{ "mode": "man", "parameter": "user_caps", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/user_caps/5/json", "generated": "2026-10-07T14:06:27Z", "synopsis": "", "sections": { "NAME": { "content": "usercaps - user-defined terminfo capability format\n", "subsections": [] }, "SYNOPSIS": { "content": "", "subsections": [ { "name": "infocmp -x", "content": "" }, { "name": "tic -x", "content": "" } ] }, "DESCRIPTION": { "content": "", "subsections": [ { "name": "Background", "content": "Before ncurses 5.0, terminfo databases used a fixed repertoire of terminal capabilities de‐\nsigned for the SVr2 terminal database in 1984, and extended in stages through SVr4 (1989),\nand standardized in the Single Unix Specification beginning in 1995.\n\nMost of the extensions in this fixed repertoire were additions to the tables of Boolean, nu‐\nmeric and string capabilities. Rather than change the meaning of an existing capability, a\nnew name was added. The terminfo database uses a binary format; binary compatibility was en‐\nsured by using a header which gave the number of items in the tables for each type of capa‐\nbility. The standardization was incomplete:\n\n• The binary format itself is not described in the X/Open Curses documentation. Only the\nsource format is described.\n\nLibrary developers rely upon the SVr4 documentation, and reverse-engineering the compiled\nterminfo files to match the binary format.\n\n• Lacking a standard for the binary format, most implementations copy the SVr2 binary for‐\nmat, which uses 16-bit signed integers, and is limited to 4096-byte entries.\n\nThe format cannot represent very large numeric capabilities, nor can it represent large\nnumbers of special keyboard definitions.\n\n• The tables of capability names differ between implementations.\n\nAlthough they may provide all of the standard capability names, the position in the ta‐\nbles differs because some features were added as needed, while others were added (out of\norder) to comply with X/Open Curses.\n\nWhile ncurses' repertoire of predefined capabilities is closest to Solaris, Solaris's\nterminfo database has a few differences from the list published by X/Open Curses. For\nexample, ncurses can be configured with tables which match the terminal databases for\nAIX, HP-UX or OSF/1, rather than the default Solaris-like configuration.\n\n• In SVr4 curses and ncurses, the terminal database is defined at compile-time using a text\nfile which lists the different terminal capabilities.\n\nIn principle, the text-file can be extended, but doing this requires recompiling and re‐\ninstalling the library. The text-file used in ncurses for terminal capabilities includes\ndetails for various systems past the documented X/Open Curses features. For example,\nncurses supports these capabilities in each configuration:\n\nmemorylock\n(meml) lock memory above cursor\n\nmemoryunlock\n(memu) unlock memory\n\nboxchars1\n(box1) box characters primary set\n\nThe memory lock/unlock capabilities were included because they were used in the X11R6\nterminal description for xterm(1). The box1 capability is used in tic to help with ter‐\nminal descriptions written for AIX.\n\nDuring the 1990s, some users were reluctant to use terminfo in spite of its performance ad‐\nvantages over termcap:\n\n• The fixed repertoire prevented users from adding features for unanticipated terminal im‐\nprovements (or required them to reuse existing capabilities as a workaround).\n\n• The limitation to 16-bit signed integers was also mentioned. Because termcap stores\neverything as a string, it could represent larger numbers.\n\nAlthough termcap's extensibility was rarely used (it was never the speaker who had actually\nused the feature), the criticism had a point. ncurses 5.0 provided a way to detect nonstan‐\ndard capabilities, determine their type and optionally store and retrieve them in a way which\ndid not interfere with other applications. These are referred to as user-defined capabili‐\nties because no modifications to the toolset's predefined capability names are needed.\n\nThe ncurses utilities tic and infocmp have a command-line option “-x” to control whether the\nnonstandard capabilities are stored or retrieved. A library function useextendednames is\nprovided for the same purpose.\n\nWhen compiling a terminal database, if “-x” is set, tic will store a user-defined capability\nif the capability name is not one of the predefined names.\n\nBecause ncurses provides a termcap library interface, these user-defined capabilities may be\nvisible to termcap applications:\n\n• The termcap interface (like all implementations of termcap) requires that the capability\nnames are 2-characters.