How to write a pm-utils hook:

PARAMETERS

A pm-utils hook is simply an executable file that accepts a single parameter.
For hooks in sleep.d, the potential values of that parameter are:
suspend -- The hook MUST perform whatever action is appropriate when the
	system is preparing for S3 sleep (or its equivalent).
suspend_hybrid -- The hook MUST perform whatever action is appropriate 
		  when entering suspend mode.  The hook SHOULD also save
		  any state it may need to bring the system back from 
		  hibernate mode.
resume -- The hook MUST perform whatever action is appropriate when the 
	system is coming out of suspend.
hibernate -- The hook MUST perform whatever action is appropriate when 
	the system is preparing for suspend-to-disk.
thaw -- The hook MUST perform whatever action is appropriate when the system
	is coming out of suspend-to-disk.
help -- If your hook parses the PM_CMDLINE environment variable for switches, 
	this function SHOULD output text describing the parameters it parses
	in a format easily understandable by an end-user.

For hooks in power.d, the potential values of that parameter are:
true -- the hook MUST perform whatever action is appropriate when the system 
	transitions TO battery power.
false -- The hook MUST perform whatever action is appropriate when the system
	transitions FROM battery power.

NAMING SCHEME

All hooks are run in lexical sort order according to the C locale.

SLEEP.D SPECIFIC NOTES

For any given sleep/wakeup cycle, the hooks in sleep.d are run twice:
* Once in C lexical sort order before the system goes to sleep, and
* Once in reverse C lexical sort order when the system wakes up.

CONVENIENCE FUNCTIONS

If your hook is a shell script that supports POSIX/SuS compatible syntax, you
MAY source /usr/lib/pm-utils/functions, which will perform the following 
actions:

1: All settings present in the files located in /etc/pm/config.d/ will be
   available as environment variables.
2: The following convenience functions will be made available:
	1: try_lock
	2: spin_lock
	3: release_lock
	4: get_power_status
	5: modunload
	6: modreload
	7: stopservice
	8: restartservice
	9: savestate
	10: restorestate
    To get an overview of what each of those functions does and the parameters
    they accept, read the fine source.  Note that other functions may be 
    present -- those functions are internal to the pm-utils package and MUST NOT
    be used by external hooks.  In the future, those functions will not be
    available to third-party hooks.