additional complication with
+ ncurses. It uses a fixed-size pool of storage locations, one per set-
+ ting of the TERM variable when tgetent is called. The screen(1) pro-
+ gram relies upon this arrangement, to improve its performance.
+
+ An application which uses only the low-level termcap functions could
+ free the memory using del_curterm, because the pool is freed using oth-
+ er functions (see curs_memleaks(3x)).
+
+
+
+ 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.
+ A few special cases apply:
-
-
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 con-
- figured to support 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 capabilities 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 applica-
- tions assume me (terminfo sgr0) does not reset the alter-
- nate character set. This implementation checks for, and
- modifies the data shown to the termcap interface to accom-
- modate termcap's limitation in this respect.
+ o If the terminal database has not been initialized, these return an
+ error.
+ o The calls with a string parameter (tgoto, tputs) check if the
+ string is null, or cancelled. Those return an error.
-
-
PORTABILITY
- The XSI Curses standard, Issue 4 describes these func-
- tions. However, they are marked TO BE WITHDRAWN and may
- be removed in future versions.
-
- Neither the XSI Curses standard nor the SVr4 man pages
- documented the return values of tgetent correctly, though
- all three were in fact returned ever since SVr1. In par-
- ticular, 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
- compatibility with the termcap library, that is a defect
- in XCurses, Issue 4, Version 2 rather than in ncurses.
-
- External variables are provided for support of certain
- termcap applications. However, termcap applications' use
- of those variables is poorly documented, e.g., not distin-
- guishing between input and output. In particular, some
- applications are reported to declare and/or modify ospeed.
+ o A call to tgoto using a capability with string parameters is an er-
+ ror.
+ o A call to tgoto using a capability with no parameters, or more than
+ two is an error.
-
+ 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, users can be surprised:
+
+ otputs("50") in a terminfo system will put out a literal "50" rather
+ than busy-waiting for 50 milliseconds.
+
+ o However, if ncurses is configured to support termcap, it may also
+ have been configured to support the BSD-style padding.
+
+ In that case, tputs inspects strings passed to it, looking for dig-
+ its at the beginning of the string.
+
+ tputs("50") in a termcap system may wait for 50 milliseconds rather
+ than put out a literal "50"
+
+ 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.
+
+
+
+ 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.
+
+
+
+ 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.
+
+
+
+ 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(3) library.
+
+ A termcap.h file was provided in ncurses 1.8.1 (November 1993). That
+ reflected influence by emacs(1) (rather than jove(1)) 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.
+
+
+