This is a very weird behavior. Lately, whenever I am trying to find a process on console with ps aux | grep foo, it is returning a grep: command not found. Ok, that could be something that I changed and did wrong, but the problem is that, after a few tries, it suddenly knows what grep is:  MM:.dev$ ps aux | grep foo -bash:  grep: command not found MM:.dev$ ps aux | grep foo -bash:  grep: command not found MM:.dev$ ps aux | grep foo -bash:  grep: command not found MM:.dev$ ps aux | grep foo MM            70953   0,0  0,0  2699108    744   ??  Ss   10:32AM   0:08.77 foo bar MM             3756   0,0  0,0  2423356    204 s004  R+   10:12AM   0:00.00 grep foo   Any ideas why is this happening?  As suggested, this is what I get when a enter type grep after both, the one failing and the one working:  MM:.dev$ ps aux | grep foo -bash:  grep: command not found MM:.dev$ type grep grep is /usr/bin/grep MM:.dev$ ps aux | grep foo MM             5694   0,0  0,0  2433796    676 s006  S+   10:47AM   0:00.00 grep foo MM:.dev$ type grep grep is /usr/bin/grep
Whenever I want to use the pipe operator in the terminal, I get a weird kind of "bug":    As is shown in the image above, I can type the exact same command twice and it will sometimes register it or sometimes include some spacing in the command, as can be seen in the error message. The only difference between the two commands was the speed I typed them, with fast typing the char sequence "| " (without the "") leading to the error. I've checked in the terminal settings if this sequence somehow triggers a shortcut, but I did not find anything.   In case it matters, I'm using a swiss keyboard. The layout is as follows:    To produce the "|" character, I press "alt + 7". Does anybody know what the cause of this problem is?
There are 8 crew members, The leading member wants that only a crew of 5 people or more could open a safe he bought, To each member he gave equal amount of keys, and locked the safe with several locks.  What's the minimal number of locks he should put:   at least 5 crew members would be required to open the safe? Any team of 5 crew members could open the safe, but none of the 4 team crew members.   1,2 stands individually of course. Universal extractors With an  of archive/compression file formats, is there a single free/open-source command line tool to rule them all? Perhaps something with a consistent / unified set of flags? (note my  friendly )  I once run into a set of aliases meant to largely simplify the task of compressing/de-compressing files with bindings to tar and other utils, but I can't find this anymore.  Update: How can I configure something like atool to not use unzip to extract zip files (which apparently can't handle files larger than 4GB) and to use gunzip instead?  $ aunpack large_file.zip error:  Zip file too big (greater than 4294959102 bytes) Archive:  large_file.zip warning [large_file.zip]:  1491344848 extra bytes at beginning or within zipfile   (attempting to process anyway) error [large_file.zip]:  start of central directory not found;   zipfile corrupt.   (please check that you have transferred or created the zipfile in the   appropriate BINARY mode and that you have compiled UnZip properly) aunpack: unzip ...: non-zero return-code Is there another saying/idiom similar to crocodile tears? Blank lines in an equation and some other similar function Why blank lines between equation makes error? there are a lot of commands in latex and almost for all of them these blank lines are not important,  but why in this case is important and is there any similar function? I'd like to have Ubuntu installed on a USB stick, that I could plug in (almost) any computer and boot from it, and that I could use (almost) normally, as if it was installed on that computer. I'd also like to have a data partition on it that could be used by (almost) any computer, mostly to store some portable apps, just in case.    I've been told that if I installed Ubuntu in BIOS mode, I wouldn't be able to boot from a computer in UEFI mode, and vice versa.  Since I'd like to be able to boot on any computer, it's a big problem.  What can I do to be able to boot on computers in BIOS or UEFI modes in my case?  I've been searching for solutions but most of them are for specific needs that are different than mine, so it's difficult to extract the minimum requirements from those solutions to apply them to my problem.  Is there a simple, "clean" and quite generic solution to this problem?  I'd appreciate some explainations about the reasons why a specific solution is good or a specific step is needed.    My current setup:   USB stick:  OS: Xubuntu 16.04 i386 installation: full install (from a Live USB built with Rufus) drivers: none proprietary file systems:    partition table:    2: , /boot/efi, 128 Mio, FAT32, [boot,esp] 3: , 128 Mio, HFS+ 4: , 2 Mio, [bios_grub] 5: swap, 512 Mio 6: , /, 24 Gio, ext4, defaults,errors=remount-ro,lazytime,commit=60 1: , /media/data, ~3.6 Gio, FAT32, defaults,lazytime,check=strict  RAM:   /tmp, tmpfs, defaults,nosuid,nodev,noexec,mode=1777   swap:    vm.swappiness=5 swap partition: 512 Mio, for emergency zRAM swap files:    /var/swap/hib.swp: same size as RAM, for hibernation, generated by a script at startup /var/swap/opt.swp: if needed, generated by a script   overprovisioning: ~5.6%   built-in: ~1.2 Gio (apparently) added: 512 Mio  scheduler: deadline This was a question from my textbook. This is how I approached it.   