and all input that has been received but not read
will be discarded before the change is made.
.SS Canonical and noncanonical mode
-The setting of the
-.B ICANON
-canon flag in
-.I c_lflag
-determines whether the terminal is operating
-in canonical mode
-.RB ( ICANON
-set)
-or noncanonical mode
-.RB ( ICANON
-unset).
-By default,
-.B ICANON
-is set.
-.P
-In canonical mode:
-.IP \[bu] 3
-Input is made available line by line.
-An input line is available when one of the line delimiters is typed
-(NL, EOL, EOL2;
-or EOF at the start of line).
-Except in the case of EOF,
-the line delimiter is included
-in the buffer returned by
-.BR read (2).
-.IP \[bu]
-Line editing is enabled
-(ERASE, KILL;
-and if the
-.B IEXTEN
-flag is set: WERASE, REPRINT, LNEXT).
-A
-.BR read (2)
-returns at most one line of input;
-if the
-.BR read (2)
-requested fewer bytes than are available in the current line of input,
-then only as many bytes as requested are read,
-and the remaining characters will be available for a future
-.BR read (2).
-.IP \[bu]
-The maximum line length is 4096 chars
-(including the terminating newline character);
-lines longer than 4096 chars are truncated.
-After 4095 characters,
-input processing
-(e.g.,
-.B ISIG
-and
-.B ECHO*
-processing)
-continues,
-but any input data after 4095 characters
-up to (but not including) any terminating newline
-is discarded.
-This ensures that
-the terminal can always receive more input
-until at least one line can be read.
-.P
-In noncanonical mode input is available immediately
-(without the user having to type a line-delimiter character),
-no input processing is performed,
-and line editing is disabled.
-The read buffer will only accept 4095 chars;
-this provides the necessary space for a newline char
-if the input mode is switched to canonical.
-The settings of MIN
-.RI ( c_cc[VMIN] )
-and TIME
-.RI ( c_cc[VTIME] )
-determine the circumstances in which a
-.BR read (2)
-completes;
-there are four distinct cases:
-.TP
-MIN == 0, TIME == 0 (polling read)
-If data is available,
-.BR read (2)
-returns immediately,
-with the lesser of the number of bytes available,
-or the number of bytes requested.
-If no data is available,
-.BR read (2)
-returns 0.
-.TP
-MIN > 0, TIME == 0 (blocking read)
-.BR read (2)
-blocks until MIN bytes are available,
-and returns up to the number of bytes requested.
-.TP
-MIN == 0, TIME > 0 (read with timeout)
-TIME specifies the limit for a timer in tenths of a second.
-The timer is started when
-.BR read (2)
-is called.
-.BR read (2)
-returns either when at least one byte of data is available,
-or when the timer expires.
-If the timer expires without any input becoming available,
-.BR read (2)
-returns 0.
-If data is already available at the time of the call to
-.BR read (2),
-the call behaves as though the data was received immediately after the call.
-.TP
-MIN > 0, TIME > 0 (read with interbyte timeout)
-TIME specifies the limit for a timer in tenths of a second.
-Once an initial byte of input becomes available,
-the timer is restarted after each further byte is received.
-.BR read (2)
-returns when any of the following conditions is met:
-.RS
-.IP \[bu] 3
-MIN bytes have been received.
-.IP \[bu]
-The interbyte timer expires.
-.IP \[bu]
-The number of bytes requested by
-.BR read (2)
-has been received.
-(POSIX does not specify this termination condition,
-and on some other implementations
-.\" e.g., Solaris
-.BR read (2)
-does not return in this case.)
-.RE
-.IP
-Because the timer is started only after the initial byte becomes available,
-at least one byte will be read.
-If data is already available at the time of the call to
-.BR read (2),
-the call behaves as though the data was received immediately after the call.
-.P
-POSIX
-.\" POSIX.1-2008 XBD 11.1.7
-does not specify whether the setting of the
-.B O_NONBLOCK
-file status flag takes precedence over the MIN and TIME settings.
-If
-.B O_NONBLOCK
-is set, a
-.BR read (2)
-in noncanonical mode may return immediately,
-regardless of the setting of MIN or TIME.
-Furthermore,
-if no data is available,
-POSIX permits a
-.BR read (2)
-in noncanonical mode to return either 0, or \-1 with
-.I errno
-set to
-.BR EAGAIN .
+See
+.BR termios (3type).
.SS Raw mode
.BR cfmakeraw ()
sets the terminal to something like the
.BR VTIME ,
see the description of
noncanonical mode
-in
-.BR termios (3).
+below.
