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TTY Devices TTY NNAAMMEE tty - general terminal interface SSYYNNOOPPSSIISS ##iinncclluuddee <<ssggttttyy..hh>> DDEESSCCRRIIPPTTIIOONN This section describes both a particular special file //ddeevv//ttttyy and the terminal drivers used for conversational computing. The Sprite terminal driver is substantial subset of the UNIX terminal driver, but there are a few features of the UNIX driver that aren't yet implemented in Sprite (see below for more details). LLiinnee ddiisscciipplliinneess.. Sprite provides only a single line discipline, which behaves like the ``new'' line discpline in UNIX. The TIOCSETD _i_o_c_t_l is not implemented in Sprite. TThhee ccoonnttrrooll tteerrmmiinnaall.. Sprite does not yet implement controlling terminals. The TIOCNOTTY _i_o_c_t_l is not implemented. PPrroocceessss ggrroouuppss.. Command processors such as _c_s_h(1) can arbitrate the terminal between different _j_o_b_s by placing related jobs in a single process group and associating this process group with the terminal. A terminal's associated process group may be set using the TIOCSPGRP _i_o_c_t_l(2): iiooccttll((ffiillddeess,, TTIIOOCCSSPPGGRRPP,, &&ppggrrpp));; or examined using TIOCGPGRP, which returns the current pro- cess group in _p_g_r_p. The new terminal driver aids in this arbitration by restricting access to the terminal by processes which are not in the current process group; see JJoobb aacccceessss ccoonnttrrooll below. MMooddeess.. The terminal drivers have three major modes, characterized by the amount of processing on the input and output charac- ters: cooked The normal mode. In this mode lines of input are collected and input editing is done. The edited line is made available when it is completed by a newline, or when the _t__b_r_k_c character (normally undefined) or _t__e_o_f_c character (normally an EOT, Sprite v1.0 May 19, 1986 1 TTY Devices TTY control-D, hereafter ^D) is entered. A carriage return is usually made synonymous with newline in this mode, and replaced with a newline whenever it is typed. All driver functions (input editing, interrupt generation, output processing such as delay generation and tab expansion, etc.) are available in this mode. CBREAK This mode eliminates the character, word, and line editing input facilities, making the input charac- ter available to the user program as it is typed. Flow control, literal-next and interrupt process- ing are still done in this mode. Output process- ing is done. RAW This mode eliminates all input processing and makes all input characters available as they are typed; no output processing is done either. The style of input processing can also be very different when the terminal is put in non-blocking I/O mode; see the FNDELAY flag described in _f_c_n_t_l(2). In this case a _r_e_a_d(2) from the control terminal will never block, but rather return an error indication (EWOULDBLOCK) if there is no input available. A process may also request that a SIGIO signal be sent it whenever input is present and also whenever output queues fall below the low-water mark. To enable this mode the FASYNC flag should be set using _f_c_n_t_l(2). IInnppuutt eeddiittiinngg.. A UNIX terminal ordinarily operates in full-duplex mode. Characters may be typed at any time, even while output is occurring, and are only lost when the system's character input buffers become completely choked, which is rare, or when the user has accumulated the maximum allowed number of input characters that have not yet been read by some pro- gram. Currently this limit is 256 characters. In RAW mode, the terminal driver throws away all input and output without notice when the limit is reached. In CBREAK or cooked mode it refuses to accept any further input and, if in the new line discipline, rings the terminal bell. Input characters are accepted in either parity (Sprite does no checking right now and ignores the EVEN and ODD bits