Hur snabbt kan jag få veta att en räknare fått en puls? Finns det någon genväg
så jag slipper låta datorn att loopa och fråga räknaren? Helst vill jag veta samtidigt
som pulsen kommer. Finns det andra enheter som kan sköta den saken istället
för owfs?
Vissa 1wire-komponenter har larm, hur fungerar det?
Sätter man bara max-resp. min-gränser där?
Mjukvaran måste läsa räknaren och jämföra med tidigare räknarvärde. !-Wire arbetar enl. kontroller/slav, dvs en slav kan inte meddela sig till kontrollern utan att först få en fråga från kontrollern.
Andra enheter än OWFS? Menar du andra mjukvaror? Ja, det finns det; digitemp för linux, BM för Windows, mfl.
Ja, vissa enheter stöder larm indikering genom jämförelse med konfigurerade värden. Det finns ett speciellt sök-läge för 1-Wire nät som gör att man kan hitta alla sensorer som larmar, utan att först behöva läsa varje sensor.
För mer detaljer rekommenderar jag dig att läsa databladen för sensorerna.
När det gäller andra enheter så funderade jag kring någon hårdvara som kollar åt mig.
Det slog mig att jag har en Basic Stamp2 liggande till ingen nytta. Kanske den kan kolla
t.ex. ena kanalen på räknaren som mäter energi medan andra kanalen övervakar något annat och
blir en sorts larm som signalerar när någon händer?
Får labba lite.
fam is a server that tracks changes to the filesystem and relays these changes to interested applications. Applications such as fm(1G) and mailbox(1) present an up-to-date view of the filesystem. In the absence of fam, these applications and others like them are forced to poll the filesystem to detect changes. fam is more efficient.
Applications can request fam to monitor any files or directories in any filesystem. When fam detects changes to monitored files, it notifies the appropriate application. The FAM API provides a programmatic interface to fam; see fam(3X).
fam is informed of filesystem changes as they happen by the kernel through the imon(7M) pseudo device driver. If asked to monitor files on an NFS mounted filesystem, fam tries to use fam on the NFS server to monitor files. If fam cannot contact a remote fam, it polls the files instead. fam also polls special files.
Normally, fam is started by inetd(1M). It is registered with portmap(1M) as performing the sgi_fam service.
OPTIONS
-l Disable polling of NFS files. It does not disable use of remote fam on NFS servers, nor does it disable polling of local files.
-t NFS_polling_interval Set the interval for polling files to NFS_polling_interval seconds. The default is six
seconds.
-T idle_timeout Set the idle timeout interval to idle_timeout. fam exits idle_timeout seconds after its
last client disconnects. A value of 0 causes fam to wait indefinitely for new connections. The default is five seconds.
-f Remain in the foreground instead of spawning a child and exiting. This option is ignored if fam is
started by inetd.
-v Turn on verbose messages.
-d Enable verbose messages and debug messages.
-p program.version Use the specified RPC program and version numbers.
-L Local-only mode. fam will only accept requests from clients running on the local machine. This overrides the local_only flag in the configuration file. This option is ignored if fam is started by inetd.
-C Compatibility mode. This disables authentication and reduces access security as described under SECURITY below. This overrides the insecure_compatibility flag in the configuration file.
-c config_file Read configuration information from the given file rather than the default, which is
/etc/fam.conf.
CONFIGURATION FILE
In addition to its command-line options, fam's behavior can also be controlled through its configuration file. By default, this is /etc/fam.conf; the -c command-line option can be used to specify an alternate file. Configuration lines are in the format option=value. Lines beginning with # or ! are ignored. fam recognizes the following options:
insecure_compatibility If set to true, this disables authentication and reduces access security as described
under SECURITY below. This is false by default. Setting this option to true is the same as using the -C command-line option.
untrusted_user This is the user name or UID of the user account which fam will use for unauthenticated clients. If a file can't be stat'ed by this user, fam will not tell unauthenticated clients about the file's existence. If an untrusted user is not given in the configuration file, fam will write an error message to the system log and terminate.
local_only If set to true, fam will ignore requests from remote fams. This is false by default. Setting
this option to true is the same as using the -L command-line option. This option is ignored if fam is started by inetd.
idle_timeout This is the time in seconds that fam will wait before exiting after its last client disconnects. The default is five seconds. This option is overridden by the -T command-line option.
nfs_polling_interval This is the interval in seconds between polling files over an NFS filesystem. The default is six seconds. This option is overridden by the -t command-line option.
xtab_verification If set to true, fam will check the list of exported filesystems when remote requests are
received to verify that the requests fall on filesystems which are exported to the requesting hosts. This is true by default. If this option is set to false, fam will service remote requests without attempting to perform the verification. If the local_only configuration option or -L command-line option is used, xtab_verification has no effect.
SECURITY
For backward compatibility, the -C command-line option and insecure_compatibility configuration option can be used to disable authentication. Configuring fam this way opens a publically known security weakness whereby a "rogue client" can obtain the names of all the files and directories on the system.
Note that fam never opens the files it's monitoring, and cannot be used by a rogue client to read the contents of any file on the system. fam only gives out the names of monitored files, and only monitors files which the client can stat(1M). Users can stat a file without having read permission on it as long as they have search permission on the directory containing it.
