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Diffstat (limited to 'share/man/man4/termios.4')
| -rw-r--r-- | share/man/man4/termios.4 | 494 |
1 files changed, 285 insertions, 209 deletions
diff --git a/share/man/man4/termios.4 b/share/man/man4/termios.4 index be8a21064c6..7032ba5c25b 100644 --- a/share/man/man4/termios.4 +++ b/share/man/man4/termios.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: termios.4,v 1.15 2001/08/20 05:57:55 mpech Exp $ +.\" $OpenBSD: termios.4,v 1.16 2001/10/05 14:45:53 mpech Exp $ .\" $NetBSD: termios.4,v 1.5 1994/11/30 16:22:36 jtc Exp $ .\" .\" Copyright (c) 1991, 1992, 1993 @@ -47,8 +47,9 @@ This describes a general terminal line discipline that is supported on tty asynchronous communication ports. .Ss Opening a Terminal Device File 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 +until a connection is established. +For most hardware, the presence of a connection is indicated by the assertion +of the hardware .Dv CARRIER line. If the termios structure associated with the terminal file has the .Dv CLOCAL @@ -70,45 +71,48 @@ an application's standard input, output, and error files. .Ss Job Control in a Nutshell 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 +member of the same session. +This structuring is used in managing groups of related processes for purposes +of .\" .Gw "job control" ; .Em "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 +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 +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 referred 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 +same process group. +A set of processes in the same process group is collectively referred 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 +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 (usually +command). +If the job is started in the foreground, the user may type a key (usually .Ql \&^Z ) which generates the terminal stop signal .Pq Dv SIGTSTP @@ -120,33 +124,37 @@ and for placing stopped or background jobs into the foreground. .Ss Orphaned Process Groups 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. +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. .Ss The Controlling Terminal -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 issuing the +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 issuing the .Dv TIOCSCTTY -ioctl. A controlling terminal -is never acquired by merely opening a terminal device file. +ioctl. +A controlling terminal is never acquired by merely opening a terminal device +file. When a controlling terminal becomes associated with a session, its foreground process group is set to the process group of the session leader. .Pp The controlling terminal is inherited by a child process during a .Xr fork 2 -function call. A process relinquishes its controlling terminal when it -creates a new session with the +function call. +A process relinquishes its controlling terminal when it creates a new session +with the .Xr setsid 2 -function; other processes -remaining in the old session that had this terminal as their controlling -terminal continue to have it. +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 @@ -154,9 +162,10 @@ 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. +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. .Ss Terminal Access Control If a process is in the foreground process group of its controlling terminal, read operations are allowed. @@ -167,7 +176,7 @@ causes a signal to be sent to the process's group unless one of the -following special cases apply: If the reading process is ignoring or +following special cases apply: If the reading process is ignoring or blocking the .Dv SIGTTIN signal, or if the process group of the reading process is orphaned, the @@ -177,7 +186,8 @@ returns -1 with set to .Er Dv EIO and no -signal is sent. The default action of the +signal is sent. +The default action of the .Dv SIGTTIN signal is to stop the process to which it is sent. @@ -196,7 +206,8 @@ is set and the process is ignoring or blocking the .Dv SIGTTOU signal, the process is allowed to write to the terminal and the .Dv SIGTTOU -signal is not sent. If +signal is not sent. +If .Dv TOSTOP is set, and the process group of the writing process is orphaned, and the writing process is not ignoring @@ -222,11 +233,13 @@ 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 imposes a limit, +process. +The system imposes a limit, .Pf \&{ Dv MAX_INPUT Ns \&} , 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 +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 .Dv IMAXBEL flag in the termios .Fa c_iflag . @@ -235,20 +248,21 @@ is sent an .Tn ASCII .Dv BEL character each time a character is received -while the input queue is full. Otherwise, the input queue is flushed -upon receiving the character. +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 +mode. +Additionally, input characters are processed according to the .Fa c_iflag and .Fa 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. +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 @@ -263,15 +277,15 @@ or If the .Dv O_NONBLOCK flag is clear, then the read request is -blocked until data is available or a signal has been received. If the +blocked until data is available or a signal