Grep regexp (linux) for extracting two words and storing them in variables
Parsing JSON with Unix tools
I want to remove all the files from different directories, and want to keep only latest files 20 files. is this the correct command to do this?  ls -t1 /mnt/dwh/ftp/dwh_ftp_cbs/ARLOGS/ | tail -n +22 | xargs rm -f Batch renaming files with pattern I have some files named like these:  63018933.mp4?token=1325697436_b0c3e70c6e339380b4a484c576a8c287  63808488.mp4?token=1325697401_4ae5f7a68d93873c8881b303e7655e14  How do I rename all them to, for example 63018933.mp4(remove characters after mp4)? How do I change a close vote to a duplicate? Voted to close a question based on "lack of minimal understanding".  Later realized the question was a duplicate.  How to I change vote to mark as duplicate instead? Is there a test for the different styles within maths mode?  What I really want is to be able to save the current style to reinvoke it later on, but a \if along the lines of \ifmmode would work just as well.  In the specific example, I want to measure how big something will be when displayed in maths mode, so I do:  \settoheight{\mathheight}{some bit of maths}   except that it complains because the some bit of maths gets put in a box and measured, and the box doesn't know that it's maths.  So instead I put:  \settoheight{\mathheight}{\(some bit of maths\)}   except that then I get the wrong answer if this is used in displayed maths.  So ideally, I want:  \ifdisplaystyle  \let\currentstyle\displaystyle \else  \iftextstyle   \let\currentstyle\textstyle  ...  \fi \fi \settoheight{\mathheight}{\(\currentstyle some bit of maths\)}   and then I'll be happy.  Is there such a test?    Okay, so \mathchoice is clearly the way to go (thanks Martin!), but its behaviour is a little odd and since I want to use it to define a macro depending on which mode I'm in, this oddity is quite important.  Here's the code:  \newcommand{\mathtest}{% \gdef\name{a}% \mathchoice{% \name \gdef\name{b}% }{% \name \gdef\name{c}% }{% \name \gdef\name{d}% }{% \name \gdef\name{e}% }% \name}  \[ \mathtest \]   If \mathchoice behaved like \if, this ought to print ab.  But it prints ae.  All the options to \mathchoice get processed (which makes me wonder a bit how it works, but that's by-the-by).  So, is there an obvious way to make \mathchoice behave a little more like \if? How to initialize private static members in C++? What is the best way to initialize a private, static data member in C++?  I tried this in my header file, but it gives me weird linker errors:  class foo {     private:         static int i; };  int foo::i = 0;   I'm guessing this is because I can't initialize a private member from outside the class.  So what's the best way to do this? How can I draw a graph like the diagram below? I'm trying, but something is wrong with my code in LaTeX: \begin{asy} pair dynkinMark(real x, real y, string s = &quot;&quot;, pen p = defaultpen, pair B = dir(45)) { if (s != &quot;&quot;) { dot(&quot;$&quot;+s+&quot;$&quot;, (x,y), B, p); }     else { dot((x,y), p); }     return (x,y); }  dynkinMark(0,1, &quot;1&quot;, dir(135)); dynkinMark(0,2, &quot;2&quot;, dir(135)); dynkinMark(0,3, &quot;3&quot;, dir(135)); dynkinMark(0,4, &quot;4&quot;, dir(135)); dynkinMark(7,1, &quot;1'&quot;); dynkinMark(7,2, &quot;2'&quot;); dynkinMark(7,3, &quot;3'&quot;); dynkinMark(7,4, &quot;4'&quot;); path p1 = (0,1)..(2,2.0)..(5,3.5)..(7,4); path p2 = (0,2)..(2,1.2)..(5,2.5)..(7,3); path p3 = (0,3)..(2,2.8)..(5,1.5)..(7,1); path p4 = (0,4)..(2,3.8)..(5,3.5)..(7,2); draw(p1, blue); draw(p2, heavycyan); draw(p3, mediumcyan); draw(p4, lightblue); dot(&quot;$12$&quot;, IP(p1, p2), dir(90), heavygreen); dot(&quot;$13$&quot;, IP(p1, p3), dir(90), heavygreen); dot(&quot;$23$&quot;, IP(p2, p3), dir(90), heavygreen); dot(&quot;$14$&quot;, IP(p1, p4), dir(90), heavygreen); dot(&quot;$24$&quot;, IP(p2, p4), dir(90), heavygreen); real y = 0.8; label(&quot;$s_1$&quot;, (IP(p1,p2).x, y), heavygreen); label(&quot;$s_2$&quot;, (IP(p1,p3).x, y), heavygreen); label(&quot;$s_1$&quot;, (IP(p2,p3).x, y), heavygreen); label(&quot;$s_3$&quot;, (IP(p1,p4).x, y), heavygreen); label(&quot;$s_2$&quot;, (IP(p2,p4).x, y), heavygreen); \end{asy} Integral vanishes on all intervals implies the function is a.e. zero I am having trouble with the following problem:      $f:\mathbb{R}\to \mathbb{R}$ is a measurable function such that for all $a$:   $$\int_{[0,a]}f\,dm=0.$$   Prove that $f=0$ for $m$ almost every $x$ (here $m$ is the Lebesgue measure).    I have no problem proving this for $f$ non-negative, or under the assumption that $f$ is integrable. But the question only assumes that $f$ is measurable and no more.  