curs_terminfo(3X)

NAME
del_curterm, putp, restartterm, set_curterm, setupterm, tigetflag, tigetnum, tigetstr, tiparm, tiparm_s, tiscan_s, tparm, tputs, vid_attr, vid_puts, vidattr, vidputs - curses interfaces to terminfo database

SYNOPSIS
#include <curses.h>
#include <term.h>

TERMINAL * cur_term;

const char * const boolnames[];
const char * const boolcodes[];
const char * const boolfnames[];
const char * const numnames[];
const char * const numcodes[];
const char * const numfnames[];
const char * const strnames[];
const char * const strcodes[];
const char * const strfnames[];

int setupterm(const char * term, int filedes, int * errret);
TERMINAL * set_curterm(TERMINAL * nterm);
int del_curterm(TERMINAL * oterm);
int restartterm(const char * term, int filedes, int * errret);

char * tparm(const char * str, ...);
	/* or */
char * tparm(const char * str, long p1 ... long p9);

int tputs(const char * str, int affcnt, int (* putc)(int));
int putp(const char * str);

int vidputs(chtype attrs, int (* putc)(int));
int vidattr(chtype attrs);
int vid_puts(attr_t attrs, short pair, void * opts, int (* putc)(int));
int vid_attr(attr_t attrs, short pair, void * opts);

int tigetflag(const char * cap-code);
int tigetnum(const char * cap-code);
char * tigetstr(const char * cap-code);

char * tiparm(const char * str, ...);

/* extensions */
char * tiparm_s(int expected, int mask, const char * str, ...);
int tiscan_s(int * expected, int * mask, const char * str);

/* deprecated */
int setterm(const char * term);

DESCRIPTION
These lower-level functions of the curses standard must be called by programs that deal directly with the terminfo database to handle certain terminal capabilities, such as programming function keys. For all other functionality, curses functions are more suitable and their use is recommended.

None of these functions use (or are aware of) multibyte character strings such as UTF-8. Capability names and codes use the POSIX portable character set. Capability string values have no associated encoding; they are strings of 8-bit characters.

  Initialization
Call setupterm from your application to have terminfo manage the terminal device; this action initializes the terminal-dependent variables listed in term_variables(3X). (A curses application calling initscr(3X) or newterm(3X) achieves the same result.) Applications can use the terminal capabilities either directly, by object definitions corresponding to capability names and codes (see term_variables(3X)) or by calling the functions documented here. setupterm initializes the terminfo variables lines and columns as described in use_env(3X).

Pass parameterized string capability values through tparm to instantiate them. All terminfo strings (including the output of tparm) should be sent to the terminal device with tputs or putp. Call reset_shell_mode(3X) to restore the terminal modes before exiting. (A curses application calling endwin(3X) achieves the same result.)

Programs that use cursor addressing should emit certain capabilities at specific times. Specifically, output enter_ca_mode upon startup, and exit_ca_mode before exiting.

Programs that execute shell subprocesses should call reset_shell_mode(3X) and output exit_ca_mode before the shell is called, and output enter_ca_mode and call reset_prog_mode(3X) after returning from the shell.

setupterm reads in the terminfo database, initializing the terminfo structures, but does not set up the output virtualization structures used by curses. Its parameters follow.

    term
        is the terminal type, a character string. If term is null, the environment variable TERM is read.

    filedes
        is the file descriptor used for getting and setting terminal I/O modes.

        Higher-level applications use newterm(3X) to initialize the terminal, passing an output stream rather than a descriptor. In curses, the two are the same because newterm calls setupterm, passing the file descriptor derived from its output stream parameter.

    errret
        points to an optional location where an error status can be returned to the caller. If errret is not null, then setupterm returns OK or ERR and stores a status value in the integer pointed to by errret. A return value of OK combined with status of 1 in errret is normal.

        If ERR is returned, examine errret.

        1   means that the terminal is a hard-copy type (lacks destructive backspace), and cannot be used for curses applications. The library determines this fact by checking the terminal type's hardcopy (hc) capability.

        0   means that the terminal could not be found, or that it is a generic type, having too little information for curses applications to run.

            setupterm determines if the entry is a generic type by checking the generic_type (gn) capability.

        -1  means that the terminfo database could not be found.

        If errret is null, setupterm reports an error message upon finding an error and exits. Thus, the simplest call is:

                setupterm((char *) NULL, 1, (int *) NULL);

        which uses all the defaults and sends the output to stdout.

  The Terminal State
setupterm stores its information about the terminal in a TERMINAL structure pointed to by the global variable cur_term. If it detects an error, or decides that the terminal is unsuitable (hardcopy or generic), it discards this information, making it unavailable to applications.