has been received. +If the .Dv O_NONBLOCK flag is set, then the read request is completed, without blocking, in one of three ways: .Bl -enum -offset indent .It If there is enough data available to satisfy the entire request, -and the read completes successfully the number of -bytes read is returned. +and the read completes successfully the number of bytes read is returned. .It If there is not enough data available to satisfy the entire request, and the read completes successfully, having read as @@ -287,13 +301,15 @@ When data is available depends on whether the input processing mode is canonical or noncanonical. .Ss Canonical Mode Input Processing In canonical mode input processing, terminal input is processed in units -of lines. A line is delimited by a newline +of lines. +A line is delimited by a newline .Ql \&\en character, an end-of-file .Pq Dv EOF character, or an end-of-line .Pq Dv EOL -character. See the +character. +See the .Sx "Special Characters" section for more information on @@ -302,10 +318,11 @@ and .Dv EOL . This means that a read request will 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 is 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. +received. +Also, no matter how many bytes are requested in the read call, +at most one line is 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 .Pf \&{ Dv MAX_CANON Ns \&} is a limit on the @@ -329,14 +346,17 @@ delimited by a newline .Dv EOF , or .Dv EOL -character. This un-delimited -data makes up the current line. The +character. +This un-delimited data makes up the current line. +The .Dv ERASE character deletes the last -character in the current line, if there is any. The +character in the current line, if there is any. +The .Dv KILL character -deletes all data in the current line, if there is any. The +deletes all data in the current line, if there is any. +The .Dv ERASE and .Dv KILL @@ -349,7 +369,8 @@ characters themselves are not placed in the input queue. .Ss Noncanonical Mode Input Processing In noncanonical mode input processing, input bytes are not assembled into -lines, and erase and kill processing does not occur. The values of the +lines, and erase and kill processing does not occur. +The values of the .Dv VMIN and .Dv VTIME @@ -366,12 +387,14 @@ function successfully returns. .Dv VTIME is a timer of 0.1 second granularity that is used to time out bursty and short term data -transmissions. If +transmissions. +If .Dv VMIN is greater than .Pf \&{ Dv MAX_INPUT Ns \&} , the response to the -request is undefined. The four possible values for +request is undefined. +The four possible values for .Dv VMIN and .Dv VTIME @@ -381,24 +404,29 @@ their interactions are described below. In this case .Dv VTIME 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 +the first byte is received. +Since it is an inter-byte timer, it is reset after a byte is received. +The interaction between .Dv VMIN and .Dv VTIME is as -follows: as soon as one byte is received, the inter-byte timer is -started. If +follows: as soon as one byte is received, the inter-byte timer is +started. +If .Dv VMIN 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 +satisfied. +If the timer expires before .Dv VMIN bytes are received, the -characters received to that point are returned to the user. Note that if +characters received to that point are returned to the user. +Note that if .Dv VTIME expires at least one byte is returned because the timer would -not have been enabled unless a byte was received. In this case +not have been enabled unless a byte was received. +In this case .Pf \&( Dv VMIN > 0, .Dv VTIME @@ -407,8 +435,8 @@ not have been enabled unless a byte was received. In this case and .Dv VTIME 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 is as +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 is as if data had been received immediately after the read(). .Ss "Case B: VMIN > 0, VTIME = 0" In this case, since the value of @@ -416,13 +444,14 @@ In this case, since the value of is zero, the timer plays no role and only .Dv VMIN -is significant. A pending read is not satisfied until +is significant. +A pending read is not satisfied until .Dv VMIN bytes are received (i.e., the pending read blocks until .Dv VMIN bytes -are received), or a signal is received. A program that uses this case to -read record-based terminal +are received), or a signal is received. +A program that uses this case to read record-based terminal .Dv I/O may block indefinitely in the read operation. @@ -432,30 +461,35 @@ In this case, since = 0, .Dv VTIME 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 are returned. If the timer does not -expire, the only way the read can be satisfied is if a byte is received. +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 are 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 will not block indefinitely waiting for a byte; if no byte is received within .Dv VTIME Ns *0.1 seconds after the read is initiated, -the read returns a value of zero, having read no data. If data is -in the buffer at the time of the read, the timer is started as if -data had been received immediately after the read. +the read returns a value of zero, having read no data. +If data is in the buffer at the time of the read, the timer