of the flags word). It is possible to simulate terminal input using the TIOCSTI _i_o_c_t_l, which takes, as its third argument, the address of a character. The system pretends that this character was Sprite v1.0 May 19, 1986 2 TTY Devices TTY typed on the argument terminal, which must be the control terminal except for the super-user (this call is not in standard version 7 UNIX). Input characters are normally echoed by putting them in an output queue as they arrive. This may be disabled by clear- ing the ECHO bit in the flags word using the _s_t_t_y(3C) call or the TIOCSETN or TIOCSETP _i_o_c_t_ls (see the SSuummmmaarryy below). In cooked mode, terminal input is processed in units of lines. A program attempting to read will normally be suspended until an entire line has been received (but see the description of SIGTTIN in JJoobb aacccceessss ccoonnttrrooll and of FIONREAD in SSuummmmaarryy, both below.) No matter how many charac- ters are requested in the read call, at most one line will be returned. It is not, however, necessary to read a whole line at once; any number of characters may be requested in a read, even one, without losing information. During input, line editing is normally done, with the erase character _s_g__e_r_a_s_e (by default, DELETE) logically erasing the last character typed and the _s_g__k_i_l_l character (default, ^U: control-U) logically erasing the entire current input line. These characters never erase beyond the beginning of the current input line or an eof. These characters may be entered literally by preceding them with `\'; the `\' will normally be erased when the character is typed. The drivers normally treat either a carriage return or a newline character as terminating an input line, replacing the return with a newline and echoing a return and a line feed. If the CRMOD bit is cleared in the local mode word then the processing for carriage return is disabled, and it is simply echoed as a return, and does not terminate cooked mode input. In the new driver there is a literal-next character (nor- mally ^V) which can be typed in both cooked and CBREAK mode preceding _a_n_y character to prevent its special meaning to the terminal handler. This is to be preferred to the use of `\' escaping erase and kill characters, but `\' is retained with its old function in the new line discipline. The new terminal driver also provides two other editing characters in normal mode. The word-erase character, nor- mally ^W, erases the preceding word, but not any spaces before it. For the purposes of ^W, a word is defined as a sequence of non-blank characters, with tabs counted as blanks. Finally, the reprint character, normally ^R, retypes the pending input beginning on a new line. Retyping occurs automatically in cooked mode if characters which would normally be erased from the screen are fouled by Sprite v1.0 May 19, 1986 3 TTY Devices TTY program output. IInnppuutt eecchhooiinngg aanndd rreeddiissppllaayy The terminal driver has several modes (not present in stan- dard UNIX Version 7 systems) for handling the echoing of terminal input, controlled by bits in a local mode word. _H_a_r_d_c_o_p_y _t_e_r_m_i_n_a_l_s. When a hardcopy terminal is in use, the LPRTERA bit is normally set in the local mode word. Charac- ters which are logically erased are then printed out back- wards preceded by `\' and followed by `/' in this mode. _C_R_T _t_e_r_m_i_n_a_l_s. When a CRT terminal is in use, the LCRTBS bit is normally set in the local mode word. The terminal driver then echoes the proper number of erase characters when input is erased; in the normal case where the erase character is a ^H this causes the cursor of the terminal to back up to where it was before the logically erased character was typed. If the input has become fouled due to interspersed asynchronous output, the input is automatically retyped. _E_r_a_s_i_n_g _c_h_a_r_a_c_t_e_r_s _f_r_o_m _a _C_R_T. When a CRT terminal is