I would like to use an external keyboard, mouse, monitor, etc and have my MacBook closed. The only issue is that I can no longer access the fingerprint scanner. Is there a way to use an external one? FYI, I have installed  which is very useful but doesn't cover all cases where a fingerprint can be used.  Yes, I read the similar question but thought this one was different since that one referenced a 10-yr old Macbook that didn't have the Touchbar. And there are ways to solve the problem in that question.

I own a mid-2009 MBP with OS X Mavericks installed. I'm a hi-tech enthusiast who wants to use the fingerprint scanning feature made available by many scanners on the market to login into my account after boot and unlock the screen after the screensaver has started.  The scanner I'm willing to buy is a DigitalPersona U.are.U-5160 which is not only FIPS 201 PIV certified, but it's also designed to work in harsh environments and situations. See:   Please note that I've already read this article on StackExchange () which talks about the same, but I've found nothing interesting in it.  In particularly, supposed that I've gotten all the Smart Card Services/CAC Libraries:   How do I switch from password login to fingerprint login? Can I use fingerprint login with FileVault 2 too? (i.e. decrypting the HD using my fingerprint, with no passwords to type)   I think these features require dedicated API's or SDK's, and Apple stopped deploying them since it bought AuthenTec. Now, all fingerprint-scanning feature are officially unsupported by Apple except for the iPhone 5S.  I've read somewhere that LastPass does a very similar job indeed, and is used for the purposes I've listed.  How can I achieve this?


I have the following code to reverse linked list But I am getting NPE at         head.next = prev; How can I resolve it?      ListNode l = new ListNode();             l.insert(4);             l.insert(10);             l.insert(12);              l.show();             l.reverse();             l.show();  public void reverse() {         ListNode nextNode = null;         ListNode curr = head;         ListNode prev = null;          while (curr != null) {              nextNode = curr.next;             curr.next = prev;             prev = curr;             curr = nextNode;         }          head = curr;         head.next = prev;      }

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 am running Windows 7, 64 bit.  I would like to install Windows 8.1, 64 bit, and have been attempting to use the MS Virtual PC hypervisor.  I attached the Windows ISO as the CD drive. It does try to boot Windows ISO, but I get the error:    This 64 bit application couldnt load becuase your PC doesn't have a 64 bit processor... error code is 0x000035a file is \windows\system32\boot\winload.exe .    I know my pc has a 64 bit processor and I know I went into the BIOS and enabled virtualization.  Have I configured the virtual machine in Virtual PC incorrectly and set it to have a 32 bit processor without realizing it?  Or is there another step I am missing to make this work as intended?

Is it possible to have 64 bit guest OSes run in Virtual PC RC on Windows 7?  I tried to install a Windows 7x64 Ultimate guest in Virtual PC, on a host PC running Windows 7x64, but got the following error:     Attempting to load a 64-bit application, however this CPU is not compatible with 64-bit mode.   From what I have read, there is no workaround for this error using Virtual PC. Does anyone know how to get around this issue?


And if that is the case, can an infinite amount of it be created? Does this mean that the potential energy or the energy that can potentially be created is infinite?

If virtual particles sometimes add more mass/energy to a system then was inputed or comes out in the output, how do they not violate conservation of mass/energy.


Closing the lid, going on the desktop to "gear"->suspend, or from terminal level calling suspend, pm-suspend, or systemctl suspend ... all of this ends up with switching off the system.  One-by-one: I try to suspend the system and it goes black (as it should) immediately. There is no indication of powering off. When I press the trackpad (or open the lid) to wake-up, the system do full boot up (restart?). This is strange since if the system would be "truly" off it would not turn-on on trackpad press (or lid action).  Editing /etc/systemd/logind.conf is not effecting anything. Also, there is nothing worrying in /var/log/pm-suspend.log after pm-suspend.  All of this happened after I ppa-purge the oibaf/graphics-drivers (re-installing this PPA also doesn't solve the problem).   P.S. My machine: Dell XPS 9350 with Intel graphics

Since I upgraded from Ubuntu 15.10 to Ubuntu 16.04 LTS on my Dell XPS 9350, suspend is broken. When closing my lid the laptop will suspend, but resuming fails and it reboots. I tried pm-suspend and tried resuming, resuming failed and the laptop rebooted. I got the following errors when I got back into Ubuntu. The odd thing in my opinion is that it claims the kernel is not an official ubuntu package. Either way my Linux knowledge is not sufficient to know what's going wrong here.      EDIT: I just tried installing kernel 4.4.8 which should fix some things, but it did not fix this problem. By now I also tried 4.4.9 and 4.6 RC7. None of them fixed it for me.


I have points in WGS84 (x,y), radiuses in meters (rx, ry), rotation angle in degrees. I would like to create a new WGS84 geometry.  I've tried this but the major/minor distances seem to be off by a few hundred meters in some cases.   Ellipse (x,y,rx,ry,rotation,#of segments in 1/4 of ellipse)  SELECT transform(  translate(   rotate(    scale(     buffer(      transform(setsrid(makepoint(0,0),4326),3395),      1,    $6),   $3,$4),  $5), x(transform(setsrid(makepoint($1,$2),4326),3395)), y(transform(setsrid(makepoint($1,$2),4326),3395))),4326)

I have the function  --Ellipse(x,y,rx,ry,rotation,#of segments in 1/4 of ellipse) SELECT ST_Translate( ST_Rotate( ST_Scale( ST_Buffer(ST_Point(0,0), 0.5, $6), $3, $4), $5), $1, $2)   I have points in WGS84 (x,y), radiuses in meters (rx, ry), rotation angle in degrees. And I need a new WGS84 geometry as a result.  As you can see I can't call this function without conversions between WGS84 and some metric SRID. But my points aren't in a definite region. So a SRID which is optimal for one point, throws an error for another point during conversion.  Is there a common way to get an optimal metric projection (SRID) for a WGS84 point? Or at least to use some rough, but world-wide universal metric projection? Or maybe there's a trick for this case?


Let me paste code first:  <?php  $category = get_the_category(); $category_id = get_cat_id( single_cat_title("",false) ); $args = array(     'posts_per_page'   => 5,     'post_type'        => array('post', 'shows', 'hosts'),     'orderby'          => 'post_date',     'order'            => 'DESC',     'category'         => $category_id );  $myposts = get_posts( $args ); foreach ( $myposts as $post ) { ?>     <!-- My Markup was here --> <?php } if( function_exists('wp_pagenavi')) { wp_pagenavi(); } ?>   Everything works fine except pagination (I mean pagenavi). Any suggestion?