\n\nWhen the capability is simple enough for use in a termcap application, it is provided as\na 2-character name.\n\n• There are other user-defined capabilities which refer to features not usable in termcap,\ne.g., parameterized strings that use more than two parameters or use more than the triv‐\nial expression support provided by termcap. For these, the terminfo database should have\nonly capability names with 3 or more characters.\n\n• Some terminals can send distinct strings for special keys (cursor-, keypad- or function-\nkeys) depending on modifier keys (shift, control, etc.). While terminfo and termcap have\na set of 60 predefined function-key names, to which a series of keys can be assigned,\nthat is insufficient for more than a dozen keys multiplied by more than a couple of modi‐\nfier combinations. The ncurses database uses a convention based on xterm(1) to provide\nextended special-key names.\n\nFitting that into termcap's limitation of 2-character names would be pointless. These\nextended keys are available only with terminfo.\n" }, { "name": "Recognized Capabilities", "content": "The ncurses library uses the user-definable capabilities. While the terminfo database may\nhave other extensions, ncurses makes explicit checks for these:\n\nAX Boolean, asserts that the terminal interprets SGR 39 and SGR 49 by resetting the fore‐\nground and background color, respectively, to the default.\n\nThis is a feature recognized by the screen program as well.\n\nE3 string, tells how to clear the terminal's scrollback buffer. When present, the\nclear(1) program sends this before clearing the terminal.\n\nThe command “tput clear” does the same thing.\n\nNQ Boolean, used to suppress a consistency check in tic for the ncurses capabilities in\nuser6 through user9 (u6, u7, u8 and u9) which tell how to query the terminal's cursor\nposition and its device attributes.\n\nRGB\nBoolean, number or string, used to assert that the setaforeground and setaback‐\nground capabilities correspond to direct colors, using an RGB (red/green/blue) conven‐\ntion. This capability allows the colorcontent function to return appropriate values\nwithout requiring the application to initialize colors using initcolor.\n\nThe capability type determines the values which ncurses sees:\n\nBoolean\nimplies that the number of bits for red, green and blue are the same. Using the\nmaximum number of colors, ncurses adds two, divides that sum by three, and assigns\nthe result to red, green and blue in that order.\n\nIf the number of bits needed for the number of colors is not a multiple of three,\nthe blue (and green) components lose in comparison to red.\n\nnumber\ntells ncurses what result to add to red, green and blue. If ncurses runs out of\nbits, blue (and green) lose just as in the Boolean case.\n\nstring\nexplicitly list the number of bits used for red, green and blue components as a\nslash-separated list of decimal integers.\n\nBecause there are several RGB encodings in use, applications which make assumptions\nabout the number of bits per color are unlikely to work reliably. As a trivial case,\nfor example, one could define RGB#1 to represent the standard eight ANSI colors, i.e.,\none bit per color.\n\nU8 number, asserts that ncurses must use Unicode values for line-drawing characters, and\nthat it should ignore the alternate character set capabilities when the locale uses\nUTF-8 encoding. For more information, see the discussion of NCURSESNOUTF8ACS in\nncurses(3NCURSES).\n\nSet this capability to a nonzero value to enable it.\n\nXM string, override ncurses's built-in string which enables/disables xterm(1) mouse mode.\n\nncurses sends a character sequence to the terminal to initialize mouse mode, and when\nthe user clicks the mouse buttons or (in certain modes) moves the mouse, handles the\ncharacters sent back by the terminal to tell it what was done with the mouse.\n\nThe mouse protocol is enabled when the mask passed in the mousemask function is\nnonzero. By default, ncurses handles the responses for the X11 xterm mouse protocol.\nIt also knows about the SGR 1006 xterm mouse protocol, but must to be told to look for\nthis specifically. It will not be able to guess which mode is used, because the re‐\nsponses are enough alike that only confusion would result.\n\nThe XM capability has a single parameter. If nonzero, the mouse protocol should be en‐\nabled. If zero, the mouse protocol should be disabled. ncurses inspects this capabil‐\nity if it is present, to see whether the 1006 protocol is used. If so, it expects the\nresponses to use the SGR 1006 xterm mouse protocol.\n\nThe xterm mouse protocol is used by other terminal emulators. The terminal database\nuses building-blocks for the various xterm mouse protocols which can be used in cus‐\ntomized terminal descriptions.