is started +as if data had been received immediately after the read. .Ss Case D: VMIN = 0, VTIME = 0 The minimum of either the number of bytes requested or the number of bytes currently available is returned without waiting for more -bytes to be input. If no characters are available, read returns a -value of zero, having read no data. +bytes to be input. +If no characters are available, read returns a value of zero, having +read no data. .Ss Writing Data and Output Processing When a process writes one or more bytes to a terminal device file, they are processed according to the .Fa c_oflag field (see the .Sx "Output Modes -section). The +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 @@ -472,11 +506,13 @@ Special character on input and is recognized if the .Dv ISIG flag (see the .Sx "Local Modes" -section) is enabled. Generates a +section) is enabled. +Generates a .Dv SIGINT signal which is sent to all processes in the foreground process group for which the terminal is the controlling -terminal. If +terminal. +If .Dv ISIG is set, the .Dv INTR @@ -485,11 +521,13 @@ discarded when processed. .It Dv QUIT Special character on input and is recognized if the .Dv ISIG -flag is enabled. Generates a +flag is enabled. +Generates a .Dv SIGQUIT signal which is sent to all processes in the foreground process group -for which the terminal is the controlling terminal. If +for which the terminal is the controlling terminal. +If .Dv ISIG is set, the .Dv QUIT @@ -498,16 +536,16 @@ processed. .It Dv ERASE Special character on input and is recognized if the .Dv ICANON -flag is set. Erases the last character in the -current line; see +flag is set. +Erases the last character in the current line; see .Sx "Canonical Mode Input Processing" . -It does not erase beyond -the start of a line, as delimited by a +It does not erase beyond the start of a line, as delimited by a .Dv NL , .Dv EOF , or .Dv EOL -character. If +character. +If .Dv ICANON is set, the .Dv ERASE @@ -516,13 +554,14 @@ discarded when processed. .It Dv KILL Special character on input and is recognized if the .Dv ICANON -flag is set. Deletes the entire line, as -delimited by a +flag is set. +Deletes the entire line, as delimited by a .Dv NL , .Dv EOF , or .Dv EOL -character. If +character. +If .Dv ICANON is set, the .Dv KILL @@ -530,16 +569,18 @@ character is discarded when processed. .It Dv EOF Special character on input and is recognized if the .Dv ICANON -flag is set. When received, all the bytes -waiting to be read are immediately passed to the +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 .Dv EOF -is discarded. Thus, if there are no bytes waiting (that +is discarded. +Thus, if there are no bytes waiting (that is, the .Dv EOF occurred at the beginning of a line), a byte count of zero is returned from the read(), -representing an end-of-file indication. If +representing an end-of-file indication. +If .Dv ICANON is set, the @@ -548,12 +589,14 @@ character is discarded when processed. .Dv NL Special character on input and is recognized if the .Dv ICANON -flag is set. It is the line delimiter +flag is set. +It is the line delimiter .Ql \&\en . .It Dv EOL Special character on input and is recognized if the .Dv ICANON -flag is set. Is an additional line delimiter, +flag is set. +Is an additional line delimiter, like .Dv NL . .It Dv SUSP @@ -576,9 +619,10 @@ recognized if the (output control) or .Dv 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. +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 .Dv IXON is set, the @@ -592,10 +636,11 @@ recognized if the (output control) or .Dv IXOFF (input -control) flag is set. Can be used to resume output that -has been suspended by a +control) flag is set. +Can be used to resume output that has been suspended by a .Dv STOP -character. If +character. +If .Dv IXON is set, the .Dv START @@ -607,7 +652,8 @@ flag is set; it is the .Ql \&\er , as denoted in the .Tn \&C -Standard {2}. When +Standard {2}. +When .Dv ICANON and .Dv ICRNL @@ -627,17 +673,21 @@ system and are not a part of 1003.1 termios. .It Dv EOL2 Secondary .Dv EOL -character. Same function as +character. +Same function as .Dv EOL. .It Dv WERASE Special character on input and is recognized if the .Dv ICANON -flag is set. Erases the last word in the current -line according to one of two algorithms. If the +flag is set. +Erases the last word in the current +line according to one of two algorithms. +If the .Dv ALTWERASE flag is not set, first any preceding whitespace is erased, and then the maximal sequence of non-whitespace -characters. If +characters. +If .Dv ALTWERASE is set, first any preceding whitespace is erased, and then the maximal sequence @@ -645,12 +695,13 @@ of alphabetic/underscores or non alphabetic/underscores. As a special case in this second algorithm, the first previous non-whitespace character is skipped in determining whether the preceding word is a sequence of -alphabetic/underscores. This sounds confusing but turns -out to be quite practical. +alphabetic/underscores. +This sounds confusing but turns out to be quite practical. .It Dv REPRINT Special character on input and is recognized if the .Dv ICANON -flag is set. Causes the current input edit line +flag is set. +Causes the current input edit line to