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30 * @Id: curs_termcap.3x,v 1.72 2023/11/25 14:32:36 tom Exp @
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42 <H1 class="no-header">curs_termcap 3x 2023-11-25 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 <EM>curses</EM> emulation of <EM>termcap</EM>
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>
92 library would store a copy of the terminal description in the
93 area referenced by this pointer. However, ncurses stores its
94 terminal descriptions in compiled binary form, which is not the
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-
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>
112 parameter 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
118 also 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
123 updated to point past the null ending this value.
125 <STRONG>o</STRONG> The return value itself is an address in the terminal
126 description 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
137 function such as <STRONG>printf(3)</STRONG>.
139 <STRONG>o</STRONG> While <STRONG>tgoto</STRONG> is assumed to be used for the two-parameter cursor
140 positioning capability, termcap applications also use it for
141 single-parameter capabilities.
143 Doing this shows a quirk in <STRONG>tgoto</STRONG>: most hardware terminals use
144 cursor addressing with <EM>row</EM> first, but the original developers of
145 the 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
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
156 parameters; <STRONG>tparm</STRONG> supports string parameters.
158 However, <STRONG>tparm</STRONG> is not a <EM>termcap</EM> feature, and portable <EM>termcap</EM>
159 applications 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
179 On the other hand, terminfo allocates memory. It uses <STRONG>setupterm</STRONG> to
180 retrieve the data used by <STRONG>tgetent</STRONG> and the functions which return
181 capability 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
188 setting of the <STRONG>TERM</STRONG> variable when <STRONG>tgetent</STRONG> is called. The <STRONG>screen(1)</STRONG>
189 program 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
193 other 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
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-PORTABILITY">PORTABILITY</a></H2><PRE>
220 </PRE><H3><a name="h3-Standards">Standards</a></H3><PRE>
221 These functions are provided for supporting legacy applications, and
222 should not be used in new programs:
224 <STRONG>o</STRONG> The XSI Curses standard, Issue 4 describes these functions.
225 However, they are marked TO BE WITHDRAWN and may be removed in
228 <STRONG>o</STRONG> X/Open Curses, Issue 5 (December 2007) marked the termcap interface
229 (along with <STRONG>vwprintw</STRONG> and <STRONG>vwscanw</STRONG>) as withdrawn.
231 Neither the XSI Curses standard nor the SVr4 man pages documented the
232 return values of <STRONG>tgetent</STRONG> correctly, though all three were in fact
233 returned ever since SVr1. In particular, an omission in the XSI Curses
234 documentation has been misinterpreted to mean that <STRONG>tgetent</STRONG> returns <STRONG>OK</STRONG>
235 or <STRONG>ERR</STRONG>. Because the purpose of these functions is to provide
236 compatibility with the <EM>termcap</EM> library, that is a defect in XCurses,
237 Issue 4, Version 2 rather than in ncurses.
240 </PRE><H3><a name="h3-Compatibility-with-BSD-Termcap">Compatibility with BSD Termcap</a></H3><PRE>
241 External variables are provided for support of certain termcap
242 applications. However, termcap applications' use of those variables is
243 poorly documented, e.g., not distinguishing between input and output.
244 In particular, some applications are reported to declare and/or modify
245 <STRONG>ospeed</STRONG>.
247 The comment that only the first two characters of the <STRONG>id</STRONG> parameter are
248 used escapes many application developers. The original BSD 4.2 termcap
249 library (and historical relics thereof) did not require a trailing null
250 NUL on the parameter name passed to <STRONG>tgetstr</STRONG>, <STRONG>tgetnum</STRONG> and <STRONG>tgetflag</STRONG>.
251 Some applications assume that the termcap interface does not require
252 the trailing NUL for the parameter name. Taking into account these
255 <STRONG>o</STRONG> As a special case, <STRONG>tgetflag</STRONG> matched against a single-character
256 identifier provided that was at the end of the terminal
257 description. You should not rely upon this behavior in portable
258 programs. This implementation disallows matches against single-
259 character capability names.
261 <STRONG>o</STRONG> This implementation disallows matches by the termcap interface
262 against extended capability names which are longer than two
265 The BSD termcap function <STRONG>tgetent</STRONG> returns the text of a termcap entry in
266 the buffer passed as an argument. This library (like other terminfo
267 implementations) does not store terminal descriptions as text. It sets
268 the buffer contents to a null-terminated string.
271 </PRE><H3><a name="h3-Other-Compatibility">Other Compatibility</a></H3><PRE>
272 This library includes a termcap.h header, for compatibility with other
273 implementations. But the header is rarely used because the other
274 implementations are not strictly compatible.
276 The original BSD termcap (through 4.3BSD) had no header file which gave
277 function prototypes, because that was a feature of ANSI C. BSD termcap
278 was written several years before C was standardized. However, there
279 were two different termcap.h header files in the BSD sources:
281 <STRONG>o</STRONG> One was used internally by the <STRONG>jove</STRONG> editor in 2BSD through 4.4BSD.
