What's the difference between these two commands?  cat /proc/uptime | awk '{print $1}'  &lt; /proc/uptime awk '{print $1}'  Specifically, how does the second command work? Doesn't the redirection operator &lt; has to be accompanied by a command? What does it mean to redirect the contents of a file like that?
Assuming file2 already exists, the command   &gt; file1 &lt; file2 cat   appears to be copying the content of file2 to file1.  But I cannot understand this structure.  I understand that "Nothing" is being directed to file1 (creating or erasing its content). Then the content of file2 is being directed to file1.  Why is cat after file2? How does it know to cat file2 if the operands are not in the correct order?
"Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset" using PHP A number of questions "has been" or "have been" asked? Formally, is it correct to write:     A number of questions has been asked here.   or:     A number of questions have been asked here.   As a non-native speaker of English, I would prefer the former: the subject seems to be "number", therefore the verb ought to be singular, I'd say. However, the latter seems more common, and therefore I believe that my gut feeling is just plain wrong — but I would really like to have a definite answer.  Moreover, is it the same for "a myriad of", "a plethora of", and so on? How to get apt-cacher-ng to download AND cache packages from Apt HTTPS repositories? Introduction to statistics for mathematicians What is a good introduction to statistics for a mathematician who is already well-versed in probability?  I have two distinct motivations for asking, which may well lead to different suggestions:   I'd like to better understand the statistics motivation behind many problems considered by probabilists. I'd like to know how to better interpret the results of Monte Carlo simulations which I sometimes do to form mathematical conjectures.   I'm open to the possibility that the best way to go is not to look for something like "Statistics for Probabilists" and just go to a more introductory source. How to find the sum $$\sum^n_{k=1} (k^2+k+1)k!$$  What I tried as follows :   $$\sum^n_{k=1} (k^2+k+1)k!$$  =$$\sum^n_{k=1} (k^2)k!+ \sum^n_{k=1} (k)k! + \sum^n_{k=1} (1)k!$$  Now we can write $\sum^n_{k=1} (k^2) $ as $$\frac{n(n+1)(2n+1)}{6}$$ but what to do with $k!$ please guide thanks....... How do you tell if a D&D book is 3.0 or 3.5? I'm a quarter Draconian, a quarter Dragonborn and half Half-Dragon? What are the differences between "Dragonborn", "Half-Dragon", and "Draconian" races in D&amp;D?  In the Hoard of the Dragon Queen adventure, for example there is  a Half-Dragon npc. I had assumed that when writing the adventure they were only allowed to use known material from Basic, and so renamed the Dragonborn into "Half-Dragon" for the sake of compatibility etc. However, the dragon breath rules are not at all similar for the half-dragon and the dragonborn, and I've also noticed wiki article that imply that they are different races entirely. (Thus introducing me to the term Draconian)  Are there clear differences between these three races, (in the same way there are differences between Goblins and Hobgoblins, or Dragonborn and Lizardfolk and Kobolds,) or are they really just three different setting names for the same basic race?  Answers can either be D&amp;D 5e specific, or be based on the lore from all editions of Dungeons and Dragons. (I'm assuming here that the answer will be the same regardless)  Here are two images, the first one is a "half-dragon" from the front of the Hoard of the Dragon queen module, and the second one is a "dragonborn" from the 5e player's Handbook.  I've included these images to help explain my confusion. Here is a question that's been bothering me since I was a sophomore in university, and should have probably asked before graduating:  In analytic (Lagrangian) mechanics, the derivation of the Euler-Lagrange equations from the principle of least action assumes that the start and end coordinates at the initial and final times are known. As a consequence, any variation on the physical path must vanish at its boundaries. This conveniently cancels out the contributions of the boundary terms after integration by parts, and setting the requirement for minimal action, we obtain the E.L. equations.  