kbd(7)kbd(7)NAMEkbd - generalized string translation module
DESCRIPTION
The STREAMS module kbd is a programmable string translation module. It
can perform two types of operations on an input stream: the first type is
simple byte-swapping via a lookup table, the second is string
translation. It is useful for code set conversion and compose-key or
dead-key character production on terminals and production of overstriking
sequences on printers. It may also be used for minor types of key-
rebinding, expansion of abbreviations, and keyboard re-arrangement (an
example of the latter would be swapping the positions of the Y and Z
keys, required for German keyboards, or providing Dvorak keyboard
emulation for QWERTY keyboards). The manual entry kbdcomp(1M) discusses
table construction, the input language, and contains sample uses. This
document is intended mainly to aid administrators in configuring the
module on a particular system; the user interface to the module is solely
through the commands kbdload(1M) and kbdset(1).
The kbd module works by modifying an input stream according to
instructions embodied in tables. It has no built in default tables.
Some tables may be loaded when the system is first brought up by pushing
the module and loading standard or often-used tables [see kbdload(1M)]
which are retained in main-memory across invocations and made available
to all users. These are called public tables. Users may also load
private tables at any time-these do not remain resident.
With the kbdset command, users may query the module for a list of
available and attached tables, attach various tables, and set the
optional per-user hot-key, hot-key mode, and verbose string for their
particular invocation.
When a user attaches more than one table, the user's hot-key may be used
to cycle to the next table in the list. If only one table is specified,
the hot-key may be used to toggle translation on and off. When multiple
tables are in use, the hot-key may be used to cycle through the list of
tables. [See kbdset(1) for a description of the available modes.]
In its initial state, kbd scans input for occurrences of bytes beginning
a translation sequence. Upon receiving such a byte, it attempts to match
subsequent bytes of the input to programmed sequences. Input is buffered
beginning with the byte which caused the state change and is released if
a match is not found. When a match fails, the first byte of the invalid
sequence is sent upstream, the buffered input is shifted, and the scan
begins again with the resulting input sequence. If the current table
contains an error entry, its value (one or more bytes) is substituted for
the offending input byte. When a sequence is found to be valid, the
entire sequence is replaced with the result string specified for it.
The kbd module may be used in either the read or write directions, or
both simultaneously. Maps and hot-keys may be specified independently
for input and output.
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kbd(7)kbd(7)
The kbd also supports the use of external kernel-resident functions as if
they were tables; once declared and attached (via kbdload and kbdset
respectively) they may be used as simple tables or members of composites.
To accomplish this, kbd understands the registration functions of the alp
module and can access any function registered with that module. Further
information on external functions and their definition is contained in
alp(7). External functions are especially useful in supporting multibyte
code set conversions that would be difficult or impossible with normal
kbd tables.
Limitations
It is not an error to attach multiple tables without defining a hot-key,
but the tables will not all be accessible. It is recommended that the
user's hot-key be set before loading and attaching tables to avoid
unpleasant side effects when an unfamiliar arrangement is first loaded.
Each user has a limitation on the amount of memory that may be used for
private and attached tables. This ``quota'' is controlled by the kbd_umem
variable described below. When a user that is not the super-user
attempts to load a table or create a composite table, the quota is
checked, and the load will fail if it would cause the quota to be
exceeded. When a composite table is attached, the space for attachment
(which requires more space than the composite table itself) is charged
against this quota (attachment of simple tables is not charged against
the quota). The quota is enforced only when loading new tables.
Detaching temporarily from unneeded composite tables may reduce the
current allocation enough to load a table that would otherwise fail due
to quota enforcement. To minimize chances of failure while loading
tables, it is advisable to load all required tables and make all required
composite tables before attaching any of them.
Configuration Parameters
The master (or space.c) file contains some configurable parameters.
NKBDU is the maximum number of tables that may be attached by a single
user. The number should be large enough to cover uncommon cases, and
must be at least 2. Default is 6.
ZUMEM, from which the variable kbd_umem is assigned, is the maximum
number of bytes that a user (other than the super user) may have
allocated to private tables (that is, the quota). Default is 4096.
KBDTIME is the default timer value for timeout mode. It is the number of
clock ticks allowed before timing out. The value of one clock tick
depends on the hardware, but is usually 1/100 or 1/60 of a second. A
timeout value of 20 is 1/5 second at 100Hz; with a 60Hz clock, a value of
12 produces a 1/5 second timeout. Values from 5 to 400 inclusive are
allowed by the module; if the value set for KBDTIME is outside this
range, the module forces it to the nearest limit. (This value is only a
default; users may change their particular stream to use a different
value depending on their own preferences, terminal baud-rate, and typing
speed.)
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kbd(7)kbd(7)FILES
/usr/lib/kbd - directory containing system standard table files.
/usr/lib/kbd/*.map - source for some system table files.
SEE ALSOkbdset(1), kbdcomp(1M), kbdload(1M), alp(7).
NOTES
NULL characters may not be used in result or input strings, because they
are used as string delimiters.
One should be able to obtain information on timeout values of currently
attached tables, and be able to reset values more easily.
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