*nix command that waits a specified number of seconds before executing another command. It is usually used in shell scripts.

sleep seconds
slashdot effect = S = slim

sleep vi.

1. [techspeak] To relinquish a claim (of a process on a multitasking system) for service; to indicate to the scheduler that a process may be deactivated until some given event occurs or a specified time delay elapses. 2. In jargon, used very similarly to v. block; also in `sleep on', syn. with `block on'. Often used to indicate that the speaker has relinquished a demand for resources until some (possibly unspecified) external event: "They can't get the fix I've been asking for into the next release, so I'm going to sleep on it until the release, then start hassling them again."

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

I have learned a lot from my sleeping (and lack thereof) experiences. For example, a lot of people aren't aware of this, but the ratio of awake time to sleep time is almost always 2:1. You can see this every day in the suggested 16 hours awake/8 hours asleep. This can also be extended to 18 hours awake/9 hours asleep and so forth. Using this knowledge, I wanted to figure out something: If I have been awake A hours and want to wake up B hours from now after a complete 2:1 sleep, in how many hours (Z) should I fall asleep? Well, after doing a small bit of math, I figured out a good formula for it. Here's a look at my work.

"Time from when I woke up until now" + "Time until I fall asleep" + "Time from when I fall asleep until I wake up" = "Time from when I woke up until now" + "Time from now until I wake up"
A + Z + (A + Z)/2 = A + B
2Z + (A + Z) = 2B
3Z = 2B - A
Z = (2B - A)/3
Thus, to figure out how long I must wait until I fall asleep, I multiply how long until I want to wake up by 2, then subtract how long I've been awake, then finally divide by three. If the number is negative, it is too late and if it is zero... SLEEP!!!
(Note: This assumes you had a full sleep and are fully awake by the time you first awake. Also, if you cannot make it, do not attempt it. If it is that long that you cannot make it, it's probably long enough to separate into two sleeps.)

Now for some examples:
Lets say I've been up since 2 pm yesterday and it is 9 am now and I want to wake up at 8 am tomorrow, when should I fall asleep (even if I could already right now). Well, I want to wake up in 23 hours and I've been up 19 hours already. Applying my formula, I should fall asleep in (46 - 19)/3, or 9 hours. That means I will have a total of 28 hours of being awake and 14 hours from 6 on (9 hours after 9AM) is 8AM. It works! My ratio is 28/14, or 2:1.
Now lets say I've been up since 6 am and it's now midnight and I need to wake up at 6 am with the correct ratio, is this possible? Well, (12 - 18)/3 < 0, so no, it isn't possible. If I fell asleep right now, my ratio would be 3:1, blegh.

Historically, sleep was thought to be a temporary death. Sleepers would have no conscious control or volition. This influenced scientific thought for a long while, even up into the beginning of the twentieth century. Many researchers and scientists believed that sleep was a rest for the mind when it went into was completely cut off from the rest of the body. Today though, we know many of these thoughts to be untrue. During sleep, the brain is not cut off from the body; in fact, it very strictly controls the body during resting hours. In addition, we know that the brain is not merely in torpor during sleep, but actually undergoes many biological processes.