.SS \f[I].c_iflag\f[] flag constants
.TP
.B IGNBRK
.I .c_cc
element to
.BR _POSIX_VDISABLE .
+.SS Canonical and noncanonical mode
+The setting of the
+.B ICANON
+canon flag in
+.I c_lflag
+determines whether the terminal is operating
+in canonical mode
+.RB ( ICANON
+set)
+or noncanonical mode
+.RB ( ICANON
+unset).
+By default,
+.B ICANON
+is set.
+.P
+In canonical mode:
+.IP \[bu] 3
+Input is made available line by line.
+An input line is available when one of the line delimiters is typed
+(NL, EOL, EOL2;
+or EOF at the start of line).
+Except in the case of EOF,
+the line delimiter is included
+in the buffer returned by
+.BR read (2).
+.IP \[bu]
+Line editing is enabled
+(ERASE, KILL;
+and if the
+.B IEXTEN
+flag is set: WERASE, REPRINT, LNEXT).
+A
+.BR read (2)
+returns at most one line of input;
+if the
+.BR read (2)
+requested fewer bytes than are available in the current line of input,
+then only as many bytes as requested are read,
+and the remaining characters will be available for a future
+.BR read (2).
+.IP \[bu]
+The maximum line length is 4096 chars
+(including the terminating newline character);
+lines longer than 4096 chars are truncated.
+After 4095 characters,
+input processing
+(e.g.,
+.B ISIG
+and
+.B ECHO*
+processing)
+continues,
+but any input data after 4095 characters
+up to (but not including) any terminating newline
+is discarded.
+This ensures that
+the terminal can always receive more input
+until at least one line can be read.
+.P
+In noncanonical mode input is available immediately
+(without the user having to type a line-delimiter character),
+no input processing is performed,
+and line editing is disabled.
+The read buffer will only accept 4095 chars;
+this provides the necessary space for a newline char
+if the input mode is switched to canonical.
+The settings of MIN
+.RI ( c_cc[VMIN] )
+and TIME
+.RI ( c_cc[VTIME] )
+determine the circumstances in which a
+.BR read (2)
+completes;
+there are four distinct cases:
+.TP
+MIN == 0, TIME == 0 (polling read)
+If data is available,
+.BR read (2)
+returns immediately,
+with the lesser of the number of bytes available,
+or the number of bytes requested.
+If no data is available,
+.BR read (2)
+returns 0.
+.TP
+MIN > 0, TIME == 0 (blocking read)
+.BR read (2)
+blocks until MIN bytes are available,
+and returns up to the number of bytes requested.
+.TP
+MIN == 0, TIME > 0 (read with timeout)
+TIME specifies the limit for a timer in tenths of a second.
+The timer is started when
+.BR read (2)
+is called.
+.BR read (2)
+returns either when at least one byte of data is available,
+or when the timer expires.
+If the timer expires without any input becoming available,
+.BR read (2)
+returns 0.
+If data is already available at the time of the call to
+.BR read (2),
+the call behaves as though the data was received immediately after the call.
+.TP
+MIN > 0, TIME > 0 (read with interbyte timeout)
+TIME specifies the limit for a timer in tenths of a second.
+Once an initial byte of input becomes available,
+the timer is restarted after each further byte is received.
+.BR read (2)
+returns when any of the following conditions is met:
+.RS
+.IP \[bu] 3
+MIN bytes have been received.
+.IP \[bu]
+The interbyte timer expires.
+.IP \[bu]
+The number of bytes requested by
+.BR read (2)
+has been received.
+(POSIX does not specify this termination condition,
+and on some other implementations
+.\" e.g., Solaris
+.BR read (2)
+does not return in this case.)
+.RE
+.IP
+Because the timer is started only after the initial byte becomes available,
+at least one byte will be read.
+If data is already available at the time of the call to
+.BR read (2),
+the call behaves as though the data was received immediately after the call.
+.P
+POSIX
+.\" POSIX.1-2008 XBD 11.1.7
+does not specify whether the setting of the
+.B O_NONBLOCK
+file status flag takes precedence over the MIN and TIME settings.
+If
+.B O_NONBLOCK
+is set, a
+.BR read (2)
+in noncanonical mode may return immediately,
+regardless of the setting of MIN or TIME.
+Furthermore,
+if no data is available,
+POSIX permits a
+.BR read (2)
+in noncanonical mode to return either 0, or \-1 with
+.I errno
+set to
+.BR EAGAIN .
.SH STANDARDS
POSIX.1-2024.
.SH HISTORY
projects / thirdparty / man-pages.git / commitdiff
