X-Git-Url: http://ncurses.scripts.mit.edu/?p=ncurses.git;a=blobdiff_plain;f=doc%2Fhtml%2Fman%2Fcurs_termcap.3x.html;h=a1d532c4f13335bc194cb945ba3175908098b0cb;hp=c958a849858b97d1951bb0334d974069ee734915;hb=HEAD;hpb=cb4427a16794d98049b4d790b810d62217501f9f diff --git a/doc/html/man/curs_termcap.3x.html b/doc/html/man/curs_termcap.3x.html index c958a849..c2763afe 100644 --- a/doc/html/man/curs_termcap.3x.html +++ b/doc/html/man/curs_termcap.3x.html @@ -1,6 +1,7 @@ -
--curs_termcap(3x) curs_termcap(3x) +curs_termcap(3x) Library calls curs_termcap(3x)
PC, UP, BC, ospeed, tgetent, tgetflag, tgetnum, tgetstr, tgoto, tputs - - direct curses interface to the terminfo capability database + curses emulation of termcap
#include <curses.h> #include <term.h> - extern char PC; - extern char * UP; - extern char * BC; - extern short ospeed; + char PC; + char * UP; + char * BC; + short ospeed; - int tgetent(const 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)); + 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));
- 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. - + ncurses provides the foregoing variables and functions as a + compatibility layer for programs that use the termcap library. The API + is the same, but behavior is emulated using the terminfo database. + Thus, it can be used only to query the capabilities of terminal + database entries for which a terminfo entry has been compiled. -
- The tgetent routine loads the entry for name. It returns: - 1 on success, +
+ tgetent loads the terminal database entry for name; see term(7). This + must be done before calling any of the other functions. It returns - 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 on success, - -1 if the terminfo database could not be found. + 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 - This differs from the termcap library in two ways: + -1 if the terminfo database could not be found. - 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. + This implementation differs from those of historical termcap libraries. - 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. + o 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. terminfo stores terminal type descriptions in compiled + form, which is not the same thing. + o 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. -
- 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 +
+ tgetflag reports the Boolean entry for id, or zero 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: + 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. 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 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. - 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 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. - o The return value itself is an address in the terminal descrip- - tion which is loaded into memory. + o The return value itself is an address in the terminal type + description loaded into memory. - Only the first two characters of the id parameter of tgetflag, tgetnum - and tgetstr are compared in lookups. +
+ String capabilities can be parameterized; see subsection "Parameterized + Strings" in terminfo(5). tgoto applies its second and third arguments + to the parametric placeholders in the capability stored in the first + argument. -
- The tgoto routine expands the given capability using the parameters. + o The capability may contain padding specifications; see subsection + "Delays and Padding" of terminfo(5). The output of tgoto should + thus be passed to tputs rather than some other output function such + as printf(3). - 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 + positioning capability, termcap applications also use it for + single-parameter capabilities. - 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 so reveals a quirk in tgoto: most hardware terminals use + cursor addressing with row first, but the original developers of + the termcap interface chose to put the col (column) parameter + first. The tgoto function swaps the order of its parameters. It + does this even for calls requiring only a single parameter. In + that case, the first parameter is merely a placeholder. - 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 without full termcap + support. In that case, tgoto uses an internal version of tparm(3x) + (a more capable function). - o Normally the ncurses library is compiled with terminfo support. In - that case, tgoto uses tparm(3x) (a more capable formatter). + Because it uses tparm internally, tgoto is able to use some term- + info features, but not all. In particular, it allows only numeric + parameters; tparm supports string parameters. - However, tparm is not a termcap feature, and portable termcap ap- - plications should not rely upon its availability. + However, tparm is not a termcap feature, and portable termcap + applications 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. + tputs is described in curs_terminfo(3x). It can retrieve capabilities + by either termcap or terminfo code. -
- The variables PC, UP and BC are set by tgetent to the terminfo entry's +
+ 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. + is not used by ncurses. PC is used by delay_output(3x). BC is used by + tgoto emulation. The variable ospeed is set by ncurses using a system- + specific encoding to indicate the terminal's data rate. + + +
+ The termcap functions provide no means of freeing memory, because + legacy termcap implementations used only the buffer areas provided by + the caller via tgetent and tgetstr. Those buffers are unused in term- + info. + + By contrast, terminfo allocates memory. It uses setupterm(3x) to + obtain the data used by tgetent and the functions that retrieve + capability values. 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 value + of the terminal name parameter given to tgetent. The screen(1) program + relies upon this arrangement to improve its performance. + + 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).
