regex for finding a particular file
What special characters must be escaped in regular expressions?
How to handle dynamic changing ID's In XPath? How to Handle Dynamic Changing IDs In XPath? for example :   //div[@id='post-body-3647323225296998740']/div[1]/form[1]/input[1]   In this xpath id "3647323225296998740" is changing every time when reloading the page.   Is there any way to handle this type of situation in Selenium? How to mount ufs file system under Debian testing? In order to mount my /dev/sda4  under /mnt/ufs_mount on Debian Testing , i have tried the following commands (it works fine under Debian Jessie):  modprobe ufs mount -r -t ufs -o ufstype=ufs2 /dev/sda4 /mnt/ufs_mount   and:  mount -t ufs -o ufstype=ufs2 /dev/sda4 /mnt/ufs_mount   But i get this error:  mount: /dev/sda4 is write-protected, mounting read-only mount: wrong fs type, bad option, bad superblock on /dev/sda4,    missing codepage or helper program, or other error     In some cases useful info is found in syslog - try    dmesg | tail or so.   The output of: dmesg | tail :  [ 1136.965142] ufs: ufs_fill_super(): bad magic number [ 1255.758946] ufs: ufs_fill_super(): bad magic number [ 2098.945757] ufs: ufs was compiled with read-only support, can't be mounted as read-write [ 2098.946045] ufs: You didn't specify the type of your ufs filesystem        mount -t ufs -o ufstype=sun|sunx86|44bsd|ufs2|5xbsd|old|hp|nextstep|nextstep-cd|openstep ...        &gt;&gt;&gt;WARNING&lt;&lt;&lt; Wrong ufstype may corrupt your filesystem, default is ufstype=old [ 2098.967212] ufs: ufs_fill_super(): bad magic number [ 2927.982112] perf: interrupt took too long (2504 &gt; 2500), lowering kernel.perf_event_max_sample_rate to 79750   Edit My sources.list:  deb http://httpredir.debian.org/debian/ stretch main deb-src http://httpredir.debian.org/debian/ stretch main  deb http://security.debian.org/debian-security stretch/updates main deb-src http://security.debian.org/debian-security stretch/updates main   And uname -a:  Linux debian 4.6.0-1-amd64 #1 SMP Debian 4.6.4-1 (2016-07-18) x86_64 GNU/Linux   How to mount ufs file system under Debian testing? Strange distance measurements in distance matrix I'm trying to create a distance matrix between two point shapefiles in QGIS 2.6. Both are in WGS84 UTM Zone 30N co-ordinates (and so is the project file), but the distance matrix returns values such as 5673346.938, instead of expected numbers of between 1 and 5km.  I saw a similar thread mentioning disabling 'on the fly projection changes' - I've done this, and no change. Threads already checked:     Here are samples of the two shapefiles I'm using, stripped down to just ID and location. I recently renewed my passport. I also have an expired passport which has my Canada visa (visitor's) valid for another three years. I have already used my Canadian visa which is multiple entry. I am planning to visit Canada this summer.  Since my valid Canadian visa is in my old/expired passport, do I need to renew/transfer my Canada visa or can I simply travel with valid visa in old passport? Currently I have a script.sh file with the following content:  #!/bin/bash wget -q http://exemple.com/page1.php; wget -q http://exemple.com/page2.php; wget -q http://exemple.com/page3.php;   I want to execute the commands one by one, when the previous finishes. Am I doing it in the right way? I've never worked with Linux before and tried to search for it but found no solutions. How to select a clustering method? How to validate a cluster solution (to warrant the method choice)? One of the biggest issue with cluster analysis is that we may happen to have to derive different conclusion when base on different clustering methods used  (including different linkage methods in hierarchical clustering).  I would like to know your opinion on this - which method will you select, and how. One might say "the best method of clustering is which gives you the right answer"; but I may question in response that cluster analysis is supposed to be an unsupervised technique - so how do I know which method or linkage is the right answer?  In general: is a clustering alone robust enough to rely on? Or we need a second method and get a shared result to be based on both?  