The path followed by sleepers has been well documented by twentieth century researchers. The journey of sleep starts out with the soon to be sleeper in a relaxed state of alpha wave production. Contrary to myth, the sleeper does not slowly drift into sleep. Rather, there is a rapid changeover to somnolence over the course of about a minute. During this changeover, the alpha waves of a relaxed state change over to theta waves. This signifies stage one sleep, the lightest of four distinct stages. During stage one sleep, the individual may experience broken or fragmented hallucinations that lack form. Also during this time, brain waves continue to slow in frequency and muscles relax throughout the sleeper’s body. After a point, stage two sleep is achieved. During stage two sleep, theta brain waves are still the dominant pattern in a sleepers brain, however, these theta waves are interrupted by spindles and K complexes. Spindles are brief periods of beta wave activity that show up during stage two sleep. K complexes are high amplitude, high frequency waves that show up individually also in stage two sleep. Approximately twenty minutes after falling asleep, the sleeper moves into stage three sleep. This state is categorized by a switch into low frequency delta waves, relaxed muscles, slowed cardiac and pulmonary rates, lower blood pressure, and a slowing of digestion. Later, the sleeper shifts over to stage four sleep. This is the deepest stage of sleep, and it is difficult to rouse an individual from this state. After this stage, though, the sleeper begins to reverse the process, going back to stage three and then to stage two sleep. Instead of going back to stage one though, a new phenomenon occurs. Brainwaves that had been in the slow delta frequency, switch over into the beta range of normal conscious thought. At the same time, all voluntary muscles relax while the eyes start to move rapidly under the eyelids. This cycle of sleep, known as REM (Rapid Eye Movement) sleep, is the time when dreams occur. It lasts for three to ten minutes. The process described above describes the first sleep cycle. Each cycle lasts for about ninety minutes. Stage one sleep occurs only in the first and last sleep cycles: right after falling asleep and right before waking up. The amount of time spent in stages three and four sleep also decrease every cycle. The brain goes through lighter and lighter sleep as the night progresses. The time spent in these deeper sleeps is replaced with REM sleep so that in the cycle before waking, an individual may experience up to forty-five minutes of dreaming.

Sleep is strictly controlled by the brain. More specifically, the brainstem and hypothalamus. The brainstem has two specialized areas that help control sleep: the raphe nuclei and the locus coeruleus. These areas use the neurotransmitters, noradrenaline, serotonin, and acetylcholine to control sleep. These areas are in turn controlled by our circadian rhythms. Circadian rhythms are our internal clocks that tell the body when to undergo different processes. Using a mixture of hormones and nervous system activity, the circadian clock keeps an almost perfect twenty-five hour day. Since a day on Earth is only twenty-four hours though, the circadian clock requires constant updates to keep it running at the proper time. These updates are received from the external environment. In humans, the suprachiasmatic nuclei, found next to the thalamus, receives direct sensory information from the eyes to help regulate the internal clock.

Sleep is required for well being. People who are deprived of sleep will begin to fall apart physically and mentally. Studies in rats have shown what happens to organisms that go without sleep. The rats would become feverish and, even though their appetite increased, they would lose weight. In addition to these symptoms, the rats would cease to groom themselves, and also developed lesions on their skins. The rats body temperatures would begin to drop as well, and they would eventually die. While, for obvious reasons, this experiment can’t be repeated with humans, it stands to reason that a human deprived of sleep long enough would show many of the same symptoms and maladies of sleep deprivation. One reason that these symptoms may occur is that several hormones are secreted during sleep. These hormones tell cells to repair themselves as well as promoting healing on a tissue level. Scientists believe that the secretions occur during the third and fourth stages of sleep when delta waves are produced. People deprived of delta sleep will begin to develop generalized muscle aches over a period of several weeks to months.

With the discovery of REM sleep, research opened up on dreams and dreaming. Scientists have found that dreams are carried out by almost all of the brain. Activity begins in the lower, more primal regions of the brain and, from there, spreads to the higher more advanced parts of the brain like the neocortex. While dreaming, rapid frequency beta waves are produced, these waves are indicative of concentration and mental activity. During dreams, activated parts of the brain, not knowing that they are asleep, send messages to muscles telling them to move. However, knowing that the brain is asleep, the brainstem sends out messages that cancel the orders sent by the motor controllers in the brain. If this were not the case, dreamers would act out the dream scenes with possibly horrible results. The brainstem allows many functions to be affected by dreaming however. Muscles controlling the eyes and ears are allowed to flex (internally in the case of the ears) trying to see or hear what is being dreamt about. At the same time, heart and respiratory rates increase. This corresponds with an increase in blood flow to the brain to support its flurry of activity.

