10-05-2001
Hello Perderabo,
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"
I know that my method leaves a sleep process running if the timed command completes in time. I think that's harmless. It will be reaped by init when it exits. That's the only real cost of a very easily coded solution. Capturing and killing that last pid will drive script back up in complexity.
"
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Does sleep process creates any kind of overhead for the unix system.
When I execute the following command (sleep 30; echo hello) &
, it create the two processes one is the shell process and the other is sleep process and the sleep process pid is always 1 greater than the shell process pid. Is it always true ?.
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LEARN ABOUT MOJAVE
caffeinate
CAFFEINATE(8) BSD System Manager's Manual CAFFEINATE(8)
NAME
caffeinate -- prevent the system from sleeping on behalf of a utility
SYNOPSIS
caffeinate [-disu] [-t timeout] [-w pid] [utility arguments...]
DESCRIPTION
caffeinate creates assertions to alter system sleep behavior. If no assertion flags are specified, caffeinate creates an assertion to pre-
vent idle sleep. If a utility is specified, caffeinate creates the assertions on the utility's behalf, and those assertions will persist for
the duration of the utility's execution. Otherwise, caffeinate creates the assertions directly, and those assertions will persist until
caffeinate exits.
Available options:
-d Create an assertion to prevent the display from sleeping.
-i Create an assertion to prevent the system from idle sleeping.
-m Create an assertion to prevent the disk from idle sleeping.
-s Create an assertion to prevent the system from sleeping. This assertion is valid only when system is running on AC power.
-u Create an assertion to declare that user is active. If the display is off, this option turns the display on and prevents the display
from going into idle sleep. If a timeout is not specified with '-t' option, then this assertion is taken with a default of 5 second
timeout.
-t Specifies the timeout value in seconds for which this assertion has to be valid. The assertion is dropped after the specified time-
out. Timeout value is not used when an utility is invoked with this command.
-w Waits for the process with the specified pid to exit. Once the the process exits, the assertion is also released. This option is
ignored when used with utility option.
EXAMPLE
caffeinate -i make
caffeinate forks a process, execs "make" in it, and holds an assertion that prevents idle sleep as long as that process is running.
SEE ALSO
pmset(1)
LOCATION
/usr/bin/caffeinate
Darwin November 9, 2012 Darwin