+.TH TERMIOS 4 "Jun 11, 1991"
+.UC 4
+.SH NAME
+termios - general terminal interface
+.SH SYNOPSIS
+#include <termios.h>
+.SH DESCRIPTION
+.PP
+This describes a general terminal line discipline that is
+supported on tty asynchronous communication ports.
+.LP
+.B "Opening a Terminal Device File"
+.LP
+When a terminal file is opened, it normally causes the process to wait
+until a connection is established. For most hardware, the presence
+of a connection is indicated by the assertion of the hardware CARRIER line.
+If the termios structure associated with the terminal file has the
+CLOCAL flag set in the cflag, or if the O_NONBLOCK flag is set
+in the open(2) call, then the open will succeed even without
+a connection being present.
+In practice, applications
+seldom open these files; they are opened by special programs, such
+as getty(2) or rlogind(2), and become
+an application's standard input, output, and error files.
+.LP
+.B "Job Control in a Nutshell"
+.LP
+Every process is associated with a particular process group and session.
+The grouping is hierarchical: every member of a particular process group is a
+member of the same session. This structuring is used in managing groups
+of related processes for purposes of "job control"; that is, the
+ability from the keyboard (or from program control) to simultaneously
+stop or restart
+a complex command (a command composed of one or more related
+processes). The grouping into process groups allows delivering
+of signals that stop or start the group as a whole, along with
+arbitrating which process group has access to the single controlling
+terminal. The grouping at a higher layer into sessions is to restrict
+the job control related signals and system calls to within processes
+resulting from a particular instance of a "login". Typically, a session
+is created when a user logs in, and the login terminal is setup
+to be the controlling terminal; all processes spawned from that
+login shell are in the same session, and inherit the controlling
+terminal.
+A job control shell
+operating interactively (that is, reading commands from a terminal)
+normally groups related processes together by placing them into the
+same process group. A set of processes in the same process group
+is collectively refered to as a "job". When the foreground process
+group of the terminal is the same as the process group of a particular
+job, that job is said to be in the "foreground". When the process
+group of the terminal is different than the process group of
+a job (but is still the controlling terminal), that job is said
+to be in the "background". Normally the
+shell reads a command and starts the job that implements that
+command. If the command is to be started in the foreground (typical), it
+sets the process group of the terminal to the process group
+of the started job, waits for the job to complete, and then
+sets the process group of the terminal back to its own process
+group (it puts itself into the foreground). If the job is to
+be started in the background (as denoted by the shell operator "&"),
+it never changes the process group of the terminal and doesn't
+wait for the job to complete (that is, it immediately attempts to read the next
+command). If the job is started in the foreground, the user may
+type a key (ususally ^Z) which generates the terminal stop signal
+(SIGTSTP) and has the affect of stopping the entire job.
+The shell will notice that the job stopped, and will resume running after
+placing itself in the foreground.
+The shell also has commands for placing stopped jobs in the background,
+and for placing stopped or background jobs into to the foreground.
+.LP
+.B "Orphaned Process Groups"
+.LP
+An orphaned process group is a process group that has no process
+whose parent is in a different process group, yet is in the same
+session. Conceptually it means a process group that doesn't have
+a parent that could do anything if it were to be stopped. For example,
+the initial login shell is typically in an orphaned process group.
+Orphaned process groups are immune to keyboard generated stop
+signals and job control signals resulting from reads or writes to the
+controlling terminal.
+.LP
+.B "The Controlling Terminal"
+.LP
+A terminal may belong to a process as its controlling terminal. Each
+process of a session that has a controlling terminal has the same
+controlling terminal. A terminal may be the controlling terminal for at
+most one session. The controlling terminal for a session is allocated by
+the session leader by issueing the TIOCSCTTY ioctl. A controlling terminal
+is never acquired by mereley opening a terminal device file.
+When a controlling terminal becomes
+associated with a session, its foreground process group shall be set to
+the process group of the session leader.
+.PP
+The controlling terminal is inherited by a child process during a fork()
+function call. A process relinquishes its controlling terminal when it
+creates a new session with the setsid() function; other processes
+remaining in the old session that had this terminal as their controlling
+terminal continue to have it.
