as you saw on the title, I got the "Failed to fetch... Hash Sum mismatch" Error. I have tried this method:  sudo rm -rf /var/lib/apt/lists/* sudo apt-get update   But it didn't work. I still got the same error.  Err http ://vn.archive.ubuntu.com trusty-updates/universe amd64 Packages Get:99 http ://vn.archive.ubuntu.com trusty-updates/universe amd64 Packages [1,789 B] Get:100 http ://vn.archive.ubuntu.com trusty-updates/main i386 Packages [1,789 B] Fetched 28.3 MB in 5min 15s (89.8 kB/s)  W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty/main/source/Sources  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/source/Sources  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/binary-amd64/Packages  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/binary-i386/Packages  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/binary-i386/Packages  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/i18n/Translation-en  Hash Sum mismatch W: Failed to fetch http://vn.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/i18n/Translation-en  Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead.   Please help! Thank you a lot!

When I check for updates, I get a "Failed To Download Repository Information" error.   This is what comes up under details:   W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch,  E: Some index files failed to download. They have been ignored, or old ones used instead.


On the command line, I find that, if I want to administer something, I must first login admin and enter password and then sudo something and enter password again. Is there a way to do this in one step, remembering the password for 60 seconds?  This is not a duplicate. I don't want to make my normal user a suoder.

I want to be able to 'su' to a specific user, allowing me to run any command without a password being entered.  For example:  If my login were user1 and the user I want to 'su' to is user2:  I would use the command:  su - user2  but then it prompts me with   Password:


suppose $a>0$, how to integrate: $$ \int_0^\infty  e^{-a^2/x^2}e^{-x^2}~\mathrm{d}x $$

I have a problem to solve and I have something that i don't know how to do.  The half-space Gaussian integral is given :  $$\int_{0}^\infty \exp(-ax^2)dx = \frac{1}2 \sqrt{\frac{\pi}{a}}$$  I have to calculate   $$\int_{0}^\infty \exp \left(-y^2 - \frac{c^2}{y^2} \right)dy$$  So I think we need to use a u-substitution but i can't find something...  Is someone have an idea ? :)  Thanks for your answers  Mathieu


Im trying to insert data into my database, it works when i dont use the $_POST['wagee'], but I cant get it to work pulling data from my form. Any help is greatly appreciated. Thank you!  here is the error I get:  You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' '2')'  at line 2   This is my code:  <?php   $message = "";   if(isset($_POST['addhoursbutton'])) {    addwage(); }   function addwage() { include 'components/sql/config.php';  $sqlupdateincome = "INSERT INTO income (username, projectname, hourlywage, totalhours) VALUES ('John', 'Ochrom Test', ". $_POST['wagee'] .", '2')";  if ($conn->query($sqlupdateincome) === TRUE) {     echo "New record created successfully"; } else {      echo  "Error: " . $sql . "<br>" . $conn->error; }  $conn->close(); } ?>

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


We have a webform and when submitting this form we would like to update user info in the database regarding values of submitted Webform.  I already managed to get the submitted values from the webform in my custom module. But I don't know how to update the user info in the database because all user info are in separated tables.  I can run a few update queries for each value but it's not a logical way for me!  Any other suggestions?

I have read this post  about how to use field_attach_update to save nodes without the overhead of node_save().  I would like to use this for users (which it should work for, as per ) . However, I'm not sure how to apply the examples to users.  Currently, this is my code:  if (isset($uid)) {     $user = user_load($uid);     $user_og_groups = $user->og_user_node[LANGUAGE_NONE];     $user_committee_positions = $user->field_committee_position_serno[LANGUAGE_NONE];     $user_data = my_module_import_user($cust_info, $cust_attributes, $drupal_countries, $employers);     $user = user_save($user, $user_data);   }   The $user_data variable is an array of data, which is what user_save expects (). user_save() doesn't work exactly the same as node_save() and doesn't accept a user object.  How then can I use field_attach_update to programmatically update users?


Is it possible to give someone your test program without giving away the logic? For example, how can the teachers give their test class that the students could use to compare their results, without actually giving the logic away of the assignment?  Thanks.

How do I lock compiled Java classes to prevent decompilation?  I know this must be very well discussed topic on the Internet, but I could not come to any conclusion after referring them.  Many people do suggest obfuscator, but they just do renaming of classes, methods, and fields with tough-to-remember character sequences but what about sensitive constant values?  For example, you have developed the encryption and decryption component based on a password based encryption technique. Now in this case, any average Java person can use  to decompile the class file and easily retrieve the password value (defined as constant) as well as  and in turn can decrypt the data by writing small independent program!  Or should such sensitive components be built in native code (for example, VC++) and call them via ?


The world may never eradicate coronavirus, but it can get it under control.  The world may never eradicate coronavirus, but it could get it under control.  The world may never eradicate coronavirus, but it might get it under control.   I know the difference between 1) and 2).What is the difference between 2) and 3)?

Let's not wait any longer. He might not turn up.   I would like to know in this sentence, could we use could instead of might? Can these two words be used alternatively?  What's the difference between this two words when come to asking about a possibility?


I've set up unattended upgrades, and wish to receive an email on every update run to make sure it's running. For whatever reason, ssmtp isn't installing so isn't an option.  How do I configure my server to use an external smtp server that uses login and ssl/tls security?  (I want to send from "noreply@example.com" on mail.example.com:465.)  No,  not asking about broken package fixing since I have default repository already. I'm asking if there's an alternative to ssmtp

I have a home server which needs a mail server for error messages, mostly.  I used postfix but I find the features/complexity compromises not optimal for my home server: there are tens of lines to check/configure, stunnel to install for TLS, ...  What simpler mail server with TLS support can I use, that is also packaged by Canonical? I'm going to only use an external relay server provided by my provider.


public static void main(String[] args) throws SAXException, ParserConfigurationException, IOException     {         String fXml="<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n" + "<Emp id=\"1\">\n" + "    <name>Pankaj</name>\n" + "    <age>25</age>\n" + "    <role>Developer</role>\n" + "    <gen>Male</gen>\n" + "</Emp>";        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();     DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();     Document doc = dBuilder.parse(fXml);      doc.getDocumentElement().normalize();      System.out.println("Root element :" + doc.getDocumentElement().getNodeName());     }   I am getting the following errors:  Exception in thread "main" java.net.MalformedURLException: no protocol: <?xml version="1.0" encoding="UTF-8" standalone="yes"?>   How do I make work as intuitive? Yeah the problem lies in the very first line but I am not sure how to correct this.

I have the following code:   DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(xmlFile);   How can I get it to parse XML contained within a String instead of a file?


Example 1:     Peter’s bag   Example 2:     Chris’s car   Is example 2 correct? If not, what is the rule for names that end with “s”?

According to my grammar book, but at variance to the answer to , the correct singular possessive if a word ends in ‑s is:     James’s car   The grammar book allows exceptions for historical nouns, so the examples in the answer to the above-linked question would pass muster.  However, I’m sure that I learnt at school (which, admittedly, was a while ago) that for a singular (proper) noun ending in ‑s, the apostrophe went after the s and there was no additional s.  I don’t wish to start a flame war on which is correct, though my question doesn't really make sense if my grammar book is wrong!  What I’m curious about is when the change occurred.  :  So my question is when did James’s become the correct form and James’ the incorrect one?


Is there a way for us know if all the contents inside an iframe are loaded completely and all of them have finished rendering? ( This is specifically for mobile browsers)  I have tried leveraging the following events but all of them are firing before the content inside the iframe is completely rendered.  It is most important for us that this is only triggered after all the content and images inside the iframe are finished rendering. We are attempting to calculate the actual time it takes for a customer to see our fully rendered frame.        iframe.attachEvent("onload", function () {             console.log(' placeholder : 1');         };       iframe.onload = function () {             console.log(' placeholder: 2');        };       iframe.onreadystatechange = function () {        if (iframe.readyState == "complete") {            console.log(' placeholder: 3');        }   Thanks in advance.

I need to execute a callback when an IFRAME has finished loading. I have no control over the content in the IFRAME, so I can't fire the callback from there.  This IFRAME is programmaticly created, and I need to pass its data as a variable in the callback, as well as destroy the iframe.  Any ideas?  EDIT:  Here is what I have now:  function xssRequest(url, callback) {     var iFrameObj = document.createElement('IFRAME');     iFrameObj.src = url;                 document.body.appendChild(iFrameObj);         $(iFrameObj).load(function()      {         document.body.removeChild(iFrameObj);         callback(iFrameObj.innerHTML);     }); }   This callsback before the iFrame has loaded, so the callback has no data returned.


Title says it all. I'm really really new with Linux stuff. Using Xfce/Crouton/Ubuntu etc.  If you can be as specific as possible, or linking me to a guide that breaks everything down step by step that would be great. Thanks!

My problem is, that I do want to create a .desktop file for Technic Launcher, which is an alternative launcher for Minecraft. It comes in the form of a .jar file and I want to create a menu entry for it. How would I write such a .desktop file?  My attempt was the following:  [Desktop Entry] Type=Application Name=Technic Launcher Comment=Minecraft Launcher for Technic Pack, Tekkit, Hack/Mine and Yogbox Exec=/home/benjamin/Applications/Minecraft/TechnicLauchner/technic-launcher-latest.jar Icon=/home/benjamin/Applications/Minecraft/TechnicLauchner/icon.png Terminal=false Categories=Game;ActionGame;AdventureGame;RolePlaying;   This didn't work, hence my question. What did I do wrong? Is it even possible to point to a .jar file?


I know we can use userinfo.CurrencyIsoCode to get currencycode for user in multi currency org. For single currency org we can manually look into company information and see currency locale.   But is there any way we can use apex to get currency code for single currency org's. I checked both organization and user object if there is any field for default currency but there is no field. Currencytype object is also not enabled in single currency org.    I need to know if there is any other salesforce object from where we can get this information. I don't want to create a custom object where admin can store this information.