My idea was the usual thing; we look at the set of points where $f$ is positive and negative and assume one of these has measure greater than zero. Then I wanted to estimate one of these by an open set, look at the integral on the open set and show that it had to be greater than zero, a contradiction. But a key part of this attack is the assumption of the absolute continuity of the integral, which only holds in the case where $f$ is integrable.  Alternatively, if it were integrable one could simply estimate $f$ by a continuous function, where the result is quite obvious.  Ultimately we are going to show that $f$ is integrable, but it is not clear to me how to show this before showing it is zero a.e. So there must be a simpler way. Does anyone have suggestions? How do I boot my PC from GRUB? No module named numpy I am trying to run Jupyter notebook from my Ubuntu subsystem in Windows 10. I've installed numpy, scipy, and pandas using the following commands:  pip install scipy numpy pip install pandas   When I load python in Ubuntu, there is no issue importing numpy in Ubuntu cmd.   But, when I run my Jupyter Notebook from Ubuntu terminal, and try to import numpy as np, or import pandas as pd, they report  ModuleNotFoundError                       Traceback (most recent call last) &lt;ipython-input-1-a9340201ed9f&gt; in &lt;module&gt;       5 import dash_html_components as html       6 import plotly.graph_objs as go ----&gt; 7 import numpy as np       8 from dash.dependencies import Input, Output       9   ModuleNotFoundError: No module named 'numpy'   Is there anyway to solve this issue? Thanks a lot. setTimeout and "this" in JavaScript I have a method that uses the  function and makes a call to another method. On initial load method 2 works fine. However, after the timeout, I get an error that says method2 is undefined. What am I doing wrong here?  ex:  test.prototype.method = function() {     //method2 returns image based on the id passed     this.method2('useSomeElement').src = "http://www.some.url";     timeDelay = window.setTimeout(this.method, 5000); };  test.prototype.method2 = function(name) {     for (var i = 0; i &lt; document.images.length; i++) {         if (document.images[i].id.indexOf(name) &gt; 1) {             return document.images[i];         }     } }; The order of words in a clause: "tell me who is the real man" vs. "tell me who the real man is" I have 2 ADS1299 analog to digital converters(). I need to give them bipolar mode supplying but I must use a powerbank of 5V 3A. I wonder how can I create a bipolar supply of +2.5v -2.5v as mention in the datasheet from the 5V of the powerbank. I am new in this field. Thank you How to identify polygons with "flag" sliver errors Working in ArcMap, I have come across errors in a polygon layer that I will call "flag slivers" (taken from similar language in parcels call "flag lots").  These sliver polygons (see image below) are typically composed of just one additional node that user has  accidentally added.    In the images below, the "flag" and the "flagpole" are one single-part feature where the "flagpole" just overlaps itself.  The left-hand image has a total of 5 nodes.     When seen alone the errors are very obvious, but when multiple polygons are adjacent, they are nearly impossible to see because they appear to be the boundary between 2 polygons.  This likely happens because they are using a shapefile based editor, and therefore I cannot implement any topology-based editing rules to prevent this from happening in the future.  Does anyone have a way of identifying and resolving these types of errors?  I would prefer an automated method of both identification and resolution since field users are the ones who created the errors, but I am stuck cleaning up after them.  Thanks. Can I travel to Schengen countries that were not on my itinerary when I applied? Windows & Ubuntu dual boot.No menu to choose OS? I just installed Ubuntu alongside Windows 7. Now I cant boot Windows 7 because it automaticaly boots Ubuntu without displaying boot menu. How can I get menu with options to choose which Os to boot? Can anyone help? Lately I see a blue screen of death a lot and want to know why it appears. Where should I gather the information so the problem can be diagnosed best? Couldn't find anything in C:\Windows\Logs. Here's the scenario...    if (entry.Properties["something"].Value != null)   attribs.something = entry.Properties["something"].Value.ToString();   While effective and working correctly, this looks ugly to me.  If I don't check for a null before performing the ToString() then it throws an exception if the property was null.  Is there a better way to handle this scenario?  Much appreciated! How to combine an SSD boot drive with a HDD data drive? Omission of "the" in "elected him president" and "made captain" I have few friends.   I have a few friends.      I thought "few" means just one, two or even none. "A few" typically means more than two. However it seems to me some people say "few" when they really mean "a few", am I right?