I've got a custom loop that I'm using to display some Real Estate listings that will be available within 60 days. I'm calling it with the following function:   <?php  $sixtydays = date('Y/m/d', strtotime('+60 days')); $paged = (get_query_var('paged')) ? get_query_var('paged') : 1; $query = new PostsOrderedByMetaQuery(array(   'post_type' => array('post', 'real-estate'),   'meta_key' => 'Time Available',   'meta_compare' => '<=',   'meta_value' => $sixtydays,   'paged' => $paged,   'orderby_meta_key' => 'Price',   'orderby_order'    => 'ASC' )); ?> <?php while ($query->have_posts()) : $query->the_post(); ?>   While the loop works great, I can't get it to paginate. It shows the first 10 (my default) posts but doesn't show the pagination. The only way to display all posts is to show them on one page by adding 'posts_per_page' => -1, I have similar loops on other pages that have no problem paginating. The only difference with this one is that there are two meta keys that are filtering the posts.   I'm using WP Page Navi for this and the rest of my pages. I'm closing the loop and adding the pagination using the following code:   <?php endwhile; // End the loop. Whew. ?> <?php wp_pagenavi(); ?> <?php wp_reset_query(); ?>   How can I go about fixing this?


Issuing lspci -vnn gave me this (relevant) output:  08:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)   I don't know how to proceed in order to get it working. Help on this is appreciated.

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


$ nautilus   Produces the following error output.  (nautilus:3653): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_->priv->connections != NULL' failed     (nautilus:3653): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_->priv->connections != NULL' failed Could not register the application: Timeout was reached (nautilus:3653): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed (nautilus:3653): GLib-GObject-WARNING **: invalid (NULL) pointer instance (nautilus:3653): GLib-GObject-CRITICAL **: g_signal_connect_object: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed   Nautilus used to work before recent Ubuntu automatic software update. Any help is appreciated.  I have tried the following based on suggestion on another similar thread.  $ sudo apt-get install --reinstall nautilus-data   It didn't change anything.  $ nautilus -c   Produces the following output.  running nautilus_self_check_file_utilities running nautilus_self_check_file_operations running nautilus_self_check_directory running nautilus_self_check_file running nautilus_self_check_canvas_container running nautilus_self_check_file_utilities running nautilus_self_check_file_operations running nautilus_self_check_directory running nautilus_self_check_file running nautilus_self_check_canvas_container

When I launch nautilus from terminal the following error is printed and nautilus doesn't open up.  (nautilus:25179): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_->priv->connections != NULL' failed  (nautilus:25179): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_->priv->connections != NULL' failed Could not register the application: Timeout was reached  (nautilus:25179): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed  (nautilus:25179): GLib-GObject-WARNING **: invalid (NULL) pointer instance  (nautilus:25179): GLib-GObject-CRITICAL **: g_signal_connect_object: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed   What could be the problem??


I always thought gauntlet had 2 definitions: the hand piece of a suit of armour, and an obstacle course, like the kind filled with swinging traps and pits.  I've looked on the internet for a definition that fits my second definition, but I can't find one anywhere. All I find is an armour glove and something where 2 rows of people attack someone walking down the middle as a form of punishment.  Does anyone else know of this obstacle course definition I'm talking about? Can someone possibly link me to a definition if one is found?  A few examples are from the first 40 seconds of this video:   And also I thought the game 'Gauntlet' was in reference to the fact that the whole game is like a gauntlet, as in an obstacle course with traps and such.  Could someone confirm if this is a real definition or if I'm just losing my marbles? Thanks!

Human tests—called clinical trials—are the gauntlet of drug   development , and have three phases   What does "gauntlet" mean in the above context?  "throw down the gauntlet" is an idiom "to issue a challenge" where gauntlet refers to a type of glove. In the above extract the word gauntlet alone has been used as a noun, what does it mean there?


Not able to install pandas and python3-pip.  Also tried these commands:   sudo apt-get install python3-pip   sudo apt-get install python3-setuptools   sudo python3 -m pip install pandas

When I try to install any package through the command line, I get an error.   $ sudo apt-get install <package> Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package <package>   Can anyone help me on this?


I am creating a least cost path model for large species that migrate over large distances across a rugged landscape  (elk, deer, etc.)  To calculate movement cost I am using a slope raster but I realize that I should also take into consideration aspect to figure out if an animal is moving downhill, uphill or just along a contour. The idea is to have no penalty for moving downhill.  I know ArcGIS has a least cost path analysis but I am not sure how to implement direction of travel and aspect. This paper  explains it well but does not give any details on how it was implemented ArcGIS. Is there something already built-in ArcMap or R that I can use?

What sort of algorithms can I use to find a least cost path through a DEM where it costs more to traverse a cell going downhill or uphill than it does to follow the contour of the land?  All the examples I've seen involve creating a least cost surface where the magnitude of the slope is part of the cost - but the direction isn't.    Additionally, the examples assume the cost to travel through a cell does not depend on the direction of travel.


On my Ubuntu box I have a crontab setup for my normal user that has the following:  0 0 * * * sudo mysqldump -u root -h localhost --all-databases | gzip > /home/<user>/mysqlbackups/db_`date +%F`.sql.gz   When I run the script from shell it runs without any issue.   sudo mysqldump -u root -h localhost --all-databases | gzip > /home/<user>/mysqlbackups/db_`date +%F`.sql.gz   But with it set as a cron job it's not running at all.  I have my user set in my cron.allow file as well (had to create the file as it didn't exist previously).  Kinda stumped at the moment and not sure what else to tweak/try to get this to run automatically at midnight.  Any ideas?  Thanks!  edit: Removed the 'sudo' and it runs fine on my normal shell execution. I'll find out if it runs off the cron automatically tonight.

Is it possible to run a  job which needs the  command?  Like:   sudo rm somefile


I've noticed that the syntax highlighter for code samples does not work with capitalization for SQL.  I just posted a question on SO and had to spend a couple extra seconds to modify it to get the highlighting to work...  Is this supposed to work?    Would it be possible to add this to the keywords list?   SELECT WHERE FROM INNER OUTER JOIN LEFT RIGHT TOP ORDER BY GROUP BY   I know there are others that would be useful, but didn't want to run through the entire list

I noticed that sometimes my code gets highlighted in different colors when rendered.   What is syntax highlighting? How does it work? Why isn't my code being highlighted correctly? How do I report a bug or request a new language? How do I use syntax highlighting? What languages are currently available on Stack Exchange?