I'm looking for a way to get the Default currency symbol (in a none-multi-currency org) of the salesforce org locale (to have it displayed on a visualforce page in a field that can't be <apex:inputField> or <apex:outputField>) preferably query-able from apex (via the database, a describe or whatever) and then again the actual symbol, meaning € for Euro, $ for dollar, and so on...  There must surely be some sort of mapping hidden in the code somewhere salesforce does this via the input/outputfields if bound to an sobject of type currency  Can anyone point me in the right direction?


Long story short,i deleted my windows 8 genuine copy while trying to install ubuntu so i am left with ubuntu now.I would like to delete ubuntu and install the free windows 10 copy as i have lost my windows key.I have access to a usb. Can someone guide me,please.

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


I'm trying to do passing a variable to form from view on Django. Simply, what I want to do is something like this below. # views.py  def tmp(request):     if request.method == 'POST':         f = tmpForm(request.POST)         if f.is_valid():         // something more here.      else:         // this will pass nothing to the form         f = tmpForm()          // want to pass variable/parameter to the form         initial = '''{                 "hoge": "hogehoge"         }'''         f = tmpForm(initial) // should be something like this maybe?      return render(request, 'tmpapp/tmp.html', {'form': f})  # forms.py  class tmpForm(forms.Form):      // retrieve the variable/parameter and set `initial` or something like that      json = forms.CharField(widget=forms.Textarea, label='', help_text='JSON formatted data here.', initial=           textwrap.dedent(                # '''{                #      "hoge": "hogehoge"                # }'''                initial // so you can use the variable like this.           )      )  So, How can I implement this?

I have a Model as follows:  class TankJournal(models.Model):     user = models.ForeignKey(User)     tank = models.ForeignKey(TankProfile)     ts = models.IntegerField(max_length=15)     title = models.CharField(max_length=50)     body = models.TextField()   I also have a model form for the above model as follows:  class JournalForm(ModelForm):     tank = forms.IntegerField(widget=forms.HiddenInput())       class Meta:         model = TankJournal         exclude = ('user','ts')   I want to know how to set the default value for that tank hidden field. Here is my function to show/save the form so far:  def addJournal(request, id=0):     if not request.user.is_authenticated():         return HttpResponseRedirect('/')      # checking if they own the tank     from django.contrib.auth.models import User     user = User.objects.get(pk=request.session['id'])      if request.method == 'POST':         form = JournalForm(request.POST)         if form.is_valid():             obj = form.save(commit=False)              # setting the user and ts             from time import time             obj.ts = int(time())             obj.user = user              obj.tank = TankProfile.objects.get(pk=form.cleaned_data['tank_id'])              # saving the test             obj.save()      else:         form = JournalForm()      try:         tank = TankProfile.objects.get(user=user, id=id)     except TankProfile.DoesNotExist:         return HttpResponseRedirect('/error/')


I have Ubuntu Server 16.04.3 and daily I am making some changes to configuration files in /etc.   I want to synchronize these files daily and take a backup of them stored on another partition? How can I achieve this?

I want to use version control for config files in Ubuntu server.    But I found it's not easy to simply use git for the whole /etc directory, because many files don't need to be tracked and sometimes the system will write to files like logs which should be ignored.    Is there an application that can do this and make it easy? If it is based on git that is better.


I accidentally unplugged the power. Now when I try to log in, the login page disappears and it looks like the password worked. But then suddenly, the screen goes back to the login page. This happens over and over again. (I know the password is correct because, if it wasn't, an error would show up.)  I tried the following:   Removed .Xauthority Reinstalled xorg Checked ~/.profile   I checked my .xsession-errors file but I don't understand much (I can login via TTY):    Is it telling me something about the login problem? Is there anything I can do to solve it?  NOTE: I think .Xauthority isn't the problem since it isn't set to root but to user:  -rw-------  1 alex alex  53 Nov 29 10:19 .Xauthority   My profile file looks kinda like this:  # if running bash if [ -n "$BASH_VERSION" ]; then     # include .bashrc if it exists     if [ -f "$HOME/.bashrc" ]; then     . "$HOME/.bashrc"     fi fi  # set PATH so it includes user's private bin if it exists if [ -d "$HOME/bin" ] ; then     PATH="$HOME/bin:$PATH" fi   I didn't check for empty new lines ... but I don't think that's the issue?

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I'm studying political science. My CGPA is awful at around 2.95, however, my GPA for the last fall, winter, and summer semester for my 3rd year have been 3.3, 4.0, 3.8 (I did really bad in first and second year). At the best, I am looking at about a 3.1/3.2 CGPA by the time I graduate.  I am wondering how competitive I actually am? Do I even have a chance with such a low CGPA knowing that meeting the requirements does not guarantee acceptance?  In terms of professors, I'm in the DSA of my program and know a couple of professors who would write me a good reference letter. I'm currently doing a independent study research project with a prof as well. And I worked through my entire undergrad: about 4 years of work experience in administrative and retail work.  Do I have a chance or is this a pipe dream? Is it true that grad schools only look at last 2 years?

When applying to a PhD program in the US, how does the admissions process work? If an applicant is weak in a particular area, is it possible to offset that by being strong in a different area?  Note that this question originated from this . Please feel free to edit the question to improve it.


As far as every question I've seen concerning "what is $\sum_{k=1}^nk^p$" is always answered with "Faulhaber's formula" and that is just about the only answer.  In an attempt to make more interesting answers, I ask that this question concern the problem of "Methods to compute $\sum_{k=1}^nk^p$ without Faulhaber's formula for fixed $p\in\mathbb N$".  I've even checked this  without finding what I want.  Rule #1: Any method to compute the sum in question for arbitrary $p$ is good, either recursively or in some manner that is not in itself a closed form solution.  Even algorithms will suffice.  Rule #2: I don't want answers confined to "only some values of $p$".  (A good challenge I have on the side is a generalized geometric proof, as that I have not yet seen)  Exception: If your answer does not generalize to arbitrary $p$, but it still generalizes to an infinite amount of special $p$'s, that is acceptable.  Preferably, the method is to be easily applied, unique, and interesting.  To start us off, I have given my answer below and I hope you all enjoy.


So many words end in "ight", such as "light", "might" and "sight".  I am curious about this -- is there an etymological reason why "ight" is used for many seemingly disparate words?  Thanks.

I am not a native speaker, and I find it very interesting that night is written with gh. Why is it spelled this way?


Hello I downloaded an app that allows me to block google play, however I can still install apps through play.google.com via another device. Is there a way I can disable this? The app I'm using is called AppLock.

My mom has an android tablet and she doesn't even know what a site is, her e-mail, or even the password of her facebook account. She's an average user. The internet is facebook in her eyes. She has no need for apps or anything, it's just, only, precisely facebook. All is facebook.  How can I completely disable installing apps in android so they can't be installed in any way or form, I mean, not by URL, not by clicking, not by app store, not even by another program. Just disable the entire thing altogether.  Doesn't need to be safe, have locks, passwords etc. I'm not trying to secure the device from intruders, attackers or robbers, I'm trying to secure it from its very own user.  Please help. I just had to remove two anti-virus apps that were opening adware pages when she tried to open facebook lite, and that's obviously a no-go, apps which she "had not installed." Clearly there's some voodoo going on here for them to just popup, or maybe she just did it unknowingly, but none of that's relevant. How can you just disable installs so this couldn't ever happen again?


I was playing Minecraft and I kept getting killed by a witch. Is there any good strategies for taking down a witch? I have tried going straight in and that did not work.

A long time ago I played an older version of Minecraft. Back then witches didn't spawn naturally, so you couldn't find them unless you found a hut. Now I'm playing again, but sometimes when I go down a cave I find one or two witches, and it's really hard to find them back.   So, what is the best you can do to kill witches, specially when two spawn at the same time and you don't have milk?


I copied my public ssh key to a remote server, but the authentication fails with the following ssh output:  ilya@workstation ~ % ssh -v ilya@remoteserver OpenSSH_6.6.1, OpenSSL 1.0.1k-fips 8 Jan 2015 debug1: Reading configuration data /home/ilya/.ssh/config debug1: /home/ilya/.ssh/config line 7: Applying options for remoteserver debug1: /home/ilya/.ssh/config line 43: Applying options for * debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 20: Applying options for * debug1: Hostname has changed; re-reading configuration debug1: Reading configuration data /home/ilya/.ssh/config debug1: /home/ilya/.ssh/config line 43: Applying options for * debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 20: Applying options for * debug1: Connecting to remoteserver.tu-darmstadt.de [130.83.70.XXX] port 22. debug1: Connection established. debug1: identity file /home/ilya/.ssh/id_rsa type 1 debug1: identity file /home/ilya/.ssh/id_rsa-cert type -1 debug1: identity file /home/ilya/.ssh/id_dsa type -1 debug1: identity file /home/ilya/.ssh/id_dsa-cert type -1 debug1: identity file /home/ilya/.ssh/id_ecdsa type -1 debug1: identity file /home/ilya/.ssh/id_ecdsa-cert type -1 debug1: identity file /home/ilya/.ssh/id_ed25519 type -1 debug1: identity file /home/ilya/.ssh/id_ed25519-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.6.1 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1 debug1: match: OpenSSH_6.6.1 pat OpenSSH_6.6.1* compat 0x04000000 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY debug1: Server host key: ECDSA 77:35:a6:ca:15:66:5d:05:33:ab:35:35:c6:65:ed:79 [MD5] debug1: Host 'remoteserver.tu-darmstadt.de' is known and matches the ECDSA host key. debug1: Found key in /home/ilya/.ssh/known_hosts:60 debug1: ssh_ecdsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: publickey debug1: Offering RSA public key: /home/ilya/.ssh/id_rsa debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Trying private key: /home/ilya/.ssh/id_dsa debug1: Trying private key: /home/ilya/.ssh/id_ecdsa debug1: Trying private key: /home/ilya/.ssh/id_ed25519 debug1: Next authentication method: password   The permission seem to fit: the ~/.ssh folder on the local workstation was set to 700 and ~/.ssh/authorized_keys on the remote server was set to 600.  Do you have any idea, what the problem cold be?  @Jakuje  $ ls -lZd ~ilya ~ilya/.ssh/ ~ilya/.ssh/authorized_keys drwxr-x--- ilya ilya ?                                /home/ilya drwxrwxr-x ilya ilya ?                                /home/ilya/.ssh/ -rw------- ilya ilya ?                                /home/ilya/.ssh/authorized_keys

I'm working from the URL I found here:    My ssh client is Ubuntu 64 bit 11.10 desktop and my server is Centos 6.2 64 bit. I have followed the directions. I still get a password prompt on ssh.  I'm not sure what to do next.


