Untill now I used everytime to filter, grep command  [root@host tests]# cat e 1 2 3 4 5 [root@host tests]# cat e | grep -Ev '2|3' &gt; filtered.txt  [root@host tests]# cat filtered.txt 1 4 5 [root@host tests]#   But right now I have a large file that needs to be filtered with hundred of strings from another file. How can I do it?
I have a couple of big text files and in the file UNIQS.txt I have a list of strings to grep from another file. The code I use is  grep -f UNIQS.txt EEP_VSL.uniqs.sam &gt; UNIQ_templates.sam   which does nothing - the file generated is empty. But when I do  grep -F -f UNIQS.txt EEP_VSL.uniqs.sam &gt; UNIQ_templates.sam   it works correctly. This confuses me because I didn't think grep would interpret the entries in UNIQS.txt as regexp patterns without quotes and slashes and so on being in the file (which there aren't). Is it the case in general that if you are getting the patterns from a file then it will automatically think that they are regexp patterns?  Edit: In the UNIQS.txt file, there are newline separated strings of the form  HWI-ST365:215:D0GH0ACXX:2:1101:10034:186783   (called template names) and the file EEP_VSL... tab separated columns, with about 14 columns and the first column is the template name, so basically I want to extract the line corresponding to each template in the file.
$\text{Tor}_0^R(M,N)\simeq M\otimes_R N$ I'm trying to understand why $\text{Tor}_0^R(M,N)\simeq M\otimes_R N$.  Let $\dots\to F_1\to F_0\to M\to 0$ be a free resolution of $M$. Then $$ F_1\to F_0\to M\to 0$$ is exact. Hence $$ F_1\otimes_R N\to F_0\otimes_R N\to M\otimes_R N\to 0$$ is exact. Call the left map $f_1$ and the right map $f_0$. Then $M\otimes N\simeq F_0\otimes N/\ker (f_0)\simeq F_0\otimes N/\text{im}(f_1)$.  But if I understand the definition correctly, to show the result we need that $M\otimes N\simeq H_0(\mathcal F)=\ker f_0/\text{im}(f_1)$. But why does $\ker f_0=F_0\otimes N$? If it does at all... Recommendations on a free library to be used for zipping files I need to zip and password-protect a file. Is there a good (free) library for this?  This needs to be opened by a third party, so the password protection needs to work with standard tools. Basic photo editing on OS X I need to edit a photo on my Mac. I wish to take two photos and paste them together to create one that's larger, containing both. I couldn't figure out how to do this with iPhoto.   For Windows you have Paint.NET.    For Linux you have Kolourpaint.   What would be the equivalent on OS X?  Please note that it must be of quality both in code and in UI. I wouldn't want to install buggyware on my Mac. Is const_cast safe? I can't find much information on const_cast.  The only info I could find (on Stack Overflow) is:     The const_cast&lt;&gt;() is used to add/remove const(ness) (or volatile-ness) of a variable.   This makes me nervous.  Could using a const_cast cause unexpected behavior?  If so, what?  Alternatively, when is it okay to use const_cast? #include&lt;iostream&gt; using namespace std;  class A  {    int a;    int b;    public:    void eat()    {       cout&lt;&lt;"A::eat()"&lt;&lt;endl;    } };  class B: public A {    public:    void eat()    {        cout&lt;&lt;"B::eat()"&lt;&lt;endl;     }  };  class C: public A {     public:    void eat()     {        cout&lt;&lt;"C::eat()"&lt;&lt;endl;     }  };  class D: public B, C {  };  int foo(A *ptr) {  ptr-&gt;eat();  } main() {  D obj; foo(&amp;(obj.B)); //error. How do i call with D's B part.  }   The above foo call is a compile time error.  I want to call foo with obj's B part without using virtual inheritance. How do i do that.   Also, in case of virtual inheritance, why the offset information need to be stored in the vtable. This can be determined at the compile time itself. In the above case, if we pass foo with D's object, at compile time only we can calculate the offset of D's A part. Should the results of a calculation happen automatically, or require a button push? This is a problem I've ran into several times, and I imagine that others have ran across it too.    Basically, I have a complicated equation, and I want the user to type in the values needed to calculate the results.  (For what it's worth, there are good default values for the variables in the equation.)  I've constructed a GUI that shows the user the names of the variables/fields that need to be provided, along with a control (like a numeric up/down, slider, etc.) to enter the values of the field.  Below that, I have an area that shows the output of the equation.  So my question is this.  Should my results area automatically change the calculated results whenever the user makes any changes to any of the input fields, or should they push a "Calculate" button to generate the results?  One other thing that probably applies is that the user is not trying to "get the right answer" out of the results.  They shouldn't be using the output to then go back and modify the input to get a better answer.  Are there any benefits to requiring the button press?  