English translation:  Hello all, can you help me fix this problem.  I installed Ubuntu on my notebook for the first time. My laptop is an ACER ASPIRE 5336 I installed Ubuntu while connected to an external HDMI monitor because my laptop does not work and you see black screen. How can  I fix this?     Original Spanish:  Problema mi portatil con pantalla negra pero HDMI monitor si funciona  Hola a todos, podéis ayudarme como solucionar el problema.  Mi portátil, queremos instalar ubuntu por primera vez.  Mi portátil tiene marca es ACER y su modelo es ASPIRE 5336 He instalado ubuntu desde HDMI monitor porque mi portátil no funciona y se ve pantalla negra.  Como se soluciona? Por favor  Mil gracias.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I was trying to export the photoshop layer as save for web that has a blending option screen set to it which makes it lighter.    But when I hide other layers and try to export that pink overlay that has screen set as blending option it gives me the darker version of it that is below.     I think its exporting it with normal blending option.

So I'm working with this image:   And I'm hoping to achieve an effect with it similar to what was done on this website , where independent image layers respond to mouse movements creating a sense of depth to the overall picture.  To do that I would have to break my image into several different layers. I'm not just not sure if that would be possible whilst still maintaining the original look of it, because a number of layers, particularly the music notes and their auras, heavily rely on blending modes like screen and color dodge, to achieve their glow. On top of that I make use of the "blend if"/"underlying layer" slider on many layers as well. If I try to disable the layers below them the blend modes lose their effect, but that's the only way I would be able to break the image down into the appropriate individual pieces.  Is there any possible way to break this image down in the way I'm aiming for? Most of the examples I've seen don't really work for what I'm ultimately trying to achieve with the depth effect. It may just be that the image is too complex for that.  Thanks


Please help me!   $$\tan\left(\frac{6\pi }{7}\right)+ 4\sin\left(\frac{5\pi }{7}\right)$$

Prove that $$4\sin\frac{2\pi}{7}- \tan\frac{\pi}{7}= \sqrt{7}$$   I think midway calculations are not easy formulas, I can't find what kind of formula transformation to solve! I think the best solution here is using right triangle . . . I have one solution too, but not pretty . !


I've submitted a new paper to Knowledge Based Systems journal for Elsevier.  But currently, after about 3 months, its status is still "Under Review"  I have to mention that about 6 weeks after the submission, its "status date" has been changed but its status not!  May you please tell me how long I have to wait for the decision about my paper?  I've checked the paper status in journalinsight.elsevier.com. For the journal, the first decision speed time is about 7.2 weeks. But my paper is still under review after about 3 months.  Thank you

I am asking this question because I've always had the impression that manuscripts submitted to a journal in my field (theoretical linguistics) take an insanely long time to get published, and sometimes I get the impression that this is because, most of the time, nobody other than the author cares about getting things done within a reasonable amount of time. Some examples from personal experience follow.   For the last paper I submitted before getting my PhD, I had to wait nine months from the submission date to get reviews back from the referees. Last week I got a review request from a journal I had never reviewed for previously. The review deadline is March 15 (almost four months). In early October, I submitted a manuscript to a journal that I know asks reviewers to return reviews within 6 weeks. I checked the status of the manuscript online and it still says "with editor". Earlier this year, I was about to start writing a review when my wife went into labor. By the time we came back from the hospital, I had forgotten about the review, so I missed the deadline. The editor didn't contact me to ask about the review until two months after the deadline. Late in 2013, I was asked to write a survey chapter for a handbook. The expected publication date of the handbook is summer 2016.   All of this is not me being unlucky with editors and referees. In private conversations through the years, many colleagues have confirmed that it is virtually unheard of to get reviews back within 3 months of submission; 5 or 6 months seems to be a good average, but in some cases it can take longer (see my first point above). In general, everybody seems to have accepted that the submission-to-printed-journal process is going to take a bare minimum of one year, and that's assuming that the manuscript is accepted without revisions. If revisions are required, two years is not out of the question. Also, it's not like our papers are ridiculously long. I've reviewed about 100 papers so far, and the longest one was about 50 single-space pages; 30-35 single-spaced pages is closer to average.  I remember that, when I was a postdoc, my astrophysics housemate mentioned that in his field the entire submission-to-printed-journal process took only three or four months. I really can't see a good reason why theoretical linguistics shouldn't operate on similar timeframes, other than the fact that everybody seems to have grown used to things taking way longer than they really need to. What are the wait times in other fields? How do you manage to get things done quickly?


I have been reading an article here in physics stack exchange that talks about if it is possible to see virtual images, and i read an answer saying it is actually your brain that understands the refracted rays and creates the image, but in high school class I remember this image of converging lenses. As it can be seen we projected the refracted rays back to form the virtual image. so I just want to clear my confusion does this really happen in the real world or is this a way we humans have developed in order to understand what happens. and can we see the object if it is put in this position, if so how would that be (how does the eye do it if there is no canvas for the image to be formed and reflect). And one more question if the image were to be seen at all in what direction should be the viewer be, on the left or the right?

In optics it is widely mentioned real images are projectable onto screens whereas virtual ones can only be seen by a person.  Isn't that contradictory?  I mean in order to see the virtual image it has to be projected onto the retina (ultimately acting as a screen).   So, why can you see  in the first place?


I have a question on sudo -i and sudo -s on APPLE. When I use sudo -i, it will change to "root" this user. I use sudo -s and this has the similar situation but there is a "bash-3.2#" on my terminal. I don't know where it is and what it is meaning for. This is the first question.  I normally think it show as "mycomputername:~ myusername$". The first string is "mycomputername" and the second string is "myusername" which is also only one user on my computer. There is a weird scenario when I switch to "root" via "sudo -i". It shows up "googleapis:~ root#". I don't know why it looks like this. Why it shows up "googleapis"?

What is the difference between the following commands:  su sudo -s sudo -i sudo bash   I know for su I need to know the root password, and for sudo I have to be in the sudoers file, but once executed what is difference?  I know there is a difference between su and sudo -s because my home directory is /root after I execute su, but my home directory is still /home/myname after sudo -s. But I suspect this is just a symptom of an underlying difference that I'm missing.


I need a very simple example of a set of Real numbers ( if there is any ) that is both closed and open on R .and the boundary of it equal empty set and it is neither empty set nor R.  like , The boundary of a set is empty if and only if the set is both closed and open (that is, a clopen set). on    to disprove this statement ,Let (X,T ) be a topological space and let A ⊆ X. If Bd(A) = ∅, then A = ∅ or A = X.

In other words, are $\emptyset$ and $\mathbb{R}$ the only open and closed sets in $\mathbb{R}$? Why/Why not?  I tried by assuming a set is equal to its interior points and contains its limit points.  A bounded set will not do since stuff like $[1,4]$ and $\{5\}$ will not work, though that is not really proof. Help please?  Anyway, it must then be unbounded.  If $a$ is a real number then $(a,\infty)$, $(-\infty,a)$, $[a,\infty)$ and $(-\infty,a]$ don't seem to cut it so it must be $\mathbb{R}$.


