I randomly tried to execute the following command in bash1  cat /some/file | ssh user@machine 'cat &gt;/destination/file   There are no keys installed on the remote machine, so the only way to authenticate is with the password mechanism. I thought this wouldn't work, since the pipe will disconnect SSH's stdin from the terminal. I was surprised when I was prompted for a password, and the file was successfully sent.  Any thoughts on how SSH is able to read the keyboard to prompt for a password, despite not being connected to it?    1I am aware there are better alternatives to copying a file between two machines.
I don’t actually need to run the command below, and I am aware of ssh keys if I did want to log in without typing a password. I would just like to know how ssh seems to circumvent my file redirection.  Running the following command, ssh prompts me for a password:  ssh nobody@192.168.1.151 &gt; /dev/null 2&gt; /dev/null &lt; /dev/null   How does this work? stdin, stdout, and stderr are all redirected, but ssh still manages to print a prompt on my screen and read what I type. I tried adding the ssh arguments -t -t and -T (not both at once), to enable or disable pseudo-tty allocation, but it made no difference.  I also tried closing all input and output this way, although I don’t know if I typed it correctly. Still, ssh prompts for a password:  (exec 0&lt;&amp;- 1&lt;&amp;- 2&lt;&amp;- 0&gt;&amp;- 1&gt;&amp;- 2&gt;&amp;-; ssh nobody@192.168.1.151)
Calculating the peak voltage of a zener diode output I have a problem with this homework, I have to calculate the peak voltage of the output after stabilizing with a zener diode.  My Input Voltage is Vin = 5V + 0.7Vsin (2pif*t) with f=10kHz  My circuit is a simple regulator with no load resistor. The series resistance is 82 Ohms, Zener voltage is 3V, max. current through the diode is 33.3mA. How can I calculate the peak output ? My problem is the offset created by 5V, wouldnt the Zener voltage be reached immidiately with this configuration ?         &ndash; Schematic created using I found the .bashrc file and I want to know the purpose/function of it. Also how and when is it used? Is it correct to use "their" instead of "his or her"? I was trying to experiment with docker, Ubuntu 14.04, 64-bit. I managed to run an image, and I gave it the path on one of my removable drives, /media/Drive1.  Now, whenever I reboot, I see there is a /media/Drive1 with only a docker directory inside it, and the actual drive which should be Drive1 ends up mounted on /media/Drive11, and this happens every reboot - even when I unmount these drives, and do a sudo rm -rfv /media/Drive1 before rebooting!  So something probably creates /media/Drive1 before it is fully mounted, and I guess that something is docker, because when I boot, I have:  $ ps axf | grep docker  2085 ?        Ssl    0:00 /usr/bin/docker -d   So, how can I disable the docker autostart, so it doesn't interfere with the mounting of external USB drives at boot? Why is.vector on a data-frame doesn't return TRUE? Are there any examples of $\frac{a}{b}+\frac{c}{d}=\frac{a+c}{b+d}$? I am writing a short discussion of Farey numbers and was wondering if there are any examples of when the mediant function is ever actually equal to the sum of the two fractions in the usual sense? (Not to produce Farey numbers, I just thought it might be an amusing way to introduce Farey addition).   Explicitly: Are there any examples of fractions $\frac{a}{b}$ and $\frac{c}{d}$ where  $$\frac{a}{b}+\frac{c}{d}=\frac{a+c}{b+d}$$ for positive integers?   Currently I have found the example  $$\frac{1}{1}+\frac{1}{i} =\frac{1+1}{1+i}$$ if we remove the integers requirement but it would be nice to find a case that didn't involve complex numbers though! Why does Type I error always occur in a NHST? Or, is NHST too weak to tell the truth? Recently I have noticed that Type I error of a test is too much persistent. Even if all the values are almost equal (variance is extremely low) and tested to that value (true mean), still there is nearly 5% Type I error of the test. I am frightened and curious to rethink, are the people who have banned (or skeptic about) NHST (null hypothesis significance testing) truly correct? Let's have a look at the following r code:       n=10000 t1err=0 set.seed(1235) for (i in 1:n){    x=rnorm(100, 10, 20)    if (((t.test(x, mu=10))$p.value)&lt;=0.05) (t1err=t1err+1)  } cat("Type I error rate in percentage is", (t1err/n)*100,"%")   It will produce roughly 5% as Type I error. Seems ok. But let's see this:      n=10000   t1err=0   set.seed(1235)   for (i in 1:n){      x=rnorm(100, 10, 0.000001)      if (((t.test(x, mu=10))$p.value)&lt;=0.05) (t1err=t1err+1)    }   cat("Type I error rate in percentage is", (t1err/n)*100,"%")   Each values are extremely close to 10. Still it produces about 5% Type I error. What conclusion we may draw from it? Or, am I missing something? Localizing Dynamic Plural Noun messages (e.g. "5 Items Processed") on iPhone using Objective-C This appears to be related to the behavior originally suggested in .  It appears to be the same issue raised in , but this post has specific steps to reproduce the issue.  Here's what happened on one site in the network earlier today:   A question was posted much earlier Someone came along, and as an unregistered, new user with no other activity, posted a spam answer to that question at 04:36:54 UTC That same user posted a comment on their own answer with the same spam link at 04:37:31 UTC The answer was deleted as spam via community votes at 07:32:07 UTC A high-rep user saw the comment and raised a custom flag on it as being spammy at 07:32:54 UTC The unregistered user account was destroyed by a moderator at 08:13:10 UTC The comment now shows as "deleted by Anonymous" with a deletion time of 08:13:10 UTC The flag on the comment remains, but the only options are "Edit" and "Decline"; there is no "Delete" action   That there is no "Delete" action possible on the flag is reasonable, since the comment is now deleted. However, the flag is/was legitimate, so to decline the flag would be wrong. There's also nothing to leave while editing out the spammy part of the comment, as the comment consists solely of the same spam URL.  