+A process does not relinquish its
+controlling terminal simply by closing all of its file descriptors
+associated with the controlling terminal if other processes continue to
+have it open.
+.PP
+When a controlling process terminates, the controlling terminal is
+disassociated from the current session, allowing it to be acquired by a
+new session leader. Subsequent access to the terminal by other processes
+in the earlier session will be denied, with attempts to access the
+terminal treated as if modem disconnect had been sensed.
+.LP
+.B "Terminal Access Control"
+.LP
+If a process is in the foreground process group of its controlling
+terminal, read operations shall be allowed.
+Any attempts by a process
+in a background process group to read from its controlling terminal shall
+cause its process group to be sent a SIGTTIN signal unless one of the
+following special cases apply: If the reading process is ignoring or
+blocking the SIGTTIN signal, or if the process group of the reading
+process is orphaned, the read() returns -1 with errno set to [EIO] and no
+signal is sent. The default action of the SIGTTIN signal is to stop the
+process to which it is sent.
+.PP
+If a process is in the foreground process group of its controlling
+terminal, write operations shall be allowed.
+Attempts by a process in a background process group to write to its
+controlling terminal shall cause the process group to be sent a SIGTTOU
+signal unless one of the following special cases apply: If TOSTOP is not
+set, or if TOSTOP is set and the process is ignoring or blocking the
+SIGTTOU signal, the process is allowed to write to the terminal and the
+SIGTTOU signal is not sent. If TOSTOP is set, and the process group of
+the writing process is orphaned, and the writing process is not ignoring
+or blocking SIGTTOU, the write() returns -1 with errno set to [EIO] and
+no signal is sent.
+.PP
+Certain calls that set terminal parameters are treated in the same
+fashion as write, except that TOSTOP is ignored; that is, the effect is
+identical to that of terminal writes when TOSTOP is set.
+.LP
+.B "Input Processing and Reading Data"
+.LP
+A terminal device associated with a terminal device file may operate in
+full-duplex mode, so that data may arrive even while output is occurring.
+Each terminal device file has associated with it an input queue, into
+which incoming data is stored by the system before being read by a
+process. The system imposees a limit, {MAX_INPUT}, on the number of
+bytes that may be stored in the input queue. The behavior of the system
+when this limit is exceeded depends on the setting of the IMAXBEL
+flag in the termios c_iflag. If this flag is set, the terminal
+is a sent an ASCII BEL character each time a character is recieved
+while the input queue is full. Otherwise, the input queue is flushed
+upon receiving the character.
+.PP
+Two general kinds of input processing are available, determined by
+whether the terminal device file is in canonical mode or noncanonical
+mode. Additionally,
+input characters are processed according to the c_iflag and
+c_lflag fields. Such processing can include echoing, which
+in general means transmitting input characters immediately back to the
+terminal when they are received from the terminal. This is useful for
+terminals that can operate in full-duplex mode.
+.PP
+The manner in which data is provided to a process reading from a terminal
+device file is dependent on whether the terminal device file is in
+canonical or noncanonical mode.
+.PP
+Another dependency is whether the O_NONBLOCK flag is set by open() or
+fcntl(). If the O_NONBLOCK flag is clear, then the read request shall be
+blocked until data is available or a signal has been received. If the
+O_NONBLOCK flag is set, then the read request shall be completed, without
+blocking, in one of three ways:
+.nf
+ (1) If there is enough data available to satisfy the entire request,
+ the read() shall complete successfully and return the number of
+ bytes read.
+
+ (2) If there is not enough data available to satisfy the entire
+ request, the read() shall complete successfully, having read as
+ much data as possible, and return the number of bytes it was
+ able to read.
+
+ (3) If there is no data available, the read() shall return -1, with
+ errno set to [EAGAIN].
+.fi
+.PP
+When data is available depends on whether the input processing mode is
+canonical or noncanonical.
+.LP
+.B "Canonical Mode Input Processing"
+.LP
+In canonical mode input processing, terminal input is processed in units
+of lines. A line is delimited by a newline ('\\n') character, an end-of-
+file (EOF) character, or an end-of-line (EOL) character. See the "Special
+Characters" section
+for
+more information on EOF and EOL. This means that a read request shall
+not return until an entire line has been typed, or a signal has been
+received. Also, no matter how many bytes are requested in the read call,
+at most one line shall be returned. It is not, however, necessary to
+read a whole line at once; any number of bytes, even one, may be
+requested in a read without losing information.
