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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));
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:
» 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. » 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 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 tgetflag, 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 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.
Routines that return pointers return NULL on error.
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 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 accommodate termcap's limitation in this respect.
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 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 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 distinguishing 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. Taking into account these issues:
|»||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 implementation disallows matches against single-character capability names.|
|»||This implementation disallows matches by the termcap interface against extended capability names which are longer than two characters.|
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|“||As soon as we started programming, we found to our surprise that it wasn't as easy to get programs right as we had thought. Debugging had to be discovered. I can remember the exact instant when I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs.||”|
|— Maurice Wilkes|