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30 * @Id: curs_termcap.3x,v 1.59 2023/04/16 18:16:40 tom Exp @
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42 <H1 class="no-header">curs_termcap 3x 2023-04-16 ncurses 6.4 Library calls</H1>
44 <STRONG><A HREF="curs_termcap.3x.html">curs_termcap(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_termcap.3x.html">curs_termcap(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>PC</STRONG>, <STRONG>UP</STRONG>, <STRONG>BC</STRONG>, <STRONG>ospeed</STRONG>, <STRONG>tgetent</STRONG>, <STRONG>tgetflag</STRONG>, <STRONG>tgetnum</STRONG>, <STRONG>tgetstr</STRONG>, <STRONG>tgoto</STRONG>, <STRONG>tputs</STRONG> -
51 <STRONG>curses</STRONG> emulation of termcap
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
56 <STRONG>#include</STRONG> <STRONG><term.h></STRONG>
58 <STRONG>extern</STRONG> <STRONG>char</STRONG> <STRONG>PC;</STRONG>
59 <STRONG>extern</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG> <STRONG>UP;</STRONG>
60 <STRONG>extern</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG> <STRONG>BC;</STRONG>
61 <STRONG>extern</STRONG> <STRONG>short</STRONG> <STRONG>ospeed;</STRONG>
63 <STRONG>int</STRONG> <STRONG>tgetent(char</STRONG> <STRONG>*</STRONG><EM>bp</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>name</EM><STRONG>);</STRONG>
64 <STRONG>int</STRONG> <STRONG>tgetflag(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>id</EM><STRONG>);</STRONG>
65 <STRONG>int</STRONG> <STRONG>tgetnum(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>id</EM><STRONG>);</STRONG>
66 <STRONG>char</STRONG> <STRONG>*tgetstr(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>id</EM><STRONG>,</STRONG> <STRONG>char</STRONG> <STRONG>**</STRONG><EM>area</EM><STRONG>);</STRONG>
67 <STRONG>char</STRONG> <STRONG>*tgoto(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>cap</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>col</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>row</EM><STRONG>);</STRONG>
68 <STRONG>int</STRONG> <STRONG>tputs(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>str</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>affcnt</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>(*</STRONG><EM>putc</EM><STRONG>)(int));</STRONG>
71 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
72 These routines are included as a conversion aid for programs that use
73 the <EM>termcap</EM> library. Their parameters are the same, but the routines
74 are emulated using the <EM>terminfo</EM> database. Thus, they can only be used
75 to query the capabilities of entries for which a terminfo entry has
79 </PRE><H3><a name="h3-Initialization">Initialization</a></H3><PRE>
80 The <STRONG>tgetent</STRONG> routine loads the entry for <EM>name</EM>. It returns:
84 0 if there is no such entry (or that it is a generic type, having
85 too little information for curses applications to run), and
87 -1 if the terminfo database could not be found.
89 This differs from the <EM>termcap</EM> library in two ways:
91 <STRONG>o</STRONG> The emulation ignores the buffer pointer <EM>bp</EM>. The <EM>termcap</EM> li-
92 brary would store a copy of the terminal description in the area
93 referenced by this pointer. However, ncurses stores its termi-
94 nal descriptions in compiled binary form, which is not the same
97 <STRONG>o</STRONG> There is a difference in return codes. The <EM>termcap</EM> library does
98 not check if the terminal description is marked with the <EM>generic</EM>
99 capability, or if the terminal description has cursor-address-
103 </PRE><H3><a name="h3-Capability-Values">Capability Values</a></H3><PRE>
104 The <STRONG>tgetflag</STRONG> routine gets the boolean entry for <EM>id</EM>, or zero if it is
107 The <STRONG>tgetnum</STRONG> routine gets the numeric entry for <EM>id</EM>, or -1 if it is not
110 The <STRONG>tgetstr</STRONG> routine returns the string entry for <EM>id</EM>, or zero if it is
111 not available. Use <STRONG>tputs</STRONG> to output the returned string. The <EM>area</EM> pa-
112 rameter is used as follows:
114 <STRONG>o</STRONG> It is assumed to be the address of a pointer to a buffer managed
115 by the calling application.
117 <STRONG>o</STRONG> However, ncurses checks to ensure that <STRONG>area</STRONG> is not NULL, and al-
118 so that the resulting buffer pointer is not NULL. If either
119 check fails, the <EM>area</EM> parameter is ignored.
121 <STRONG>o</STRONG> If the checks succeed, ncurses also copies the return value to
122 the buffer pointed to by <EM>area</EM>, and the <EM>area</EM> value will be updat-
123 ed to point past the null ending this value.
