terminfo(3NCURSES)

✨ terminfo — Library calls ✨

okay bestie, buckle UP 💅 this is the terminfo(3NCURSES) page, and it's a whole journey. This is part 1 of 3 so don't you dare close the tab.

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🎀 NAME 🎀

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

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🌸 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);

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💖 DESCRIPTION 💖

so these are the lower-level functions from the curses standard, and they exist for one specific reason: if your program wants to talk <em>directly</em> to the terminfo database to handle certain terminal capabilities — like programming your function keys, bestie — these are the ones you call. For literally everything else, the regular higher-level curses functions are the move. Use those. The manpage says it's recommended, and I'm inclined to agree. 👑

Lowkey important caveat before we go any further: none of these functions use (or are even aware of) multibyte character strings like UTF-8. Not one. Zero. They do not know her. 😭

• Capability names and codes use the POSIX portable character set.
• Capability string values have no associated encoding; they are just strings of 8-bit characters.

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🌈 Initialization 🌈

Call setupterm from your app to hand terminfo the reins on managing the terminal device. That's the moment everything kicks off — it initializes all those terminal-dependent variables listed over in terminfo_variables(3NCURSES). (And yes, a curses application calling initscr(3NCURSES) or newterm(3NCURSES) gets the same result, so you don't have to do both. pick a lane, she's flexible ✨)

Once that's done, applications can grab terminal capabilities either:

• directly, using object definitions that correspond to capability names and codes (see terminfo_variables(3NCURSES)), or
• by calling the functions documented right here.

setupterm also initializes the terminfo variables lines and columns as described in use_env(3NCURSES).

Now — parameterized string capability values have to be run through tparm to instantiate them. And every terminfo string (including whatever tparm hands back to you) should be sent to the terminal device via tputs or putp. Before you exit, call reset_shell_mode(3NCURSES) to restore the terminal modes. (Curses apps calling endwin(3NCURSES) get the same result. iconic.)

Programs that use cursor addressing need to emit certain capabilities at very specific moments. Specifically, output:

• enter_ca_mode upon startup, and
• exit_ca_mode before exiting.

And if your program executes shell subprocesses, you should:

• call reset_shell_mode(3NCURSES) and output exit_ca_mode before the shell is called, and
• output enter_ca_mode and call reset_prog_mode(3NCURSES) after returning from the shell.

setupterm reads in the terminfo database and initializes the terminfo structures — but heads up, it does not set up the output virtualization structures that curses uses. Its parameters go like this:

• term — the terminal type, a character string. If term is null, the environment variable TERM is read instead.
• filedes — the file descriptor used for getting and setting terminal I/O modes.

Higher-level applications use newterm(3NCURSES) to initialize the terminal, passing an output stream rather than a descriptor. In curses, the two are the same thing, because newterm calls setupterm, passing along 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 a status of 1 in errret is normal. 🫶

If ERR is returned, examine errret:

• 1 — means the terminal is a hard-copy type (it lacks destructive backspace), and cannot be used for curses applications. The library figures this out by checking the terminal type's hardcopy (hc) capability.
• 0 — means the terminal could not be found, or that it's a generic type, having too little information for curses applications to run. setupterm determines whether the entry is a generic type by checking the generic_type (gn) capability.
• -1 — means the terminfo database could not be found. 💀

If errret is null, setupterm reports an error message upon finding an error and then exits. So the simplest call is literally just:

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

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

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🦋 The Terminal State 🦋

setupterm stores everything it knows about the terminal in a TERMINAL structure pointed to by the global variable cur_term. If it detects an error, or decides the terminal is unsuitable (hardcopy or generic), it discards that information, making it unavailable to your application. gone. not coming back. 🙈

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 you call it for different types, setupterm allocates new storage for each set of terminal capabilities.

set_curterm sets cur_term to nterm, which makes 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, then references to any of the terminfo Boolean, numeric, and string capabilities thereafter may refer to invalid memory locations until setupterm is called again. be so careful bestie.

restartterm is similar to setupterm, but it's meant to be used after restoring program memory to a previous state — like when you're reloading an application that got suspended from one terminal session and restored in another. restartterm assumes 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. So accordingly, restartterm saves the relevant terminal state, calls setupterm, then restores that state. 🧚

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✨ 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 the % expressions within. But application developers, listen — there are quirks to this interface, and you need to know them:

• 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 the newer form of tparm — it uses stdarg.h rather than a fixed-length parameter list. Its numeric parameters are ints rather than longs.

Both tparm and tiparm assume the application is passing parameters consistent with the terminal description. ncurses provides two extensions as alternatives for dealing with untrusted data:

• The tiparm_s extension is a safer formatting function than tparm or tiparm, because it lets the developer tell the curses library how many parameters to expect in the parameter list, and which of them 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 lets the application inspect a formatting capability to see what the curses library would assume.