Many theories exist that attempt to explain why people dream. One researcher suggests that dreaming is exercise for the brain. In the young, it would help to establish neural connections, and in the mature would make sure that everything is in working order. Another theory suggests that dreams are used to program instinctual behaviors. Dreams teach the brain to do things that at first are only available to us in our genetic code. Yet another theory tells us that dreaming is a way to reinforce our memory. Dreams would reactivate the circuits in our brain where memory is stored, thus strengthening them. There is evidence to help hold up this theory in that those deprived of REM sleep often have trouble learning and remembering. Sigmund Freud, a famous psychologist, theorized that dreams were the brains way of showing repressed impulses and desires to the conscious mind. However, since the conscious mind doesn’t want to see much of what is being shown, the dreams come in code. Instead of being forthright, the images in dreams come in symbols and codes that may be interpreted by those who know what they mean. This may be the reason that many people from many different cultures and areas report having dreams with similar themes. These themes include falling, flying, and being chased, as well as the presence of certain animals, fire, and water.

During sleep, an individual may experience scary or terrifying experiences. These tend to fall in to one of two categories: nightmares and night terrors. Nightmares occur during REM sleep. They occur as normal dreams that in some way scare the dreamer. Depending on how horrifying the dream is, the sleeper may stay asleep and continue to experience the dream, or wake in attempt to escape it. In the latter case, nightmares are often remembered by the now awake individual. Night terrors though are a completely different story. Affecting mostly young children, night terrors occur during delta sleep. The child will suddenly wake screaming or crying with very little or no memory of what occurred other than the fact that it was terrifying. He or she may continue to scream or cry for several minutes before calming down. Often the child will then return to sleep and have mostly or entirely have forgotten about the experience by morning. The adult versions of night terrors are called incubus. During stage four sleep, a sufferer of this phenomenon will suddenly wake up. This rousing is accompanied by a feeling of weight on the chest as well as an indescribable feeling of anxiety. The sufferer will not have any memory of any dreams though that caused this state.

"Methought I heard a voice cry "Sleep no more!
Macbeth does murder sleep," the innocent sleep, (2.2.33)
Sleep that knits up the ravell'd sleave of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great nature's second course, (2.2.36)
Chief nourisher in life's feast,--"

--From "Macbeth -- Act 2 Scene 2" by William Shakespeare

Macbeth utters these lines as he ruminates with Lady Macbeth, his wife; upon the murderous deeds he has just completed, namely killing King Duncan in his sleep, therefore effectively removing the most difficult obstacle to his own ascendancy to the throne. In these few lines William Shakespeare, the author of Macbeth; paints a picture of brutality and at the same time reinforces the idea of sleep as innocence incarnate, the very essence of it. One of the few things we keep from our childhood, it is a moment where, as Macbeth so murderously illustrated, we are at our most vulnerable.

Just a moment of rest at the twilight of the day, yet also a gateway into sublimity and the unconscious mind, we rarely can sleep well if around someone we don't trust or like. But being in the presence of a trusted or loved one, we can instantly drift, without hesitation or fear. Macbeth knows this, as he fears that by betraying the trust of sleep, he has actually 'murdered' sleep for himself, sleep that is precious and the "Chief nourisher in life's feast,".

In these lines and the scene before, Macbeth has not only murdered another human being, and not only sleep, but trust and innocence as well, the qualities of sleep. We all sleep in our beds and under the roofs of our houses so soundly, because we trust these places and that warmth that is trust envelopes us as sleep. Like angels coming and sprinkling glittering jewels of sleep on our persons. If one day I were to lose sleep over something I have done, like Macbeth, who will "Sleep no more!", I will surely know that I have lost something inside of me.

The fear, during childhood, of monsters and demons, that haunt us, just before we fade away, pulling us back to the waking world, returns as guilt and sorrow and other psyche-polluting creatures, in our adulthood, and then we begin to treasure how immeasureably beautiful the simple act of resting our heads and laying down our bodies truly is. Metallica sings of these childhood fears, in "Enter Sandman" where James Hetfield, the lead singer admonishes the sleepy protagonist to "Say your prayers, little one," an appropriate piece of advice.

Tonight before I sleep, I will say a prayer, I think, of gratitude for my lively sleep.