It appears that Ruby class variables aren't fully highlighted on Stack Overflow:  class Foo   @class_instance_var = 1 # fine   @@class_var = 2         # not fully highlighted end   The class instance variable gets full highlighting, but the double @ seems to throw the highlighter a bit.   Here's an SO question with this in action:   Update: 5th April  I've , with a patch that appears to solve the problem. Thanks to @CodyGray for the information.


I have the need to create a Live USB to install Windows but from Ubuntu, I've tried to emulate the tools that make the same function from windows but I just do not work.  I would be very helpful to know how. Thanks

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


I want to highlight a certain row in a list view based on a certain condition being true.I tried the following code and I get a Null Pointer exception.  public class BillsCustomList extends ArrayAdapter<String> {     private String[] doc_no;     private String[]date;     private String[] cust_name;     private String[] cust_number;     private String[] item_count;     private String[]total_wt;     private String[]total;     private String[]balance;     private String[]bill_type;     private String[]status;      private Activity context;      public BillsCustomList(Activity context, String[] doc_no, String[] date, String[] cust_name,String[] cust_number,                            String[] item_count,String[] total_wt,String[] total,String[] balance,String[] bill_type,String[] status)     {         super(context, R.layout.bills_list_view, doc_no);         this.context =context;         this.doc_no=doc_no;         this.date = date;         this.cust_name = cust_name;         this.cust_number = cust_number;         this.item_count= item_count;         this.total_wt = total_wt;         this.total = total;         this.balance = balance;         this.bill_type = bill_type;         this.status = status;      }      @Override     public View getView(int position, View listViewItem, ViewGroup parent)     {         if (null == listViewItem) {             LayoutInflater inflater = context.getLayoutInflater();             listViewItem = inflater.inflate(R.layout.bills_list_view, null, true);         }         TextView textViewDocno = (TextView) listViewItem.findViewById(R.id.textViewInvNo);         TextView textViewDt = (TextView) listViewItem.findViewById(R.id.textViewDt);         TextView textViewName = (TextView) listViewItem.findViewById(R.id.textViewName);         TextView textViewNumber = (TextView) listViewItem.findViewById(R.id.textViewNumber);         TextView textViewCount = (TextView) listViewItem.findViewById(R.id.textViewCount);         TextView textViewTotwt = (TextView) listViewItem.findViewById(R.id.textViewTotwt);         TextView textViewTot = (TextView) listViewItem.findViewById(R.id.textViewTot);         TextView textViewBal = (TextView) listViewItem.findViewById(R.id.textViewBalanace);         TextView textViewBt = (TextView) listViewItem.findViewById(R.id.textViewBt);         TextView textViewStatus = (TextView) listViewItem.findViewById(R.id.textView_status);         LinearLayout ll = (LinearLayout) listViewItem.findViewById(R.id.ll_bills);          textViewDocno.setText(doc_no[position]);         textViewDt.setText(date[position]);         textViewName.setText(cust_name[position]);         textViewNumber.setText(cust_number[position]);         textViewCount.setText(item_count[position]);         textViewTotwt.setText(total_wt[position]);         textViewTot.setText(total[position]);         textViewBal.setText(balance[position]);         textViewBt.setText(bill_type[position]);         textViewStatus.setText(status[position]);          try         {             if (textViewStatus.getText().toString().equalsIgnoreCase("true"))             {                 ll.setBackgroundColor(Color.RED);              }          }catch (NullPointerException e)         {             Log.d("NULL ERROR", "position"+position+e);         }             return listViewItem;     }   }      I have simple use case if the status is true make the row of a certain   color.Else don't do anything.I get the following error when I try the   above code.      NULL ERROR: position0java.lang.NullPointerException: Attempt to invoke   virtual method 'boolean   java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object   reference   I get these null pointer exceptions at 0 and 1 position.Can anyone explain why is this happening and what would be the correct way to do it. Any help or suggestion is welcome.Thank you.

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?


So I recently thought of a problem, which I have tried to solve many ways but couldn't. It's very simple to describe... Find the function which is distance $1$ from parabola $y=x^2$ along its normals. .  This one of the things I've tried... This function would get the corresponding $x$ value on the function we want to find from an $x$ value on curve $y=x^2$. The inverse would give the corresponding $x $ value on $x^2$ for a given $x$ value which would make it trivial to determine the $y$ value. $$ f(x)=x+\sin(\arctan(2x)) $$ This can be resolved to this... $$ f(x)=x+\frac{2x\sqrt{1+4x^2}}{1+4x^2} $$ However I don't know how to get the inverse of this function.

I have a simple parabola in the form $y = a + bx^2$. I would like to find the formula for a curve which is parallel to this curve by distance $c$. By parallel I mean that there is an equal distance along a line perpendicular to the tangent to my curve at all points.  I've established that the curve isn't in the form $y = a + c + dx^2$, whilst I can make this satisfy for $x=0$ and $x$ equal to one other number is isn't valid across the range.  Any help much appreciated.  Rob


We are going to replace the carpet in our living room with engineered hardwood flooring. We’ve installed the flooring elsewhere in our home so that part isn’t a problem. The problem is what do we do against the rock hearth? Everywhere else we’ve installed flooring there is baseboard or hardwood quarter round (kitchen). Can’t do baseboard around the hearth. Does quarter round that matches the floor work?

We are installing a laminate floor in our family room and have precisely the same problem as described in .  The brick is not even close to flat where it meets the floor, leading to ugly gaps. The solutions given in the linked question are not what we'd like to have.  No trim or border.  We'd really much rather have the "floor underneath" look, where the floor appears to simply disappear underneath everything in the room, including the fireplace brick. This implies that we have to cut the brick somehow.  I've seen a few online videos showing how to do this, but they were lucky enough to have a grout line at floor level.  There is no grout line at the correct level - the floor goes right into the physical brick. I am looking for methods and suggestions regarding how to best cut the brick.  Tools, gotchas, ways to make sure it looks neat, etc.  I only get one shot at getting this right.  :) As an alternative, I'd consider using some kind of a "gap filler" to hide the gap, as long as it is level with the floor and can be colored to match either the grout or the floor.


Does the speed of light vary?   Special Relativity says it's constant in all Inertial frames; but what if it was to travel through different media?