My question is not only about possible ways to validate / evaluate clustering performance, but is broader - on what basis do we select/prefer one clustering method/algorithm over another one. Also, is there common warnings that we should look around when we are selecting a method to cluster our data?  I know that it is very general question and very difficult to answer. I only would like to know if you have any comment or any advise or any suggestion for me to learn more about this. Mysterious contact by advanced aliens; leaves humans insane It'd be great if anyone could remember the source of this short story I only dimly remember, but recall finding quite haunting back in my youth.  I read it maybe 20 years ago in a paperback that probably dated from the '80s.  It begins with the protagonist (a young man) being being woken by a deafening noise coming through his cochlear implant.  He's on a spaceship, and has volunteered to be put in a capsule and fired off to a remote part of the solar system.  Once in place in their capsule, the volunteers are visited by what is (presumably) a highly intelligent alien life-form, and gifted with some artefact containing priceless knowledge, like, for example, the cure for cancer.  The (unexplained) encounter leaves the them completely and irrevocably insane, perhaps terrified out of the minds.  Yet despite this, volunteers still clamour to be chosen for the mission. How to replace a character by a newline in Vim I'm trying to replace each , in the current file by a new line:  :%s/,/\n/g    But it inserts what looks like a ^@ instead of an actual newline. The file is not in DOS mode or anything.  What should I do?  If you are curious, like me, check the question  as well. How it this possible? Even if the gif is fake, the Mythbusters did it and with a large sail it really moves forward. What is the explanation? Nonphysical entities cannot be observed. Therefore such entities cannot be verified by observation. How could statements like "God exists" be even considered true? Why would anyone appeal to the metaphysical realm at all?  It seems to me that the best method by which we should go about in understanding the world is by initially ruling out the possibility of the metaphysical altogether for the simplest answer (a sort of null hypothesis). Once we can get a hold of a natural cause of some phenomenon, we should be satisfied that that is all there is to it. Formulating some nonphysical cause would be unnecessary, superfluously complicated, or even cluttered. Now if there was some problem that we were certain could not be solved by observation or experimentation or whose solution could not possibly exist in the observable realm, yet must be true, I would consider the possibility of a metaphysical cause.      That said, I don't think that if you can't empirically observe something, it doesn't exist; rather, I would declare total agnosticism and say that it is unknowable. Complete list of Lollipop system icons shown in notification bar? Is there a complete list of these? I've seen lots of Q&amp;A about "What does x icon mean" but it would be really useful if there were a complete list for reference! How are Wolverine's claws still in his body? Everyone knows that Wolverine's adamantium claws are super-sharp — sharper than even a razor — and virtually indestructible. What puzzled me the first time I saw Wolverine is: how do the claws stay in his body?  As it is shown, Wolverine's flesh and skin are human in strength, but the healing factor makes it superhumanly durable and strong. Still, when Wolverine slashes something, or someone, extremely hard, dense, or thick (as he has to use great amount of force), the claws don't tear through his hand and leave his hand through the opposite side of the palm (because of the action having equal and opposite reaction). Avoid synchronized(this) in Java? Calculus book recommendations (for complete beginner) Well I have not started calculus yet but I am really keen to. I would love if you suggest some books.  Points to be noted:   I really don't like the way textbooks are written so please no "textbooks"  I am COMPLETELY beginner in calculus. I know a little bit of trigonometry and what functions are but not really in depth.The book should start from the base, I mean really from the base. I may require a precalculus book too if the books don't cover that. I would really love if the book shows how calculus was developed, why it was developed and things like that.   