125 <STRONG>o</STRONG> The return value itself is an address in the terminal descrip-
126 tion which is loaded into memory.
128 Only the first two characters of the <STRONG>id</STRONG> parameter of <STRONG>tgetflag</STRONG>, <STRONG>tgetnum</STRONG>
129 and <STRONG>tgetstr</STRONG> are compared in lookups.
132 </PRE><H3><a name="h3-Formatting-Capabilities">Formatting Capabilities</a></H3><PRE>
133 The <STRONG>tgoto</STRONG> routine expands the given capability using the parameters.
135 <STRONG>o</STRONG> Because the capability may have padding characters, the output of
136 <STRONG>tgoto</STRONG> should be passed to <STRONG>tputs</STRONG> rather than some other output func-
137 tion such as <STRONG>printf(3)</STRONG>.
139 <STRONG>o</STRONG> While <STRONG>tgoto</STRONG> is assumed to be used for the two-parameter cursor po-
140 sitioning capability, termcap applications also use it for single-
141 parameter capabilities.
143 Doing this shows a quirk in <STRONG>tgoto</STRONG>: most hardware terminals use cur-
144 sor addressing with <EM>row</EM> first, but the original developers of the
145 termcap interface chose to put the <EM>column</EM> parameter first. The
146 <STRONG>tgoto</STRONG> function swaps the order of parameters. It does this also
147 for calls requiring only a single parameter. In that case, the
148 first parameter is merely a placeholder.
150 <STRONG>o</STRONG> Normally the ncurses library is compiled with terminfo support. In
151 that case, <STRONG>tgoto</STRONG> uses an internal version of <STRONG><A HREF="curs_terminfo.3x.html">tparm(3x)</A></STRONG> (a more ca-
154 With terminfo support, <STRONG>tgoto</STRONG> is able to use some of the terminfo
155 features, but not all. In particular, it allows only numeric pa-
156 rameters; <STRONG>tparm</STRONG> supports string parameters.
158 However, <STRONG>tparm</STRONG> is not a <EM>termcap</EM> feature, and portable <EM>termcap</EM> ap-
159 plications should not rely upon its availability.
161 The <STRONG>tputs</STRONG> routine is described on the <STRONG><A HREF="curs_terminfo.3x.html">curs_terminfo(3x)</A></STRONG> manual page.
162 It can retrieve capabilities by either termcap or terminfo name.
165 </PRE><H3><a name="h3-Global-Variables">Global Variables</a></H3><PRE>
166 The variables <STRONG>PC</STRONG>, <STRONG>UP</STRONG> and <STRONG>BC</STRONG> are set by <STRONG>tgetent</STRONG> to the terminfo entry's
167 data for <STRONG>pad_char</STRONG>, <STRONG>cursor_up</STRONG> and <STRONG>backspace_if_not_bs</STRONG>, respectively. <STRONG>UP</STRONG>
168 is not used by ncurses. <STRONG>PC</STRONG> is used in the <STRONG>tdelay_output</STRONG> function. <STRONG>BC</STRONG>
169 is used in the <STRONG>tgoto</STRONG> emulation. The variable <STRONG>ospeed</STRONG> is set by ncurses
170 in a system-specific coding to reflect the terminal speed.
173 </PRE><H3><a name="h3-Releasing-Memory">Releasing Memory</a></H3><PRE>
174 The termcap functions provide no means for freeing memory, because
175 legacy termcap implementations used only the buffer areas provided by
176 the caller via <STRONG>tgetent</STRONG> and <STRONG>tgetstr</STRONG>. Those buffers are unused in ter-
179 On the other hand, terminfo allocates memory. It uses <STRONG>setupterm</STRONG> to re-
180 trieve the data used by <STRONG>tgetent</STRONG> and the functions which return capabil-
181 ity values such as <STRONG>tgetstr</STRONG>. One could use
183 <STRONG>del_curterm(cur_term);</STRONG>
186 to free this memory, but there is an additional complication with
187 ncurses. It uses a fixed-size <EM>pool</EM> of storage locations, one per set-
188 ting of the <STRONG>TERM</STRONG> variable when <STRONG>tgetent</STRONG> is called. The <STRONG>screen(1)</STRONG> pro-
189 gram relies upon this arrangement, to improve its performance.
191 An application which uses only the low-level termcap functions could
192 free the memory using <STRONG>del_curterm</STRONG>, because the pool is freed using oth-
193 er functions (see <STRONG><A HREF="curs_memleaks.3x.html">curs_memleaks(3x)</A></STRONG>).