I know that if we solve the Maxwell equation, we will end up with the phase velocity of light being related to the permeability and the permittivity of the material. But this is not what I'm interested in - I want to go deeper than that. We know that the real speed of light is actually not changing, the decrease in speed is just apparent. Material is mostly empty, the light will still travel with $c$ in the spacing. The rare atoms will disturb the light in some way. So I am interested in how the atoms affect the light. Photon absorption-emission theory Some textbooks that I read explain it in a way kind of like this: In a material the photons are absorbed by atom and then re-emitted a short time later, then they travel a short distance to the next atom and get absorbed&emitted again and so on. How quickly the atoms in a material can absorb and re-emit the photon and how dense the atoms decides the apparent speed of light in that material. So the light appears slower because it has a smaller “drift speed”. Interference theory But recently I realize an alternative explanation: Atoms respond to the light by radiating electromagnetic wave. This “new light” interferes with the “old light” in some way that results in delayed light (advanced in phase), this can easily be shown by using simple phasor diagram. Consequently effectively the light covers a smaller phase each second, which gives the impression of a lower phase velocity. However the group velocity is changing in a complicated way. I think that the first explanation does not explain the change in phase velocity of light. if we consider light travelling into a slab of negative refractive index non-dispersive material, let’s say the light is directed perpendicular to the slab. The phase velocity’s direction will be flipped, but group velocity’s direction in the material will not change. Only the second explanation can explain the flipped phase velocity direction. I guess that the velocity that we get in the first explanation is actually belongs to the group velocity. It makes sense to me that the front most of the photon stream determines the first information that the light delivers. So the question is What really cause the phase velocity of light to be decreased?  "drift velocity" of photons (they aren't the same photons, they are re-emitted all the time) phase difference between absorbed and emitted light something else  And also, I still don't really understand detailed explanation of the absorption-emission process for small light's wavelength (for large lambda compare to the atoms spacing, the photons will be absorbed by the phonons). The dispersion relation that we know is continuous and also some material is non-dispersive, therefore the absorption process must occur in all frequency for a certain range. So definitely it doesn't involve the atomic transition, otherwise it will be quantized. My guess is that the relevant absorption process gets smooth out by the dipole moment. What makes the spectrum continuous? EDIT: link for dispersion relation:


I've plotted 5 plots individually, but I'd like to have something like in the picture:  where the y_max and the ymin is always the same and goes from 0.651 to 0.6535, but on different level like in the picture. The x axis goes from 19.0 to 19:2. 'Till now I wrote only separately cause I can't make it work.  \documentclass[a4paper,12pt]{book} %\usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english,italian]{babel} \usepackage{url,amsfonts,epsfig} \usepackage{amsmath} \usepackage{caption} \usepackage{subcaption}  \usepackage{matlab-prettifier}   \usepackage{fancyhdr} \pagestyle{fancy} \renewcommand{\footrulewidth}{0.5pt} \fancyhead[]{}  \fancyhead[LO]{\nouppercase{\rightmark}}  \fancyhead[RE]{\nouppercase{\leftmark}}  \fancyfoot{} \fancyfoot[LO,RE]{\thepage}    \renewcommand{\sectionmark}[1]{\markright{#1}} \parindent 0ex    \usepackage{tikz} \usepgflibrary{arrows.meta} \usetikzlibrary{calc,quotes,angles}  \usepackage{pgfplots} \usetikzlibrary{calc}   \begin{document}  \begin{figure}[h]     \centering     \begin{tikzpicture}[yscale=0.6]     \begin{axis}[name=plot,     xmin=19, xmax=19.2, xlabel={$[s]$}, ylabel={$Ampiezza$},     ymin=0.651,ymax=0.6535,width=1\textwidth]     \addplot[blue,mark=.] table{10Hz.txt};     \end{axis}     \end{tikzpicture}     \caption{\textit{Oscillazioni a 10Hz}}   \label{fig:10Hz}      \begin{tikzpicture}[yscale=0.6]     \begin{axis}[name=plot,     xmin=19, xmax=19.2, xlabel={$[s]$}, ylabel={$Ampiezza$},     ymin=0.651,ymax=0.6535,width=1\textwidth]     \addplot[blue,mark=.] table{20Hz.txt};     \end{axis}     \end{tikzpicture}     \caption{\textit{Oscillazioni a 20Hz}}   \label{fig:20Hz}      \begin{tikzpicture}[yscale=0.6]     \begin{axis}[name=plot,     xmin=19, xmax=19.2, xlabel={$[s]$}, ylabel={$Ampiezza$},     ymin=0.651,ymax=0.6535,width=1\textwidth]     \addplot[blue,mark=.] table{30Hz.txt};     \end{axis}     \end{tikzpicture}     \caption{\textit{Oscillazioni a 30Hz}}   \label{fig:30Hz}      \begin{tikzpicture}[yscale=0.6]     \begin{axis}[name=plot,     xmin=19, xmax=19.2, xlabel={$[s]$}, ylabel={$Ampiezza$},     ymin=0.651,ymax=0.6535,width=1\textwidth]     \addplot[blue,mark=.] table{40Hz.txt};     \end{axis}     \end{tikzpicture}     \caption{\textit{Oscillazioni a 40Hz}}   \label{fig:40Hz}      \begin{tikzpicture}[yscale=0.6]     \begin{axis}[name=plot,     xmin=19, xmax=19.2, xlabel={$[s]$}, ylabel={$Ampiezza$},     ymin=0.651,ymax=0.6535,width=1\textwidth]     \addplot[blue,mark=.] table{50Hz.txt};     \end{axis}     \end{tikzpicture}     \caption{\textit{Oscillazioni a 50Hz}}   \label{fig:50Hz} \end{figure}    \end{document}

How do I create a graph multiple Y axes(more than 2) stacked one over the other with a common X axis?    See attached figure.   Each zero in y direction represents the beginning of new y axis.


I'm trying to prove the following statement related to the Zermelo–Fraenkel set theory, which looks rather basic yet I'm still unable to solve it.  Problem: Let $A$ be a nonempty well-ordered set. Prove that for every set $B$ the following two statements are equivalent:   There exists an injective function from $A$ to $B$. There exists surjective function from $B$ to $A$.   Any comments, ideas and suggestions would be very much welcome. As usual, thank you in advance!  EDIT: Here is the a modification of the original:  Let $A$ be a nonempty well-ordered set. Prove that for every set $B$ such that there exists an injective function from $A$ to $B$ then there exists surjective function from $B$ to $A$ and vice versa.

Theorem. Let $X$ and $Y$ be sets with $X$ nonempty. Then (P) there exists an injection $f:X\rightarrow Y$ if and only if (Q) there exists a surjection $g:Y\rightarrow X$.  For the P $\implies$ Q part, I know you can get a surjection $Y\to X$ by mapping $y$ to $x$ if $y=f(x)$ for some $x\in X$ and mapping $y$ to some arbitrary $\alpha\in X$ if $y\in Y\setminus f(X)$. But I don't know about the Q $\implies$ P part.  Could someone give an elementary proof of the theorem?