+.PP
+{MAX_CANON} is a limit on the
+number of bytes in a line.
+The behavior of the system when this limit is
+exceeded is the same as when the input queue limit {MAX_INPUT}, is exceeded.
+.PP
+Erase and kill processing occur when either of two special characters,
+the ERASE and KILL characters (see the Special Characters section), is received.
+This processing affects data in the input queue that has not yet been
+delimited by a newline (NL), EOF, or EOL character. This un-delimited
+data makes up the current line. The ERASE character deletes the last
+character in the current line, if there is any. The KILL character
+deletes all data in the current line, if there is any. The ERASE and
+KILL characters have no effect if there is no data in the current line.
+The ERASE and KILL characters themselves are not placed in the input
+queue.
+.LP
+.B "Noncanonical Mode Input Processing"
+.LP
+In noncanonical mode input processing, input bytes are not assembled into
+lines, and erase and kill processing does not occur. The values of the
+MIN and TIME members of the c_cc array are used to determine how to
+process the bytes received.
+.PP
+MIN represents the minimum number of bytes that should be received when
+the read() function successfully returns. TIME is a timer of 0.1 second
+granularity that is used to time out bursty and short term data
+transmissions. If MIN is greater than {MAX_INPUT}, the response to the
+request is undefined. The four possible values for MIN and TIME and
+their interactions are described below.
+.LP
+.B "Case A: MIN > 0, TIME > 0"
+.LP
+In this case TIME serves as an inter-byte timer and is activated after
+the first byte is received. Since it is an inter-byte timer, it is reset
+after a byte is received. The interaction between MIN and TIME is as
+follows: as soon as one byte is received, the inter-byte timer is
+started. If MIN bytes are received before the inter-byte timer expires
+(remember that the timer is reset upon receipt of each byte), the read is
+satisfied. If the timer expires before MIN bytes are received, the
+characters received to that point are returned to the user. Note that if
+TIME expires at least one byte shall be returned because the timer would
+not have been enabled unless a byte was received. In this case (MIN > 0,
+TIME > 0) the read shall block until the MIN and TIME mechanisms are
+activated by the receipt of the first byte, or a signal is received. If
+data is in the buffer at the time of the read(), the result shall be as
+if data had been received immediately after the read().
+.LP
+.B "Case B: MIN > 0, TIME = 0"
+.LP
+In this case, since the value of TIME is zero, the timer plays no role
+and only MIN is significant. A pending read is not satisfied until MIN
+bytes are received (i.e., the pending read shall block until MIN bytes
+are received), or a signal is received. A program that uses this case to
+read record-based terminal I/O may block indefinitely in the read
+operation.
+.LP
+.B "Case C: MIN = 0, TIME > 0"
+.LP
+In this case, since MIN = 0, TIME no longer represents an inter-byte
+timer. It now serves as a read timer that is activated as soon as the
+read() function is processed. A read is satisfied as soon as a single
+byte is received or the read timer expires. Note that in this case if
+the timer expires, no bytes shall be returned. If the timer does not
+expire, the only way the read can be satisfied is if a byte is received.
+In this case the read shall not block indefinitely waiting for a byte; if
+no byte is received within TIME*0.1 seconds after the read is initiated,
+the read() shall return a value of zero, having read no data. If data is
+in the buffer at the time of the read(), the timer shall be started as if
+data had been received immediately after the read().
+.LP
+.B "Case D: MIN = 0, TIME = 0"
+.LP
+The minimum of either the number of bytes requested or the number of
+bytes currently available shall be returned without waiting for more
+bytes to be input. If no characters are available, read() shall return a
+value of zero, having read no data.
+.LP
+.B "Writing Data and Output Processing"
+.LP
+When a process writes one or more bytes to a terminal device file, they
+are processed according to the c_oflag field (see the Output Modes
+section). The
+implementation may provide a buffering mechanism; as such, when a call to
+write() completes, all of the bytes written have been scheduled for
+transmission to the device, but the transmission will not necessarily
+have completed. See also 6.4.2 for the effects of O_NONBLOCK on write().