in use, the LCRTERA bit may be set to cause input to be erased from the screen with a "backspace-space-backspace" sequence when character or word deleting sequences are used. A LCRTKIL bit may be set as well, causing the input to be erased in this manner on line kill sequences as well. _E_c_h_o_i_n_g _o_f _c_o_n_t_r_o_l _c_h_a_r_a_c_t_e_r_s. If the LCTLECH bit is set in the local state word, then non-printing (control) characters are normally echoed as ^X (for some X) rather than being echoed unmodified; delete is echoed as ^?. The normal modes for use on CRT terminals are speed depen- dent. At speeds less than 1200 baud, the LCRTERA and LCRTKILL processing is painfully slow, and _s_t_t_y(1) normally just sets LCRTBS and LCTLECH; at speeds of 1200 baud or greater all of these bits are normally set. _S_t_t_y(1) summar- izes these option settings and the use of the new terminal driver as "newcrt." OOuuttppuutt pprroocceessssiinngg.. When one or more characters are written, they are actually transmitted to the terminal as soon as previously-written characters have finished typing. (As noted above, input characters are normally echoed by putting them in the output queue as they arrive.) When a process produces characters more rapidly than they can be typed, it will be suspended when its output queue exceeds some limit. When the queue has drained down to some threshold the program is resumed. Sprite v1.0 May 19, 1986 4 TTY Devices TTY Even parity is normally generated on output. The EOT char- acter is not transmitted in cooked mode to prevent terminals that respond to it from hanging up; programs using RAW or CBREAK mode should be careful. The Sprite terminal driver does not provide any automatic delay generation on output; the related bits in the tty flags word are ignored. Sprite also does not provide automatic mapping between upper and lower case on terminals lacking lower case; we assume that such terminals have long since become extinct. Finally, there is a output flush character, normally ^O, which sets the LFLUSHO bit in the local mode word, causing subsequent output to be flushed until it is cleared by a program or more input is typed. This character has effect in both cooked and CBREAK modes and causes pending input to be retyped if there is any pending input. An _i_o_c_t_l to flush the characters in the input or output queues, TIOCFLUSH, is also available. UUppppeerr ccaassee tteerrmmiinnaallss aanndd HHaazzeellttiinneess Sprite does not support the LCASE tty flag or the LTILDE bit of the local mode word. FFllooww ccoonnttrrooll.. There are two characters (the stop character, normally ^S, and the start character, normally ^Q) which cause output to be suspended and resumed respectively. Extra stop charac- ters typed when output is already stopped have no effect, unless the start and stop characters are made the same, in which case output resumes. Sprite does not support the TANDEM mode. LLiinnee ccoonnttrrooll aanndd bbrreeaakkss.. There are several _i_o_c_t_l calls available to control the state of the terminal line. The TIOCSBRK _i_o_c_t_l will set the break bit in the hardware interface causing a break condition to exist; this can be cleared (usually after a delay with _s_l_e_e_p(3)) by TIOCCBRK. Break conditions in the input are reflected as a null character in RAW mode or as the inter- rupt character in cooked or CBREAK mode. The TIOCCDTR _i_o_c_t_l will clear the data terminal ready condition; it can be set again by TIOCSDTR. When the carrier signal from the dataset drops (usually because the user has hung up his terminal) a SIGHUP hangup signal is sent to the processes in the distinguished process Sprite v1.0 May 19, 1986 5 TTY Devices TTY group of the terminal; this usually causes them to ter- minate. The SIGHUP can be suppressed by setting the LNOHANG bit in the local state word of the driver. Access to the terminal by other processes is then normally revoked, so any further