- 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. + The return values of tgetent, tgetflag, tgetname, and tgetstr are + documented above. - Routines that return pointers return NULL on error. + tgoto returns NULL on error. Error conditions include: + o uninitialized state (tgetent was not called successfully), -
- 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. + o cap being a null pointer, + + o cap referring to a canceled capability, + + o cap being a capability with string-valued parameters (a term- + info-only feature), and + + o cap being a capability with more than two parameters. + + See curs_terminfo(3x) regarding tputs. + + +
+ ncurses compares only the first two characters of the id parameter of + tgetflag, tgetnum, and tgetstr to the capability names in the database.
- 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. + These functions are no longer standardized (and the variables never + were); ncurses provides them to support legacy applications. They + should not be used in new programs. + + +
+ o X/Open Curses, Issue 4, Version 2 (1996), describes these + functions, marking them as "TO BE WITHDRAWN". + + o X/Open Curses, Issue 7 (2009) marks the termcap interface (along + with vwprintw and vwscanw) as withdrawn. + + 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. + + Compatibility with BSD termcap + Externally visible variables are provided for support of certain + termcap applications. However, their correct usage is poorly + documented; for example, it is unclear when reading and writing them is + meaningful. In particular, some applications are reported to declare + and/or modify ospeed. + + 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. Some applications thus + assume that the termcap interface does not require the trailing null + character for the capability identifier. + + o 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 terminfo + implementations, does not store terminal type 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 + implementations are not strictly compatible. + + +
+ Bill Joy originated a forerunner of termcap called "ttycap", dated + September 1977, and released in 1BSD (March 1978). 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, followed in 2BSD (May 1979), + adding tgoto and tputs. The former applied at that time only to cursor + positioning capabilities, 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. + + 4BSD (November 1980) renamed termlib to termcap and added another test + program. The library remained much the same though 4.3BSD (June 1986). + 4.4BSD-Lite (June 1994) refactored it, 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. + + o One was used internally by jove(1) from 4.3BSD onward. It declared + global symbols for the termcap variables that it used. + + o The other appeared in 4.4BSD-Lite Release 2 (June 1995) as part of + libedit (also known as the editline 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 editline + 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: + + o global symbols used by emacs, + + o const-qualified function prototypes, and + + o 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. + + +
+ If you call tgetstr to fetch column_address (ch) or any other + parameterized string capability, be aware that it is returned in term- + info notation, not the older and not-quite-compatible termcap notation. + This does not cause problems if all you do with it is call tgoto or + tparm, which both parametrically expand terminfo-style string + capabilities as terminfo does. (If ncurses is configured to support + termcap, tgoto checks whether the string is terminfo-style by looking + for "%p" parameters or "<...>" delays, and invokes a termcap-style + parser if the string appears not to use terminfo syntax.) + + Because terminfo's syntax for padding in string capabilities differs + from termcap's, users can be surprised. + + o tputs("50") in a terminfo system transmits "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 BSD-style padding. + + In that case, tputs inspects strings passed to it, looking for + digits at the beginning of the string. + + tputs("50") in a termcap system may busy-wait for 50 milliseconds + rather than transmitting "50". + + termcap has nothing analogous to terminfo's set_attributes (sgr) + capability. One consequence is that termcap applications assume that + "me" (equivalent to terminfo'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.
- curses(3x), terminfo(5), term_variables(3x), putc(3). + curses(3x), curs_terminfo(3x), putc(3), term_variables(3x), terminfo(5) https://invisible-island.net/ncurses/tctest.html - curs_termcap(3x) +ncurses 6.5 2024-04-20 curs_termcap(3x)