+.LP
+.B "Special Characters"
+.LP
+Certain characters have special functions on input or output or both.
+These functions are summarized as follows:
+.nf
+ INTR Special character on input and is recognized if the ISIG
+ flag (see the Local Modes section) is enabled. Generates
+ a SIGINT
+ signal which is sent to all processes in the foreground
+ process group for which the terminal is the controlling
+ terminal. If ISIG is set, the INTR character is
+ discarded when processed.
+
+ QUIT Special character on input and is recognized if the ISIG
+ flag is enabled. Generates a SIGQUIT signal which is
+ sent to all processes in the foreground process group
+ for which the terminal is the controlling terminal. If
+ ISIG is set, the QUIT character is discarded when
+ processed.
+
+ ERASE Special character on input and is recognized if the
+ ICANON flag is set. Erases the last character in the
+ current line; see "Canonical Mode Input Processing".
+ It shall not erase beyond
+ the start of a line, as delimited by an NL, EOF, or EOL
+ character. If ICANON is set, the ERASE character is
+ discarded when processed.
+
+ KILL Special character on input and is recognized if the
+ ICANON flag is set. Deletes the entire line, as
+ delimited by a NL, EOF, or EOL character. If ICANON is
+ set, the KILL character is discarded when processed.
+
+ EOF Special character on input and is recognized if the
+ ICANON flag is set. When received, all the bytes
+ waiting to be read are immediately passed to the
+ process, without waiting for a newline, and the EOF is
+ discarded. Thus, if there are no bytes waiting (that
+ is, the EOF occurred at the beginning of a line), a byte
+ count of zero shall be returned from the read(),
+ representing an end-of-file indication. If ICANON is
+ set, the EOF character is discarded when processed.
+
+ NL Special character on input and is recognized if the
+ ICANON flag is set. It is the line delimiter ('\\n').
+
+ EOL Special character on input and is recognized if the
+ ICANON flag is set. Is an additional line delimiter,
+ like NL.
+
+ SUSP If the ISIG
+ flag is enabled, receipt of the SUSP character causes a
+ SIGTSTP signal to be sent to all processes in the
+ foreground process group for which the terminal is the
+ controlling terminal, and the SUSP character is
+ discarded when processed.
+
+ STOP Special character on both input and output and is
+ recognized if the IXON (output control) or IXOFF (input
+ control) flag is set. Can be used to temporarily
+ suspend output. It is useful with fast terminals to
+ prevent output from disappearing before it can be read.
+ If IXON is set, the STOP character is discarded when
+ processed.
+
+ START Special character on both input and output and is
+ recognized if the IXON (output control) or IXOFF (input
+ control) flag is set. Can be used to resume output that
+ has been suspended by a STOP character. If IXON is set,
+ the START character is discarded when processed.
+
+ CR Special character on input and is recognized if the
+ ICANON flag is set; it is the '\\r', as denoted in the
+ C Standard {2}. When ICANON and ICRNL are set and IGNCR
+ is not set, this character is translated into a NL, and
+ has the same effect as a NL character.
+
+.fi
+The following special characters are extensions defined by this
+system and are not a part of 1003.1 termios.
+.nf
+
+ EOL2 Secondary EOL character. Same function as EOL.
+
+ WERASE Special character on input and is recognized if the
+ ICANON flag is set. Erases the last word in the current
+ line according to one of two algorithms. If the ALTWERASE
+ flag is not set, first any preceding whitespace is
+ erased, and then the maximal sequence of non-whitespace
+ characters. If ALTWERASE is set, first any preceding
+ whitespace is erased, and then the maximal sequence
+ of alphabetic/underscores or non alphabetic/underscores.
+ As a special case in this second algorithm, the first previous
+ non-whitespace character is skippied in determining
+ whether the preceding word is a sequence of
+ alphabetic/undercores. This sounds confusing but turns
+ out to be quite practical.
+
+ REPRINT Special character on input and is recognized if the
+ ICANON flag is set. Causes the current input edit line
+ to be retyped.