reads will fail, and programs that read a terminal and test for end-of-file on their input will terminate appropriately. Note: Sprite provides only partial support for modems at present. It is possible to ask that the phone line be hung up on the last close with the TIOCHPCL _i_o_c_t_l; this is normally done on the outgoing lines and dialups. IInntteerrrruupptt cchhaarraacctteerrss.. There are several characters that generate interrupts in cooked and CBREAK mode; all are sent to the processes in the control group of the terminal, as if a TIOCGPGRP _i_o_c_t_l were done to get the process group and then a _k_i_l_l_p_g(2) system call were done, except that these characters also flush pending input and output when typed at a terminal ('_a`'_l_a TIOCFLUSH). The characters shown here are the defaults; the field names in the structures (given below) are also shown. The characters may be changed. ^C tt__iinnttrrcc (ETX) generates a SIGINT signal. This is the normal way to stop a process which is no longer interesting, or to regain control in an interactive program. ^\ tt__qquuiittcc (FS) generates a SIGQUIT signal. This is used to cause a program to terminate and produce a core image, if possible, in the file ccoorree in the current directory. ^Z tt__ssuussppcc (EM) generates a SIGTSTP signal, which is used to suspend the current process group. ^Y tt__ddssuussppcc (SUB) generates a SIGTSTP signal as ^Z does, but the signal is sent when a program attempts to read the ^Y, rather than when it is typed. JJoobb aacccceessss ccoonnttrrooll.. When using the new terminal driver, if a process which is not in the distinguished process group of its control termi- nal attempts to read from that terminal its process group is sent a SIGTTIN signal. This signal normally causes the members of that process group to stop. If, however, the pro- cess is ignoring SIGTTIN, has SIGTTIN blocked, or is in the middle of process creation using _v_f_o_r_k(2)), the read will return -1 and set _e_r_r_n_o to EIO. Sprite v1.0 May 19, 1986 6 TTY Devices TTY When using the new terminal driver with the LTOSTOP bit set in the local modes, a process is prohibited from writing on its control terminal if it is not in the distinguished pro- cess group for that terminal. Processes which are holding or ignoring SIGTTOU signals or which are in the middle of a _v_f_o_r_k(2) are excepted and allowed to produce output. TTeerrmmiinnaall//wwiinnddooww ssiizzeess.. In order to accommodate terminals and workstations with variable-sized windows, the terminal driver provides a mechanism for obtaining and setting the current terminal size. The driver does not use this infor- mation internally, but only stores it and provides a uniform access mechanism. When the size is changed, a SIGWINCH sig- nal is sent to the terminal's process group so that knowledgeable programs may detect size changes. This facil- ity was added in 4.3BSD and is not available in earlier ver- sions of the system. SSuummmmaarryy ooff mmooddeess.. Unfortunately, due to the evolution of the terminal driver, there are 4 different structures which contain various por- tions of the driver data. The first of these (ssggttttyybb) con- tains that part of the information largely common between version 6 and version 7 UNIX systems. The second contains additional control characters added in version 7. The third is a word of local state added in 4BSD, and the fourth is another structure of special characters added for the new driver. In the future a single structure may be made avail- able to programs which need to access all this information; most programs need not concern themselves with all this state. _B_a_s_i_c _m_o_d_e_s: _s_g_t_t_y. The basic _i_o_c_t_ls use the structure defined in <_s_g_t_t_y._h>: ssttrruucctt ssggttttyybb {{ cchhaarr ssgg__iissppeeeedd;; cchhaarr ssgg__oossppeeeedd;; cchhaarr ssgg__eerraassee;; cchhaarr ssgg__kkiillll;; sshhoorrttssgg__ffllaaggss;; }};; The _s_g__i_s_p_e_e_d and _s_g__o_s_p_e_e_d fields describe the input and output speeds of the device according to the following table, which corresponds to the DEC DH-11 interface. If other hardware is used, impossible speed changes are ignored. Symbolic values in the table are as defined in <_s_g_t_t_y._h>. B0 0 (hang up dataphone) Sprite v1.0 May 19, 1986 7 TTY Devices TTY B50 1 50 baud B75 2 75 baud B110 3 110 baud B134 4 134.5 baud B150 5 150 baud B200 6 200 baud B300 7 300 baud B600 8 600 baud B1200 9 1200 baud B1800 10 1800 baud B2400 11 2400 baud B4800 12 4800 baud B9600 13 9600 baud EXTA 14 External A EXTB 15 External B Code conversion and line control required for IBM 2741's (134.5 baud) must be implemented by the user's program. The half-duplex line discipline required for the 202 dataset (1200 baud) is not supplied; full-duplex 212 datasets work fine. The _s_g__e_r_a_s_e and _s_g__k_i_l_l fields of the argument structure specify the erase and kill characters respectively. (Defaults are DELETE and ^U.) The _s_g__f_l_a_g_s field of the argument structure contains several bits that determine the system's treatment of the terminal: ALLDELAY 0177400 Delay algorithm selection BSDELAY 0100000 Select backspace delays (not implemented): BS0 0 BS1 0100000 VTDELAY 0040000 Select form-feed and vertical-tab delays (not supported in Sprite): FF0 0 FF1 0040000 CRDELAY 0030000 Select carriage-return delays (not supported in Sprite): CR0 0 CR1 0010000 CR2 0020000 CR3 0030000 TBDELAY 0006000 Select tab delays (not supported in Sprite): TAB0 0 TAB1 0002000 TAB2 0004000 XTABS 0006000 NLDELAY 0001400 Select new-line delays (not supported in Sprite): NL0 0 NL1 0000400 NL2 0001000 NL3 0001400 Sprite v1.0 May 19, 1986 8 TTY Devices TTY EVENP 0000200 Even parity allowed on input (ignored in Sprite) ODDP 0000100 Odd parity allowed on input (ignored in Sprite) RAW 0000040 Raw mode: wake up on all characters, 8-bit interface CRMOD 0000020 Map CR into LF; output LF as CR-LF ECHO 0000010 Echo (full duplex) LCASE 0000004 Map upper case to lower on input and lower to upper on output CBREAK 0000002 Return each character as soon as typed TANDEM 0000001 Automatic flow control (not supported in Sprite) At present, Sprite does not generate any output delays, nor does it generate or check parity. RAW disables all processing save output flushing with LFLUSHO; full 8 bits of input are given as soon as it is available; all 8 bits are passed on output. A break condi- tion in the input is reported as a null character. If the input queue overflows in raw mode all data in the input and output queues are discarded; this applies to both new and old drivers. CRMOD causes input carriage returns to be turned into new- lines, and output and echoed new-lines to be output as a carriage return followed by a line feed. CBREAK is a sort of half-cooked (rare?) mode. Programs can read each character as soon as typed, instead of waiting for a full line; all processing is done except the input edit- ing: character and word erase and line kill, input reprint, and the special treatment of \ and EOT are disabled. TANDEM mode is not supported in Sprite. NNoottee:: The same ``stop'' and ``start'' characters are used for both directions of flow control; the _t__s_t_o_p_c character is accepted on input as the character that stops output and is produced on output as the character to stop input, and the _t__s_t_a_r_t_c character is accepted on input as the character that restarts output and is produced on output as the char- acter to restart input. _B_a_s_i_c _i_o_c_t_l_s A large number of _i_o_c_t_l(2) calls apply to terminals. Some have the general form: ##iinncclluuddee <<ssggttttyy..hh>> iiooccttll((ffiillddeess,, ccooddee,, aarrgg)) ssttrruucctt ssggttttyybb **aarrgg;; The applicable codes are: Sprite v1.0 May 19, 1986 9 TTY Devices TTY TIOCGETP Fetch the basic parameters associated with the terminal, and store in the pointed-to _s_g_t_t_y_b