This is all nice and dandy, but our intention is finding the location of a particle at a time in the future, which we do not know a priori; after we derive any equations of motion for a system, we solve them by applying initial values instead of boundary conditions.   How are these two approaches consistent? How often did Gandalf return to Hobbiton after the events of The Hobbit? "I who has" vs "I who have." Possible Duplicate:          Am aware it is correct to say "I have written..." and "I am a doctor who has writen..."  I have, however, severally come across the sentence "I, Tertius, who have written...". Shouldn't it be "I, Tertius, who has written..."? I have imported a mesh (AutoCad DXF) and I'm experiencing strange shading behavior. I've done the following to try and address the problem with no luck:  Recalculate Normals Remove Doubles Delete Loose Geometry Cleared Seam, Sharp, and Bevel Weights  There are no modifiers on the mesh.  The original imported mesh looks fine in smooth shading but I need the mesh to be in quads which causes the shading to mess up as shown in photo. I can add my .blend file but I'm not sure how to do that. I hope to receive my PhD in Mathematics in May of 2015, so I am currently applying for jobs.  Due to life circumstances, I'm fairly certain that I will only be staying at my next position for about 2 years.  Does this mean I shouldn't even try to apply for tenure-track positions?  Will a hiring committee not even consider me for the position if I'm not willing to commit to staying with them for a certain amount of time?  I would love to get a teaching/lecturing position at any institute of higher education (4-year research university, liberal arts school, community college), but as I look for openings, a lot of them are tenure-track assistant professor positions.  Should I go through the effort of sending in an application, or will that be a waste of my, and the committee's, time?  Thanks for any advice you have!  Edit (to address Nate's comment):  My wife is currently applying for 2 year graduate degree programs in various cities in the US, so I'm applying for jobs in the same cities.  When she finishes her program, we plan to move outside of the US (Africa or Southeast Asia), where I do hope to remain in academia, teaching mathematics to college-aged students. Yesterday, one of our computers dropped to grub shell or honestly, I am unsure what shell it was when we turned on the machine.  It showed that it can't mount the root filesystem or something in this sense, because of inconsistencies.  I ran, I believe:  fsck -fy /dev/sda2   Rebooted and the problem was gone.  Here comes the question part:  I already have in her root's crontab:   @reboot /home/ruzena/Development/bash/fs-check.sh    while the script contains:  #!/bin/bash touch /forcefsck   Thinking about it, I don't know, why I created script file for such a short command, but anyways...  Further, in the file:  /etc/default/rcS   I have defined:   FSCKFIX=yes    So I don't get it. How could the situation even arise?    What should I do to force the root filesystem check (and optionally a fix) at boot?  Or are these two things the maximum, that I can do?  OS: Linux Mint 18.x Cinnamon 64-bit.  fstab:  cat /etc/fstab | grep ext4   shows:   UUID=a121371e-eb12-43a0-a5ae-11af58ad09f4    /    ext4    errors=remount-ro    0    1    grub:   fsck.mode=force    was already added to the grub configuration. It's the first time I'm using Tikz on Latex. I have to draw this block diagram (this is a low resolution snip from a paper)   In Tikz I have done this:   That is very similar but I need some adjustments, like the u_i arrow and the node sum after the H(s) block.  