There is also no undelete option on the comment, so it's not possible to undelete the comment and then mark the flag as helpful by re-deleting the comment.  Effectively, this means that while the comment itself is effectively gone, the flag on it is in limbo and there is no good choice for what to do with the flag.  When deleting comments normally, my understanding is that any flags associated with those comments are automatically marked as helpful. However, it appears that the deletion of comments when destroying the user who posted them does not do that.  Therefore, I suggest that whenever comments are deleted as part of the owning user being destroyed, any pending flags against those comments should be marked as helpful at the same time.  It would also be a nice touch if those comments showed as deleted by Community♦, instead of Anonymous, but that's less of a concern in my case. I've grown quite fond of HTTP reverse proxies in our development environment and found the DNS based virtual host reverse proxy quite useful. Having only one port (and the standard one) open on the firewall makes it much easier for management.  I'd like to find something similar to do SSH connections but haven't had much luck. I'd prefer not to simply use SSH tunneling since that requires opening port ranges other than the standard. Is there anything out there that can do this?  Could HAProxy do this? I got to read Volume I of Feynmann's lectures. It said that at absolute zero, molecular motion doesn't cease at all, because if that happens, we will be able to make precise determination of position and momentum of the atom. We do know that Heisenberg uncertainty principle holds for microscopic particles in motion. But what then is wrong to consider that all molecular motion ceases at absolute zero? In other words, does the uncertainty principle not hold when there is no motion?  Need some help! I know that python has a len() function that is used to determine the size of a string, but I was wondering why it's not a method of the string object.  Update  Ok, I realized I was embarrassingly mistaken. __len__() is actually a method of a string object. It just seems weird to see object oriented code in Python using the len function on string objects. Furthermore, it's also weird to see __len__ as the name instead of just len. Difference between correlation and covariance: is covariance only useful if the relation is linear? I'm trying to understand better the difference between  covariance and correlation, besides the fact that the correlation coefficient is a dimensional and has values between $-1$ and $1$.   One unclear point is the following: the correlation coefficient can highlight only a linear relation between two variables, but does  covariance only work for linear relations too? Supposing that the relation is not linear, is the covariance not zero? Is it bigger than in the case in which the relation is linear?   Cauchy inequality says $$|\sigma_{xy}|&lt;\sigma_{x} \sigma_{y}$$  Which seems to say that the covariance is maximum when there is a perfect linear relation.    So I do not get what does happen if the relation is not linear, and, if covariance is not a suitable parameter in that cas I don't get the reason for that, since simply looking at the definition:  $$\sigma_{xy}=\frac{\sum(x-\bar{x})(y-\bar{y})}{N}$$  it looks like that this should be non zero for any kind of relation (like parabolic).  So can this be a difference between the use of covariance and correlation coefficient? (The first is useful for any kind of relation, the second one only for linear ones). Proof by induction that $ 169 \mid 3^{3n+3}-26n-27$ $ 169$ | $3^{3n+3}-26n-27$ ?  Fulfilled for $n=0$. Induction to $n+1$: An integer $x$ exists so that  $ 169x= 3^{3n+6}-26n-27-26$ $ 169x= 27*3^{3n+3}-26n-27-26$ $ 169x= 26*3^{3n+3}+3^{3n+3}-26n-27-26$  An integer $m$ exists so that   $ 169x= 26*3^{3n+3}+169m-26$ ($ 13x= 2*(3^{3n+3}-1)+13m$)  Now I'm stuck although it looks simple. Thanks for any input in advance. How to Create a Vinyl Plastic Toy Shader? How can I make one of the vinyl toy plastic material like this?    Video: Is $29$ the only prime of the form $p^p+2$? How did Harry become a Horcrux? Problem with patching babel package I am trying to use babel and biblatex package together but I am getting following error:    ! Package biblatex Error: Patching 'babel' package failed.    This is my code example:  \documentclass[12pt,a4paper,twoside,openright]{book} \usepackage{cmap} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[slovak]{babel} \usepackage{xpatch} \usepackage{csquotes} \usepackage{biblatex} \begin{document} \enquote{quote} \end{document}   I would need the result look like this:    Well, it seems like I could get rid of the error when using xpatch package, but it works only when I delete 'slovak' option for babel package. That way the result look like this:    Please, is there any workaround for this problem? I am really stuck in this. Turning off and on images in figures Is it possible to prevent the contents of a figure from being rendered? I have a large book document, and to speed up compiling while working on a draft, I would like to have some way of ignoring the content of the images, but ensuring that the figure size remains.  In several cases I am using a line like:  \includegraphics[width=\linewidth]{figure.pdf}     so I do not know the actual size of the image. How can I remap Caps lock to both Escape and Control?