If setupterm is called repeatedly for the same terminal type, it reuses the information. It maintains only one copy of a given type's capabilities in memory. If called for different types, setupterm allocates new storage for each set of terminal capabilities.

set_curterm sets cur_term to nterm, making all of the terminfo Boolean, numeric, and string capabilities use the values from nterm. It returns the old value of cur_term.

del_curterm releases the memory pointed to by oterm. If oterm is the same as cur_term, references to any of the terminfo Boolean, numeric, and string capabilities thereafter may refer to invalid memory locations until setupterm is called again.

restartterm is similar to setupterm, but is intended for use after restoring program memory to a previous state (for example, when reloading an application that has been suspended from one terminal session and restored in another). restartterm assumes that the display dimensions and the input and output options are the same as when memory was saved, but the terminal type and line speed may differ. Accordingly, restartterm saves relevant terminal state, calls setupterm, then restores that state.

  Formatting Output
tparm instantiates the string str with parameters pi. It returns a pointer to a character string representing str with the parameters applied to “%” expressions within. Application developers should keep in mind some quirks of the interface. Although tparm's actual parameters may be integers or strings, the prototype expects long (integer) values. Aside from the set_attributes (sgr) capability, most terminal capabilities require no more than one or two parameters. Padding information is ignored by tparm; it is interpreted by tputs. The capability string is null-terminated. Use “\200” where an ASCII NUL is needed in the output.

tiparm is a newer form of tparm that uses stdarg.h rather than a fixed-length parameter list. Its numeric parameters are ints rather than longs.

tparm and tiparm assume that the application passes parameters consistent with the terminal description. ncurses provides two extensions as alternatives to deal with untrusted data. The tiparm_s extension is a safer formatting function than tparm or tiparm, because it allows the developer to tell the curses library how many parameters to expect in the parameter list, and which may be string parameters.

    The mask parameter has one bit set for each of the parameters (up to 9) passed as char pointers rather than numbers. The extension tiscan_s allows the application to inspect a formatting capability to see what the curses library would assume.

  Output Functions
String capabilities can contain padding, a time delay (accommodating performance limitations of hardware terminals) expressed as $<n> , where n is a nonnegative integral count of milliseconds. If n exceeds 30,000 (thirty seconds), ncurses caps it at that value.

tputs interprets time delays in the string str and acts upon them. The str parameter must be a terminfo string capability or the return value of tparm or tiparm. affcnt is the number of lines affected, or 1 if not applicable. putc is a putchar-like function to which the characters are passed, one at a time.

tputs processes each time delay with the delay_output(3X) function, routing any resulting padding characters through this function.

putp calls “tputs( str, 1, putchar) ”. The output of putp always goes to stdout, rather than the filedes specified in setupterm.

vidputs displays the string on the terminal in the video attribute mode attrs, which is any combination of the attributes listed in curses(3X). The characters are passed to the putchar-like function putc.

vidattr is like vidputs, except that it outputs through putchar(3).

vid_attr and vid_puts correspond to vidattr and vidputs, respectively. They use multiple parameters to represent the character attributes and color; namely, attrs, of type attr_t, for the attributes and pair, of type short, for the color pair number.

Use the attribute constants prefixed with “WA_” with vid_attr and vid_puts.

X/Open Curses reserves the opts argument for future use, saying that applications must provide a null pointer for that argument; but see section “EXTENSIONS” below.

While putp is a lower-level function that does not use higher-level curses state, ncurses declares it in curses.h because System V did so (see section “HISTORY” below).

  Terminal Capability Functions
tigetflag, tigetnum, and tigetstr return the value of the capability corresponding to the terminfo cap-code, such as xenl, passed to them. The cap-code for each capability is given in the table column of that name in the “Capabilities” section of terminfo(5).

These functions return special values to denote errors.

tigetflag returns

-1  if cap-code is not a Boolean capability, or

0   if it is canceled or absent from the terminal description.

tigetnum returns

-2  if cap-code is not a numeric capability, or

-1  if it is canceled or absent from the terminal description.

tigetstr returns

(char *)-1
    if cap-code is not a string capability, or

NULL
    if it is canceled or absent from the terminal description.

  Terminal Capability Names
These null-terminated arrays contain the short terminfo names (“codes”), the termcap names (“names”), and the long terminfo names (“fnames”)

for each standard terminfo capability name.

    const char *boolnames[], *boolcodes[], *boolfnames[]
    const char *numnames[], *numcodes[], *numfnames[]
    const char *strnames[], *strcodes[], *strfnames[]

  Releasing Memory
Each successful call to setupterm allocates memory to hold the terminal description. As a side effect, it sets cur_term to point to this memory. If an application calls
        del_curterm(cur_term);
the memory will be freed.