structure. TIOCSETP Set the parameters according to the pointed- to _s_g_t_t_y_b structure. The interface delays until output is quiescent, then throws away any unread characters, before changing the modes. TIOCSETN Set the parameters like TIOCSETP but do not delay or flush input. Input is not preserved, however, when changing to or from RAW. With the following codes _a_r_g is ignored. TIOCEXCL Set "exclusive-use" mode: no further opens are permitted until the file has been closed. TIOCNXCL Turn off "exclusive-use" mode. TIOCHPCL When the file is closed for the last time, hang up the terminal. This is useful when the line is associated with an ACU used to place outgoing calls. With the following codes _a_r_g is a pointer to an iinntt. TIOCGETD _a_r_g is a pointer to an iinntt into which is placed the current line discipline number. TIOCSETD _a_r_g is a pointer to an iinntt whose value becomes the current line discipline number. TIOCFLUSH If the iinntt pointed to by _a_r_g has a zero value, all characters waiting in input or output queues are flushed. Otherwise, the value of the iinntt is for the FREAD and FWRITE bits defined in <<ssyyss//ffiillee..hh>>; if the FREAD bit is set, all characters waiting in input queues are flushed, and if the FWRITE bit is set, all characters waiting in output queues are flushed. The remaining calls are not available in vanilla version 7 UNIX. In cases where arguments are required, they are described; _a_r_g should otherwise be given as 0. TIOCSTI the argument points to a character which the system pretends had been typed on the termi- nal. Sprite v1.0 May 19, 1986 10 TTY Devices TTY TIOCSBRK the break bit is set in the terminal. TIOCCBRK the break bit is cleared. TIOCSDTR data terminal ready is set. TIOCCDTR data terminal ready is cleared. TIOCSTOP output is stopped as if the ``stop'' charac- ter had been typed. TIOCSTART output is restarted as if the ``start'' char- acter had been typed. TIOCGPGRP _a_r_g is a pointer to an iinntt into which is placed the process group ID of the process group for which this terminal is the control terminal. TIOCSPGRP _a_r_g is a pointer to an iinntt which is the value to which the process group ID for this termi- nal will be set. TIOCOUTQ not supported in Sprite. FIONREAD returns in the iinntt pointed to by _a_r_g the number of characters immediately readable from the argument descriptor. This works for files, pipes, and terminals. _T_c_h_a_r_s The second structure associated with each terminal specifies characters that are special in both the old and new terminal interfaces: The following structure is defined in <_s_y_s/_i_o_c_t_l._h>, which is automatically included in <_s_g_t_t_y._h>: ssttrruucctt ttcchhaarrss {{ cchhaarr tt__iinnttrrcc;; //** iinntteerrrruupptt **// cchhaarr tt__qquuiittcc;; //** qquuiitt **// cchhaarr tt__ssttaarrttcc;; //** ssttaarrtt oouuttppuutt **// cchhaarr tt__ssttooppcc;; //** ssttoopp oouuttppuutt **// cchhaarr tt__eeooffcc;; //** eenndd--ooff--ffiillee **// cchhaarr tt__bbrrkkcc;; //** iinnppuutt ddeelliimmiitteerr ((lliikkee nnll)) **// }};; The default values for these characters are ^C, ^\, ^Q, ^S, ^D, and -1. A character value of -1 eliminates the effect of that character. The _t__b_r_k_c character, by default -1, acts like a new-line in that it terminates a `line,' is echoed, and is passed to the program. The `stop' and `start' characters may be the same, to produce a toggle Sprite v1.0 May 19, 1986 11 TTY Devices TTY effect. It is probably counterproductive to make other spe- cial characters (including erase and kill) identical. The applicable _i_o_c_t_l calls are: TIOCGETC Get the special characters and put them in the specified structure. TIOCSETC Set the special characters to those given in the structure. _L_o_c_a_l _m_o_d_e The third structure associated with each terminal is a local mode word. The bits of the local mode word are: LCRTBS 000001 Backspace on erase rather than