Is there anybody that can help me with this?  my code:      \tikzstyle{block} = [draw, fill=white, rectangle,  minimum height=2em, minimum width=3em] \tikzstyle{sum} = [draw, fill=white, circle, radius=1mm, node distance=1.5cm] \tikzstyle{input} = [coordinate] \tikzstyle{output} = [coordinate] \tikzstyle{pinstyle} = [pin edge={to-,thin,black}]  \begin{tikzpicture}[auto, node distance=2cm,&gt;=latex'] \node [input, name=input] {}; \node [input, above of=input](input1) {}; \node [sum, right of=input] (sum) {}; \node [block, right of=sum] (controller) {$K(s)$}; \node [sum, right of=controller] (sum1) {}; \node [block, right of=sum1] (filterinv) {$H^{-1}(s)$}; \node [block, right of=filterinv] (system) {$G(s)$}; \node [output, right of=system] (output) {}; \node [output, above of=output] (output1) {}; \node [block, below of=filterinv] (filter) {$H(s)$}; \node [block, above of=controller] (delay) {$D(s)$}; \node [sum, below of=sum1] (sum2) {};  \draw [-&gt;] (filterinv) -- node[name=u] {$u_{i}$} (system); \draw [draw,-&gt;] (input) -- node {$s_{i-1}$} (sum); \draw [-&gt;] (sum) -- node {$e_{i}$} (controller); \draw [-&gt;] (system) -- node [name=q] {$q_{i}$}(output); \draw [-&gt;] (q) |- (filter); \draw [-&gt;] (filter) -- node {} (sum2); \draw [-&gt;] (controller) -- node {} (sum1); \draw [-&gt;] (sum1) -- node[name=xi] {$\xi_{i}$} (filterinv); \node [input, below of=sum1](input2) {}; \draw [draw,-&gt;] (input2) -- node {$r_{i}$} (sum2); \draw [-&gt;] (sum2) -| node[pos=0.99] {$-$}      node [near end] {$\tilde{s}_i$} (sum); \draw [-&gt;] (delay) -| node[] {}      node [near end] {} (sum1); \draw [draw,-&gt;] (input1) -- node[pos=0.15] {$u_{i-1}$} (delay); \draw [-&gt;] (u) |- node[pos=0.99] {$u_i$}      node [near end] {} (output1);  \end{tikzpicture} "viruses" or "virii"? Removing control chars (including console codes / colours) from script output I can use the "script" command to record an interactive session at the command line.  However, this includes all control characters and colour codes.  I can remove control characters (like backspace) with "col -b", but I can't find a simple way to remove the colour codes.  Note that I want to use the command line in the normal way, so don't want to disable colours there - I just want to remove them from the script output.  Also, I know can play around and try find a regexp to fix things up, but I am hoping there is a simpler (and more reliable - what if there's a code I don't know about when I develop the regexp?) solution.  To show the problem:   spl62 tmp: script Script started, file is typescript spl62 lepl: ls add-licence.sed  build-example.sh  commit-test         push-docs.sh add-licence.sh   build.sh          delete-licence.sed  setup.py asn              build-test.sh     delete-licence.sh   src build-doc.sh     clean             doc-src             test.ini spl62 lepl: exit Script done, file is typescript spl62 tmp: cat -v typescript Script started on Thu 09 Jun 2011 09:47:27 AM CLT spl62 lepl: ls^M ^[[0m^[[00madd-licence.sed^[[0m  ^[[00;32mbuild-example.sh^[[0m  ^[[00mcommit-test^[[0m         ^[[00;32mpush-docs.sh^[[0m^M ^[[00;32madd-licence.sh^[[0m   ^[[00;32mbuild.sh^[[0m          ^[[00mdelete-licence.sed^[[0m  ^[[00msetup.py^[[0m^M ^[[01;34masn^[[0m              ^[[00;32mbuild-test.sh^[[0m     ^[[00;32mdelete-licence.sh^[[0m   ^[[01;34msrc^[[0m^M ^[[00;32mbuild-doc.sh^[[0m     ^[[00;32mclean^[[0m             ^[[01;34mdoc-src^[[0m             ^[[00mtest.ini^[[0m^M spl62 lepl: exit^M  Script done on Thu 09 Jun 2011 09:47:29 AM CLT spl62 tmp: col -b &lt; typescript  Script started on Thu 09 Jun 2011 09:47:27 AM CLT spl62 lepl: ls 0m00madd-licence.sed0m  00;32mbuild-example.sh0m  00mcommit-test0m         00;32mpush-docs.sh0m 00;32madd-licence.sh0m   00;32mbuild.sh0m          00mdelete-licence.sed0m  00msetup.py0m 01;34masn0m              00;32mbuild-test.sh0m     00;32mdelete-licence.sh0m   01;34msrc0m 00;32mbuild-doc.sh0m     00;32mclean0m             01;34mdoc-src0m             00mtest.ini0m spl62 lepl: exit  Script done on Thu 09 Jun 2011 09:47:29 AM CLT How do I sort a list of dictionaries by a value of the dictionary? How to complain about a user? I  and a user was rude to me in a comment and in an answer. Even though I can't downvote, that answer got -5 and it was automatically deleted. I want to complain about that user. How can I do that? How are the number of views in a question calculated? Grouping functions (tapply, by, aggregate) and the *apply family