curs\_util(3X) Library calls curs\_util(3X) # [NAME](#NAME) **delay\_output**, **filter**, **flushinp**, **getwin**, **key\_name**, **keyname**, **nofilter**, **putwin**, **unctrl**, **use\_env**, **use\_tioctl**, **wunctrl** - miscellaneous *curses* utility routines # [SYNOPSIS](#SYNOPSIS) ``` #include ``` ``` const char * unctrl(chtype ch); wchar_t * wunctrl(cchar_t * wch); ``` ``` const char * keyname(int c); const char * key_name(wchar_t wc); ``` ``` void filter(void); /* extension */ void nofilter(void); ``` ``` void use_env(bool bf); /* extension */ void use_tioctl(bool bf); ``` ``` int putwin(WINDOW * win, FILE * filep); WINDOW * getwin(FILE * filep); ``` ``` int delay_output(int ms); ``` ``` int flushinp(void); ``` # [DESCRIPTION](#DESCRIPTION) ## unctrl, wunctrl **unctrl** returns a null-terminated character string printably representing the *curses* character *ch*, often one that originated in keyboard input; see [**getch**(3X)](/man/os/ncurses/getch.3X). - Printable characters represent themselves as a one-character string. - Control characters are expressed in **^X** notation, where *X* is the printable symbol of the control code's value plus 32 in the ISO 646/“ASCII” character set. - DEL (character code 127) is represented as **^?**. - A character code greater than 127 is represented in one of two ways. If the screen has not been initialized or is in meta mode (see [**meta**(3X)](/man/os/ncurses/meta.3X)), it is expressed in **M-X** notation, where X is the representation of the code's value minus 128, as described above. If the screen is not in meta mode, the character code is assumed to represent itself. It nevertheless may not be printable; this is the case for character codes 128-159 in ISO 8859 encodings. *ncurses*'s [**use\_legacy\_coding**(3X)](/man/os/ncurses/use_legacy_coding.3X) function configures **unctrl**'s handling of these character codes. **wunctrl** returns a null-terminated wide-character string printably representing the *curses* complex character *wch*. Both functions ignore the attributes and color pair selection of their argument. ## [keyname, key\_name](#keyname,_key_name) The **keyname** routine returns a character string corresponding to the key *c*. Key codes are different from character codes. - Key codes below 256 are characters. They are displayed using **unctrl**. - Values above 256 may be the codes for function keys. The function key name is displayed. - Otherwise (if there is no corresponding name and the key is not a character) 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 multibyte character string corresponding to the wide-character value *wc*. The two functions (**keyname** and **key\_name**) do not return the same set of strings. - **keyname** returns null where **key\_name** would display a meta character. - **key\_name** does not return the name of a function key. ## [filter, nofilter](#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\_screen** (**clear**)**,** **cursor\_down** (**cud1**)**,** **parm\_down\_cursor** (**cud**)**,** **cursor\_address** (**cup**)**,** **cursor\_up** (**cuu1**)**,** **parm\_up\_cursor** (**cuu**)**,** and **row\_address** (**vpa**) are disabled; - the capability **clear\_eos** (**ed**) is disabled if **back\_color\_erase** (**bce**) is defined; and - the **cursor\_home** (**home**) capability is set to the value of the **carriage\_return** (**cr**) capability. 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 the *TERM* environment variable. The limitation arises because the **filter** routine modifies the in-memory copy of the terminal information. ## [use\_env](#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. *curses* also updates the screen size in response to *SIGWINCH*, unless overridden by the *LINES* or *COLUMNS* environment variables, ## [use\_tioctl](#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. - It checks whether 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 that set the screen size. The **use\_env** and **use\_tioctl** routines combine as follows. **use\_env** **use\_tioctl** **Summary** **TRUE** **FALSE** *ncurses* uses operating system calls unless overridden by *LINES* or *COLUMNS* environment variables; default. **TRUE** **TRUE** *ncurses* updates *LINES* and *COLUMNS* based on operating system calls. **FALSE** **TRUE** *ncurses* ignores *LINES* and *COLUMNS*, using operating system calls to obtain size. ## [putwin, getwin](#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. - Each of the window's character cells contain only its color pair identifier, not the pair's color indices. If cells in the retrieved window use color pairs that have not been created in the application using **init\_pair ,** they are not colored when the window is refreshed. ## [delay\_output](#delay_output) The **delay\_output** routine inserts an *ms* millisecond pause in output. Employ this function judiciously when terminal output uses padding, because *ncurses* transmits null characters (consuming CPU and I/O resources) instead of sleeping and requesting resumption from the operating system. Padding is used unless: - the terminal description has **npc** (**no\_pad\_char**) capability, or - the environment variable **NCURSES\_NO\_PADDING** is set. If padding is not in use, *ncurses* uses **napms** to perform the delay. If the value of *ms* exceeds 30,000 (thirty seconds), it is capped at that value. ## [flushinp](#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](#RETURN_VALUE) Except for **flushinp**, functions that return integers return **ERR** upon failure and **OK** upon success. Functions that return pointers return a null pointer on failure. In *ncurses*, - **flushinp** returns **ERR** if the terminal was not initialized, and - **putwin** returns **ERR** if its associated [*write*(2)](/man/os/ncurses/write.2) calls return **ERR**. # [NOTES](#NOTES) **key\_name** and **wunctrl** are part of *ncurses*'s wide-character API, and are not available in its non-wide-character configuration. # [PORTABILITY](#PORTABILITY) Applications employing *ncurses* extensions should condition their use on the visibility of the **NCURSES\_VERSION** preprocessor macro. X/Open Curses Issue 4 describes these functions. It specifies no error conditions for them. SVr4 describes a successful return value only as “an integer value other than *ERR*”. ## [filter](#filter) The SVr4 documentation describes the action of *filter* only in the vaguest terms. The description here is adapted from X/Open Curses, which erroneously fails to describe the disabling of **parm\_up\_cursor** (**cuu**). ## *delay\_output* padding The limitation to 30 seconds and the use of *napms* differ from other implementations. - SVr4 *curses* does not delay if no padding character is available. - NetBSD *curses* uses *napms* when no padding character is available, but does not take timing into account when using the padding character. Neither limits the delay. ## [keyname](#keyname) The *keyname* function may return the names of user-defined string capabilities that are defined in the *terminfo* entry via the **-x** option of **tic**. *ncurses* automatically assigns at runtime key codes to user-defined strings that begin with “k”. The key codes 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 that have been loaded. The [**use\_extended\_names**(3X)](/man/os/ncurses/use_extended_names.3X) function controls whether this data is loaded when the terminal description is read by the library. ## *putwin*/*getwin* file format 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 *curses*, and *PDCurses*, as well as older *ncurses* versions. *ncurses ,* since version 6 (2015), and *xcurses* use textual dumps. The implementations that use binary dumps use block I/O ([*write*(2)](/man/os/ncurses/write.2) and [*read*(2)](/man/os/ncurses/read.2) 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. *ncurses* reduces the problem on writes by flushing the output. However, reading from a file written using mixed schemes may not be successful. ## unctrl, wunctrl X/Open Curses Issue 4 describes these functions. It specifies no error conditions for them. It states that *unctrl* and *wunctrl* return a null pointer if unsuccessful. *ncurses* 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 the *ncurses* extension function [**use\_legacy\_coding**(3X)](/man/os/ncurses/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*. *ncurses* permits that, and returns the “~@”, etc., values in that case. • The parameter value is outside the 0 to 255 range. *unctrl* returns a null pointer. The strings returned by *unctrl* in *ncurses* 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. *ncurses* uses 8 bits but does not modify the string to reflect locale. The *ncurses* extension function [**use\_legacy\_coding**(3X)](/man/os/ncurses/use_legacy_coding.3X) allows the caller to change the output of *unctrl*. Likewise, the *meta* 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)](/man/os/ncurses/use_legacy_coding.3X) and *meta* 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*), *ncurses* returns strings “M-^@”, “M-^A”, etc. X/Open Curses documents *unctrl* as declared in *unctrl.h*, which *ncurses* does. However, *ncurses*'s *curses.h* includes *unctrl.h*, matching the behavior of SVr4 *curses*. Other implementations may not do that. ## [use\_env, use\_tioctl](#use_env,_use_tioctl) If *ncurses* is configured to provide the screen pointer functions extension, you can update the use of the environment and the operating system's terminal driver by calling *use\_env* and/or *use\_tioctl* before creating each *SCREEN* rather than once only; see [**curs\_sp\_funcs**(3X)](/man/os/ncurses/curs_sp_funcs.3X). Other implementations of *curses* do not provide this feature of *use\_env*. # [HISTORY](#HISTORY) 4BSD (1980) introduced *unctrl*, defining it as a macro in *unctrl.h*. SVr2 (1984) added *delay\_output*, *flushinp*, and *keyname*. SVr3 (1987) supplied *filter*. Later that year, SVr3.1 brought *getwin* and *putwin*, reading and writing window dumps with [*fread*(3)](/man/os/ncurses/fread.3) and [*fwrite*(3)](/man/os/ncurses/fwrite.3), respectively. SVr4 (1989) furnished *use\_env*. X/Open Curses Issue 4 (1995) specified *key\_name* and *wunctrl*. *ncurses* 5.6 (2006) added *nofilter*, and 6.0 (2015) *use\_tioctl*. # [SEE ALSO](#SEE_ALSO) [**curses**(3X)](/man/os/ncurses/curses.3X), [**curs\_color**(3X)](/man/os/ncurses/curs_color.3X), [**curs\_initscr**(3X)](/man/os/ncurses/curs_initscr.3X), [**curs\_inopts**(3X)](/man/os/ncurses/curs_inopts.3X), [**curs\_kernel**(3X)](/man/os/ncurses/curs_kernel.3X), [**curs\_scr\_dump**(3X)](/man/os/ncurses/curs_scr_dump.3X), [**curs\_sp\_funcs**(3X)](/man/os/ncurses/curs_sp_funcs.3X), [**curs\_variables**(3X)](/man/os/ncurses/curs_variables.3X), [**legacy\_coding**(3X)](/man/os/ncurses/legacy_coding.3X) 2026-09-19 ncurses 6.6 --- Document: putwin(3x) from ncurses 6.6.20260926-r0 (Chainguard OS) Source: https://github.com/ThomasDickey/ncurses-snapshots