Some Sleep Facts

• Your heart can stop beating for as long as 9 seconds while you’re asleep.
• Sleep deprivation lasting more than 48 hours typically causes hallucinations and psychosis.
• The world record for going without sleep is 11 days (264 hours and 12 minutes) a feat considered extremely dangerous by sleep researchers.
• 30 million Americans suffer from sleep disorders. Most men begin having problems falling asleep in their mid-twenties; women have the same difficulty during their mid-forties.
• While normal sleepers change body positions about 30 times per night, insomniacs may toss and turn more than 100 times.
• Dream sleep has been observed in all animals studied except the spiny anteater.
• Sleep studies show that if your sleeping partner is absent in your sleep, you’ll almost always mover over to the side the bed normally occupied by him or her. (I know for a fact I do.)
• An afternoon nap is healthy. One study indicates that afternoon nappers are 30 percent less likely to suffer coronary artery disease, although the reasons behind this are not yet known.
• Humans stay awake much longer than many animals. Bats, cats, porcupines, lions, gorillas, and opossums sleep 18 to 20 hours a day, and some woodchucks snooze for as long as 22 hours.
• Pigeons frequently open their eyes during sleep to watch for predators. The dolphin, remarkably, only “half” sleeps: its brain shuts down only one hemisphere at a time.
• Horses and rats dream 20 percent of the time during sleep. Cows kept in barns dream 40 minutes per night, while cows sleeping in meadows dream only half as much.

http://abc.net.au/science/sleep/default.htm
http://www.prescriptionforsleep.com/index.html
http://www.brpt.org/sleep_facts.htm
and research I did for a college course

Our sleep doctor, a pulmonologist, gave us a wonderful update talk on sleep in early 2009.

He said, "First of all, I hate that blue butterfly." For those who do not watch tv or read magazines in the United States, the blue butterfly is in advertisements for a sleep medicine.

"The blue butterfly lies," he said. "Eight hours sleep is NOT normal and NOT average."

The average amount of sleep for an adult is 7.5 hours. Some people need more, some people need less. I need 6 to 6.5 except on the first day of menses, when my body prefers 10-11 hours. Too much information?

"Catching up is a myth." He said that we don't catch up on sleep after the first night. I get people all the time in clinic who say that they haven't slept for a month and "need to catch up." The first night with a sleep medicine, people catch up some but that is it. After that, their body returns to their average.

Alcohol is bad for sleep. Yes, I know, it makes you fall asleep faster. However, it is not normal sleep and you will wake when it wears off, in 3-5 hours. And you may be a bit jittery and anxious, especially if you have more than 2 drinks a night routinely. Hello, I said that is the alcohol wearing off. Are you partly addicted? Tell me you can't fall asleep at all without it? Want a pill instead?

Sleep pills are really alcohol in pill form. Really, really, really. We use benzodiazepines -- that is, valium, ativan, librium, etc. for alcohol withdrawal because it has the same mechanism of action. In other words, we are substituting the benzo for the alcohol and then withdrawing you more slowly. Withdrawing from heroin or narcotics makes the pain receptors go completely gonzo, but it doesn't kill you. It just makes you writhe with pain and wish you were dead. Withdrawing from alcohol causes the blood pressure to go too high and can cause a stroke or seizures and kill you. So how enthusiastic am I about adding that lovely blue butterfly sleep pill to the 3-5 alcoholic drinks that someone has at night? NOT. Gosh, if we get the dose high enough, mix of alcohol and benzodiazepines the person could throw up and drown in their own vomit or just become sedated enough to stop breathing entirely and die, or just enough for brain damage. That's fun.

And we don't know if sleep pills are safe long term. Read the fine print. Most of them are approved for use for two weeks. Right. Not 10 years. We don't know what the hell they do to your brain if you use them for 10 years. One sleep pill has been tested for longer term use: that is, six whole weeks. So I am stingy when it comes to sleep pills. I give people 8. Yes, 8, and tell them not to use them more often than once every three days because I am NOT going to give them 30 a month. I am going to give them 8 a month and that with reluctance. That is a conservative approach to long term use. And if they drink anything over 1-2 drinks a night, they have to cut that down first.

"But doctor, I wake up in the night!" And you are between 40 and 60 years old? That would be normal. Yes, I said normal. NORMAL NORMAL NORMAL. Ok, here's the story. Little babies wake 4-5 times a night, right? Really. Ask any new mom or dad. Eventually they "sleep through the night". No, actually they don't really. They still wake 4-5 times a night but they fall back asleep really quickly and without howling. They keep doing this as children, teens, young adults, adults.....and then sometime in the 40-60 year old range the wake up periods get a little longer. And we remember them. It is normal. It is ok. Do not drug it.