I am soon to submit my PhD thesis and I am currently looking for postdoc positions. I would eventually like to stay in academia and was concerned if my past gap year would harm my chances in getting a position.  After my master's degree, I got an R&D job and worked there for 4 months before quitting it as I did not enjoy it there. My plan was to join my master's lab as a research fellow, and I had an offer for that from my advisor. But, I got a bad disease and I fell ill for 3 months. I was not hospitalized, but had to live with my parents for the period. As I always wanted to pursue PhD, I was searching for a position in the meantime. During the 3 months, I gave GRE (scored poorly, thanks to my illness) and applied to universities and professors. I got a positive response and I was sure of getting a PhD position.  However, it was already February and if I were to join a PhD program, I would have to wait till September. Also, the visa process and other formalities take time. So, I decided to not go further with the research fellow, and take time to complete the visa processing, spend time with parents and travel around.  I had a blast of time. Learned so much during that time. But, I don't have anything concrete to show for that 9-10 months period.  My concern is, how much will that affect my future career?

I am starting a Master's conversion course (in Computing and IT Management) but I am still very unsure about all of the details about doing a PhD such as where and what I want to do it in. Some programs require that you have you Master's certificate to hand when applying too, and I haven't even started my MSc yet.  I was thinking of taking a gap year after the MSc to continue my entrepreneurial activities and goals, to find some temp/contractual work and to give myself more time to apply to PhD applications.  Would this be beneficial or detrimental to my applications and academic prospects?


I installed libimobiledevice package and I can access the pictures of my iPhone using the files browser.  But my iPhone doesn't show up in Rhythmbox. Why is that? What could I do to transfer music into my iPhone in this case?

What ubuntu applications provide support? (guides, how to's, status) Also, specifically, details on support for syncing music to iPhone's and iPod's with the latest OS version:   Can you sync music to apple devices using >iOS4? (iPhone & iPod) What applications allow you to do this and how? (guides, how to's, status)    What has already been established is:   Apple does not support Linux and has no plans to.  provides some support, however it currently does not support music/video synchronization with devices >iOS4. Go to  and scroll to the section titled "" to see if your device version is supported.


I and my research advisor have a manuscript that still requires some final polish to be sent for peer review. In the meantime, I am applying for graduate school. Some graduate schools allow me to upload any additional material I think helpful. First note: We are not worried about our idea been stolen even if we expose it on the internet(My advisor even put all his finished manuscripts on arXiv, including those rejected by peer review. He in fact wants his work be read by more people and more people could exchange ideas with him, unlike the majority of academia who would keep their work not openly-accessible before published). I ask my advisor for consent that if I can include the current version of the manuscript as a draft of our work in my application to those schools? The advisor is not familiar with how grad school admission goes in the US so he said he understood that I want to present research experience but he prefers that I state them in SoP instead. He further said nevertheless if I really want to present a draft, I need to follow the ethics code in that the ultimate rule is that I cannot damage his academic reputation, at least point out in the draft that it's not the final version in his view. Although I have this consent, I still hesitate about it. Which one makes a stronger application? Including a Draft? or just state my work in SoP? Or the difference is trivial?


I have confusion about following words because it's Gujarati meaning for all are same. What is actual difference between following words   Look, See, Watch   If possible then explain with example.

When should I use "look", "see", and "watch"?     I'm watching "Star Trek".   Have you seen "Star Trek"?   Are the examples above correct?


------ NOTICE ------ The above put box "This question already has answers here:  " is wrong and void: it has a title that sounds similar to my question but the question goes into Arxiv and the answers are in regard to Arxiv ("Arxiv is not peer reviewed") which is not the issue discussed here. The question here is why "peer-reviewed government funded alternatives" are not used.  The field of science is under-funded but we follow a publication system that has two major (expensive) options for publishing:  Paywall journals: Scientists do the science and write the papers (using mainly tax money). Scientists act as editors and reviewers check the quality (while paid with more tax money). Once years of work have gone into a paper the journal takes it without paying the authors, academic editors and/or reviewers a single cent and puts the paper behind a paywall. Now universities have to pay the journal huge amounts of money (exact numbers are usually not available due to NDAs) to access the paper to which the journal did not contribute anything (apart from minor formatting issues and putting a pdf on a webpage maybe). Open access journals: Same as above (scientists do all the work) but authors even pay the journal a substantial amount of money which can easily go up to 6000 USD in "respected" journals (I am not talking about predatory open-access journals here – the 6k is for example for the journals of the American Chemical Society which publishes a few of the leading journals in our field). For this amount of money the journals do the minor formatting issues mentioned above and upload a pdf on their webpage. There is just no relation between their fees and what they do for it. Here 60-100 USD would be more appropriate than 6000 USD.  Is this not fundamentally wrong that scientists do the work and journals skim off the profit? Why do scientists (and tax payers!) still put up with this? I do understand that historically :  Journals made sense as someone needed to print the articles into books to make them accessible to everybody and layouting might have been something non-trivial but nowadays this is not the case any-more. Scientists have brought themselves into a dead-lock due to a publish (in high impact and "respected" journals)    or perish in which you have to publish in certain journals in order    to be seen as a good scientist.  But would it not make much more sense to have tax-money funded    web-portals that use editors and reviewers to assess quality of    articles and make them available for download as journals do it currently? That would cost a fraction of    the paywall and open access fees that journals make money from at the    moment. Why does science still stick with journals? My feeling is that the field of science does not need the journals at all anymore - what am I missing here? I have never really gotten a satisfactory answer from other scientists (mostly things like "this is how things are and we can not change them") therefore I am asking here  ...

I am new to research and I have yet to internalize the concept of journals and their utility in archiving scientific literature.  Almost all the papers I have read recently are from this website called . Arxiv calls itself to be a preprint archive. Anyone can upload a PDF file to the repository and it counts as a valid research. Large companies like Google and Facebook post all their research here. The research is peer reviewed, It does not have the tyranny of a fixed format and the publishing is instantaneous unlike journals which are painfully slow. It is also open access and unlike open access journals it does not cost a fortune to publish a paper.  My question is, why were journals used to begin with? Why are they used now?   I have heard some people say that if a paper is not published in a  journal then it does not have any value. Then why are so many people publishing here? As far as I know citations from arxiv are picked up by google scholar.   EDIT: Ok, so the entire system is a huge mess.


Let's say my $string = "XXXXXTPXXXXTPXXXXTP"; If I want to match: $string =~ /TP/; multiple times and return the position for each, how would I do so?  I have tried$-[0], $-[1], $-[2] but I only get a position for $-[0].  EDIT: I have also tried the global modifier //g and it still does not work.

I need to write a function that receives a string and a regex. I need to check if there is a match and return the start and end location of a match. (The regex was already compiled by qr//.)  The function might also receive a "global" flag and then I need to return the (start,end) pairs of all the matches.  I cannot change the regex, not even add () around it as the user might use () and \1. Maybe I can use (?:).  Example: given "ababab" and the regex qr/ab/, in the global case I need to get back 3 pairs of (start, end).


"iPhone is king" I am referring here to the article being missed. As far as I know that when a noun is used in a singular form, then we should add an article a/an for the first time, if the noun has been mentioned previously then you can add the. However, in some cases (like this case) I see no article in front of the noun even though it's a noun. Is there an exception or what?

I'm used to always hearing or seeing a  before certain nouns.  Yet on certain occasions the article is totally omitted, and it bothers me.  I'm wondering what the justification for omitting the article is, especially when the definite article would seem to be required, or if it is just bad English either on the part of the individual in question or more likely by tradition.  The most frequent place I hear this is at the doctor or dentist's office. In every one I have ever visited, the receptionist or assistant always says things like "Doctor will see you shortly" instead of "The doctor will see you shortly."  The wikipedia article linked above says this: "A definite article indicates that its noun is a particular one (or ones) identifiable to the listener".  In the case of a clinical setting, I know who the doctor is, especially if this is not my first visit.  The people in the office know the doctor even better than I, so it would seem to be inappropriate to omit the article. Even the indefinite article would be incorrect. It further says, under "Zero article":  "In languages having a definite article, the lack of an article specifically indicates that the noun is indefinite."  Since the noun is not indefinite, why are they omitting the article?  Another place I see the article omitted is with the word "bar".  Bartenders apparently don't say "I tend the bar" they say "I tend bar".  Unless a bartender works in multiple bars, it would seem like an article would be required.  Furthermore, "the bar" can mean any bar a person goes to, so even in a case like , it seems like the word "the" should be in the sentence.  The only thing I can think of in this case is maybe the speaker doesn't want to confuse the listener into thinking they work in the legal field.  Is this just a bad habit, a historical corruption or tradition, or is there really a valid reason (or perhaps more than one) for these omissions?


I have crontab setup on my CentOS VPS and it is not running...  Here's the cron file:  * * * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1min.php * * * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1minemail.php */15 * * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/15min.php */30 * * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/30min.php 0 */1 * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/hourly.php 0 0 */1 * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/daily.php 0 0 */7 * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/weekly.php 0 0 */30 * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/bimonthly.php 0 0 * * * php -f /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/clearreport.php   I've also tried another variation of that:  * * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1min.php * * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1minemail.php */15 * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/15min.php */30 * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/30min.php 0 */1 * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/hourly.php 0 0 */1 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/daily.php 0 0 */7 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/weekly.php 0 0 */30 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/bimonthly.php 0 0 * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/clearreport.php  * * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1min.php * * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/1minemail.php */15 * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/15min.php */30 * * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/30min.php 0 */1 * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/hourly.php 0 0 */1 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/daily.php 0 0 */7 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/weekly.php 0 0 */30 * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/bimonthly.php 0 0 * * * php -q /var/zpanel/hostdata/zadmin/public_html/pingrglobe_com/crons/clearreport.php   I am able to run the files from my web browser, but not from crontab.

