Provided by: ncurses-doc_6.1-1ubuntu1_all bug


       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 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.

       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 area parameter is used as follows:

          ·   It is assumed to be the address of a pointer to a buffer  managed  by  the  calling

          ·   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 parameter is

          ·   If  the  checks succeed, ncurses also copies the return value to the buffer pointed
              to by area, and the area value will be updated to point past the null  ending  this

          ·   The  return  value itself is an address in the terminal description which is loaded
              into memory.

       Only the first two characters of the id parameter of tgetflag,  tgetnum  and  tgetstr  are
       compared in lookups.

       The tgoto routine expands the given capability using the parameters.

       ·   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.

       ·   While tgoto is assumed to be used for the two-parameter cursor positioning capability,
           termcap applications also use it for single-parameter capabilities.

           Doing  this shows 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
           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.

       ·   Normally  the  ncurses library is compiled with terminfo support.  In that case, tgoto
           uses tparm(3X) (a more capable formatter).

           However, tparm is not a termcap feature, and portable termcap applications should  not
           rely upon its availability.

       The  tputs  routine  is  described on the terminfo(3NCURSES) 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.


       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.


       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

       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.


       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

       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.


       ncurses(3NCURSES), terminfo(5), terminfo_variables(3NCURSES), putc(3).