"But I can't go back to sleep." Ok, here are the sleep hygiene rules. No violent tv or any screen time (yes, that includes computers, you addicts) for the last hour before bed. No caffeine after noon. Bed is for sleeping and sex only. If you want to read, get out of bed. A cushy armchair by the bed is fine, but get out of bed. Sorry, but you asked. Music is ok before bed and so is radio. The screen activates weird parts of the brain, so that's why no screen. Don't listen to music or radio that sends your blood pressure through the roof. Exercise is best at least 4 hours before you are trying to drop off. A cool bedroom turns out to be better for sleep than a really warm one: turn down the heat and save money. Warm milk actually works.

"But doctor..." Ok, I know, you CAN'T do some part of the above. Do what you can.

"My teenager falls asleep in classes all the time." Ah, teens are interesting. The brain essentially melts when puberty hits, at around 12, and is done with the major rewiring by age 25. Teens need MORE sleep than kids or adults. 10-12 hours. They are working hard on puberty. Our sleep doctor said that the time the teen wakes up on the weekend indicates their real circadian rhythm. So, if a teen wakes at 1 pm on Saturday and Sunday, and is going to bed at two, that is where their circadian rhythm is set. Of course they are groggy as heck when they get up at 7 and trundle off to school and that history teacher is boring and drones in a monotone. How do we reset the rhythm? It takes time. The teen has to set an alarm on the weekend and get up progressively earlier. And they STILL need 10-11 hours so guess what? If the goal is 7 am, they should be going to bed by 9 pm. "HA, HA, HA, HA!" laughs the parent. Most teens are not getting enough sleep and are not catching up on the weekend. Parents can have influence. The sleep needs start to decrease as teens are entering their 20s.

What medicines do I use to help people sleep? I don't like the benzodiazepine related drugs, which is most of the advertised New Fancy Expensive sleep medicines. I do use old medicines: antidepressants in low doses, very low. Trazodone, amitriptyline and nortriptyline. They are cheap and we are actually using the side effect; that is, they make people drowsy. I prescribe at doses way below the theraputic dose for depression.

Geriatrics. Well, it's a difficult group. It's not good to make someone drowsy who needs to get up at night twice to urinate and is a bit shaky on their pins and who won't turn on the light for fear of disturbing someone. If I make them drowsy they trip and then we have a hip fracture. Mostly it is education: yes, they are waking up, maybe more than once and it's normal. I have had people really cheer up once we've had this discussion. Oh, they say, I'm normal. They've been confused by that damn blue butterfly.

Sleep well. Moderate your alcohol, caffeine, television and computer, exercise, eat right, drink enough water and put your doctor right out of business. And the blue butterfly too.

To all you people who aren't asleep,

Why not give it a try.

And soon you'll see the edging creep,

Around the edge of your eyes.

And sing a song, a lullaby,

Or maybe you would rather not,

Cause one day you'll be dead.

Sleep was a memorable Californian stoner rock band from the 1990s. Their first album, Volume One, was released in 1991 on Tupelo Records, and is their most overlooked or ignored album. The vocals have a little more bite to them than on other releases, adding a tinge of hardcore to their music which was more often thought of as doom metal. In 1993 Sleep's Holy Mountain was released by Earache Records. It's a fan favourite, and is fondly imagined as what a long-lost Black Sabbath album from the early 70s might sound like, around the Master of Reality era.

There were technically two more Sleep albums but they are nearly identical, having been reworked and released under a different name and label. At the end of it all, 1999's Jerusalem became 2003's Dopesmoker: 63 minutes of weed-laced riffs and sing-chanting through endless bongloads. It's all one song, and although Dopesmoker is the preferred version, Jerusalem has its share of proponents who appreciate the rougher cut.

