acpid - Advanced Configuration and Power Interface event daemon
acpid is designed to notify user-space programs of ACPI events. acpid
should be started during the system boot, and will run as a background
process, by default. It will open an events file (/proc/acpi/event by
default) and attempt to read whole lines which represent ACPI events.
If the events file does not exist, acpid will attempt to connect to the
Linux kernel via the input layer and netlink. When an ACPI event is
received from one of these sources, acpid will examine a list of rules,
and execute the rules that match the event. acpid will ignore all
incoming ACPI events if a lock file exists (/var/lock/acpid by
Rules are defined by simple configuration files. acpid will look in a
configuration directory (/etc/acpi/events by default), and parse all
regular files that do not begin with a period (’.’) or end with a tilde
(~). Each file must define two things: an event and an action. Any
blank lines, or lines where the first character is a hash (’#’) are
ignored. Extraneous lines are flagged as warnings, but are not fatal.
Each line has three tokens: the key, a literal equal sign, and the
value. The key can be up to 63 characters, and is case-insensitive
(but whitespace matters). The value can be up to 511 characters, and
is case and whitespace sensitive.
The event value is a regular expression (see regcomp(3)), against which
events are matched.
The action value is a commandline, which will be invoked via /bin/sh
whenever an event matching the rule in question occurs. The
commandline may include shell-special characters, and they will be
preserved. The only special characters in an action value are "%"
escaped. The string "%e" will be replaced by the literal text of the
event for which the action was invoked. This string may contain
spaces, so the commandline must take care to quote the "%e" if it wants
a single token. The string "%%" will be replaced by a literal "%".
All other "%" escapes are reserved, and will cause a rule to not load.
This feature allows multiple rules to be defined for the same event
(though no ordering is guaranteed), as well as one rule to be defined
for multiple events. To force acpid to reload the rule configuration,
send it a SIGHUP.
In addition to rule files, acpid also accepts connections on a UNIX
domain socket (/var/run/acpid.socket by default). Any application may
connect to this socket. Once connected, acpid will send the text of
all ACPI events to the client. The client has the responsibility of
filtering for messages about which it cares. acpid will not close the
client socket except in the case of a SIGHUP or acpid exiting.
acpid will log all of its activities, as well as the stdout and stderr
of any actions, to syslog.
All the default files and directories can be changed with commandline
-c, --confdir directory
This option changes the directory in which acpid looks for
rule configuration files. Default is /etc/acpi/events.
-C, --clientmax number
This option changes the maximum number of non-root socket
connections which can be made to the acpid socket. Default
-d, --debug This option increases the acpid debug level by one. If the
debug level is non-zero, acpid will run in the foreground,
and will log to stderr, in addition to the regular syslog.
-e, --eventfile filename
This option changes the event file from which acpid reads
events. Default is /proc/acpi/event.
This option forces acpid to use the Linux kernel input
layer and netlink interface for ACPI events.
This option keeps acpid in the foreground by not forking at
This option tells acpid to log information about all events
-L, --lockfile filename
This option changes the lock file used to stop event
processing. Default is /var/lock/acpid.
-g, --socketgroup groupname
This option changes the group ownership of the UNIX domain
socket to which acpid publishes events.
-m, --socketmode mode
This option changes the permissions of the UNIX domain
socket to which acpid publishes events. Default is 0666.
-s, --socketfile filename
This option changes the name of the UNIX domain socket
which acpid opens. Default is /var/run/acpid.socket.
-S, --nosocket filename
This option tells acpid not to open a UNIX domain socket.
This overrides the -s option, and negates all other socket
-p, --pidfile filename
This option tells acpid to use the specified file as its
pidfile. If the file exists, it will be removed and over-
written. Default is /var/run/acpid.pid.
Print version information and exit.
-h, --help Show help and exit.
This example - placed in /etc/acpi/events/power - will shut down your
system if you press the power button.
The script power.sh gets called and will see the complete event string
as parameter $1.
acpid should work on any linux kernel released since 2003.
There are no known bugs. To file bug reports, see AUTHORS below.
regcomp(3), sh(1), socket(2), connect(2)
Tim Hockin <email@example.com>