\n\nThe terminal database building blocks for this mouse feature also have an experimental\ncapability xm. The “xm” capability describes the mouse response. Currently there is\nno interpreter which would use this information to make the mouse support completely\ndata-driven.\n\nxm shows the format of the mouse responses. In this experimental capability, the para‐\nmeters are\n\np1 y-ordinate\n\np2 x-ordinate\n\np3 button\n\np4 state, e.g., pressed or released\n\np5 y-ordinate starting region\n\np6 x-ordinate starting region\n\np7 y-ordinate ending region\n\np8 x-ordinate ending region\n\nHere are examples from the terminal database for the most commonly used xterm mouse\nprotocols:\n\nxterm+x11mouse|X11 xterm mouse protocol,\nkmous=\\E[M, XM=\\E[?1000%?%p1%{1}%=%th%el%;,\nxm=\\E[M\n%?%p4%t%p3%e%{3}%;%' '%+%c\n%p2%'!'%+%c\n%p1%'!'%+%c,\n\nxterm+sm+1006|xterm SGR-mouse,\nkmous=\\E[<, XM=\\E[?1006;1000%?%p1%{1}%=%th%el%;,\nxm=\\E[<%i%p3%d;\n%p1%d;\n%p2%d;\n%?%p4%tM%em%;,\n" }, { "name": "Extended Key Definitions", "content": "Several terminals provide the ability to send distinct strings for combinations of modified\nspecial keys. There is no standard for what those keys can send.\n\nSince 1999, xterm(1) has supported shift, control, alt, and meta modifiers which produce dis‐\ntinct special-key strings. In a terminal description, ncurses has no special knowledge of\nthe modifiers used. Applications can use the naming convention established for xterm to find\nthese special keys in the terminal description.\n\nStarting with the curses convention that capability codes describing the input generated by a\nterminal's key caps begin with “k”, and that shifted special keys use uppercase letters in\ntheir names, ncurses's terminal database defines the following names and codes to which a\nsuffix is added.\n\nCode Description\n─────────────────────────────────────────────────────────────────────────────────────────\nkDC shifted kdch1 (delete character)\nkDN shifted kcud1 (cursor down)\nkEND shifted kend (end)\nkHOM shifted khome (home)\nkLFT shifted kcub1 (cursor back)\nkNXT shifted knext (next)\nkPRV shifted kprev (previous)\nkRIT shifted kcuf1 (cursor forward)\nkUP shifted kcuu1 (cursor up)\n\nKeycap nomenclature on the Unix systems for which curses was developed differs from today's\nubiquitous descendants of the IBM PC/AT keyboard layout. In the foregoing, interpret “back‐\nward” as “left”, “forward” as “right”, “next” as “page down”, and “prev(ious)” as “page up”.\n\nThese are the suffixes used to denote the modifiers:\n\nValue Description\n──────────────────────────────────\n2 Shift\n3 Alt\n4 Shift + Alt\n5 Control\n6 Shift + Control\n7 Alt + Control\n8 Shift + Alt + Control\n9 Meta\n10 Meta + Shift\n11 Meta + Alt\n12 Meta + Alt + Shift\n13 Meta + Ctrl\n14 Meta + Ctrl + Shift\n15 Meta + Ctrl + Alt\n16 Meta + Ctrl + Alt + Shift\n\nNone of these are predefined; terminal descriptions can refer to names which ncurses will al‐\nlocate at runtime to key-codes. To use these keys in an ncurses program, an application\ncould do this:\n\n• using a list of extended key names, ask tigetstr(3NCURSES) for their values, and\n\n• given the list of values, ask keydefined(3NCURSES) for the key-code which would be re‐\nturned for those keys by wgetch(3NCURSES).\n" } ] }, "PORTABILITY": { "content": "The “-x” extension feature of tic and infocmp has been adopted in NetBSD curses. That imple‐\nmentation stores user-defined capabilities, but makes no use of these capabilities itself.\n", "subsections": [] }, "AUTHORS": { "content": "Thomas E. Dickey\nbeginning with ncurses 5.0 (1999)\n", "subsections": [] }, "SEE ALSO": { "content": "infocmp(1), tic(1)\n\nThe terminal database section NCURSES USER-DEFINABLE CAPABILITIES summarizes commonly-used\nuser-defined capabilities which are used in the terminal descriptions. Some of those fea‐\ntures are mentioned in screen(1) or tmux(1).\n\nXTerm Control Sequences provides further information on the xterm(1) features that are used\nin these extended capabilities.\n\nncurses 6.4 2024-01-13 usercaps(5)", "subsections": [] } }, "summary": "usercaps - user-defined terminfo capability format", "flags": [], "examples": [], "see_also": [ { "name": "infocmp", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/infocmp/1/json" }, { "name": "tic", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/tic/1/json" }, { "name": "screen", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/screen/1/json" }, { "name": "tmux", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/tmux/1/json" }, { "name": "xterm", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/xterm/1/json" } ] }