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


I have three tables, many-to-many relation:   BOOKS          CREATE TABLE `books` (           `id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,           `title` VARCHAR(100) NOT NULL,           `condition` ENUM('mint', 'new', 'medium', 'poor', 'needs replacement'),           `date_added` DATE          ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;  AUTHORS          CREATE TABLE `authors` (           `id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,           `name` VARCHAR(50) NOT NULL,           `pseudonim` VARCHAR(50) NOT NULL,           `year_of_birth` INT(4) NOT NULL         ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;  AUTHORS_BOOKS table:         CREATE TABLE `authors_books` (           `author_id` INT(11) UNSIGNED NOT NULL,           `book_id` INT(11) UNSIGNED NOT NULL,         PRIMARY KEY (`author_id`, `book_id`),          CONSTRAINT `fk1_authors_authors_id` FOREIGN KEY (`author_id`) REFERENCES `authors` (`id`)          ON UPDATE CASCADE ON DELETE CASCADE,           CONSTRAINT `fk2_books_book_id` FOREIGN KEY (`book_id`) REFERENCES `books` (`id`)          ON UPDATE CASCADE ON DELETE CASCADE         ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;    What I am trying to make is to fetch data containing the following info:   book id book title,  author's name   My query does not return the relevant data, I probably have missed the correct join somewhere, but as I see, the biggest problem is in my understanding. I would appreciate if anyone could check the consequence of things to be done as I see it:   specify the exact columns I need in my view:   SELECT b.id, b.title, a.name FROM books as b    join the pivoting table on book_id:   INNER JOIN authors_books as ab on b.id = ab.book_id    Since I need the names of the authors, I am making one more join to bring into the game the authors table:   INNER JOIN authors AS a ON ab.authors_id = a.id   So in the end I have the following query  SELECT b.id, b.title, a.name FROM books as b INNER JOIN authors_books as ab on b.id = ab.book_id INNER JOIN authors AS a ON ab.authors_id = a.id   that returns me an incomplete list of books skipping most of them. I can't get how does it happen. Where is the mistake I am making, what concept am I missing?

Also how do LEFT JOIN, RIGHT JOIN and FULL JOIN fit in?


I want to try out Linux Mint. I am on Ubuntu 11.10 now. How can I mount .iso file on USB? And also, will my other files disappear in USB when I mount it? Thank you.

I want to burn a Windows ISO to a USB device in Ubuntu. How do I do this?   I know how to burn a Ubuntu ISO into a USB device, but with a Windows ISO it's not the same.


I am currently using  VS Code to learn Python . So i have to run scripts like 10-15 times a minute , just doing small edits and learning all things. I am running the scripts in integrated terminal of VS code So apparently the terminal gets horribly cluttered and i have to always clear the terminal manually by running clear, I want the terminal to automatically get cleared every time I execute the Python script . Please note that I am not looking for a keyboard shortcut to clear terminal , rather I need the terminal to automatically clear the old output before displaying the output of the present script. I couldn't find anything that does this , hopefully someone can provide a way out

Like most Python developers, I typically keep a console window open with the Python interpreter running to test commands, dir() stuff, help() stuff, etc.  Like any console, after a while the visible backlog of past commands and prints gets to be cluttered, and sometimes confusing when re-running the same command several times.  I'm wondering if, and how, to clear the Python interpreter console.  I've heard about doing a system call and either calling cls on Windows or clear on Linux, but I was hoping there was something I could command the interpreter itself to do.  Note: I'm running on Windows, so Ctrl+L doesn't work.


If we Google "Panera" google shows Panera Bread as the top ranked result and below the description there's things like "Menu", "Locations", etc. How do we get these rendered for an Angular App that only performs client side rendering?

My website used to have sitelinks and now it doesn't. It's very possible that it's due to changing the website to a sidebar design instead of having an "interstitial" type landing page which limited the number of choices, but I'm not sure.  Here is how sitelinks might look for a site:    What are some things that I can do to improve my chances of getting sitelinks?


Let's suppose I have the following loop:  for i in {1..3} do  mkdir $i  done   Since I have many other loops in the main code and I am going to change regularly the size of the sequence, I would like to define the start and end of the loop and use these variables in the for loop(s).  I tried this without success:  start=1; end=1;  for i in {$start..$end} do  mkdir $i  done   Any suggestion?

I want to use $var in a shell brace expansion with a range, in bash. Simply putting {$var1..$var2} doesn't work, so I went "lateral"...   The following works, but it's a bit kludgey.    # remove the split files echo rm foo.{$ext0..$extN} rm-segments > rm-segments source rm-segments   Is there a more "normal" way?


The solution to the answer is what I am trying to understand. I have two vectors denoted by $V_{1}=(1,-2,3)$ and $V_{2}=(0,5,-3)$ The question states to enlarge ($V_{1}$ and $V_{2}$) to a basis for $\mathbb{R}^3$.  the solution says $V_{3}=(a,b,c)$ with $9a-3b-5c$.  I put the vectors in a column of a matrix then I augmented it by a $3 \times3$ identity matrix.The reduced echelon form that I got is \begin{equation} \begin{bmatrix} 1& 0 & 0& \frac13 & \frac59  \\ 0&1&0 & \frac13 & \frac29 \\ 0&0&1 & -\frac13 & -\frac59 \end{bmatrix} \end{equation}                                                                   I understand that the first two columns correspond to the first two vectors so then the third column is the missing vector $V_{3}=(0,0,1)$. The solution however is different and I am wondering what procedures I am missing so I can derive the given solution.

For instance, let $v_{1}=(1,-2,3),v_{2}=(0,-1,2)$. The set $\{v_{1},v_{2}\}$ is linearly independent. Enlarging $\{v_{1},v_{2}\}$ to a basis for $\mathbb{R}^3$ I simply form a matrix using $v_{1},v_{2}$ as columns and then augment one of the elementary columns from $I_{3}$ and see whether the resulting echelon form has $3$ pivots, from then I conclude that it spans $\mathbb{R}^3$ and is linearly independent.   But the book I am using gives a solution as: $(a,b,c)$ with $9a-3b-5c\neq 0$. What method was use here and how might I arrive at such an answer? Thanks.


I have defined many objects, and for some of them, i defined a function :  template <typename Ratio>  auto print(const T &t, bool a= true, bool b= true) {     std::stringstream ss;     // ... do stuff ...     return ss.str(); }   where T is the type of one of the objects for which print is defined. Ratio is used inside the function.  My question is : Is there a way for a type T to find if this function exists ?   For others uses, i already used templates and SFINAE to detect if a class member method exists. But for my problem here, i can't find the solution ... Anyone ?  Thanks, Ben  PS : Example of SFINAE use in my code, where i needed to detect if a class member method exists .  static T none() { ... }  /**  * SFINAE for checking id none method exists  */ template <class T> static auto hasNoneMethod(int)     -> std::integral_constant<bool, std::is_same<T, decltype(T::none())>::value>; template <class> static auto hasNoneMethod(...) -> std::false_type;  /**  * Type-Function  */ template <typename T> struct HasNoneMethod: decltype(detail::hasNoneMethod<T>(0)) { };

Is it possible to write a template that changes behavior depending on if a certain member function is defined on a class?  Here's a simple example of what I would want to write:  template<class T> std::string optionalToString(T* obj) {     if (FUNCTION_EXISTS(T->toString))         return obj->toString();     else         return "toString not defined"; }   So, if class T has toString() defined, then it uses it; otherwise, it doesn't. The magical part that I don't know how to do is the "FUNCTION_EXISTS" part.


have made a simple dynamic login page.you have to enter username and password in order to view data.I have pasted the code below and the screenshot of error.code in config.php is the connection made with database.name of db is department and tablename is user.     if($_POST)    {      $unam=$_POST["uname"];     $pwd=$_POST["pwd"];     include ("config.php");      $res=mysqli_query($con,"select * from user where uname=$unam AND password=$pwd ");     $row=mysqli_fetch_array($res);      //also tried     //while($row=mysqli_fetch_array($res);     if($res){ ?> Click here to view<?php }      else { ?> login failed <?php }     }

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


My sentence is     In Charles Dickens' book Oliver Twist, the stingy orphanage director doles out just one small bit of soup to the hungry orphans.   The main question is should it be doles or doled? Could it be either?

I am preparing a book for publication which contains the following passage:     Stromberg in Religious Liberalism in Eighteenth-Century England   (1954) noted that 'the critical moment in the emergence of a positive   spirit of reform...consisted in the awareness of evil as being social   and remediable. It begins about 1750.'   My proof reader (my wife) has picked this out suggesting it should be the past tense. However if I say It began about 1750 it seems to convey too much certainty about the exact date. I just want to convey an impression of it being something which emerges in the mid-eighteenth century. I believe use of the present tense is the way to go.   But what is this artifice called, this use of the present to convey mild uncertainty?


I have a system with 4gb of RAM and Intel i5 processor. I want to know how much memory I should allocate to SWAP. Will allocating more memory help increase the system performance.  In the past i have always allocated 4gb for SWAP.

I read many places that the rule of thumb for swap space is to double the amount of physical RAM. However, 32 GB does seem a LOT. Do I need that much? Do I need it at all with this high amount of physical RAM?


Here's what I have so far:  Given $\epsilon > 0$, we want to find N such that $\sqrt{n^2+n}-n < \epsilon$ for all $n>N$. And so:  $( \sqrt{n^2+n}-n-\frac{1}{2}) \cdot \frac{\sqrt{n^2+n}-(n+\frac{1}{2})}{\sqrt{n^2+n}-(n+\frac{1}{2})}$  $= \frac{(n^2+n)-(n+\frac{1}{2})}{\sqrt{n^2+n} + (n+\frac{1}{2})}$  And I'm not sure how to go on from here. Help would be appreciated.