When Luke went to look for Yoda on the planet Dagobah, he   landed/crashed quite close to Yoda's home.  This implies Dagobah is a rather small planet. I mean, if it was as big as the Earth or Mars, I guess it would be rather unlikely to   find Yoda that quickly. Luke would have to fly above the planet's surface until he either senses a force-sensitive entity (that might be a first test of how good Luke is in using the force) or Yoda made himself recognizable somehow.  I'd say Dagobah can't be much bigger than Pluto. And given the fact that it has an Earth-like surface gravity it seems to be very dense too. Dagobah's atmosphere doesn't seem to be very high either and it's fully cloudy/foggy which again implies a small and dense planet. Wookieepedia claims the planet is 14,410 kilometers (8,954 miles) in diameter but that seems unlikely.   How would Luke find Yoda otherwise that quickly on an entire planet bigger than Earth?

In The Empire Strikes Back, Luke crashes his X-Wing on Dagobah after scanning the planet for technology and lifeforms.  LUKE (into comlink) I'm not picking up any cities or technology.  Massive life-form       readings, though.  There's something alive down there...  Followed by:  EXT. SPACE - DAGOBAH -  LUKE'S X-WING The X-wing continues its flight through the twilight above the cloud- covered planet. INT.  LUKE'S X-WING - COCKPIT Luke sees the cloud race by as he takes his craft closer to the planet.   He must operate his controls carefully since the cloud cover has  completely obscured his vision.  An alarm buzzes in the background,  Artoo beeps and whistles frantically. LUKE (into comlink) I know, I know!  All the scopes are dead.  I can't see a thing! Just hang on, I'm going to start the landing cycle...   According to , Dagobah has a diameter of 8,900 km, which means that it has approximately 50% of the surface area of Earth. Landing randomly on the planet, it's unlikely he would land within walking distance of Yoda's hut. How did Luke know where to land his X-Wing? From the script, it does not sound like he intentionally landed anywhere. Was he guided by the Force? Did Kenobi's Force ghost tell him where to land off-screen? Something else?


I need to track an error related with the inclusion of header files, I'm suspecting that one or more files have unmatched curly brackets and/or parentheses and I think that would be useful to take a look to the file that pre-processor brings to the compiler; that is the file with all the macro substitution done and all the contents of the headers pasted altogether.  I know that there's a compiler option to save this temporary files to disk, but after googling around I'm not able to found the search string that brings me that information, so I'm asking for help:  What compiler option enables saving into disk the output of the pre-processor?  I'm interested in this option for the following compilers:   gcc clang msvc

Let's say I have a source file with many preprocessor directives. Is it possible to see how it looks after the preprocessor is done with it?


I have laptop which from the beginning running Windows 8, I later wiped the hard-drive and installed Ubuntu 14.04. Now I want to wipe the hard-drive and install Windows 10. In BIOS I have selected to boot from USB. But whenever I boot my computer it does not boot on the USB, it just starts Ubuntu. What can I do about it?  I downloaded the .iso file from Microsoft. Then I used Rufus to put it to my USB    I have also tried the following in Rufus which ended in an error message  ""The file system currently selected can not be used with this type of ISO. PLease select a different file system or use a different ISO"     I have looked at these three questions, but I did not find them helpful.        Solution

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.


In the chapter of magnetic effect of current I came across cyclotron limitations.  Statement:  The cyclotron cannot accelerate the particles to velocities as high as comparable to the speed of light.  Reason:  The reason is that at these velocities the mass of a particle increases with increasing velocity.  MyDoubt:  The reason for the statement is difficult for me to digest since I have never seen a particle or read about such a particle that follows this kind of reason as mentioned.  Can you provide some answers related to this?

I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy.     However, the equation breaks down when the electron velocity approaches the speed of light as mass increases. At such velocities, one needs to do relativistic correction to the mass so that it becomes[...]   We all know about the famous theory of relativity, but I couldn't quite grasp the "why" of its concepts yet. This might shed new light on what I already know about time slowing down for me if I move faster.  Why does the (relativistic) mass of an object increase when its speed approaches that of light?


I am trying to find alert but can't find it under man or info. I found a similar question involving type and it turned out it was under bash. How does one find a command like this without having to go through google? Also if anyone knows how to get alert that would certainly help as well.   type link:

I tried to find information about  command using man pages and info    $ man type  No manual entry for type info type   I think this is info menu page.   Is it just happening to me?? Why did Ubuntu developers remove type command manual page. Did they ever make a manual page for type command?


In Harry Potter and the Half Blood Prince, it was mentioned that Moody attended Dumbledore's funeral.  Did Moody take part in the Battle of the lightning struck tower?  There seems to be no mentioning of Moody during this battle.  Can someone explain?  Thanks.

Where was Alastor Moody during Harry Potter and the Half Blood Prince?  He did survive the Battle of Department of Mysteries in Harry Potter and the Order of the Phoenix, and he somehow disappeared in Harry Potter and the Half Blood Prince, and re-appeared again at the start of book Harry Potter and the Deathly Hallows.  Why was he missing/not mentioned?


When I enter text on stdin in an OS X Terminal, a single line is limited to 1024 characters. For example, cat > /dev/null beeps after I type (or paste) a line longer than this, and refuses to accept more characters. A problematic example is when I want to count characters from pasted text with cat | wc -c: the cat blocks at the first long line.  This seems to be a general problem with pasting to stdin. Can this observed stdin limitation of 1024 characters per line be removed or pushed to a higher limit?  I need this because I want to paste text that has lines longer than 1024 characters.  I could also use a "heredoc" << EOT and paste my long lines without any problem, but then the text appears in my shell history, which I don't want.

So I have a lot of data WITHOUT NEW LINES on the clipboard (it's a large SVG file on one line). I went  $ cat >file.svg   then tried to paste (in Gnome Terminal), but only the first 4kB characters were accepted.  I assume this is a readline feature/limitation.  Is there a way to read from STDIN that would avoid this problem?  EDIT  Test case: Create a demo file. This one will have ~4k "=" symbols followed by "foo bar".  { printf '=%.0s' {1..4095} ; echo "foo bar" ; } > test.in   Copy that into your clipboard  xclip test.in   (if you want to middle-click to insert) or  xclip -selection clipboard test.in   (if you want to use Ctrl-Shift-Insert to past it in)  Then cat >test.out, paste (whichever way). Press Ctrl-D to end the stream. cat test.out - do you see "foo bar"?  On my set-up (Ubuntu 12.04, Gnome Terminal, zsh) when I paste I only see the = and I don't see foo bar. Same when I inspect test.out.