+
+ DSUSP Has similar actions to the SUSP character, except that
+ the SIGTSTP signal is delivered when one of the processes
+ in the foreground process group issues a read() to the
+ controlling terminal.
+
+ LNEXT Special character on input and is recognized if the IEXTEN
+ flag is set. Receipt of this character causes the next
+ character to be taken literally.
+
+ DISCARD Special character on input and is recognized if the IEXTEN
+ flag is set. Receipt of this character toggles the flushing
+ of terminal output.
+
+ STATUS Special character on input and is recognized if the ICANON
+ flag is set. Receipt of this character causes a SIGINFO
+ signal to be sent to the forground process group of the
+ terminal. Also, if the NOKERNINFO flag is not set, it
+ causes the kernel to write a status message to the terminal
+ that displays the current load average, the name of the
+ command in the foreground, its process ID, the symbolic
+ wait channel, the number of user and system seconds used,
+ the percentage of cpu the process is getting, and the resident
+ set size of the process.
+
+
+.fi
+.pp
+The NL and CR characters cannot be changed.
+The values for all the remaining characters can be set and are
+described later in the document under Special Control Characters.
+.PP
+Special
+character functions associated with changeable special control characters
+can be disabled individually by setting their value to {_POSIX_VDISABLE};
+see "Special Control Characters".
+.PP
+If two or more special characters have the same value, the function
+performed when that character is received is undefined.
+.LP
+.B "Modem Disconnect"
+.LP
+If a modem disconnect is detected by the terminal interface for a
+controlling terminal, and if CLOCAL is not set in the c_cflag field for
+the terminal, the SIGHUP signal is sent to the controlling
+process associated with the terminal. Unless other arrangements have
+been made, this causes the controlling process to terminate.
+Any subsequent call to the read() function shall return the value zero,
+indicating end of file. Thus, processes that read a terminal
+file and test for end-of-file can terminate appropriately after a
+disconnect. If the [EIO] condition specified in 6.1.1.4 that applies
+when the implementation supports job control also exists, it is
+unspecified whether the EOF condition or the [EIO] is returned. Any
+subsequent write() to the terminal device returns -1, with errno set to
+[EIO], until the device is closed.
+.LP
+.B "General Terminal Interface"
+.LP
+.B "Closing a Terminal Device File"
+.LP
+The last process to close a terminal device file shall cause any output
+to be sent to the device and any input to be discarded. Then, if HUPCL
+is set in the control modes, and the communications port supports a
+disconnect function, the terminal device shall perform a disconnect.
+.LP
+.B "Parameters That Can Be Set"
+.LP
+Routines that need to control certain terminal I/O characteristics shall
+do so by using the termios structure as defined in the header
+<termios.h>.
+This structure contains minimally four scalar elements of bit flags
+and one array of special characters. The scalar flag elements are
+named: c_iflag, c_oflag, c_cflag, and c_lflag. The character array
+is named c_cc, and its maximum index is NCCS.
+.LP
+.B "Input Modes"
+.LP
+Values of the c_iflag field describe the basic
+terminal input control, and are composed of
+following masks:
+.nf
+ (XXX cael - make into table)
+ IGNBRK /* ignore BREAK condition */
+ BRKINT /* map BREAK to SIGINTR */
+ IGNPAR /* ignore (discard) parity errors */
+ PARMRK /* mark parity and framing errors */
+ INPCK /* enable checking of parity errors */
+ ISTRIP /* strip 8th bit off chars */
+ INLCR /* map NL into CR */
+ IGNCR /* ignore CR */
+ ICRNL /* map CR to NL (ala CRMOD) */
+ IXON /* enable output flow control */
+ IXOFF /* enable input flow control */
+ IXANY /* any char will restart after stop */
+ IMAXBEL /* ring bell on input queue full */
+.fi
+.PP
+In the context of asynchronous serial data transmission, a break
+condition is defined as a sequence of zero-valued bits that continues for
+more than the time to send one byte. The entire sequence of zero-valued
+bits is interpreted as a single break condition, even if it continues for
+a time equivalent to more than one byte. In contexts other than
+asynchronous serial data transmission the definition of a break condition
+is implementation defined.