196 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
197 Except where explicitly noted, routines that return an integer return
198 <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> (SVr4 only specifies "an integer value other
199 than <STRONG>ERR</STRONG>") upon successful completion.
201 Routines that return pointers return <STRONG>NULL</STRONG> on error.
203 A few special cases apply:
205 <STRONG>o</STRONG> If the terminal database has not been initialized, these return an
208 <STRONG>o</STRONG> The calls with a string parameter (<STRONG>tgoto</STRONG>, <STRONG>tputs</STRONG>) check if the
209 string is null, or cancelled. Those return an error.
211 <STRONG>o</STRONG> A call to <STRONG>tgoto</STRONG> using a capability with string parameters is an er-
214 <STRONG>o</STRONG> A call to <STRONG>tgoto</STRONG> using a capability with more than two parameters is
218 </PRE><H2><a name="h2-BUGS">BUGS</a></H2><PRE>
219 If you call <STRONG>tgetstr</STRONG> to fetch <STRONG>ca</STRONG> or any other parameterized string, be
220 aware that it will be returned in terminfo notation, not the older and
221 not-quite-compatible termcap notation. This will not cause problems if
222 all you do with it is call <STRONG>tgoto</STRONG> or <STRONG>tparm</STRONG>, which both expand terminfo-
223 style strings as terminfo. (The <STRONG>tgoto</STRONG> function, if configured to sup-
224 port termcap, will check if the string is indeed terminfo-style by
225 looking for "%p" parameters or "$<..>" delays, and invoke a termcap-
226 style parser if the string does not appear to be terminfo).
228 Because terminfo conventions for representing padding in string capa-
229 bilities differ from termcap's, users can be surprised:
231 <STRONG>o</STRONG> <STRONG>tputs("50")</STRONG> in a terminfo system will put out a literal "50" rather
232 than busy-waiting for 50 milliseconds.
234 <STRONG>o</STRONG> However, if ncurses is configured to support termcap, it may also
235 have been configured to support the BSD-style padding.
237 In that case, <STRONG>tputs</STRONG> inspects strings passed to it, looking for dig-
238 its at the beginning of the string.
240 <STRONG>tputs("50")</STRONG> in a termcap system may wait for 50 milliseconds rather
241 than put out a literal "50"
243 Note that termcap has nothing analogous to terminfo's <STRONG>sgr</STRONG> string. One
244 consequence of this is that termcap applications assume <STRONG>me</STRONG> (terminfo
245 <STRONG>sgr0</STRONG>) does not reset the alternate character set. This implementation
246 checks for, and modifies the data shown to the termcap interface to ac-
247 commodate termcap's limitation in this respect.
250 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
252 </PRE><H3><a name="h3-Standards">Standards</a></H3><PRE>
253 These functions are provided for supporting legacy applications, and
254 should not be used in new programs:
256 <STRONG>o</STRONG> The XSI Curses standard, Issue 4 describes these functions. Howev-
257 er, they are marked TO BE WITHDRAWN and may be removed in future
260 <STRONG>o</STRONG> X/Open Curses, Issue 5 (December 2007) marked the termcap interface
261 (along with <STRONG>vwprintw</STRONG> and <STRONG>vwscanw</STRONG>) as withdrawn.
263 Neither the XSI Curses standard nor the SVr4 man pages documented the
264 return values of <STRONG>tgetent</STRONG> correctly, though all three were in fact re-
265 turned ever since SVr1. In particular, an omission in the XSI Curses
266 documentation has been misinterpreted to mean that <STRONG>tgetent</STRONG> returns <STRONG>OK</STRONG>
267 or <STRONG>ERR</STRONG>. Because the purpose of these functions is to provide compati-
268 bility with the <EM>termcap</EM> library, that is a defect in XCurses, Issue 4,
269 Version 2 rather than in ncurses.
272 </PRE><H3><a name="h3-Compatibility-with-BSD-Termcap">Compatibility with BSD Termcap</a></H3><PRE>
273 External variables are provided for support of certain termcap applica-
274 tions. However, termcap applications' use of those variables is poorly
275 documented, e.g., not distinguishing between input and output. In par-
276 ticular, some applications are reported to declare and/or modify <STRONG>os-</STRONG>
277 <STRONG>peed</STRONG>.
279 The comment that only the first two characters of the <STRONG>id</STRONG> parameter are
280 used escapes many application developers. The original BSD 4.2 termcap
281 library (and historical relics thereof) did not require a trailing null
282 NUL on the parameter name passed to <STRONG>tgetstr</STRONG>, <STRONG>tgetnum</STRONG> and <STRONG>tgetflag</STRONG>.