In , it is argued that all photons are necessarily circularly polarized, and linearly-polarized photons must be a superposition of such circularly-polarized photons. Besides, it and suggests that Bell experiments may really be measuring correlations of photon pairs.  My question is, do all Bell tests assume linear polarization, and will the Bell's theorem be invalidated if all photons are really as described in the mentioned paper?

While trying to understand polarization in quantum field theory, I wondered how a single photon could go through a linear polarizer. I found a  which asked "Is a single photon always circularly polarized?"   This paper proposes an experiment to determine if a single photon can be linearly polarized, or if only pairs of photons can be linearly polarized.  It suggests that there may be non-trivial consequences regarding all Bell experiments with a "linearly polarized single photon" (because such thing may not exist).  The paper is from 2014 and the experiment seems simple if you have the right equipment, so do we have the result of the experiment yet?


I am rendering a animation, I originally had a white background but that was taking forever, so I turned on transparent background. The issue still persists, Blender wants to render the scene, each portion of the render fly's through, but 1 full transparent frame takes 25 seconds. Is there a way I can tell blender to not care about transparent portions.    The animation is a phone coming up and rotating.

If I wanted to create an animation, each frame would have several seconds of rendering a completely transparent part, which adds up obviously. Is there a way to eliminate this waste of time?


Yes please answer my question as I am not sure if I am right. Thanks in advance.

By conservation of energy, the solid is left in a lower energy state following emission of a photon.  Clearly absorption and emission balance at thermal equilibrium, however, thermodynamic equilibrium is a statement of the mean behaviour of the system, not a statement that the internal energy is constant on arbitrarily short timescales.  The energy has to come from somewhere during emission, and go somewhere during absorption.  Energy in a solid can be stored as kinetic and potential energy of electrons and nuclei, either individually or in collective modes such as phonons and plasmons.  In thermal equilibrium energy will be stored more or less in various forms depending on the temperature and material.  However, even if most of the thermal energy in a particular solid at temperature $T$ is stored in the form of phonons, it could be that phonons primarily interact with light indirectly via electrons, e.g. a phonon excites an electron in a phonon-electron interaction, which can interact with light via the EM field.  Given that light is an EM field, it makes sense to me that it is emitted and absorbed by charged particles.  The electron-photon interaction is probably dominant for visible and ultraviolet light, given that metals are opaque, while semiconductors and insulators are transparent to (visible and UV) light with energy lower than their bandgap. However, once you get into energies in the IR and below, or X-rays and above, other mechanisms apparently take over.  For example, on the high-energy end of the spectrum I've heard that gamma rays can interact directly with nuclear degrees of freedom, which is reasonable considering that gamma rays are emitted during a lot of nuclear reactions.  A review of  might give clues to important light-matter interactions over a broad range of wavelengths.  Whether all of the these processes are involved in blackbody emission is a somewhat different question.  What physical processes mediate energy transfer during blackbody emission, and in which energy ranges are the various processes dominant?


I am working to help a charity that receives computers cast off by hospitals and schools. I don't want to have to install Ubuntu on my own desktop in order to get access to all the download features for a bootable USB.   Is it possible to download the whole program in a bootable/installable state onto a USB key so that I can use it to install on another computer, often one with a password protected and time-limited blocked Windows OS, in order to completely install Ubuntu over Windows?

This is the third time I've tried to install Ubuntu Server 14.04.03 64-bit on the same laptop, and each time it caused different problems.  Each time I wrote the same iso image to a USB flash drive by using a different application and OS.   Universal USB Installer (pendrivelinux.com) from Windows WinImage writer from Windows built-in image writer from Linux Mint 17.2    The iso image is the same in all three cases, the USB flash drive is the same, and the laptop is the same. However each time the installation of Ubuntu gave me different installation options. For example, the last time I installed Ubuntu, it didn't show all the packages to choose while installing (Basic Ubuntu server, etc.).


int i = 4; string text = "Player "; cout << (text + i);   I'd like it to print Player 4.  The above is obviously wrong but it shows what I'm trying to do here. Is there an easy way to do this or do I have to start adding new includes?

I thought this would be really simple, but it's presenting some difficulties. If I have std::string name = "John"; int age = 21;  How do I combine them to get a single string "John21"?


Let F be a non-empty ordered field. Can F be a finite field and if so does there exist a simple example of such an F?

I have a set S={0,1}, and the addition and multiplication rules are  \begin{array}{c|cc} +&0&1\\ \hline 0&0&1\\ 1&1&0 \end{array}  \begin{array}{c|cc} *&0&1\\ \hline 0&0&0\\ 1&0&1 \end{array}  It is sure that it is a field. How can I prove this field can be ordered or not?


I have been reading Stack Exchange for years - mostly not logged in, and have never posted (this is my first). I'm simply not very talkative, and very good at googling.  Recently a few occasions have come up when I've wanted to comment on a question.  I wanted either to ask for, or provide, clarification which did not warrant a new answer.  How do I gain enough reputation to comment without:   asking questions which have already been answered or that I can figure out on my own, or posting my comment like as an answer (i.e. being  rude)?

Users with less than 50 reputation points cannot write comments on questions and answers that they don't own.  Why does this limit exist? But I want to contribute now. What should I do instead? But I can't write a good answer without more information! Shouldn't I be allowed to post comments if I have reputation on a different site? But I saw a new user posting a comment! How did they do it? Why do I need 50 reputation to comment on my own post?   See also:    in the Help Center


I have so far shown that $\phi: \mathbb{Z} \to F$ is a unique ring homomorphism if $\phi(n)=n$ and that $ker(\phi) = (n) = \{nm|m \in \mathbb{Z}\}$ with $n = 0$ or $n=p$ with $p$ a prime number. ($n$ is called the characteristic of $F$).   Now, I have to show the following two points.    If $F$ has characteristic $p \gt 0$, $\phi$ induces an injective homomorphism $\mathbb{F}_{p} \hookrightarrow F$. ($\mathbb{F}_{p}$ is a subfield of $F$).  Let $F$ be a finite field with $q$ elements. Show that $q$ is a positive power of the characteristic $p$ of $F$.    I just really have no clue how to approach these problems and would appreciate a lot if help is given. I am also not even sure what $\hookrightarrow$ means. Can anybody help? Thanks.

Let $F$ be a finite field. How do I prove that the order of $F$ is always of order $p^n$ where $p$ is prime?


I like Windows better than Ubuntu and want to install windows on my ubuntu laptop.  It had windows on it before.  Can anyone help me with how to open ISO's on Ubuntu?