Here's the question: Prove that $\lim_{n \to \infty} (\sqrt{n^2+n}-n) = \frac{1}{2}.$  Here's my attempt at a solution, but for some reason, the $N$ that I arrive at is incorrect (I ran a computer program to test my solution against some test cases, and it spits out an error). Can anyone spot the error for me?  $\left|\sqrt{n^2+n}-n-\frac{1}{2}\right| < \epsilon$  $\Rightarrow \left|\frac{n}{\sqrt{n^2+n}+n} - \frac{1}{2}\right| < \epsilon$  $\Rightarrow \frac{1}{2}-\frac{1}{\sqrt{1+\frac{1}{n}}+1} < \epsilon$  $\Rightarrow \frac{1}{\sqrt{1+\frac{1}{n}}+1} > \frac{1}{2} - \epsilon = \frac{1-2 \epsilon}{2}$  $\Rightarrow \frac{1}{\sqrt{1+\frac{1}{n}}} > \frac{1-2 \epsilon}{2}$  $\Rightarrow \frac{1}{\sqrt{\frac{1}{n}}} > \frac{1-2 \epsilon}{2}$  $\Rightarrow \sqrt{n} > \frac{1-2 \epsilon}{2}$  $\Rightarrow n > \frac{4 {\epsilon}^2-4 \epsilon +1}{4}$


I've a laptop which dual boots Windows 10 and Ubuntu (16.10). I'm based in India and the time that I see is 5.30 hours ahead. i.e. 5.30PM when the local time is 12.00PM I've tried to set the Hw clock with   sudo hwclock --localtime   This is what I see  sudo hwclock -r 2017-03-04 17:30:43.420286+5:30   Timezone     cat /etc/timezone     Asia/Kolkata  Raw output  sudo hwclock --debug hwclock from util-linux 2.28.2 Using the /dev interface to the clock. Assuming hardware clock is kept in UTC time. Waiting for clock tick... ...got clock tick Time read from Hardware Clock: 2017/03/04 12:44:07 Hw clock time : 2017/03/04 12:44:07 = 1488631447 seconds since 1969 Time since last adjustment is 1488631447 seconds Calculated Hardware Clock drift is 0.000000 seconds 2017-03-04 18:14:06.075863+5:30   In the Time Applet I've set it to get time automatically and that still reutrns this time.  Any help is much appreciated   EDIT: This is the solution  In terminal:  gksu gedit /etc/default/rcS   You may need to install gksu. In which case:  sudo apt-get install gksu   else ensure the file says:  UTC=no   Save and exit  Boot to Windows. Set correct time with the time applet. Boot to Ubuntu.  The correct time should be up

Dual boot system Windows XP Pro and Ubuntu 12.04.  I have the bios set for the correct time and Ubuntu set for US Eastern time.  Ubuntu will boot up and the time will be off by -4 hours.  If I correct the time in Ubuntu then when I boot up in Windows XP the time will be off by + 4 hours.  This is a fresh install of 12.04. I did not have this problem before reinstalling Ubuntu.


I have seen the sentence like 'I have been waiting on Beyonce to call me.' on the internet. And I can't understand the meaning of 'waiting on Beyonce' part. What is the meaning of the sentence 'I have been waiting on Beyonce to call me.' Please tell me.

Officials are waiting on autopsy results for Oscar-winning actor Philip Seymour Hoffman. New York police suspect a drug overdose, possibly heroin.   I am curious about the preposition on in the sentence, because I usually say "wait for" instead of "wait on". Does it still have the same meaning if I change on to for? Just as follows:     Officials are waiting for autopsy results for Oscar-winning actor Philip Seymour Hoffman. New York police suspect a drug overdose, possibly heroin.


I am trying to find the correlation or association  between a categorical variable - classes from 1 -4 from a GIS (geographic information system) classification - and a continuous variable with values between 0 and 9. What would be the best test to use for this?

I would like to find the correlation between a continuous (dependent variable) and a categorical (nominal: gender, independent variable) variable. Continuous data is not normally distributed. Before, I had computed it using the Spearman's $\rho$. However, I have been told that it is not right.  While searching on the internet, I found that the boxplot can provide an idea about how much they are associated; however, I was looking for a quantified value such as Pearson's product moment coefficient or Spearman's $\rho$. Can you please help me on how to do this? Or, inform on which method would be appropriate?  Would Point Biserial Coefficient be the right option?


Given the letters "BALL", how many arrangements of two letters exists? Using brute force, i.e. without using any counting technique, I get the following arrangements:   AB AL BA BL LA LB LL   Please let me know how I can get the correct answer using a counting formula. For example, if I wanted to know the number of arrangements that include all the letters, it would be $\frac{4!}{2!}$; where the 2! accounts for the duplicate L's in BALL.

Is there a general formula for the number of distinguishable arrangements of length $\ell$ of a sequence of size $s$, given the repeated elements? So,  For example, would there be a general formula to solve the problem:  How many distinguishable 5-letter arrangements are there of the word "PROBABILITY" ?  I'm looking for a general formula.


I'm trying to identify a Scifi/Fantasy novel book I read about 10 years ago, some time in the early to mid 2000s   I think there are more books about this setting (I think I read two) Protagonist is not human, belongs to an alien species (but looks human - I think) He has to prove himself worthy in an maze-like trial with a lot of different levels (including deadly traps and fights) There are a lot of references to these trials He has excellent combat/survival skills  He uses a "ship" to travel through dimensions, visiting other worlds/dimensions Works as a spy(?) and has a hidden agenda    Story-related    At some point he visits a machine-powered world inhibited by dwarf-like creatures  I think the dwarfs work mostly to retain functionality of their (maybe floating) world He/it rescues some inhabitants from destruction and travels with them in his ship  He/it has a conflicted personality, although he rescues some of the creatures he is not stereo-typically "good" (e.g. he doesn't prevent fights among them caused by the long journey in a small vessel).

I'm trying to identify fantasy book series I encountered some time ago. Here are things I remember:   it was a fantasy setting but with some s-f elements; with many worlds and possibility to travel between them; resembling  setting a little, the two main races were non-human and probably hostile to each other,  a labyrinth (?), which somehow played an important role in the plot, a protagonist was some kind of emissary and was sent on a mission to another worlds  time period: 80s - 90s    Does anyone know what it is the name of the series?


If I Use 's Activated ability of "{t}, sacrifice a creature: Proliferate" and then target  with the activated ability of "Sacrifice Vampire Hexmage: remove all counters from target permanent", what happens?  Will Plaguemaw Beast force Hexmage to be sacrificed without being able to activate the ablity?  Will Plaguemaw Beast lose a valid target if Vampire Hexmage's ability is activated in response to sacrificed, so now Plaguemaw cannot Proliferate?  Will the Plaguemaw Beast's ability activate along with Vampire Hexmage's Activated ablity with Hexmage as a target?

Say I have a Zombie token, , and  on the battlefield. Can I sacrifice the Zombie token to activate both the Altar's and Seer's abilities?  Similarly, if I have one card in hand, and  and  on the battlefield can I discard the one card to both of their abilities?  If I have a  with 3 charge counters can I activate both of its abilities by tapping it to add a counter, and tapping it to remove 3 counters and destroy a permanent without untapping it in between?


Good afternoon, Please, I would like you to help me with a solution to this problem, if you want: Let $ \widetilde{X} $ and $ \widetilde{Y} $ be two simply connected covering spaces for linearly connected and locally connected spaces $X$ and $Y$, respectively. Show that if $ X\simeq Y $ (homotopically equivalent), then $ \widetilde{X}\simeq\widetilde{Y}$. I tried to start from the definition of the concept of covered space and from the definition of the homotopically equivalence between two spaces. Along with these, I read the definition of the concept of lift maps, with the results of existence and uniqueness, but, unfortunately, I fail to build the connection between all of  these.

As part of am exam question (Q21F ), I'm trying to prove that if $X$ and $Y$ are path-connected, locally path-connected spaces with universal covers $\widetilde{X}$ and $\widetilde{Y}$, respectively, then if $X \simeq Y$ then $\widetilde{X} \simeq \widetilde{Y}$.  My attempt might be correct, but it seems too complicated and amongst the jumble I may have made some incorrect assumptions. So what I'm looking for is (a) verification or correction; and (b) ideas as to how I could simplify my argument.    My argument:  Let $p:\widetilde{X} \to X$ and $q:\widetilde{Y} \to Y$ be the covering maps, and let $X \overset{f}{\underset{g}{\leftrightarrows}} Y$ be a homotopy equivalence.  Fix a point $\widetilde{x} \in \widetilde{X}$, let $x=p(x) \in X$ and $y=f(x) \in Y$, and fix $\widetilde{y} \in q^{-1}(\{y\}) \subseteq \widetilde{Y}$. Also let $x' = g(y) \in X$ and fix $\widetilde{x'} \in p^{-1}(\{x'\}) \subseteq \widetilde{X}$.  Define a map $\widetilde{f} : \widetilde{X} \to \widetilde{Y}$ as follows. For $\widetilde{z} \in \widetilde{X}$ let $\widetilde{u}:[0,1] \to \widetilde{X}$ be a path from $\widetilde{x}$ to $\widetilde{z}$. Let $z=p(z)$ so that $u=p\widetilde{u}$ is a path in $X$ from $x$ to $z$. Let $v=fu$, so that $v$ is a path in $Y$ from $y$ to $f(z)$. Lift $v$ to a path $\widetilde{v}$ in $\widetilde{Y}$ with $\widetilde{v}(0) = \widetilde{y}$. Define $\widetilde{f}(\widetilde{z}) = \widetilde{v}(1)$.  Notice that $q\widetilde{v}=v$ so that $q\widetilde{f} = fp$.  Define $\widetilde{g}:Y \to X$ analogously: For $\widetilde{z} \in \widetilde{Y}$ let $\widetilde{a}:[0,1] \to \widetilde{Y}$ be a path from $\widetilde{y}$ to $\widetilde{z}$. Let $z=q(z)$ so that $a=q\widetilde{a}$ is a path in $Y$ from $y$ to $z$. Let $b=fa$, so that $b$ is a path in $X$ from $x'$ to $g(z)$. Lift $b$ to a path $\widetilde{b}$ in $\widetilde{X}$ with $\widetilde{b}(0) = \widetilde{x'}$. Define $\widetilde{g}(\widetilde{z}) = \widetilde{b}(1)$.  Likewise, notice that $p\widetilde{g}=gq$.  Claim: $\widetilde{X} \overset{\widetilde{f}}{\underset{\widetilde{g}}{\leftrightarrows}} \widetilde{Y}$ is a homotopy equivalence.  We have $p\widetilde{g}\widetilde{f} = gq\widetilde{f}=gfp \simeq p$ and $q\widetilde{f}\widetilde{g} = fp\widetilde{g} = fgq \simeq q$.  This shows that $\widetilde{g}\widetilde{f}$ and $\widetilde{f}\widetilde{g}$ are covering translations (deck transformations) and are therefore homotopic to the respective identity maps. So we have a homotopy equivalence.    Any comments would be appreciated.