echoing erase LPRTERA 000002 Printing terminal erase mode LCRTERA 000004 Erase character echoes as backspace-space-backspace LTILDE 000010 Convert ~ to ` on output (not supported in Sprite) LMDMBUF 000020 Stop/start output when carrier drops (not supported in Sprite) LLITOUT 000040 Suppress output translations LTOSTOP 000100 Send SIGTTOU for background output (not supported in Sprite) LFLUSHO 000200 Output is being flushed LNOHANG 000400 Don't send hangup when carrier drops (not supported in Sprite) LETXACK 001000 Diablo style buffer hacking (unimplemented) LCRTKIL 002000 BS-space-BS erase entire line on line kill LPASS8 004000 Pass all 8 bits through on input, in any mode (not supported in Sprite) LCTLECH 010000 Echo input control chars as ^X, delete as ^? LPENDIN 020000 Retype pending input at next read or input character LDECCTQ 040000 Only ^Q restarts output after ^S, like DEC systems (not supported in Sprite) LNOFLSH 100000 Inhibit flushing of pending I/O when an interrupt character is typed (not supported in Sprite) The applicable _i_o_c_t_l functions are: TIOCLBIS _a_r_g is a pointer to an iinntt whose value is a mask containing the bits to be set in the local mode word. TIOCLBIC _a_r_g is a pointer to an iinntt whose value is a mask containing the bits to be cleared in the local mode word. TIOCLSET _a_r_g is a pointer to an iinntt whose value is stored in the local mode word. TIOCLGET _a_r_g is a pointer to an iinntt into which the current local mode word is placed. _L_o_c_a_l _s_p_e_c_i_a_l _c_h_a_r_s The final control structure associated with each terminal is the _l_t_c_h_a_r_s structure which defines control characters for Sprite v1.0 May 19, 1986 12 TTY Devices TTY the new terminal driver. Its structure is: ssttrruucctt llttcchhaarrss {{ cchhaarr tt__ssuussppcc;; //** ssttoopp pprroocceessss ssiiggnnaall **// cchhaarr tt__ddssuussppcc;; //** ddeellaayyeedd ssttoopp pprroocceessss ssiiggnnaall **// cchhaarr tt__rrpprrnnttcc;; //** rreepprriinntt lliinnee **// cchhaarr tt__fflluusshhcc;; //** fflluusshh oouuttppuutt ((ttoogggglleess)) **// cchhaarr tt__wweerraasscc;; //** wwoorrdd eerraassee **// cchhaarr tt__llnneexxttcc;; //** lliitteerraall nneexxtt cchhaarraacctteerr **// }};; The default values for these characters are ^Z, ^Y, ^R, ^O, ^W, and ^V. A value of -1 disables the character. The applicable _i_o_c_t_l functions are: TIOCSLTC _a_r_g is a pointer to an _l_t_c_h_a_r_s structure which defines the new local special characters. TIOCGLTC _a_r_g is a pointer to an _l_t_c_h_a_r_s structure into which is placed the current set of local special characters. _W_i_n_d_o_w/_t_e_r_m_i_n_a_l _s_i_z_e_s Each terminal has provision for storage of the current ter- minal or window size in a _w_i_n_s_i_z_e structure, with format: ssttrruucctt wwiinnssiizzee {{ uunnssiiggnneedd sshhoorrtt wwss__rrooww;; //** rroowwss,, iinn cchhaarraacctteerrss **// uunnssiiggnneedd sshhoorrtt wwss__ccooll;; //** ccoolluummnnss,, iinn cchhaarraacctteerrss **// uunnssiiggnneedd sshhoorrtt wwss__xxppiixxeell;; //** hhoorriizzoonnttaall ssiizzee,, ppiixxeellss **// uunnssiiggnneedd sshhoorrtt wwss__yyppiixxeell;; //** vveerrttiiccaall ssiizzee,, ppiixxeellss **// }};; A value of 0 in any field is interpreted as ``undefined;'' the entire structure is zeroed on final close. The applicable _i_o_c_t_l functions are: TIOCGWINSZ _a_r_g is a pointer to a ssttrruucctt wwiinnssiizzee into which will be placed the current terminal or window size information. TIOCSWINSZ _a_r_g is a pointer to a ssttrruucctt wwiinnssiizzee which will be used to set the current terminal or window size information. If the new information is different than the old infor- mation, a SIGWINCH signal will be sent to the terminal's process group. Sprite v1.0 May 19, 1986 13 TTY Devices TTY FFIILLEESS /dev/tty /dev/tty* /dev/console SSEEEE AALLSSOO csh(1), stty(1), tset(1), ioctl(2), sigvec(2), stty(3C), getty(8) Sprite v1.0 May 19, 1986 14