be retyped. .It Dv DSUSP Has similar actions to the @@ -664,20 +715,22 @@ controlling terminal. .It Dv LNEXT Special character on input and is recognized if the .Dv IEXTEN -flag is set. Receipt of this character causes the next -character to be taken literally. +flag is set. +Receipt of this character causes the next character to be taken literally. .It Dv DISCARD Special character on input and is recognized if the .Dv IEXTEN -flag is set. Receipt of this character toggles the flushing -of terminal output. +flag is set. +Receipt of this character toggles the flushing of terminal output. .It Dv STATUS Special character on input and is recognized if the .Dv ICANON -flag is set. Receipt of this character causes a +flag is set. +Receipt of this character causes a .Dv SIGINFO signal to be sent to the foreground process group of the -terminal. Also, if the +terminal. +Also, if the .Dv NOKERNINFO flag is not set, it causes the kernel to write a status message to the terminal @@ -716,12 +769,13 @@ field for the terminal, the .Dv 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. +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 returns 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. +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 .\" .Er EIO .\" condition specified in 6.1.1.4 that applies @@ -740,7 +794,8 @@ until the device is closed. .Sh General Terminal Interface .Ss Closing a Terminal Device File The last process to close a terminal device file causes any output -to be sent to the device and any input to be discarded. Then, if +to be sent to the device and any input to be discarded. +Then, if .Dv HUPCL is set in the control modes, and the communications port supports a disconnect function, the terminal device performs a disconnect. @@ -751,7 +806,8 @@ characteristics do so by using the termios structure as defined in the header .Aq Pa termios.h . This structure contains minimally four scalar elements of bit flags -and one array of special characters. The scalar flag elements are +and one array of special characters. +The scalar flag elements are named: .Fa c_iflag , .Fa c_oflag , @@ -802,16 +858,17 @@ following masks: .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. +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 .Dv 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 +is, not put on the input queue and therefore not read by any process. +If .Dv IGNBRK is not set and .Dv BRKINT @@ -820,7 +877,8 @@ input and output queues and if the terminal is the controlling terminal of a foreground process group, the break condition generates a single .Dv SIGINT -signal to that foreground process group. If neither +signal to that foreground process group. +If neither .Dv IGNBRK nor .Dv BRKINT @@ -852,7 +910,8 @@ X, where .Ql \&\e0 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 +in error. +To avoid ambiguity in this case, if .Dv ISTRIP is not set, a valid character of @@ -871,13 +930,14 @@ break) is given to the application as a single character .Pp If .Dv INPCK -is set, input parity checking is enabled. If +is set, input parity checking is enabled. +If .Dv 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 +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 .Sx "Control Modes" ) . If parity detection is enabled but input parity checking is disabled, the hardware to which the terminal is @@ -895,12 +955,14 @@ is set, a received .Dv NL character is translated into a .Dv CR -character. If +character. +If .Dv IGNCR is set, a received .Dv CR character is ignored (not -read). If +read). +If .Dv IGNCR is not set and .Dv ICRNL @@ -913,22 +975,26 @@ character. .Pp If .Dv IXON -is set, start/stop output control is enabled. A received +is set, start/stop output control is enabled. +A received .Dv STOP character suspends output and a received .Dv START character -restarts output. If +restarts output. +If .Dv IXANY is also set, then any character may -restart output. When +restart output. +When .Dv IXON is set, .Dv START and .Dv STOP characters are not -read, but merely perform flow control functions. When +read, but merely perform flow control functions. +When .Dv IXON is not set, the @@ -939,8 +1005,8 @@ characters are read. .Pp If .Dv IXOFF -is set, start/stop input control is enabled. The system shall -transmit one or more +is set, start/stop input control is enabled. +The system shall transmit one or more .Dv STOP characters, which are intended to cause the terminal device to stop transmitting data, as needed to prevent the input @@ -951,7 +1017,8 @@ and shall transmit one or more 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 +overflowing the input queue. +The precise conditions under which .Dv STOP and START @@ -1087,7 +1154,8 @@ flow control of output */ The .Dv CSIZE bits specify the byte size in bits for both transmission and -reception. The +reception. +The .Fa c_cflag is masked with .Dv CSIZE @@ -1098,25 +1166,26 @@ values .Dv CS7 , or .Dv CS8 . -This size does not include the parity bit, if any. If +This size does not include the parity bit, if any. +If .Dv CSTOPB -is set, two stop bits are used, otherwise one stop bit. For example, at -110 baud, two stop bits are normally used. +is set, two stop bits are used, otherwise one stop bit. +For