curs_util(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | SEE ALSO | COLOPHON

curs_util(3X)                                              curs_util(3X)

NAME         top

       delay_output, filter, flushinp, getwin, key_name, keyname,
       nofilter, putwin, unctrl, use_env, use_tioctl, wunctrl -
       miscellaneous curses utility routines

SYNOPSIS         top

       #include <curses.h>

       const char *unctrl(chtype c);
       wchar_t *wunctrl(cchar_t *c);

       const char *keyname(int c);
       const char *key_name(wchar_t w);

       void filter(void);
       void nofilter(void);

       void use_env(bool f);
       void use_tioctl(bool f);

       int putwin(WINDOW *win, FILE *filep);
       WINDOW *getwin(FILE *filep);

       int delay_output(int ms);
       int flushinp(void);

DESCRIPTION         top

   unctrl
       The unctrl routine returns a character string which is a
       printable representation of the character c, ignoring attributes.
       Control characters are displayed in the ^X notation.  Printing
       characters are displayed as is.  The corresponding wunctrl
       returns a printable representation of a wide character.

   keyname/key_name
       The keyname routine returns a character string corresponding to
       the key c:

       •   Printable characters are displayed as themselves, e.g., a
           one-character string containing the key.

       •   Control characters are displayed in the ^X notation.

       •   DEL (character 127) is displayed as ^?.

       •   Values above 128 are either meta characters (if the screen
           has not been initialized, or if meta(3X) has been called with
           a TRUE parameter), shown in the M-X notation, or are
           displayed as themselves.  In the latter case, the values may
           not be printable; this follows the X/Open specification.

       •   Values above 256 may be the names of the names of function
           keys.

       •   Otherwise (if there is no corresponding name) the function
           returns null, to denote an error.  X/Open also lists an
           “UNKNOWN KEY” return value, which some implementations return
           rather than null.

       The corresponding key_name returns a character string
       corresponding to the wide-character value w.  The two functions
       do not return the same set of strings; the latter returns null
       where the former would display a meta character.

   filter/nofilter
       The filter routine, if used, must be called before initscr or
       newterm are called.  Calling filter causes these changes in
       initialization:

       •   LINES is set to 1;

       •   the capabilities clear, cud1, cud, cup, cuu1, cuu, vpa are
           disabled;

       •   the capability ed is disabled if bce is set;

       •   and the home string is set to the value of cr.

       The nofilter routine cancels the effect of a preceding filter
       call.  That allows the caller to initialize a screen on a
       different device, using a different value of $TERM.  The
       limitation arises because the filter routine modifies the in-
       memory copy of the terminal information.

   use_env
       The use_env routine, if used, should be called before initscr or
       newterm are called (because those compute the screen size).  It
       modifies the way ncurses treats environment variables when
       determining the screen size.

       •   Normally ncurses looks first at the terminal database for the
           screen size.

           If use_env was called with FALSE for parameter, it stops here
           unless use_tioctl was also called with TRUE for parameter.

       •   Then it asks for the screen size via operating system calls.
           If successful, it overrides the values from the terminal
           database.

       •   Finally (unless use_env was called with FALSE parameter),
           ncurses examines the LINES or COLUMNS environment variables,
           using a value in those to override the results from the
           operating system or terminal database.

           Ncurses also updates the screen size in response to SIGWINCH,
           unless overridden by the LINES or COLUMNS environment
           variables,

   use_tioctl
       The use_tioctl routine, if used, should be called before initscr
       or newterm are called (because those compute the screen size).
       After use_tioctl is called with TRUE as an argument, ncurses
       modifies the last step in its computation of screen size as
       follows:

       •   checks if the LINES and COLUMNS environment variables are set
           to a number greater than zero.

       •   for each, ncurses updates the corresponding environment
           variable with the value that it has obtained via operating
           system call or from the terminal database.

       •   ncurses re-fetches the value of the environment variables so
           that it is still the environment variables which set the
           screen size.

       The use_env and use_tioctl routines combine as summarized here:

        use_env   use_tioctl   Summary
        ────────────────────────────────────────────────────────────────
        TRUE      FALSE        This is the default behavior.  ncurses
                               uses operating system calls unless
                               overridden by $LINES or $COLUMNS
                               environment variables.
        TRUE      TRUE         ncurses updates $LINES and $COLUMNS
                               based on operating system calls.
        FALSE     TRUE         ncurses ignores $LINES and $COLUMNS,
                               uses operating system calls to obtain
                               size.
        FALSE     FALSE        ncurses relies on the terminal database
                               to determine size.

   putwin/getwin
       The putwin routine writes all data associated with window (or
       pad) win into the file to which filep points.  This information
       can be later retrieved using the getwin function.

       The getwin routine reads window related data stored in the file
       by putwin.  The routine then creates and initializes a new window
       using that data.  It returns a pointer to the new window.  There
       are a few caveats:

       •   the data written is a copy of the WINDOW structure, and its
           associated character cells.  The format differs between the
           wide-character (ncursesw) and non-wide (ncurses) libraries.
           You can transfer data between the two, however.

       •   the retrieved window is always created as a top-level window
           (or pad), rather than a subwindow.

       •   the window's character cells contain the color pair value,
           but not the actual color numbers.  If cells in the retrieved
           window use color pairs which have not been created in the
           application using init_pair, they will not be colored when
           the window is refreshed.

   delay_output
       The delay_output routine inserts an ms millisecond pause in
       output.  This routine should not be used extensively because
       padding characters are used rather than a CPU pause.  If no
       padding character is specified, this uses napms to perform the
       delay.

   flushinp
       The flushinp routine throws away any typeahead that has been
       typed by the user and has not yet been read by the program.

