Terminals 1305ICANON
Setting the ICANON flag enables canonical mode input. Input is gathered into lines,
and special interpretation of the EOF, EOL, EOL2, ERASE, LNEXT, KILL,
REPRINT, and WERASE characters is enabled (but note the effect of the IEXTEN
flag described below).
IEXTEN
Setting the IEXTEN flag enables extended processing of input characters. This flag
(as well as ICANON) must be set in order for the following characters to be inter-
preted: EOL2, LNEXT, REPRINT, and WERASE. The IEXTEN flag must also be set
for the IUCLC flag to be effective. SUSv3 merely says that the IEXTEN flag enables
extended (implementation-defined) functions; details may vary on other UNIX
implementations.
IMAXBEL
On Linux, the setting of the IMAXBEL flag is ignored. On a console login, the bell is
always rung when the input queue is full.
IUTF8
Setting the IUTF8 flag enables cooked mode (Section 62.6.3) to correctly handle
UTF-8 input when performing line editing.
NOFLSH
By default, when a signal is generated by typing the INTR, QUIT, or SUSP character,
any outstanding data in the terminal input and output queues is flushed (dis-
carded). Setting the NOFLSH flag disables such flushing.
OPOST
Setting the OPOST flag enables output postprocessing. This flag must be set in order
for any of the flags in the c_oflag field of the termios structure to be effective. (Put
conversely, disabling the OPOST flag prevents all output postprocessing.)
PARENB, IGNPAR, INPCK, PARMRK, and PARODD
The PARENB, IGNPAR, INPCK, PARMRK, and PARODD flags are concerned with parity genera-
tion and checking.
The PARENB flag enables generation of parity check bits for output characters
and parity checking for input characters. If we want to perform only output parity
generation, then we can disable input parity checking by turning INPCK off. If the
PARODD flag is set, then odd parity is used in both cases; otherwise, even parity is
used.
The remaining flags specify how an input character with parity errors should be
handled. If the IGNPAR flag is set, the character is discarded (not passed to the reading
process). Otherwise, if the PARMRK flag is set, then the character is passed to the read-
ing process, but is preceded by the 2-byte sequence 0377 + 0. (If the PARMRK flag is set
and ISTRIP is clear, then a real 0377 character is doubled to become 0377 + 0377.) If
PARMRK is not set, but INPCK is set, then the character is discarded, and a 0 byte is