example, at 110 baud, two stop bits are normally used. .Pp If .Dv CREAD -is set, the receiver is enabled. Otherwise, no character is -received. -Not all hardware supports this bit. In fact, this flag -is pretty silly and if it were not part of the +is set, the receiver is enabled. +Otherwise, no character is received. +Not all hardware supports this bit. +In fact, this flag is pretty silly and if it were not part of the .Nm -specification -it would be omitted. +specification it would be omitted. .Pp If .Dv PARENB is set, parity generation and detection are enabled and a parity -bit is added to each character. If parity is enabled, +bit is added to each character. +If parity is enabled, .Dv PARODD specifies odd parity if set, otherwise even parity is used. @@ -1125,18 +1194,21 @@ If .Dv HUPCL is set, the modem control lines for the port are lowered when the last process with the port open closes the port or the process -terminates. The modem connection is broken. +terminates. +The modem connection is broken. .Pp If .Dv CLOCAL is set, a connection does not depend on the state of the modem -status lines. If +status lines. +If .Dv CLOCAL is clear, the modem status lines are monitored. .Pp Under normal circumstances, a call to the open() function waits for -the modem connection to complete. However, if the +the modem connection to complete. +However, if the .Dv O_NONBLOCK flag is set or if @@ -1222,7 +1294,8 @@ and .Pp If .Dv ECHO -is set, input characters are echoed back to the terminal. If +is set, input characters are echoed back to the terminal. +If .Dv ECHO is not set, input characters are not echoed. .Pp @@ -1234,7 +1307,8 @@ are set, the .Dv ERASE character causes 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 +possible. +If there is no character to erase, an implementation may echo an indication that this was the case or do nothing. .Pp If @@ -1256,17 +1330,14 @@ and .Dv ICANON are set, the .Dv KILL -character causes -the current line to be discarded and the system causes -the terminal -to erase the line from the display. +character causes the current line to be discarded and the system causes +the terminal to erase the line from the display. .Pp If .Dv ECHOPRT and .Dv ICANON -are set, the system assumes -that the display is a printing device and prints a +are set, the system assumes that the display is a printing device and prints a backslash and the erased characters when processing .Dv ERASE characters, followed by a forward slash. @@ -1296,9 +1367,9 @@ is not set. .Pp If .Dv 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 +is set, canonical processing is enabled. +This enables the erase and kill edit functions, and the assembly of input +characters into lines delimited by .Dv NL, .Dv EOF , and @@ -1309,13 +1380,14 @@ as described in If .Dv ICANON is not set, read requests are satisfied directly from the input -queue. A read is not satisfied until at least +queue. +A read is not satisfied until at least .Dv VMIN -bytes have been -received or the timeout value +bytes have been received or the timeout value .Dv VTIME -expired between bytes. The time value -represents tenths of seconds. See +expired between bytes. +The time value represents tenths of seconds. +See .Sx "Noncanonical Mode Input Processing" for more details. .Pp @@ -1327,12 +1399,14 @@ control characters .Dv QUIT , and .Dv SUSP -(job control only). If an input -character matches one of these control characters, the function -associated with that character is performed. If +(job control only). +If an input character matches one of these control characters, the function +associated with that character is performed. +If .Dv ISIG is not set, no -checking is done. Thus these special input functions are possible only +checking is done. +Thus these special input functions are possible only if .Dv ISIG is set. @@ -1340,7 +1414,8 @@ is set. If .Dv IEXTEN is set, implementation-defined functions are recognized -from the input data. How +from the input data. +How .Dv IEXTEN being set interacts with @@ -1377,8 +1452,8 @@ If and .Dv ICANON is set, an upper case character is preserved on input if prefixed by -a \\ character. In addition, this prefix is added to upper case -characters on output. +a \\ character. +In addition, this prefix is added to upper case characters on output. .Pp In addition, the following special character translations are in effect: .Pp @@ -1398,9 +1473,11 @@ is set, the signal .Dv 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 +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 .Dv SIGTTOU signals are excepted and allowed to produce output and the .Dv SIGTTOU @@ -1418,8 +1495,8 @@ characters (see The special control characters values are defined by the array .Fa 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 +and the system default value. +For an accurate list of the system defaults, consult the header file .Aq Pa ttydefaults.h . .Pp .Bl -column "Index Name" "Special Character" -offset indent -compact @@ -1465,8 +1542,7 @@ entries of the array. .Pp The initial values of the flags and control characters -after open() is set according to -the values in the header +after open() is set according to the values in the header .Aq Pa sys/ttydefaults.h . .Sh SEE ALSO .Xr tcgetattr 3 , |