The formatting functions tparm and tiparm extend the storage allocated by setupterm as follows. They add the “static” terminfo variables [a-z]. Before ncurses 6.3, those were shared by all screens. With ncurses 6.3, those are allocated per screen. See terminfo(5). To improve performance, ncurses 6.3 caches the result of analyzing terminfo strings for their parameter types. That is stored as a binary tree referenced from the TERMINAL structure.

The higher-level initscr and newterm functions use setupterm. Normally they do not free this memory, but it is possible to do that using the delscreen(3X) function.

RETURN VALUE
Functions that return integers return ERR upon failure and OK upon success.

In ncurses,

del_curterm
    fails if its terminal parameter is null.

putp
    calls tputs, returning the same error codes.

restartterm
    fails if the associated call to setupterm returns ERR.

setupterm
    fails if it cannot allocate enough memory, or create the initial windows (stdscr, curscr, and newscr). Other error conditions are documented above.

tparm
    returns a null pointer if the capability would require unexpected parameters; that is, too many, too few, or incorrect types (strings where integers are expected, or vice versa).

tputs
    fails if the string parameter is null. It does not detect I/O errors: X/Open Curses states that tputs ignores the return value of the output function putc.

NOTES
The vid_attr function in ncurses is a special case. It was originally implemented based on a draft of X/Open Curses, as a macro, before other parts of the ncurses wide-character API were developed, and unlike the other wide-character functions, is also provided in the non-wide-character configuration.

EXTENSIONS
The functions marked as extensions originated in ncurses, and are not found in SVr4 curses, 4.4BSD curses, or any other previous curses implementation.

ncurses allows opts to be a pointer to int, which overrides the pair (short) argument.

PORTABILITY
Except for setterm, X/Open Curses Issue 4 describes these functions. It specifies no error conditions for them.

SVr4 describes a successful return value except where “otherwise noted” as “an integer value other than ERR”.

  Header Files
On legacy curses systems, include curses.h and term.h in that order to make visible the definitions of the string arrays storing the capability names and codes.

  Compatibility Macros
ncurses implements a few macros for early System V curses compatibility (see section “HISTORY” below). They include crmode, fixterm, gettmode, nocrmode, resetterm, saveterm, and setterm.

In SVr4, these are found in curses.h, but except for setterm, are likewise macros. The one function, setterm, is mentioned in the manual page. It further notes that setterm was replaced by setupterm, stating that the call
        setupterm(term, 1, (int *)0)
provides the same functionality as
        setterm(term)
and discouraging the latter for new programs.

  Legacy Data
setupterm copies the terminal name to the array ttytype. This behavior is not specified by X/Open Curses, but is assumed by some applications.

Other implementations may not declare the capability name arrays. Some provide them without declaring them. X/Open Curses does not specify them.

Extended terminal capability names, as defined by “tic -x”, are not stored in the arrays described here.

  Output Buffering
Older versions of ncurses assumed that the file descriptor passed to setupterm from initscr or newterm used buffered I/O, and wrote to the corresponding stdio stream. In addition to the limitation that the terminal was left in block-buffered mode on exit (like System V curses), it was problematic because ncurses did not allow a reliable way to clean up on receiving SIGTSTP.

ncurses 6.x uses output buffers managed directly by ncurses. The lower-level functions described here that write to the terminal device do so via the standard output stream; they thus are not signal-safe. The higher-level functions in ncurses employ alternate versions of these functions using a more reliable buffering scheme.

  Function Prototypes
The X/Open Curses prototypes are based on the SVr4 curses header declarations, which were defined at the same time the C language was first standardized in the late 1980s. X/Open Curses uses const less effectively than a later design might, sometimes applying it needlessly to function parameters that are passed by value (and therefore copied), and in most cases overlooking parameters that normally would benefit from const. Passing const-qualified parameters to functions that do not declare them const may prevent the program from compiling. On the other hand, “writable strings” are an obsolescent C language feature.

    As an extension, ncurses can be configured to change the function prototypes to use the const keyword. The ncurses ABI 6 enables this feature by default. X/Open Curses prototypes tparm with a fixed number of parameters, rather than a variable argument list.

    ncurses uses a variable argument list, but can be configured to use the fixed-parameter list. Portable applications should provide nine parameters after the format; zeroes are fine for this purpose.

    In response to review comments by Thomas E. Dickey, X/Open Curses Issue 7 proposed the tiparm function in mid-2009.