Well,thanks in advance! Why do we need to use:  extern "C" { #include &lt;foo.h&gt; }   Specifically:     When should we use it? What is happening at the compiler/linker level that requires us to use it?   How in terms of compilation/linking does this solve the problems which require us to use it? Any Set with Associativity, Left Identity, Left Inverse is a Group Related Link:    Reference: Fraleigh p. 49 Question 4.38 in A First Course in Abstract Algebra     I will present my proof (distinct from those in the link) for critique and then ask my question.  $G$ is a set and $ \times $ is an associative binary operation.  Suppose that there exists a $e \in G$ such that, for all $a \in G$, $ea = a$ and $a^{-1}a = e$ for some $a^{-1} \in G$.  Show that for the same $e$, $ae = a$ and $aa^{-1} = e$.  $a^{-1}(aa^{-1})a = (a^{-1}a)(a^{-1}a) = ee = e = a^{-1}a = a^{-1}(a^{-1}a)a$  Since $a^{-1} \in G$, it has a left inverse; apply it to both ends, and we have $(aa^{-1})a = (a^{-1}a)a$.  As a result, $ae$ = $a(a^{-1}a) = (aa^{-1})a = (a^{-1}a)a = ea$.  For the right inverse, start with $aa^{-1} = a(a^{-1}a)a^{-1} = (aa^{-1})(aa^{-1})$.  Since $\times$ is a binary operation, $aa^{-1} \in G$ and has a left inverse; apply it to both ends, and we have $e = aa^{-1}$.  In second comment following the question in the link, Mr. Derek Holt pointed out that the requester did not word his/her question correctly.  Specifically, the identity in the second axiom is not well-defined.     Let $(G, *)$ be a semi-group. Suppose    1. $ \exists e \in G$ such that $\forall a \in G,\  ae = a$;    2. $\forall a \in G, \exists a^{-1} \in G$ such that $aa^{-1} = e$.    How can we prove that $(G,*)$ is a group?    This formulation makes the same technical error as many textbooks. The $e$ in your second axiom is not well-defined. "But obviously it's intended to be the same $e$ as in the first axiom" you reply. But the first axiom does not necessarily specify a unique element $e$. So should we interpret the second axiom as meaning "for some $e$ as in 1" or "for all $e$ as in 1"? –  Derek Holt Sep 17 '11 at 15:31   Was he saying that if, in axiom 1, we have $ae_1 = a, ae_2 = a$, but $e_1 \neq e_2$,  when we get to axiom 2, do we have $aa^{-1} = e_1, aa^{-1} = e_2$, or two different inverses so that $aa_1^{-1} =  e_1, aa^{-1}_2 = e_2$?  I think my wording eliminated the ambiguity.  It does not imply that $e$ is unique, but if $e$ is a left identity and produces left inverses, then it is also a right identity and produces right inverses. I tried really hard on this one; please kindly point out my mistakes. Redirect output from all commands to file, not just last Using while loop to ssh to multiple servers I have a file servers.txt, with list of servers:  server1.mydomain.com server2.mydomain.com server3.mydomain.com   when I read the file line by line with while and echo each line, all works as expected. All lines are printed.  $ while read HOST ; do echo $HOST ; done &lt; servers.txt server1.mydomain.com server2.mydomain.com server3.mydomain.com   However, when I want to ssh to all servers and execute a command, suddenly my while loop stops working:  $ while read HOST ; do ssh $HOST "uname -a" ; done &lt; servers.txt Linux server1 2.6.30.4-1 #1 SMP Wed Aug 12 19:55:12 EDT 2009 i686 GNU/Linux   This only connects to the first server in the list, not to all of them. I don't understand what is happening here. Can somebody please explain?  This is even stranger, since using for loop works fine:  $ for HOST in $(cat servers.txt ) ; do ssh $HOST "uname -a" ; done Linux server1 2.6.30.4-1 #1 SMP Wed Aug 12 19:55:12 EDT 2009 i686 GNU/Linux Linux server2 2.6.30.4-1 #1 SMP Wed Aug 12 19:55:12 EDT 2009 i686 GNU/Linux Linux server3 2.6.30.4-1 #1 SMP Wed Aug 12 19:55:12 EDT 2009 i686 GNU/Linux   It must be something specific to ssh, because other commands work fine, such as ping:  $ while read HOST ; do ping -c 1 $HOST ; done &lt; servers.txt Should log file streams be opened/closed on each write or kept open during a desktop application's lifetime? Is it possible to cross the Wagan border by car? I was planning a trip by car when I found something a bit weird in :if you try to cross from Lahore to India, it tells that you have to 6457 km detour.  Is it possible to cross this border driving? If not, is there another way to cross without having to make more than 6000 km?