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. When a line is received (an
event), acpid will examine a list of rules, and execute the rules that
match the event.
Rules are defined by simple configuration files. acpid will look in a
configuration directory (/etc/acpi/events by default), and parse all
files that do not begin with a period (’.’). Each file must define two
things: an event and an action. Any blank lines, or lines where the
first character is a pound sign (’#’) 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 sen-
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 command-
line 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 comman-
dline 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 it’s activities, as well as the stdout and stderr
of any actions to a log file (/var/log/acpid by default).
All the default file 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.
-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 stdout/stderr, rather than a log file.
-e, --eventfile filename
This option changes the event file from which acpid reads
events. Default is /proc/acpi/event.
-g, --socketgroup groupname
This option changes the group ownership of the UNIX domain
socket to which acpid publishes events.
-l, --logfile filename
This option changes the log file to which acpid writes.
Default is /var/log/acpid.
-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
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.
Please make sure you are using the latest ACPI code possible. This is
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>
August 2001 acpid(8)
Man(1) output converted with