+.PP
+If IGNBRK is set, a break condition detected on input is ignored, that
+is, not put on the input queue and therefore not read by any process. If
+IGNBRK is not set and BRKINT is set, the break condition shall flush the
+input and output queues and if the terminal is the controlling terminal
+of a foreground process group, the break condition shall generate a
+single SIGINT signal to that foreground process group. If neither IGNBRK
+nor BRKINT is set, a break condition is read as a single '\\0', or if
+PARMRK is set, as '\\377', '\\0', '\\0'.
+.PP
+If IGNPAR is set, a byte with a framing or parity error (other than
+break) is ignored.
+.PP
+If PARMRK is set, and IGNPAR is not set, a byte with a framing or parity
+error (other than break) is given to the application as the three-
+character sequence '\\377', '\\0', X, where '\\377', '\\0' is a two-character
+flag preceding each sequence and X is the data of the character received
+in error. To avoid ambiguity in this case, if ISTRIP is not set, a valid
+character of '\\377' is given to the application as '\\377', '\\377'. If
+neither PARMRK nor IGNPAR is set, a framing or parity error (other than
+break) is given to the application as a single character '\\0'.
+.PP
+If INPCK is set, input parity checking is enabled. If INPCK is not set,
+input parity checking is disabled, allowing output parity generation
+without input parity errors. Note that whether input parity checking is
+enabled or disabled is independent of whether parity detection is enabled
+or disabled (see "Control Modes"). If parity detection is enabled but input
+parity checking is disabled, the hardware to which the terminal is
+connected shall recognize the parity bit, but the terminal special file
+shall not check whether this bit is set correctly or not.
+.PP
+If ISTRIP is set, valid input bytes are first stripped to seven bits,
+otherwise all eight bits are processed.
+.PP
+If INLCR is set, a received NL character is translated into a CR
+character. If IGNCR is set, a received CR character is ignored (not
+read). If IGNCR is not set and ICRNL is set, a received CR character is
+translated into a NL character.
+.PP
+If IXON is set, start/stop output control is enabled. A received STOP
+character shall suspend output and a received START character shall
+restart output. If IXANY is also set, then any character shall
+restart output. When IXON is set, START and STOP characters are not
+read, but merely perform flow control functions. When IXON is not set,
+the START and STOP characters are read.
+.PP
+If IXOFF is set, start/stop input control is enabled. The system shall
+transmit one or more STOP characters, which are intended to cause the
+terminal device to stop transmitting data, as needed to prevent the input
+queue from overflowing and causing the undefined behavior described in
+"Input Processing and Reading Data", and shall transmit one or more
+START characters, which are
+intended to cause the terminal device to resume transmitting data, as
+soon as the device can continue transmitting data without risk of
+overflowing the input queue. The precise conditions under which STOP and
+START characters are transmitted are implementation defined.
+.PP
+If IMAXBEL is set and the input queue is full, subsequent input
+shall causes an ASCII BEL character to be transmitted to the
+the output queue.
+.PP
+The initial input control value after open() is implementation defined.
+.LP
+.B "Output Modes"
+.LP
+Values of the c_oflag field describe the basic terminal output control,
+and are composed of the following masks:
+.nf
+ (XXX cael - make into table)
+ OPOST /* enable following output processing */
+ ONLCR /* map NL to CR-NL (ala CRMOD) */
+ OXTABS /* expand tabs to spaces */
+ ONOEOT /* discard EOT's (^D) on output) */
+.fi
+.PP
+If OPOST is set, the remaining flag masks are interpreted as follows;
+otherwise characters are transmitted without change.
+.PP
+If ONLCR is set, newlines are translated to carriage return, linefeeds.
+.PP
+If OXTABS is set, tabs are expanded to the appropiate number of
+spaces (assuming 8 column tab stops).
+.PP
+If ONOEOT is set, ASCII EOT's are discarded on output.
+.LP
+.B "Control Modes"
+.LP
+Values of the c_cflag field describe the basic
+terminal hardware control, and are composed of the
+the following masks.
+Not all values
+specified are supported by all hardware.