282 It defined global symbols for the termcap variables which it used.
284 <STRONG>o</STRONG> The other appeared in 4.4BSD Lite Release 2 (mid-1993) as part of
285 <EM>libedit</EM> (also known as the <EM>editline</EM> library). The CSRG source
286 history shows that this was added in mid-1992. The <EM>libedit</EM> header
287 file was used internally, as a convenience for compiling the
288 <EM>editline</EM> library. It declared function prototypes, but no global
291 The header file from <EM>libedit</EM> was added to NetBSD's termcap library in
294 Meanwhile, GNU termcap was under development, starting in 1990. The
295 first release (termcap 1.0) in 1991 included a termcap.h header. The
296 second release (termcap 1.1) in September 1992 modified the header to
297 use <STRONG>const</STRONG> for the function prototypes in the header where one would
298 expect the parameters to be read-only. This was a difference versus
299 the original BSD termcap. The prototype for <STRONG>tputs</STRONG> also differed, but
300 in that instance, it was <EM>libedit</EM> which differed from BSD termcap.
302 A copy of GNU termcap 1.3 was bundled with <EM>bash</EM> in mid-1993, to support
303 the <STRONG>readline(3)</STRONG> library.
305 A termcap.h file was provided in ncurses 1.8.1 (November 1993). That
306 reflected influence by <STRONG>emacs(1)</STRONG> (rather than <STRONG>jove(1)</STRONG>) and GNU termcap:
308 <STRONG>o</STRONG> it provided declarations for a few global symbols used by <STRONG>emacs</STRONG>
310 <STRONG>o</STRONG> it provided function prototypes (using <STRONG>const</STRONG>).
312 <STRONG>o</STRONG> a prototype for <STRONG>tparam</STRONG> (a GNU termcap feature) was provided.
314 Later (in mid-1996) the <STRONG>tparam</STRONG> function was removed from ncurses. As a
315 result, there are differences between any of the four implementations,
316 which must be taken into account by programs which can work with all
317 termcap library interfaces.
320 </PRE><H2><a name="h2-BUGS">BUGS</a></H2><PRE>
321 If you call <STRONG>tgetstr</STRONG> to fetch <STRONG>ca</STRONG> or any other parameterized string
322 capability, be aware that it is returned in <EM>terminfo</EM> notation, not the
323 older and not-quite-compatible <EM>termcap</EM> notation. This does not cause
324 problems if all you do with it is call <STRONG>tgoto</STRONG> or <STRONG>tparm</STRONG>, which both
325 expand <EM>terminfo</EM>-style strings as <EM>terminfo</EM> does. (The <STRONG>tgoto</STRONG> function,
326 if configured to support <EM>termcap,</EM> checks if the string is indeed
327 <EM>terminfo</EM>-style by looking for "<STRONG>%p</STRONG>" parameters or "<STRONG><</STRONG>...<STRONG>></STRONG>" delays, and
328 invokes a <EM>termcap</EM>-style parser if the string appears not to use
329 <EM>terminfo</EM> syntax.)
331 Because <EM>terminfo</EM>'s syntax for padding in string capabilities differs
332 from <EM>termcap</EM>'s, users can be surprised.
334 <STRONG>o</STRONG> <STRONG>tputs("50")</STRONG> in a <EM>terminfo</EM> system transmits "50" rather than busy-
335 waiting for 50 milliseconds.
337 <STRONG>o</STRONG> However, if <EM>ncurses</EM> is configured to support <EM>termcap</EM>, it may also
338 have been configured to support BSD-style padding.
340 In that case, <STRONG>tputs</STRONG> inspects strings passed to it, looking for
341 digits at the beginning of the string.
343 <STRONG>tputs("50")</STRONG> in a <EM>termcap</EM> system may busy-wait for 50 milliseconds
344 rather than transmitting "50".
346 <EM>termcap</EM> has nothing analogous to <EM>terminfo</EM>'s <STRONG>sgr</STRONG> string. One
347 consequence is that <EM>termcap</EM> applications assume that <STRONG>me</STRONG> (equivalent to
348 <EM>terminfo</EM>'s <STRONG>sgr0</STRONG> capability) does not reset the alternate character set.
349 <EM>ncurses</EM> checks for, and modifies the data shared with, the <EM>termcap</EM>
350 interface to accommodate the latter's limitation in this respect.
353 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
354 <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>
356 https://invisible-island.net/ncurses/tctest.html
360 ncurses 6.4 2023-11-25 <STRONG><A HREF="curs_termcap.3x.html">curs_termcap(3x)</A></STRONG>
364 <li><a href="#h2-NAME">NAME</a></li>
365 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
366 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
368 <li><a href="#h3-Initialization">Initialization</a></li>
369 <li><a href="#h3-Capability-Values">Capability Values</a></li>
370 <li><a href="#h3-Formatting-Capabilities">Formatting Capabilities</a></li>
371 <li><a href="#h3-Global-Variables">Global Variables</a></li>
372 <li><a href="#h3-Releasing-Memory">Releasing Memory</a></li>
375 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</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-BUGS">BUGS</a></li>
384 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>