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💅 Output Functions 💅

String capabilities can contain padding — a time delay that accommodates the 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. no cap, literally, it caps it. 💀

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(3NCURSES) function, routing any resulting padding characters through this function.

putp calls tputs(str, 1, putchar). And note — the output of putp always goes to stdout, rather than the filedes specified in setupterm. okay periodt.

vidputs displays the string on the terminal in the video attribute mode attrs, which can be any combination of the attributes listed in ncurses(3NCURSES). The characters get 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 the section EXTENSIONS below. 👀

And one last thing for this stretch: while putp is a lower-level function that doesn't use higher-level curses state, ncurses declares it in curses.h because System V did so (see the section HISTORY below). legacy behaviour, we respect her.

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more coming bestie, don't go anywhere — part 2 is right behind this 💜

💖 Terminal Capability Functions 💖

okay bestie, first up: the trio tigetflag, tigetnum, and tigetstr. They hand you back the value of the capability that matches the terminfo cap-code you pass them — stuff like xenl, yk? And where do you find the cap-code for each capability? It's literally sitting in the table column named that in the "Capabilities" section of terminfo(5). iykyk.

Now, these functions don't just return normal stuff when things go sideways. They return special little error values instead. That's the whole vibe.

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.

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🌈 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[]

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🧹 Releasing Memory 🧹

Every successful call to setupterm allocates memory to hold the terminal description. And as a lil side effect, it sets cur_term to point at that memory. So if an application calls

del_curterm(cur_term);

then that memory gets freed. cleanup era. 💅

The formatting functions tparm and tiparm extend the storage allocated by setupterm like this:

• 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(3NCURSES) function.

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✨ RETURN VALUE ✨

So like, functions that return integers? They return ERR upon failure and OK upon success. Standard behavior, no surprises.

But in ncurses specifically, here's the breakdown:

• 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.

🚨 bestie pay attention: tputs is NOT catching I/O errors for you. X/Open Curses literally says it ignores what putc gives back. So don't come crying to it when your writes flop.

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🫶 NOTES 🫶

The vid_attr function in ncurses is a special case. The way it happened: 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, it is also provided in the non-wide-character configuration. quirky but iconic.

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👑 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. homegrown ✨

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

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🌍 PORTABILITY 🌍

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

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. Order matters here bestie, do not freestyle it.

🔁 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. so yeah, setterm is giving legacy, don't be starting new projects with it fr fr.

🗃️ 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. 😭 messy.

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. vintage, in the bad way.

• 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. yeah, both. pick your struggle:

• 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.

🙈 the library can verify that a capability is handling strings right, but it genuinely cannot see whether your program put the strings in the right slots. that part is on you, bestie.

🪟 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 ✨

okay bestie, storytime 📖✨ because terminfo has lore. SVr2 (that's 1984, ancient times fr) introduced the whole terminfo feature, and its programming manual name-dropped these low-level functions:

• 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 — and it straight up commented that they “may go away at a later date” 💀 foreshadowing much:

• 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 got their capability values from the TERMINAL structure, initialized by setupterm. the way that's so vintage of them 🎀

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Then SVr3 (1987) showed up and extended terminfo by adding functions to retrieve capability values (like the termcap interface does), and by reusing tgoto and tputs. slay:

• 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, and documented them as obsolete. rest in peace besties 🪦:

• crmode — replaced by cbreak
• fixterm — replaced by reset_prog_mode
• gettmode — replaced by n/a
• nocrmode — replaced by nocbreak
• resetterm — replaced by reset_shell_mode
• saveterm — replaced by def_prog_mode
• setterm — replaced by setupterm

SVr3 kept the mvcur, vidattr, and vidputs functions, along with putp, tparm, and tputs. Those last ones were needed to support padding, and to handle capabilities accessed by functions such as vidattr — which used more than the two parameters that tgoto supports. two parameters?? in this economy?? 😭

SVr3 also introduced the functions for switching between terminal descriptions — for example, set_curterm. Some of the changes were just incremental glow-ups to the SVr2 library:

• The TERMINAL type definition was introduced in SVr3.01, for the term structure that SVr2 provided.
• Various global variables such as boolnames were mentioned in the programming manual at this point, even though the variables had actually been provided back in SVr2. not them getting credit late 🙈

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. And those ones SVr3 labelled “obsolete”? They remained in use by System V's vi(1) editor. iconic behaviour honestly, refusing to let go 👑

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🌈 SEE ALSO 🌈

• ncurses(3NCURSES)
• initscr(3NCURSES)
• kernel(3NCURSES)
• memleaks(3NCURSES)
• termcap(3NCURSES)
• curses_variables(3NCURSES)
• putc(3)
• terminfo_variables(3NCURSES)
• terminfo(5)

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and that's a wrap on the whole page, bestie 🫶 go forth and interrogate your terminal's capabilities with confidence. this was ncurses 6.6, dated 2025-11-11 — a true classic, no cap. mwah 💋💖