    While tiparm is always provided in ncurses, the older form is available only as a build-time configuration option. If not specially configured, tparm is the same as tiparm.

Both forms of tparm have drawbacks. Most calls to tparm require only one or two parameters. Passing nine on each call is awkward.

    Using long for the numeric parameter type is a workaround to make the parameter use the same amount of stack memory as a pointer. That approach dates to the mid-1980s, before C was standardized. Since ANSI C (1989), C language standards do not require a pointer to fit in a long). Providing the right number of parameters for a variadic function such as tiparm can be a problem, in particular for string parameters. However, only a few terminfo capabilities use string parameters (for instance, the ones used for programmable function keys).

    The ncurses library checks usage of these capabilities, and returns ERR if the capability mishandles string parameters. But it cannot check if a calling program provides strings in the right places for the tparm calls.

    ncurses's tput(1) checks its use of these capabilities with a table, so that it calls tparm correctly.

  Special TERM treatment
If ncurses is configured to use a terminal driver that does not employ the POSIX termios API, as with the MinGW port, setupterm interprets a missing or empty TERM variable as the special value “unknown”.

    SVr4 curses uses the special value “dumb”.

    The difference between the two is that the former uses the generic_type (gn) terminfo capability, while the latter does not. A generic terminal is unsuitable for full-screen applications. setupterm allows explicit use of the Microsoft Windows console driver by checking whether the TERM environment variable has the value “#win32con” or an abbreviation of that string.

  Other Portability Issues
In SVr4, set_curterm returns an int, OK or ERR. We have chosen to implement the X/Open Curses semantics.

In SVr4, the third argument of tputs has the type “int (*)(char)”.

At least one implementation of X/Open Curses (Solaris xcurses) returns a value other than OK or ERR from tputs. It instead returns the length of the string, and does no error checking.

Very old versions of AIX curses required inclusion of curses.h before term.h.

HISTORY
SVr2 (1984) introduced the terminfo feature. Its programming manual mentioned the following low-level functions.

Function | Description
fixterm | restore terminal to “in curses” state
gettmode | establish current terminal modes
mvcur | low level cursor motion
putp | use tputs to send characters via putchar
resetterm | set terminal modes to “out of curses” state
resetty | reset terminal flags to stored value
saveterm | save current modes as “in curses” state
savetty | store current terminal flags
setterm | establish terminal with given type
setupterm | establish terminal with given type
tparm | interpolate parameters into string capability
tputs | apply padding information to a string
vidattr | like vidputs, but output through putchar
vidputs | write string to terminal, applying specified attributes

The programming manual also mentioned functions provided for termcap compatibility (commenting that they “may go away at a later date”).

Function | Description
tgetent | look up termcap entry for given name
tgetflag | get Boolean entry for given id
tgetnum | get numeric entry for given id
tgetstr | get string entry for given id
tgoto | apply parameters to given capability
tputs | write characters via a function parameter, applying padding

Early terminfo programs obtained capability values from the TERMINAL structure initialized by setupterm.

SVr3 (1987) extended terminfo by adding functions to retrieve capability values (like the termcap interface), and reusing tgoto and tputs.

Function | Description
tigetflag | get Boolean entry for given id
tigetnum | get numeric entry for given id
tigetstr | get string entry for given id

SVr3 also replaced several of the SVr2 terminfo functions that had no counterpart in the termcap interface, documenting them as obsolete.

Function | Replaced by
crmode | cbreak
fixterm | reset_prog_mode
gettmode | n/a
nocrmode | nocbreak
resetterm | reset_shell_mode
saveterm | def_prog_mode
setterm | setupterm

SVr3 kept the mvcur, vidattr, and vidputs functions, along with putp, tparm, and tputs. The latter were needed to support padding, and to handle capabilities accessed by functions such as vidattr (which used more than the two parameters supported by tgoto).

SVr3 introduced the functions for switching between terminal descriptions; for example, set_curterm. Some changes reflected incremental improvements to the SVr2 library. The TERMINAL type definition was introduced in SVr3.01, for the term structure provided in SVr2. Various global variables such as boolnames were mentioned in the programming manual at this point, though the variables had been provided in SVr2.

SVr4 (1989) added the vid_attr and vid_puts functions.

Other low-level functions are declared in the curses header files of Unix systems, but none are documented. Those noted as “obsolete” by SVr3 remained in use by System V's vi(1) editor.

SEE ALSO
curses(3X), curs_initscr(3X), curs_kernel(3X), curs_memleaks(3X), curs_termcap(3X), curs_variables(3X), putc(3), term_variables(3X), terminfo(5)