For the first part, you can do c(10,5) so you choose 5 of the 10 to be on a team.   For the second part, you have 10 ways to choose the "best player" and you multiply it by c(10,4) to pick the other 4 players. However, I am not sure how you can exclude the "worst player". Although this sounds subjective, I believe the question is saying that the "best" and "worst" players are distinct, whereas the other players aren't. Possible Duplicate:          The  describes the expansion of the $n$th power of the sum $(a+b)$:  $$(a+b)^n = \sum_{k = 0}^n {n\choose k}a^kb^{n-k}$$  In calculus, there is a generalization of the product rule called , which describes the expansion of the $n$th derivative of the product of two functions $f$ and $g$:  $$(fg)^{(n)} = \sum_{k = 0}^n {n\choose k}f^{(k)}g^{(n-k)}$$  It's not difficult to prove using the product rule and induction, what I'm really trying understand here is why the formula is true. Is there a way to prove it using the binomial formula? How are these two formulas related? Is there a combinatorial proof for Leibniz's rule like there is for the ?   I understand this question is a bit vague, but I hope you'll agree that these two formulas look so similar it just feels like there should be some relation between the two. Of course this is not necessarily true, but I'm hoping it's not just a crazy coincidence. On the meta home page I noticed the  is listed as doing something, but cannot figure out what it is.  There is nothing on the  or its , but the recent activity is listed with the same timestamp. Give $\ker(\phi)$  for $\phi: \mathbb{Z} \to \mathbb{Z_7}$ such that $\phi(1) = 4$  So the generator of $\mathbb{Z}$ maps to $4$ and $\langle 4 \rangle = \{0,1,2,3,4,5,6\}$ so it has order seven.  so $\ker(\phi) = 7\mathbb{Z}$ because every seventh element will map to the identity under the given map. Is that the correct reasoning? A famous exercise which one encounters while doing Complex Analysis (Residue theory) is to prove that the given integral: $$\int\limits_0^\infty \frac{\sin x} x \,\mathrm  dx = \frac \pi 2$$ Well, can anyone prove this without using Residue theory?  I actually thought of using the series representation of $\sin x$: $$\int\limits_0^\infty \frac{\sin x} x \, dx = \lim\limits_{n \to \infty} \int\limits_0^n \frac{1}{t} \left( t - \frac{t^3}{3!} + \frac{t^5}{5!} + \cdots \right) \,\mathrm  dt$$ but I don't see how $\pi$ comes here, since we need the answer to be equal to $\dfrac{\pi}{2}$. References to a comment on a deleted answer can break Stack Exchange JS For the following URL, JavaScript breaks:  https://stackoverflow.com/questions/16356382/splitting-a-braces-grouped-string-in-python/16356421?noredirect=1#comment23433042_16356421   This is a link to a , the answer I can see as a 10K+ user (although users &lt;10k ).  With Chrome (26, Mac OS X) the console sez:  Uncaught TypeError: Cannot call method 'replace' of undefined   for line 83 of full.js.  Firefox (20, Mac still), the web console spits out:  [12:48:28.459] TypeError: c.attr(...) is undefined @ http://cdn.sstatic.net/js/full.js?v=c9131e40e3fb:83   Safari (6.0.4 on, you guessed it, Mac OS X) has this to complain about:  TypeError: 'undefined' is not an object (evaluating 'c.attr("id").replace')   for line 83 of full.js.  Because of this, the Answer text box on Stack Overflow is lacking all niceties such as an actual WMD editor.  If you remove the hash reference #comment23433042_16356421 from the end of the URL, things work again. Removing the ?noredirect=1 query parameter makes no difference. Network simplex method, leaving and entering variables Factoring $-3x^2 - 2xy + 8y^2 + 11x - 8y - 6$ What is the difference between a HMAC and a hash of data? Embed vimeo video into the body field How to sort an array of objects containing null elements? If $P(x^5)+xQ(x^5)+x^2R(x^5)=(x^4+x^3+x^2+x+1)S(x)$ , then prove that $P(x)$ is divisible by $x-1$ $P,Q,R,S$ are polynomials such that: $P(x^5)+xQ(x^5)+x^2R(x^5)=(x^4+x^3+x^2+x+1)S(x)$ , then prove that $P(x)$ is divisible by $x-1$   I thought a lot on this but no result!! By the way,one idea is to insert some values for $x$ and try to produce a system of equations for the given polynomials,but I'm not sure it works. I have a 10 stock portfolio and considering market conditions that are on the rise when this question in being asked, a few of them did hit their 52-week high price.  I would like to call myself a long term investor and I do not like to trade so much. If I take "Buy low sell high" as gospel then this is in my opinion a good selling position.  On one hand, I think I should lock my profit because stocks don't hit a 52-week high every day, but on the other hand, there is nothing wrong with the company and it is very well positioned to go up even further.  Any suggestions? Keep items in inventory on death in Minecraft How can I find the right lens cap for my lens? I own a Nikon D3000 Camera with the AF-S 18-55mm VR Kit Lens. Last week I lost the lens cap and now I want to buy a new one.  But when I went to , I got confused with the different ranges of lens names —  LC-62, LC-78, etc.  My concern is what if I order one lens cap and it won't fit correctly on my lens?  If you guys have an D3000, can you please let me know how to find the correct lens cap names?