Open System Services System Calls Reference Manual (G06.25+, H06.03+)

tty(7) OSS System Calls Reference Manual
echoed as a return and does not terminate canonical mode input.
Input Modes
The termios structure has an input mode field c_iflag, which controls basic terminal input
characteristics. These characteristics are masks that can be bitwise inclusive ORed. The masks
include:
BRKINT An interrupt is signaled on a break condition.
ICRNL All carriage returns are mapped to newline characters when input.
IGNBRK Break conditions are ignored.
IGNCR Carriage returns are ignored.
INLCR Newline characters are mapped to carriage returns when they are input.
ISTRIP The 8th bit (parity bit) is stripped on input characters.
IXOFF STOP and START characters are sent to enable input flow control.
IXON STOP and START characters are recognized for output flow control.
PARMRK Parity errors are marked with a 3-character sequence.
The input mode mask bits can be combined for the following results.
• If IGNBRK is set, input break conditions are ignored. If IGNBRK is not set but
BRKINT is set, the break condition has the same effect as if the VINTR control charac-
ter had been typed; that is, a SIGINT signal is generated. If neither IGNBRK nor
BRKINT are set, then the break condition is input as a single character 0x00 (zero). If
the PARMRK flag is also set, then the input is read as three characters, 0xff, 0x00, and
0x00.
• If PARMRK is set, a byte with a parity or framing error, except for breaks, is passed as
the three characters 0xff, 0x00, and X, where X is the character data received in error. If
ISTRIP is not set, the valid character 0xff is passed as 0xff, 0xff. If PARMRK is not
set, framing or parity errors, including breaks, are passed as the single character 0x00.
• Setting ISTRIP causes the 8th bit of the 8 valid input bits to be stripped before process-
ing. If ISTRIP is not set, all 8 bits are processed.
• Setting INLCR causes a newline character to be read as a carriage return character. If
IGNCR is also set, the carriage return is ignored. If IGNCR is not set, INLCR works as
described earlier in Input Modes.
• The STOP character (normally <Ctrl-S>) suspends output, and the START character
(normally <Ctrl-Q>) restarts output. Setting IXON enables stop/start output control, in
which the START and STOP characters are not read but rather perform flow control
functions. Extra STOP characters typed when output is already stopped have no effect,
unless the START and STOP characters are made the same, in which case output
resumes. If IXON is not set, the START and STOP characters are read.
• If IXOFF is set, stop/start input control is enabled. When IXOFF is set, the terminal
device is sent STOP characters to halt the transmission of data when the input queue is
in danger of overflowing (exceeds the size MAX_INPUT/2). When enough characters
are read to reduce the amount of data queued to an acceptable level, a START character
is sent to the device to allow it to continue transmitting data. This mode is useful when
the terminal is actually another machine that obeys these conventions.
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