PC, UP, BC, ospeed, tgetent, tgetflag, tgetnum, tgetstr, tgoto, tputs - direct curses interface to the terminfo capability database
#include <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(char *id); int tgetnum(char *id); char *tgetstr(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 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 (or that it is a generic type, having too little information for curses ap- plications 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 library would store a copy of the terminal description in the area referenced by this pointer. However, ncurses stores its terminal 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-addressing.
The tgetflag routine gets the boolean entry for id, or ze- ro 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 re- turned string. 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 also that the resulting buffer pointer is not NULL. If either check fails, the area parame- ter is ignored. o If the checks succeed, ncurses also copies the re- turn value to the buffer pointed to by area, and the area value will be updated to point past the null ending this value. o The return value itself is an address in the termi- nal description which is loaded into memory. Only the first two characters of the id parameter of tget- flag, 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 function such as printf. o While tgoto is assumed to be used for the two-parame- ter cursor positioning capability, termcap applica- tions also use it for single-parameter capabilities. Doing this shows a quirk in tgoto: most hardware ter- minals use cursor 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 (a more capa- ble formatter). 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.
Except where explicitly noted, routines that return an in- teger return ERR upon failure and OK (SVr4 only specifies "an integer value other than ERR") upon successful comple- tion. Routines that return pointers return NULL on error.
If you call tgetstr to fetch ca or any other parameterized string, be aware that it will be returned in terminfo no- tation, not the older and not-quite-compatible termcap no- tation. 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.
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. 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. Tak- ing into account these issues: o As a special case, tgetflag matched against a single- character identifier provided that was at the end of the terminal description. You should not rely upon this behavior in portable programs. This implementa- tion disallows matches against single-character capa- bility names. o This implementation disallows matches by the termcap interface against extended capability names which are longer than two characters.
curses(3x), terminfo(5), term_variables(3x), putc(3). http://invisible-island.net/ncurses/tctest.html curs_termcap(3x)