283 Some applications assume that the termcap interface does not require
284 the trailing NUL for the parameter name. Taking into account these is-
287 <STRONG>o</STRONG> As a special case, <STRONG>tgetflag</STRONG> matched against a single-character
288 identifier provided that was at the end of the terminal descrip-
289 tion. You should not rely upon this behavior in portable programs.
290 This implementation disallows matches against single-character ca-
293 <STRONG>o</STRONG> This implementation disallows matches by the termcap interface
294 against extended capability names which are longer than two charac-
297 The BSD termcap function <STRONG>tgetent</STRONG> returns the text of a termcap entry in
298 the buffer passed as an argument. This library (like other terminfo
299 implementations) does not store terminal descriptions as text. It sets
300 the buffer contents to a null-terminated string.
303 </PRE><H3><a name="h3-Other-Compatibility">Other Compatibility</a></H3><PRE>
304 This library includes a termcap.h header, for compatibility with other
305 implementations. But the header is rarely used because the other im-
306 plementations are not strictly compatible.
308 The original BSD termcap (through 4.3BSD) had no header file which gave
309 function prototypes, because that was a feature of ANSI C. BSD termcap
310 was written several years before C was standardized. However, there
311 were two different termcap.h header files in the BSD sources:
313 <STRONG>o</STRONG> One was used internally by the <STRONG>jove</STRONG> editor in 2BSD through 4.4BSD.
314 It defined global symbols for the termcap variables which it used.
316 <STRONG>o</STRONG> The other appeared in 4.4BSD Lite Release 2 (mid-1993) as part of
317 <EM>libedit</EM> (also known as the <EM>editline</EM> library). The CSRG source his-
318 tory shows that this was added in mid-1992. The <EM>libedit</EM> header
319 file was used internally, as a convenience for compiling the <EM>edit-</EM>
320 <EM>line</EM> library. It declared function prototypes, but no global vari-
323 The header file from <EM>libedit</EM> was added to NetBSD's termcap library in
326 Meanwhile, GNU termcap was under development, starting in 1990. The
327 first release (termcap 1.0) in 1991 included a termcap.h header. The
328 second release (termcap 1.1) in September 1992 modified the header to
329 use <STRONG>const</STRONG> for the function prototypes in the header where one would ex-
330 pect the parameters to be read-only. This was a difference versus the
331 original BSD termcap. The prototype for <STRONG>tputs</STRONG> also differed, but in
332 that instance, it was <EM>libedit</EM> which differed from BSD termcap.
334 A copy of GNU termcap 1.3 was bundled with <EM>bash</EM> in mid-1993, to support
335 the <STRONG>readline(3)</STRONG> library.
337 A termcap.h file was provided in ncurses 1.8.1 (November 1993). That
338 reflected influence by <STRONG>emacs(1)</STRONG> (rather than <STRONG>jove(1)</STRONG>) and GNU termcap:
340 <STRONG>o</STRONG> it provided declarations for a few global symbols used by <STRONG>emacs</STRONG>
342 <STRONG>o</STRONG> it provided function prototypes (using <STRONG>const</STRONG>).
344 <STRONG>o</STRONG> a prototype for <STRONG>tparam</STRONG> (a GNU termcap feature) was provided.
346 Later (in mid-1996) the <STRONG>tparam</STRONG> function was removed from ncurses. As a
347 result, there are differences between any of the four implementations,
348 which must be taken into account by programs which can work with all
349 termcap library interfaces.
352 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
353 <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG>putc(3)</STRONG>, <STRONG><A HREF="term_variables.3x.html">term_variables(3x)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>.
355 https://invisible-island.net/ncurses/tctest.html
359 ncurses 6.4 2023-04-16 <STRONG><A HREF="curs_termcap.3x.html">curs_termcap(3x)</A></STRONG>
363 <li><a href="#h2-NAME">NAME</a></li>
364 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
365 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
367 <li><a href="#h3-Initialization">Initialization</a></li>
368 <li><a href="#h3-Capability-Values">Capability Values</a></li>
369 <li><a href="#h3-Formatting-Capabilities">Formatting Capabilities</a></li>
370 <li><a href="#h3-Global-Variables">Global Variables</a></li>
371 <li><a href="#h3-Releasing-Memory">Releasing Memory</a></li>
374 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
375 <li><a href="#h2-BUGS">BUGS</a></li>
376 <li><a href="#h2-PORTABILITY">PORTABILITY</a>
378 <li><a href="#h3-Standards">Standards</a></li>
379 <li><a href="#h3-Compatibility-with-BSD-Termcap">Compatibility with BSD Termcap</a></li>
380 <li><a href="#h3-Other-Compatibility">Other Compatibility</a></li>
383 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>