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termio(7I) Ioctl Requests SunOS 5.5

The ERASE andKILL characters may be entered literally by preceding them with the

escape character (\). In this case, the escape character is not read. The erase and kill

characters may be changed.

Non-canonical mode

input processing

In non-canonical mode input processing, input characters are not assembled into lines,

and erase and kill processing does not occur. The MIN and TIME values are used to

determine how to process the characters received.

MIN represents the minimum number of characters that should be received when the

read is satisﬁed (that is, when the characters are returned to the user). TIME is a timer of

0.10-second granularity that is used to timeout bursty and short-term data transmissions.

The four possible values for MIN and TIME and their interactions are described below.

Case A: MIN >0,TIME >0

In this case, TIME serves as an intercharacter timer and is activated after the ﬁrst

character is received. Since it is an intercharacter timer, it is reset after a character

is received. The interaction between MIN and TIME is as follows: as soon as one

character is received, the intercharacter timer is started. If MIN characters are

received before the intercharacter timer expires (note that the timer is reset upon

receipt of each character), the read is satisﬁed. If the timer expires before MIN

characters are received, the characters received to that point are returned to the

user. Note that if TIME expires, at least one character will be returned because

the timer would not have beenenabled unless a character was received. In this

case (MIN >0,TIME > 0), the read sleeps until the MIN and TIME mechanisms

are activated by the receipt of the ﬁrst character. If the number of characters read

is less than the number of characters available, the timer is not reactivated and

the subsequent read is satisﬁed immediately.

Case B: MIN >0,TIME =0

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 untilMIN characters are

received (the pendingread sleeps until MIN characters are received). A program

that uses this case to read record based terminalI/O may block indeﬁnitely in the

read operation.

Case C: MIN =0,TIME >0

In this case, since MIN =0,TIME no longer represents an intercharacter timer: it

now serves as a read timer that is activated as soon as a read is done. A read is

satisﬁed as soon as a single character is received or the read timer expires. Note

that, in this case, if the timer expires, no character is returned. If the timer does

not expire, the only way the read can be satisﬁed is if a character is received. In

this case, the read will not block indeﬁnitely waiting for a character; if no charac-

ter is received within TIME∗.10 seconds after the read is initiated, the read

returns with zero characters.

Case D: MIN =0,TIME =0

In this case, return is immediate. The minimum of either the number of charac-

ters requested or the number of characters currently available is returned

without waiting for more characters to be input.

7I-348 modiﬁed 30 May 1995

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