+.nf
+ (XXX cael - make into table)
+ CSIZE /* character size mask */
+ CS5 /* 5 bits (pseudo) */
+ CS6 /* 6 bits */
+ CS7 /* 7 bits */
+ CS8 /* 8 bits */
+ CSTOPB /* send 2 stop bits */
+ CREAD /* enable receiver */
+ PARENB /* parity enable */
+ PARODD /* odd parity, else even */
+ HUPCL /* hang up on last close */
+ CLOCAL /* ignore modem status lines */
+ CCTS_OFLOW /* CTS flow control of output */
+ CRTSCTS /* same as CCTS_OFLOW */
+ CRTS_IFLOW /* RTS flow control of input */
+ MDMBUF /* flow control output via Carrier */
+.fi
+.PP
+The CSIZE bits specify the byte size in bits for both transmission and
+reception. The c_cflag is masked with CSIZE and compared with the
+values CS5, CS6, CS7, or CS8. This size does not include the parity bit, if any. If CSTOPB
+is set, two stop bits are used, otherwise one stop bit. For example, at
+110 baud, two stop bits are normally used.
+.PP
+If CREAD is set, the receiver is enabled. Otherwise, no characters shall
+be received. Not all hardware supports this bit. In fact, this flag
+is pretty silly and if it were not part of the termios(4) specification
+it would be ommitted.
+.PP
+If PARENB is set, parity generation and detection is enabled and a parity
+bit is added to each character. If parity is enabled, PARODD specifies
+odd parity if set, otherwise even parity is used.
+.PP
+If HUPCL is set, the modem control lines for the port shall be lowered
+when the last process with the port open closes the port or the process
+terminates. The modem connection shall be broken.
+.PP
+If CLOCAL is set, a connection does not depend on the state of the modem
+status lines. If CLOCAL is clear, the modem status lines shall be
+monitored.
+.PP
+Under normal circumstances, a call to the open() function shall wait for
+the modem connection to complete. However, if the O_NONBLOCK flag is set
+or if CLOCAL has been set, the open() function shall return
+immediately without waiting for the connection.
+.PP
+The CCTS_OFLOW (CRTSCTS) flag is currently unused.
+.PP
+If MDMBUF is set then output flow control is controlled by the state
+of Carrier Detect.
+.PP
+If the object for which the control modes are set is not an asynchronous
+serial connection, some of the modes may be ignored; for example, if an
+attempt is made to set the baud rate on a network connection to a
+terminal on another host, the baud rate may or may not be set on the
+connection between that terminal and the machine it is directly connected
+to.
+.LP
+.B "Local Modes"
+.LP
+Values of the c_lflag field describe the control of
+various functions, and are composed of the following
+masks.
+.nf
+ (XXX cael - make into table)
+ ECHOKE /* visual erase for line kill */
+ ECHOE /* visually erase chars */
+ ECHO /* enable echoing */
+ ECHONL /* echo NL even if ECHO is off */
+ ECHOPRT /* visual erase mode for hardcopy */
+ ECHOCTL /* echo control chars as ^(Char) */
+ ISIG /* enable signals INTR, QUIT, [D]SUSP */
+ ICANON /* canonicalize input lines */
+ ALTWERASE /* use alternate WERASE algorithm */
+ IEXTEN /* enable DISCARD and LNEXT */
+ EXTPROC /* external processing */
+ TOSTOP /* stop background jobs from output */
+ FLUSHO /* output being flushed (state) */
+ NOKERNINFO /* no kernel output from VSTATUS */
+ PENDIN /* XXX retype pending input (state) */
+ NOFLSH /* don't flush after interrupt */
+.fi
+.PP
+If ECHO is set, input characters are echoed back to the terminal. If
+ECHO is not set, input characters are not echoed.
+.PP
+If ECHOE and ICANON are set, the ERASE character shall cause the terminal
+to erase the last character in the current line from the display, if
+possible. If there is no character to erase, an implementation may echo
+an indication that this was the case or do nothing.
+.PP
+If ECHOK and ICANON are set, the KILL character shall
+cause the current line to be discarded and the system shall
+echo the '\\n'
+character after the KILL character.
+.PP
+If ECHOKE and ICANON are set, the KILL character shall cause
+the current line to be discarded and the system shall cause
+the terminal
+to erase the line from the display.