I hear this word more often nowadays.  Can someone native explain what is the meaning of swag.   The dictionary says "goods or money obtained illegally." But I don't think the following sentence implies that.  Example:      It's my swag.      You Ain't Got No Swag.

Source:   Example:     In his State of the Union address, Obama displayed similar swag and bluster against both the Kremlin and congressional Republicans, seemingly without regard for any recent events. As the president explained: ...   I hear it a lot, but what does this slang word really mean?


I don't understand what the probabilities for an election actually mean. I was reading this  but I still don't get it. What could it possibly mean to say that candidate A has 70% chance of winning while candidate B has 30% chance of winning.  There is no randomness at any point of the election. Votes are not random, people don't usually show up to the voting places and flip a coin, they already know who they are voting for. The counting process is also not random.  The repeating events interpretation also makes no sense. It sort of implies that some people would vote different in each trial, which also makes no sense to me, unless we are talking of non-independent trials.  The only way I can interpret these probabilities is if we are talking about the probabilities of getting those poll results assuming one of the outcomes.   Gelman clearly thinks this view is wrong, so my guess is I must be wrong. What am I missing?

As the election is a one time event, it is not an experiment that can be repeated. So exactly what does the statement "Hillary has a 75% chance of winning" technically mean? I am seeking a statistically correct definition not an intuitive or conceptual one.  I am an amateur statistics fan who is trying to respond to this question that came up in a discussion. I am pretty sure there's a good objective response to it but I can't come up with it myself...


I want to know how to view images (.jpg, .png) via terminal (xterm or gnome).  Please help me. How to enable visual support inside terminal?

This is a quick mockup I copy and pasted together. I imagine this being super cool and useful.  Does something like this exist already?


I was wondering how big a document (picture, voice, video) can be "iMessaged" from an iPhone. Also, would the iMessage data size be any different if you are iMessaging from within Mountain Lion.

I'm trying to send a 36 MB .mp4 video via Messages, but I'm not exactly sure if it's working.  After sending the file, the CPU usage of the processes VTDecoderXPCService and IMTranscoderAgent goes up very high (~300%) and then only about 11 MB of data are send.  I doubt that Messages is performing some magical compression that results in <30% of the original video file size for the transfer, instead I assume that the whole file is not send. But I'm not receiving a warning such as: "Could not transfer file. Attachment too large..."  Is there a limit for the attachment size in Messages?


I understand that when I open a terminal emulator like xterm, and then list the processes using ps, I can see xterm running as a process.  But when I type Ctrl+Alt+F#, I get a "full screen terminal", is this "full screen terminal" also a process? or is it a UI provided by the kernel without being an actual process?

I think these terms almost refer to the same thing, when used loosely:   terminal shell tty console   What exactly does each of these terms refer to?


I have Ubuntu 12.04 and I use File Browser Panel plugin in GEdit. I can increase the size of file browser bar. But the minimum width of file browser bar is about 30% of screen width. How to decrease minimum width of the File Browser bar in GEdit?  When I open gedit using terminal then I can decrease the size of the file browser bar. But when I open gedit without using terminal I can't be decrease the size of the file browser bar.

My laptop screen is fairly small and gedit's side panel won't go smaller than about 400 px. It is a little exasperating because I can't have any other windows visible if I want to use anything in the sidebar, because it crowds out my document.  Is there a setting someplace that I can fiddle to make it smaller?  I've looked everywhere I can think of for it!    I can drag it down to the width you see below, but I can't drag it any farther than that.


I use Virtualbox and yesterday it display me this error Kernel  driver not installed (rc=-1908) The VirtualBox Linux kernel driver is either not loaded or not set up correctly. Please reinstall virtualbox-dkms package and load the kernel module by executing 'modprobe vboxdrv' as root. If your system has EFI Secure Boot enabled you may also need to sign the kernel modules (vboxdrv, vboxnetflt, vboxnetadp, vboxpci) before you can load them. Please see your Linux system's documentation for more information. where: suplibOsInit what: 3 VERR_VM_DRIVER_NOT_INSTALLED (-1908) - The support driver is not installed. On linux, open returned ENOENT. I found a lot of tips and tutorials but nothing wworks. I'm using Ubuntu 20.04

I tried to use my Virtual Box and this is the error I received - (I just updated to the new Ubuntu also) and I am VERY new at this Linux OS.     Kernel driver not installed (rc=-1908)      The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or   there is a permission problem with /dev/vboxdrv. Please reinstall the   kernel module by executing      '/etc/init.d/vboxdrv setup'      as root. Users of Ubuntu, Fedora or Mandriva should install the DKMS   package first. This package keeps track of Linux kernel changes and   recompiles the vboxdrv kernel module if necessary.


Is there any  channel for Stack Exchange?  Reason for asking the question:  I was trying to figure out best out of two books which have very less information on Internet in forms of review, etc. So I thought I should ask it on a Stack Exchange site. But I came to know that Stack Exchange doesn't encourage recommendation type questions. That's where the thought of IRC channel came to my mind. I am open to suggestions and any information.

Will there be any way of accessing the chat over IRC?  As beautiful ajax interfaces are ... IRC is still #1 for chats.


This stems from   I re-read the description of Spell Bombardment     When you roll damage for a spell and roll the highest number possible on any of the dice, choose one of those dice, roll it again and add that roll to the damage.   and noticed that the wording is different than other features adding damage dice, which usually say "extra".  Does the Spell Bombardment's die count as damage die? Or it is counted as a modifier, because the wording says "add that roll to the damage"?

At level 18,  get the  feature (PHB, p. 103):     Beginning at 18th level, when you roll damage for a spell and roll the highest number possible on any of the dice, choose one of those dice, roll it again and add that roll to the damage. You can use the feature only once per turn.   When you score a critical hit with an attack (even a spell attack), you double the amount of dice you roll.  Does the additional damage die from Spell Bombardment also get rolled twice on a critical hit?


I am looking for a book that has stuff on quantum states, entanglement, etc. I am aware of the book, Geometry of Quantum States.  I have read Ballentine's book, Quantum Mechanics: A modern development

I'm really interested in quantum theory and would like to learn all that I can about it. I've followed a few tutorials and read a few books but none satisfied me completely. I'm looking for introductions for beginners which do not depend heavily on linear algebra or calculus, or which provide a soft introduction for the requisite mathematics as they go along.  What are good introductory guides to QM along these lines?


How small must an object be in order for it to be subject to the laws of quantum mechanics?

I apologize if this question is posted on the wrong portion of the website, but I knew no better place to ask.  I've come to see that some effects, such as super-conduction may happen at either extremely low temperatures, or at extreme temperatures (the recent discovery of superconducting iron in the bowels of the earth, for one), and this is fascinating.  My question is: can (does?) the same principle be applied to quantum effects? Would it be applicable to, for example, say that although quantum effects happen at nano scales and below they may happen on a grand scale of say, the entire Universe (as a solitary unit)?  Can said quantum effects happen at moments of say, picoseconds after the Big Bang due to the turbulence of forces involves in such an event? Or even within the core of a dying star?  Thank you for any answers or clarification of my misinformation.


Since the split, the  tag is no longer relevant, but people are still using it to tag new questions here. Back when this site was Meta Stack Overflow, this tag was used to indicate if a question specifically applied to the Stack Exchange network of sites, while the  tag was used to indicate Stack Overflow-specific questions. However, this site's scope is now the entire Stack Exchange network, making it redundant.  Can it be mass-removed?

It looks like the  tag (later renamed to ) is a holdover from the pre-split days when this site was called Meta Stack Overflow and also served as the meta site for Stack Overflow (in addition to its current purpose). It was intended to disambiguate questions about the SE network as a whole from questions specifically about Stack Overflow (). It has nearly 1,500 uses, so it's too big to clean up manually. It looks like people are still using it on new questions, and I just saw a suggested edit that only added this tag. Since all questions here should be about Stack Exchange, can we burninate this, the ultimate meta tag?


Consider the following code:  function someObj() {     this.someFunction = function() {         console.log('someFunction');     } }  someObj.prototype.foo = function() {     console.log('foo'); }   I can call both like so:  var test = new someObj(); test.someFunction();     // Logs 'someFunction' test.foo();              // Logs 'foo'   How would variable scope be affected here? Is there an advantage / disadvantage to each approach?

What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something };


Is there a function $f:\mathbb R\to\mathbb R$ which is differentiable but such that the derivative is nowhere continuous?

Could someone give an example of a ‘very’ discontinuous derivative? I myself can only come up with examples where the derivative is discontinuous at only one point. I am assuming the function is real-valued and defined on a bounded interval.


I am confused with both the C# version and .NET framework version. In other words, I want to know the relationship with C# version and .NET framework. E.g: which is C# version in .NET framework 3.0?

What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?  This question is primarily to aid those who are searching for an answer using an incorrect version number, e.g. C# 3.5. The hope is that anyone failing to find an answer with the wrong version number will find this question and then search again with the right version number.


