NAME¶
PC,
UP,
BC,
ospeed,
tgetent,
tgetflag,
tgetnum,
tgetstr,
tgoto,
tputs - direct
curses interface to the terminfo capability database
SYNOPSIS¶
#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));
DESCRIPTION¶
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.
INITIALIZATION¶
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.
CAPABILITY VALUES¶
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
terminfo(3NCURSES) manual
page. It can retrieve capabilities by either termcap or terminfo name.
GLOBAL VARIABLES¶
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.
RETURN VALUE¶
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.
Routines that return pointers return
NULL on error.
BUGS¶
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 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 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.
PORTABILITY¶
The XSI Curses standard, Issue 4 describes these functions. 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 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.
SEE ALSO¶
ncurses(3NCURSES),
terminfo(5),
terminfo_variables(3NCURSES),
putc(3).
http://invisible-island.net/ncurses/tctest.html