NIO CommKit Host Interface Installation and System Administration Manual

3-16

Control Tables (from AT&T 255-110-127)

srvtab

NOTE: Different login names can be specified, based on the originating group name. For

example, luucp might be used for requests from local hosts, while nuucp would be

used for requests from unknown or “network” hosts. See the section Fixed User ID

Mapping, later in this chapter.

whoami The whoami service maps to an invocation of the echo

command and is used to echo back a string showing the

requester’s user number and originating group name.

Other services in the /etc/opt/dk/srvtab directory are provided as examples.

Flags Field

The flags ﬁeld of a server table mapping line contains one or more ﬂags that

may be used to control or modify the actions the server takes when process-

ing a call request that has been mapped to that line. Flags specify options

that are unique to the mapped line. A brief description of each ﬂag is pro-

vided in Table 3-1.

Table 3-1 Server Table Flags

Flag Description

a Additional arguments should be read from the incoming data channel be-

fore execution of the program. This flag should be specified only for re-

mote execution channels (see x option).

e Arranges for the exit code of the program to be passed back to the originat-

ing system. This flag should be specified only for remote execution chan-

nels.

h Invokes the mapped program with the SIGHUP hangup signal ignored. See

signal(2).

t Opens the tty mode data service and invokes the program with the stdin,

stdout, and stderr files attached to the /dev/dkt/?.??? device for the tty

channel. Note that the t flag should be used with caution when it is associ-

ated with non-standard service. The t flag uses a TTY interface that echoes

its input by default. Origination endpoints other than a user terminal (from

a DESTINATION prompt or a dkcu) will not receive the echoed data. If

the data is not drained by the originating endpoint the network will flow

control the echoed data, which will build up on the destination host. The

UNIX system STREAMS module ldterm that actually echoes the data, does

not honor flow control and will consume all of the STREAMS resources.