My previous question was on , but now am asking the same thing about Palma.   We are planning a two-night trip to Palma Majorca (PMI airport we are flying to). Travel dates are last week of November, so I guess weather should be okay. I have never been to these islands. I'd like to sleep on the beach in a tent or mattresses. Is that possible, safety, legality, and weather? It would also be nice to know how populated with tourists the islands are. Also what are some nice areas where if sleeping is hard , walking is nice. Nice meaning peaceful and quiet.

We are planning a two-night trip to the Canary Islands. The cheapest options include Lanzarote and Las Palmas for flights. Travel dates are last week of November, so I guess weather should be okay. I have never been to these islands. I'd like to sleep on the beach in a tent or mattresses. Is that possible, safety, legality, and weather? It would also be nice to know how populated with tourists the islands are.


I have a generic C# interface as follows:  public interface ISerialiser<TV> {     void Write( BinaryWriter output, TV value );      TV Read( BinaryReader input );      Type GetValueType(); }   of which I have several implementations, this being one of them:  public class BooleanSerialiser : ISerialiser<bool> {     public void Write( BinaryWriter output, bool value )     {         output.Write( value );     }      public bool Read( BinaryReader input )     {         return input.ReadBoolean();     }      public Type GetValueType()     {         return typeof(bool);     } }   This and the other implementations need to be added to a linked list - something like this:  private readonly LinkedHashMap<Type,ISerialiser<?>> theSerialisers =                   new LinkedHashMap<Type, ISerialiser<?>>();   As you can see, I'm using the Java-style wildcard to signify that there are different types of serialiser to add - I realise this won't possibly compile in C# :)  My question is: how do I 'change things around' so that I'm able to populate the HashMap with whatever type of serialiser I wish, and call the interface methods in the same (or similar) way when I eventually pull the objects out of the HashMap?

I'm developing an application where I the need to invoke a method of a generic class and I don't care about the instances actual type. Something like the following Java code:  public class Item<T>{   private T item;    public doSomething(){...} }  ... public void processItems(Item<?>[] items){  for(Item<?> item : items)    item.doSomething(); }   At the time I was on a hurry, so I solved my problem by defining a interface with the methods I needed to invoke and made the generic class implement it.  public interface IItem   {    void doSomething(); }  public class Item<T> : IItem {   private T item;    public void doSomething(){...} }  ... public void processItems(IItem[] items) {  foreach(IItem item in items)    item.doSomething(); }   This workaround works fine, but I'd like to know what is the correct way to achieve the same behavior.    EDIT:  I forgot to refer that the caller of processItems doesn't know the actual types. Actually the idea was that the array passed as argument to processItems could contain intermixed types. Since its not possible to have such an array in .Net, using a non generic base class or interface seems to be the only way.


I just wanna know,how I can get the execution time of my javascript code.For example I have any javascript code(loop,function etc..) I wanna know how much time takes to executing it.Or test my code how many operations it makes for example per second or minute.

I need to get execution time in milliseconds.  I originally asked this question back in 2008. The accepted answer then was to use  However, we can all agree now  that using the standard  API is more appropriate. I am therefore changing the accepted answer to this one.


Question :   If $a,b,c$ and $d$ non-zero natural number such   that $ab=cd$  Show that :   $a^2+b^2+c^2+d^2$ is not prime number   My try :   Call $m$ : $\gcd$ of $a,b$ then $m|_a$ and $m|_b$  Then $\exists \alpha,\beta$ such that :   $a=m.\alpha$ and $b=m.\beta$   So $b\alpha=d\beta$  But how I complete ??

Let $ a, b, c, d $ be natural numbers such that $ ab=cd $. Prove that $ a^2+b^2+c^2+d^2 $ is not a prime.  I am clueless on this one. I tried contradiction, but didn't get anywhere.   Can you help?  Edit: I understand natural numbers to be strictly positive, excluding $0 $.


Many websites say that water drain in different directions in Northern, Southern hemispheres. Some people say that  Coriolis effect causes it.  Some people say that it's not true.

There is a common myth that water flowing out from a sink should rotate in direction governed by on which hemisphere we are; this is shown false in many household experiments, but how to show it theoretically?


I'm writing some induction proofs for my homework.  What is considered to be best convention for writing these kind of proofs?

I need to write some mathematical induction using LaTeX. Are there any packages that I can use for that purpose?


What I've understood about time complexity is that it measures the no. of operations performed with respect to input. For example code{   for(int i=0;i<n;i++){     // n opertions   print(array[i]);  }   for(int i=0;i<n;i++{      // n operations   print(array[i}  } }  If each loop performs n operations then the total no. of operations performed will be 2n Right? Why not include that in the Time Complexity? I mean why is 2 neglected  in O(n) instead of O(2n) If n=5 then the first for loop will perform 5 operation and second will perform 5 , So totally it'll perform 10 operations. If n=10 then first loop will perform 10 and second loop will perform 10 operations , So totally the it'll perform 20 operations which is 2n. The above no. of operations will not change no matter how slow your computer performs the no.of operations performed will be 2n. Then my question is why O(n) instead of O(2n).

I'd prefer as little formal definition as possible and simple mathematics.


How can I make apt display the URL it's downloading, e.g. apt install or apt download? Consider the following example: $ apt download libvirglrenderer0  Get:1 http://deb.debian.org/debian buster/main amd64 libvirglrenderer0 amd64 0.7.0-2 [164 kB] Fetched 164 kB in 5s (30.6 kB/s)     apt might display hints regarding the URL (http://deb.debian.org/debian buster/main amd64 libvirglrenderer0 amd64 0.7.0-2), but I cannot use it with e.g. curl.

I want to see all URLs that for packages that would be downloaded for apt install <pkg> without actually installing the package.  Normally, the URLs can be extracted from the screen output after installing the package (as above).  An example of a URL I want to list:    Is it only possible to get such list of URLs beforehand by looking through all the apt's package source lists?


Let $X,Y$ be adapted, positive integrable processes and $E(X_{n+1}\vert \mathcal{F}_{n})\leq X_{n}+Y_{n}$ and $\sum Y_{n} < \infty$.   How can I define a supermartingale by the above?  Background: I want to show that $X_{n}$ converges a.s. to a finite limit, using a stopping time. It is defined as: $\tau:=\inf\{n:\sum\limits_{i=1}^{n}Y_{i}>K\}$ for some $K >0$  How can I show that $(X_{n})_{n}$ is a supermartingale from the facts $(*)$ or must I define a new supermartingale?

I am have a problem with proving a convergence of a sequence of random variables in the given context:  Let $F_n$ be a filtration. Assume that $X_n$ and $Y_n$ are non-negative and integrable $F_n$-adapted random variables for $n\geq 0$. Furthermore, I assume that: $\mathbb{E}[X_{n+1} \mid F_n]\leq X_n+Y_n$ and that  $\sum_{n}Y_n < \infty$. Under the above conditions, I should show that $X_n$ converges almost surely for $n\rightarrow \infty$.  My approach has been to define a variable $Z_n=X_n-\sum_{i=0}^{n-1} Y_i$, and to set this into the expression for the conditional mean of $X_{n+1}$, but this did not gave any result. Anybody has an idea to this?


Electrons have more energy with higher voltage so it seems that voltage would be what actually determines how harmful it is, because it would have more energy to lose.

Though voltage and current are two interdependent physical quantity, I would like to know what gives more "shock" to a person - Voltage or Current? In simple words, will it cause more "electric - shock" when the voltage is high or Current is more?


I've been very interested in mathematics for a while now and, after being inspired by reading Feynman's biography, would also like to learn about physics.  My mathematics background is fairly extensive.  I've taken courses through calc BC, the basics of multivariable calculus and a fair amount of linear algebra, with plans to take statistics next year.  My physics background is okay, in that I know what many of the individual symbols mean, but have never seen them put together in such a way that they yield all the wonderful results we see today.  Could anyone recommend a good place to start that makes use of this math background without being incomprehensible to my fledgeling physics knowledge and a freely available online textbook to accompany the former?  Thank you very much!

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta:


Sending Email is not working in server side but working in local system. I  tried port 25 and 465 instead of 587. But it doesn't work .  MailMessage msg = new MailMessage("from@gmail.com",ToEmail,"Password reset", message);      msg.IsBodyHtml = true; SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587);  smtp.UseDefaultCredentials = true; smtp.Credentials = new NetworkCredential("from@gmail.com", "pswd"); smtp.EnableSsl = true; smtp.Send(msg);

Instead of relying on my host to send an email, I was thinking of sending the email messages using my Gmail account. The emails are personalized emails to the bands I play on my show.   Is it possible to do it?


I need to run same command separately for each file at the same time.  I've tried   for file in *.txt; do ./script <"$file"; done   but It starts the first one and waits until it get finished then goes to the next one.  I need to start them all together.

I have a small script that loops through all files of a folder and executes a (usually long lasting) command. Basically it's  for file in ./folder/*; do     ./bin/myProgram $file > ./done/$file done   (Please Ignore syntax errors, it's just pseudo code).  I now wanted to run this script twice at the same time. Obviously, the execution is unnecessary if ./done/$file exists. So I changed the script to  for file in ./folder/*; do     [ -f ./done/$file ] || ./bin/myProgram $file >./done/$file done   So basically the question is: Is it possible that both scripts (or in general more than one script) actually are at the same point and check for the existance of the done file which fails and the command runs twice?   it would be just perfect, but I highly doubt it. This would be too easy :D If it can happen that they process the same file, is it possible to somehow "synchronize" the scripts?


When trying to evolve Feebas into Milotic in Pokemon GO, you can either use 100 Feebas Candies to evolve it, or it says:     Walk with you buddy to evolve this Pokemon   There is then a progress bar underneath, which you can fill by walking with Feebas as a buddy, and it becomes full once you've walked 20Km.  I've now filled this bar by walking the 20Km, but Feebas still hasn't evolved. What do I need to do in order to evolve it?

I made it my buddy and I have 106 candies, now it says I have to walk my buddy 20 more km.   So I removed my buddy and replaced it with something else and it still would not evolve, can someone help?