+.PP
+If ECHOPRT and ICANON are set, the system shall assume
+that the display is a printing device and shall print a
+backslash and the erased characters when processing ERASE
+characters, followed by a forward slash.
+.PP
+If ECHOCTL is set, the system shall echo control characters
+in a visible fashion using a carrot followed by the control character.
+.PP
+If ALTWERASE is set, the system will use an alternative algorithm
+for determining what constitutes a word when processing WERASE
+characters (see WERASE).
+.PP
+If ECHONL and ICANON are set, the '\\n' character shall be echoed even if
+ECHO is not set.
+.PP
+If ICANON is set, canonical processing is enabled. This enables the
+erase and kill edit functions, and the assembly of input characters into
+lines delimited by NL, EOF, and EOL, as described in "Canonical Mode
+Input Processing".
+.PP
+If ICANON is not set, read requests are satisfied directly from the input
+queue. A read shall not be satisfied until at least MIN bytes have been
+received or the timeout value TIME expired between bytes. The time value
+represents tenths of seconds. See "Noncanonical Mode Input Processing"
+for more details.
+.PP
+If ISIG is set, each input character is checked against the special
+control characters INTR, QUIT, and SUSP (job control only). If an input
+character matches one of these control characters, the function
+associated with that character is performed. If ISIG is not set, no
+checking is done. Thus these special input functions are possible only
+if ISIG is set.
+.PP
+If IEXTEN is set, implementation-defined functions shall be recognized
+from the input data. It is implementation defined how IEXTEN being set
+interacts with ICANON, ISIG, IXON, or IXOFF. If IEXTEN is not set, then
+implementation-defined functions shall not be recognized, and the
+corresponding input characters shall be processed as described for
+ICANON, ISIG, IXON, and IXOFF.
+.PP
+If NOFLSH is set, the normal flush of the input and output queues
+associated with the INTR, QUIT, and SUSP characters
+shall not be done.
+.PP
+If TOSTOP is set, the signal
+SIGTTOU is sent to the process group of a process that tries to write to
+its controlling terminal if it is not in the foreground process group for
+that terminal. This signal, by default, stops the members of the process
+group. Otherwise, the output generated by that process is output to the
+current output stream. Processes that are blocking or ignoring SIGTTOU
+signals are excepted and allowed to produce output and the SIGTTOU signal
+is not sent.
+.PP
+If NOKERNINFO is set, the kernel shall not produce a status message
+when processing STATUS characters (see STATUS).
+.LP
+.B "Special Control Characters"
+.LP
+The special control characters values are defined by the array c_cc.
+This table lists the array index, the corresponding special character,
+and the system default value. For an accurate list of
+the system defaults, consult the header file <ttydefaults.h>.
+.nf
+ (XXX cael - make into table)
+ Index Name Special Character Default Value
+ ---------- ----------------- -------------
+ VEOF EOF ^D
+ VEOL EOL _POSIX_VDISABLE
+ VEOL2 EOL2 _POSIX_VDISABLE
+ VERASE ERASE ^? ('\\177')
+ VWERASE WERASE ^W
+ VKILL KILL ^U
+ VREPRINT REPRINT ^R
+ VINTR INTR ^C
+ VQUIT QUIT ^\\ ('\\34')
+ VSUSP SUSP ^Z
+ VDSUSP DSUSP ^Y
+ VSTART START ^Q
+ VSTOP STOP ^S
+ VLNEXT LNEXT ^V
+ VDISCARD DISCARD ^O
+ VMIN --- 1
+ VTIME --- 0
+ VSTATUS STATUS ^T
+.fi
+.PP
+If the
+value of one of the changeable special control characters (see "Special
+Characters")
+is {_POSIX_VDISABLE}, that function shall be disabled; that is, no input
+data shall be recognized as the disabled special character. If ICANON is
+not set, the value of {_POSIX_VDISABLE} has no special meaning for the
+VMIN and VTIME entries of the c_cc array.
+.PP
+The initial values of the flags and control characters
+after open() is set according to
+the values in the header <sys/ttydefaults.h>.
projects / unix-history / commitdiff