Sleep's music has been used in a couple films. Jim Jarmusch (a noted doom metal enthusiast if the all-Boris/Sunn O)))/Earth soundtrack to The Limits of Control is any indication) included a 10 minute long edit of Dopesmoker on the soundtrack of Broken Flowers, although it can only be heard in the film for about 10 seconds while it blares through the speakers of a car radio. The song Dragonaut plays for an extended period of time in the surreal Harmony Korine film Gummo while two central characters ride bikes down the main drag like they own it.

For most of its existence Sleep had only three members: Al Cisneros doing bass and vocals, Matt Pike handling guitar, and Chris Hakius on drums. Second guitarist Justin Marler was only around in the beginning, and left soon after Volume One. Chris Hakius would also leave, in 1997, and was replaced by Jason Roeder until the group disbanded in 2003. Matt Pike is currently involved with fronting the trio High On Fire, a faster, thrashier, and certainly more popular band than Sleep ever was. Al Cisneros and Chris Hakius went off and became known as OM, taking with them the mellow, soulful stoner vibe from Sleep, after High On Fire had plundered all of its violence and gravity.

Sleep reunited on stage at the 2009 All Tomorrow's Parties: The Fans Strike Back Festival, playing two special "never to be repeated" shows with the classic Cisneros-Hakius-Pike lineup. They later reformed for a second ATP festival in September 2010, this time in their home country, and embarked on a small tour.

Sleep (?), obs.

imp. of Sleep. Slept.

Chaucer.

Sleep, v. i. [imp. & p. p. Slept (?); p. pr. & vb. n. Sleeping.] [OE. slepen, AS. slpan; akin to OFries. slpa, OS. slapan, D. slapen, OHG. slafan, G. schlafen, Goth. slpan, and G. schlaff slack, loose, and L. labi to glide, slide, labare to totter. Cf. Lapse.]

1.

To take rest by a suspension of the voluntary exercise of the powers of the body and mind, and an apathy of the organs of sense; to slumber.

Chaucer.

Watching at the head of these that sleep. Milton.

2. Figuratively: (a)

To be careless, inattentive, or uncouncerned; not to be vigilant; to live thoughtlessly.

We sleep over our happiness. Atterbury.

(b)

To be dead; to lie in the grave

.

Them also which sleep in Jesus will God bring with him. 1 Thess. iv. 14.

(c)

To be, or appear to be, in repose; to be quiet; to be unemployed, unused, or unagitated; to rest; to lie dormant; as, a question sleeps for the present; the law sleeps

.

How sweet the moonlight sleep upon this bank! Shak.

Sleep, v. t.

1.

To be slumbering in; -- followed by a cognate object; as, to sleep a dreamless sleep.

Tennyson.

2.

To give sleep to; to furnish with accomodations for sleeping; to lodge.

[R.]

Blackw. Mag.

To sleep away, to spend in sleep; as, to sleep away precious time. -- To sleep off, to become free from by sleep; as, to sleep off drunkeness or fatigue.

Sleep, n. [AS. slp; akin to OFries. slp, OS. slap, D. slaap, OHG. slaf, G. schlaf, Goth. slps. See Sleep, v. i.]

A natural and healthy, but temporary and periodical, suspension of the functions of the organs of sense, as well as of those of the voluntary and rational soul; that state of the animal in which there is a lessened acuteness of sensory perception, a confusion of ideas, and a loss of mental control, followed by a more or less unconscious state.

"A man that waketh of his sleep."

Chaucer.

O sleep, thou ape of death. Shak.

Sleep is attended by a relaxation of the muscles, and the absence of voluntary activity for any rational objects or purpose. The pulse is slower, the respiratory movements fewer in number but more profound, and there is less blood in the cerebral vessels. It is susceptible of greater or less intensity or completeness in its control of the powers. <-- the dreaming portions of sleep occurs periodically, and is associated with "rapid eye movements" (REM), and in this state the sleeper is more easily wakened; the dreamiong alternates with a more profound sleep, from which it is more difficult to awake the sleeper. -->

Sleep of plants Bot., a state of plants, usually at night, when their leaflets approach each other, and the flowers close and droop, or are covered by the folded leaves.

Syn. -- Slumber; repose; rest; nap; doze; drowse.

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