Is the extra click to see the results worth those benefits? Is redirecting homepage to a page with keyword it's targeting helps in SEO? Why is Jupiter so sharply defined? In photographs of Jupiter, . Being a gas giant, my naive self thinks that the atmosphere should have a more gradual cut off, creating a hazy effect similar to that on Titan. I am aware of Jupiter's immense size, so each pixel in the linked photograph is likely tens or hundreds of kilometers. Even so, wouldn't there be some small smudge? Does perhaps Jupiter's terrific gravity have any effect on the apparent edge of its atmosphere? Android app intermittently shows blank body in questions and answers (multiple sites) Is there a word for a person who gives out too many extraneous details? What's your preferred way of getting current system status (current CPU, RAM, free disk space, etc.) in Python? Bonus points for *nix and Windows platforms.  There seems to be a few possible ways of extracting that from my search:   Using a library such as  (that currently seems not actively developed and not supported on multiple platform) or something like  (again no activity since 2007 it seems and no support for Windows). Using platform specific code such as using a os.popen("ps") or similar for the *nix systems and MEMORYSTATUS in ctypes.windll.kernel32 (see ) for the Windows platform. One could put a Python class together with all those code snippets.   It's not that those methods are bad but is there already a well-supported, multi-platform way of doing the same thing? Does the limit $\lim _{x\to 0} \frac 1x \int_0^x \left|\cos \frac 1t \right| dt$ exists? Does the limit $\lim _{x\to 0} \frac 1x \int_0^x \left|\cos \frac 1t \right| dt$ exists ? If it does then what is the value ?   I don't think even L'Hospital's rule can be applied . Please help . Thanks in advance is $\sqrt{x}$ always positive? Prime ideal and nilpotent elements Is there a way to view Google Chrome browsing history past three months ago? I'm trying to find a page I looked at months ago but it looks like it's disappeared off the face of the planet. I thought I would have better luck looking through my Google Chrome browsing history, but I can't see history past September. Can I force Google Chrome to display history further into the past? Can I retrieve the history manually from a directory? Is the history data gone? Host alias for ssh There are a few SSH destinations I will frequently be connecting to and I'm wondering if rather than remember the IP address I can create a host alias for them.  I'd like to be able to use...  ssh -p xx user@domain.ssh  I've tried establishing this host in /etc/hosts and unless there's a service I needed to restart it had no effect. Short story (+radio play?) in which astronauts outside their ship slowly drift apart in space Looking for a short story in which the crew of a spaceship for some reason find themselves outside the ship, drifting apart in outer space. They can communicate via their radios but are individually drifting apart.  One by one, they lose communication as they drift further away from each other.  Might have also been adapted into a radio play? Equivalent Definitions of the Operator Norm How do you prove that these four definitions of the operator norm are equivalent? $$\begin{align*} \lVert A\rVert_{\mathrm{op}} &amp;= \inf\{ c\;\colon\; \lVert Av\rVert\leq c\lVert v\rVert \text{ for all }v\in V\}\\ &amp;=\sup\{ \lVert Av\rVert\;\colon\; v\in V\text{ with }\lVert v\rVert\leq 1\}\\ &amp;=\sup\{\lVert Av\rVert\;\colon\; v\in V\text{ with }\lVert v\rVert = 1 \}\\ &amp;=\sup\left\{ \frac{\lVert Av\rVert}{\lVert v\rVert}\;\colon\; v\in V\text{ with }v\neq 0\right\}. \end{align*}$$ What are some examples of manifolds that do not have boundaries and are not boundaries of higher dimensional manifolds?  Is any $n$-dimensional closed manifold a boundary of some $(n+1)$-dimensional manifold? I was reading a bit of Landau and Lifshitz's Mechanics the other day and ran into the following part, where the authors are about to derive the kinetic energy of a free particle. They use the fact that the Lagrangian of this particle must be the same (or at most, differ by the total time derivative of a function of co-ordinates and time) in different inertial frames.     We have $L'=L(v'^2)=L(v^2+2\mathbf{v}\cdot\boldsymbol{\epsilon}+\boldsymbol{\epsilon}^2)$. Expanding this expression in powers of $\boldsymbol{\epsilon}$ and neglecting terms above the first order, we obtain    $$L(v'^2)=L(v^2)+\frac{\partial L(v^2)}{\partial (v^2)}2\mathbf{v}\cdot\boldsymbol{\epsilon}.$$   I think I'm ok with all the physics in this section. What I don't get is just the part I quoted above (so maybe this post is better suited for the math site, but since this is book is so physics-y I thought I'd post it here). My math is pretty rusty, so I'm not really sure- how do the authors expand the function to arrive at the above expression? It reminds me a bit of a Taylor expansion, but not very much. What's the process used to arrive at it?