RETURN VALUE         top

       Except for flushinp, routines that return an integer return ERR
       upon failure and OK (SVr4 specifies only "an integer value other
       than ERR") upon successful completion.

       Routines that return pointers return NULL on error.

       X/Open does not define any error conditions.  In this
       implementation

          flushinp
               returns an error if the terminal was not initialized.

          putwin
               returns an error if the associated fwrite calls return an
               error.

PORTABILITY         top

   filter
       The SVr4 documentation describes the action of filter only in the
       vaguest terms.  The description here is adapted from the XSI
       Curses standard (which erroneously fails to describe the
       disabling of cuu).

   keyname
       The keyname function may return the names of user-defined string
       capabilities which are defined in the terminfo entry via the -x
       option of @TIC@.  This implementation automatically assigns at
       run-time keycodes to user-defined strings which begin with “k”.
       The keycodes start at KEY_MAX, but are not guaranteed to be the
       same value for different runs because user-defined codes are
       merged from all terminal descriptions which have been loaded.
       The use_extended_names(3X) function controls whether this data is
       loaded when the terminal description is read by the library.

   nofilter/use_tioctl
       The nofilter and use_tioctl routines are specific to ncurses.
       They were not supported on Version 7, BSD or System V
       implementations.  It is recommended that any code depending on
       ncurses extensions be conditioned using NCURSES_VERSION.

   putwin/getwin
       The putwin and getwin functions have several issues with
       portability:

       •   The files written and read by these functions use an
           implementation-specific format.  Although the format is an
           obvious target for standardization, it has been overlooked.

           Interestingly enough, according to the copyright dates in
           Solaris source, the functions (along with scr_init, etc.)
           originated with the University of California, Berkeley (in
           1982) and were later (in 1988) incorporated into SVr4.
           Oddly, there are no such functions in the 4.3BSD curses
           sources.

       •   Most implementations simply dump the binary WINDOW structure
           to the file.  These include SVr4 curses, NetBSD and PDCurses,
           as well as older ncurses versions.  This implementation (as
           well as the X/Open variant of Solaris curses, dated 1995)
           uses textual dumps.

           The implementations which use binary dumps use block-I/O (the
           fwrite and fread functions).  Those that use textual dumps
           use buffered-I/O.  A few applications may happen to write
           extra data in the file using these functions.  Doing that can
           run into problems mixing block- and buffered-I/O.  This
           implementation reduces the problem on writes by flushing the
           output.  However, reading from a file written using mixed
           schemes may not be successful.

   unctrl/wunctrl
       The XSI Curses standard, Issue 4 describes these functions.  It
       states that unctrl and wunctrl will return a null pointer if
       unsuccessful, but does not define any error conditions.  This
       implementation checks for three cases:

       •   the parameter is a 7-bit US-ASCII code.  This is the case
           that X/Open Curses documented.

       •   the parameter is in the range 128-159, i.e., a C1 control
           code.  If use_legacy_coding(3X) has been called with a 2
           parameter, unctrl returns the parameter, i.e., a one-
           character string with the parameter as the first character.
           Otherwise, it returns “~@”, “~A”, etc., analogous to “^@”,
           “^A”, C0 controls.

           X/Open Curses does not document whether unctrl can be called
           before initializing curses.  This implementation permits
           that, and returns the “~@”, etc., values in that case.

       •   parameter values outside the 0 to 255 range.  unctrl returns
           a null pointer.

       The strings returned by unctrl in this implementation are
       determined at compile time, showing C1 controls from the
       upper-128 codes with a “~” prefix rather than “^”.  Other
       implementations have different conventions.  For example, they
       may show both sets of control characters with “^”, and strip the
       parameter to 7 bits.  Or they may ignore C1 controls and treat
       all of the upper-128 codes as printable.  This implementation
       uses 8 bits but does not modify the string to reflect locale.
       The use_legacy_coding(3X) function allows the caller to change
       the output of unctrl.

       Likewise, the meta(3X) function allows the caller to change the
       output of keyname, i.e., it determines whether to use the “M-”
       prefix for “meta” keys (codes in the range 128 to 255).  Both
       use_legacy_coding(3X) and meta(3X) succeed only after curses is
       initialized.  X/Open Curses does not document the treatment of
       codes 128 to 159.  When treating them as “meta” keys (or if
       keyname is called before initializing curses), this
       implementation returns strings “M-^@”, “M-^A”, etc.

       X/Open Curses documents unctrl as declared in <unctrl.h>, which
       ncurses does.  However, ncurses' <curses.h> includes <unctrl.h>,
       matching the behavior of SVr4 curses.  Other implementations may
       not do that.

   use_env/use_tioctl
       If ncurses is configured to provide the sp-functions extension,
       the state of use_env and use_tioctl may be updated before
       creating each screen rather than once only (curs_sp_funcs(3X)).
       This feature of use_env is not provided by other implementation
       of curses.

SEE ALSO         top

       curses(3X), curs_initscr(3X), curs_inopts(3X), curs_kernel(3X),
       curs_scr_dump(3X), curs_sp_funcs(3X), curs_variables(3X),
       legacy_coding(3X).

COLOPHON         top

       This page is part of the ncurses (new curses) project.
       Information about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
       a bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
       project's upstream Git mirror of the CVS repository
       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-04-01.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-03-28.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

                                                           curs_util(3X)