I'm on Fedora 27. I want to delete a symlink from /usr/lib, but can't because of Operation not permitted. I'm under root and here are commands and the output:  [root@thinkpad lib]# ls -al cpp lrwxrwxrwx 1 root root 10 Sep 15 15:01 cpp -> ../bin/cpp ... [root@thinkpad lib]# lsattr ../bin/cpp --------------e---- ../bin/cpp ... [root@thinkpad lib]# rm -f cpp rm: cannot remove 'cpp': Operation not permitted   SELinux is disabled. Why can't I delete this symlink?  The reason why I want to delete this symlink is because I can't update packages because of this. When I run dnf update, I get the following error:    Upgrading        : cpp-7.3.1-5.fc27.x86_64                                                                                29/77  Error unpacking rpm package cpp-7.3.1-5.fc27.x86_64 Error unpacking rpm package cpp-7.3.1-5.fc27.x86_64 error: unixODBC-2.3.5-2.fc27.i686: install failed error: unpacking of archive failed on file /usr/lib/cpp;5aa2d6ee: cpio: symlink

I'm on Fedora 27 and experience problems with updating the packages by dnf update. The problem is exactly as described here:   I tried to delete symlink under /usr/lib, but can't, even under root:  vplagov@thinkpad:~ $ sudo rm -f /usr/lib/cpp  rm: cannot remove '/usr/lib/cpp': Operation not permitted ... vplagov@thinkpad:~ $ file /usr/lib/cpp  /usr/lib/cpp: symbolic link to ../bin/cpp ... vplagov@thinkpad:~ $ ls -al /usr/lib/cpp  lrwxrwxrwx. 1 root root 10 Sep 15 15:01 /usr/lib/cpp -> ../bin/cpp   I see that file has a dot at the end of file permissions. By googling I found commands to remove the SELinux context or ACL (I don't know what are those). But still can't fix it:  vplagov@thinkpad:~ $ sudo setfacl -b /usr/lib/cpp ... vplagov@thinkpad:~ $ ls -al /usr/lib/cpp  lrwxrwxrwx. 1 root root 10 Sep 15 15:01 /usr/lib/cpp -> ../bin/cpp ...  vplagov@thinkpad:~ $ sudo rm -f /usr/lib/cpp  rm: cannot remove '/usr/lib/cpp': Operation not permitted ... vplagov@thinkpad:~ $ sudo setfattr -x security.selinux /usr/lib/cpp  setfattr: /usr/lib/cpp: Permission denied   Is there a "healthy" option to fix this?


I'm learning java and I have a problem:  import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; import java.io.PrintWriter; import java.util.*;   public class edytor{   public static void main(String[] args) throws FileNotFoundException     {     Scanner czynowy = new Scanner(System.in);      System.out.println("Do you wanna editing existing file?");     String tn = czynowy.nextLine() ;     if(tn=="t") {System.out.println("bleble"); }     Scanner odpowiedz = new Scanner(System.in);      System.out.println("Type file name");     String polozenie = odpowiedz.nextLine() ;         System.out.println("################################");       PrintWriter zapis = new PrintWriter(polozenie);     Scanner tekst = new Scanner(System.in);     String tekst1 = tekst.nextLine() ;       zapis.println(tekst1);       zapis.close();    } }   It's compiling, but when in string tn I type t char this doesn't print "bleble". What should I do to make it work? Greetings!

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


When I need to run a program with direct disk access, like read/write from /dev/sdb, I simply add the user to 'disk' group. In this way we don't need to disclose the root account the the user. However the user would also be able to access any other disks on the same machine.  Is there any finer-grained access control over this need? Could we assign full-access of disks, volumes, or volume groups to some users or groups? When a user need a physical disk to do his own stuff, I won't have the concern that he may destroy the other parts of the system.  (I tried to set owner of a /dev/sdb to a users, but it does not work.)

I have a card reader attached on /dev/sdb.  What I do is giving all permissions to owner, group and the rest of the world, using:  sudo chmod 777 /dev/sdb   Can I just use another combination, allowing only the owner (me) to use the card reader?  There is only one user account.


My Samsung Galaxy SIII comes with a battery with an Near Field Communications (NFC) label on it. Several earlier Android modles don't come with such a label on the battery. I would like to know what the NFC functionality on the battery enables Android devices and their OS to do with the battery.

Why is the NFC in the Galaxy Nexus embedded in the battery?  Wouldn't it make more sense to separate the two things? Is there any hardware advantage of being this way?  Disadvantages I can see several, like replacing the battery with another, without NFC...


I’m trying to add Products to my OrderLine (which is held by an Order) but when I try I get the NullPointerException.  import java.util.*; public class OrderLine;  private HashMap<Integer, Integer> products = new HashMap<Integer, Integer>();  //setter and getter for products  public void add(int productNbr, int amount) {     int newAmount = this.products.get(productNbr) + amount;     this.products.put(productNbr, newAmount); }   And my Main-tester;  public class Main {  public static void main(String[] args) {  OrderLine ol = new OrderLine(); ol.add(1, 661); ol.add(1, 5); //key 1 should hold value 666 System.out.println(ol.getProducts()); //Should print out {1, 666}   But all I get is "Exception in thread "main" java.lang.NullPointerException".  I get the feeling that it works if I define/initiate the value before I add anything to it, but I shouldn't have to do that every time. Any ideas?  UPDATE: Fixed version;  public void add(int productNbr, int amount) {     if (this.products.get(productNbr) != null) {         int newAmount = this.products.get(productNbr) + amount;         this.products.put(productNbr, newAmount);     } else {         this.products.put(productNbr, amount);     } }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I'm planning on buying a new 16-inch MacBook Pro. However, it will come with Catalina, and I still rely on several 32-bit apps. I was wondering if it's possible to downgrade to Mojave?  I was thinking maybe through a Time Machine backup... I've restored from Time Machine before to downgrade from High Sierra to Sierra. Would it be possible to set up the new computer from a Time Machine backup with Mojave?  I'm worried the new hardware would not accept an older OS...  Thanks

Did anyone succeed in installing Mojave on the MacBook Pro 16”? It ships with Catalina but my corporate requires Mojave to connect to the corporate network.  I  but once I select booting from the Mojave external drive I get a “forbidden” icon and the system shuts down.


In the 10K tools flags queue I've come across   and  answer.  Or a similar  which does have another answer.  They both are the sole answers on the OP's own question. The answers basically indicates that the OP couldn't find the delete option for their original post. Initially my idea was to close-vote the question but they doesn't look that bad.  Should those answers be flagged as not answer? Should a comment to the OP be enough to point out that a question can be deleted?

While reviewing the 10k queue just now, I noticed that someone has evidently searched for and flagged self-accepted answers like        What is the proper way to handle ? Should they be flagged as "not an answer", or should they be left alone?  On the one hand, these answers obviously make no attempt to answer the question. On the other hand, these answers may imply that "I'm no longer looking for an answer — don't bug me."


Having another Linux system mounted on /sys2. AFAIK passwords are stored there in second file of /sys2/etc/shadow file.  I'd like to set new password there. How to generate hash, which I can put there into second filed of desired row?  Btw. Is there nowadays one standard way of hashing passwords across Linux systems? I've checked on my three setups with different distributions and for same passwords I have same hashes.  P.S.   passwd -R /sys2 - option -R does not do the job for me. I do not have all mounts for chrooting. And system I mount is arm, and I mount it on x86. passwd -r ... - I couldn't figure out how to use -r repository option to work for me.

In /etc/shadow file there are encrypted password.  Encrypted password is no longer crypt(3) or md5 "type 1" format. () Now I have a   $6$somesalt$someveryverylongencryptedpasswd   as entry.  I can no longer use    openssl passwd -1 -salt salt hello-world  $1$salt$pJUW3ztI6C1N/anHwD6MB0   to generate encrypted passwd.  Any equivalent like (non existing) .. ?   openssl passwd -6 -salt salt hello-world


If I buy one of those weird top level domains, like example.pizza, or example.love, etc, I understand that there is a private company owning each of them, which save the records and redirect using their own servers. (obligated to ICANN) Question is, if this company closed, or go out of business, or just decide they don't want to provide service anymore, what happens to all the websites with this extension? In other words, is it safe to buy one of those top level domains? also, can it reduce speed if they don't operate well enough?

I have recently registered some domains on the basically brand new .directory gTLD. Because of operating costs to maintain a gTLD, it is assumed that many of the hundreds being rolled out this year and next will fail. I will admit I am not very knowledgeable on how the TLD process works.   What exactly does a new TLD failing mean? I realize that they lose ICANN accreditation, but does that just mean that they will be no longer be sold? If the .directory TLD were to go under, would my .directory domains be affected? I bought it from domain registrar Gandi if that helps.


I have many files in directory(with folders so i think solution must be recursive in deep)   root-folder   file-1.png file-2.png file-3.png file-4.png file-5.png folder-1   file-1.png file-2.png file-3.png     I need to rename all files, which contains - character to _.   file-1.png -> file_1.png   But. I have little remark. folder-1 and root-folder must be not affected.  How i can do that?

I have a few hundred files named hortstu01-01-14 then hortstu01-02-14... Do you get the idea?  Well half of the files are named hortstu_01-03-14 then hortstu_01-04-14.  This messes up sorting the files by name and getting them in the order I'd prefer them to be.  So I'd like to rename the ones without the underscore to hortstu_    Is it possible to do this in a batch operation?  If so how?


By mistake, the positive and negative terminal of a 9v rechargeable battery were connected to each other by me, and when I noticed it, I quickly removed it and the battery became hot a little. Did it caused any harm to my battery, Or should I use the battery or is it damaged now? Will it explode if I put it to charging now?

I intended to make a simple electromagnet, then I saw  where the user is connecting wires together with no resistance at all. I was wondering why it doesn't short out and make the battery dead.   Does this  have internal resistance that will prevent shorting out?   If so what will be the current flowing through the battery and how long the battery can last powering the electromagnet, since capacity (like 1000mAh) is not mentioned on it?