I'm running into trouble trying to mount a large iso:  dev@dev-OptiPlex-745:~$ sudo mount -o loop /home/dev/Hämtningar/matlab2011a_64.iso /cdrom mount: warning: /cdrom seems to be mounted read-only. dev@dev-OptiPlex-745:~$    Can you tell me how I should do it?


For example: Bugbear (with Powerful Build) and a class feature similar to that (I do believe a bear totem barbarian can do that) would that give them a carrying capacity of a huge creature? Or just a large creature?

Does the Goliath's carrying capacity increase from its Powerful Build feature stack with the Barbarian's carrying capacity doubling from its Bear Totem feature? For example, would those two together give a character with Strength 20 a carrying capacity of 1200 lbs?


In a project with different makefiles:  $ make -f foo1.make ... ... $ testing testing ... ... $ !ma make -f foo1.make    Good! But then if I by accident do:  $ make -f foo1.make ... ... $ testing testing ... ... $ make make: *** No targets specified and no makefile found.  Stop.   And now I am sad:  $ !!ma makema No command 'makema' found, did you mean:   ... ...   Now I have to pick through all my testing commands with the up arrow like an animal. Unacceptable*!  Is there any way to re-run that full make -f foo1.make command using ! or some variant thereof?  *: I will not even dignify the suggestion that I just retype the entire command with a response!

On the bash command-line, ↑ gives me the previous command. On the command-lines in ipython or matlab, when I type a few characters, ↑ gives me the previously entered command starting with those characters. How can I enable exactly this behaviour in bash? I am aware of more advanced ways of searching through the command-line history, but sometimes a simple way is more convenient.


I am trying to update software of my Ubuntu 14.04 but there is an error:   malformed line /etc/apt/sources.list.d/virtualbox.list (dist) ; access to this source denied. E:opening etc/apt/sources.list.d/virtualbox.list-ifstream::ifstream(13: Permission denied) E: List of source could not be read E:The package lists or status file could not be parsed or opened.   Could you please help me to remove this virtualbox.list.  I really appreciate yourhelp.

I have unistalled and reinstalled the Ubuntu Software Center as per info I found in a similar thread and I got the same response about line 91 or something like that.  I just tried to upload a screen shot but since I'm new it won't allow me to.  I also can not figure out how to cut and paste anything so I have to hand type what the error screen says, both when I attempt to open the software center and nothing happens, when I try to enter commands into the terminal to uninstall, reinstall, whatever I get the same following:  COULD NOT INTITIALIZE THE PACKAGE INFORMATION An unresolvable problem occured while initializing the package information Please report t:his bug against the 'update-manager' package and include the following error message: 'E: Malformed line 91 in source list/etc/apt/sources.list (dist parse)  E: The list of sources could not be read.,  E: The package list of status file could not be parsed or opened.   How do I report bugs?  What can be done about this.  I have searched and everything everyone says to do leads me back to the same line error message.  So, I don't know how to get to line 91 in the source list; to tell you what it says. Sorry, I'm really new to this. That is what I need is to find out how to get there and fix what it says. I would really like to NOT have to re partition my hard drive and start from scratch, so I'm really looking forward to getting this problem solved. I need to be able to install new software.


Consider the sequence of complex-valued functions $f_n(z)=z^n$, for $n=1,2,3,\dots$. How to show that this sequence does not converge uniformly to $f(z)=0$ on all of the unit disc. However it converges uniformly in every compact subset of the unit disc to $f(z)=0$?

Show that $f_n(z)=z^n$ converges locally uniformly on $|z|<1$ but not uniformly.   I am really confused. I saw a seemingly reliable reference stating that $z^n$ does not converge uniformly to $0$ on $\{|z|<1\}$ but it does converge uniformly on $\{|z|\le r,r<1\}$. What is the nuance between the two former sets? With $r_n<1,r_n\to 1$, shouldn't one conclude that $f_n(z)$ uniformly converges on $\{|z|<1\}$? And besides, this source tells me what I have to prove for Homework is disproved, which really makes it more frustrating.  I would appreciate any help.


I just read that logarithms were not initially defined in terms of their inverse relationship to exponential functions (and that Euler was the first to develop them in this way).  So how were they initially defined? All I could find on an (admittedly cursory) internet search was that logarithms were used to streamline multiplication and division, and also the calculation of "sines", for which extensive tables were constructed. Does anyone know how these tables were made?  And is there a reason that the etymology of "logarithm" seems to be "ratio-number"? From       1610s, Mod.L. logarithmus, coined by Scot. mathematician John Napier (1550-1617), lit. "ratio-number," from Gk. logos "proportion, ratio, word" (see logos) + arithmos "number" (see arithmetic). Related: Logarithmic.

In the wikipedia article on logarithms, I am clueless about the approach and motivation for the following computations done by Napier (and the mysterious appearance of Euler's number) in this . Please help me understand:       By repeated subtractions Napier   calculated $10^7(1 − 10^{−7})^L$ for L   ranging from 1 to 100. The result for   $L=100$ is approximately $0.99999 = 1  − 10^{-5}$. Napier then calculated the   products of these numbers with $10^7(1  − 10^{−5})^L$ for L from 1 to 50, and   did similarly with $0.9995 ≈ (1 −  10^{−5})^{20}$ and $0.99 ≈ 0.995^{20}$.   These computations, which occupied 20   years, allowed him to give, for any   number ''N'' from 5 to 10 million, the   number ''L'' that solves the equation      $$N=10^7 {(1-10^{-7})}^L$$      In modern notation, the relation to   natural logarithms is:      $$L = \log_{(1-10^{-7})} \!\left(  \frac{N}{10^7} \right) \approx 10^7  \log_{ \frac{1}{e}} \!\left(  \frac{N}{10^7} \right) = -10^7 \log_e  \!\left( \frac{N}{10^7} \right)$$      where the very close approximation   corresponds to the observation that      $${(1-10^{-7})}^{10^7} \approx  \frac{1}{e}. $$   I understand the computations, but I don't know what's going on.


Show that are logically equivalent (without truth table)  (p → r) ∧ (q → r) and (p ∨ q) → r My solution:  (p→r)∧(q→r) ≡(¬p∨r)∧(¬q∨r)  ≡(¬p∧¬q)∨(r∨r) ≡(¬p∧¬q)∨r    ≡¬(p∨q)∨r ≡(p∨q)→r   (p → r) ∨ (q → r) and (p ∧ q) → r  (p→r)∨(q→r) ≡(¬p∨r)∨(¬q∨r)     ≡(¬p∨¬q)∨r ≡¬(p∧q)∨r    ≡(p∧q)→r   Is it correct ?

Can you answer me , please.  1- Show that (p→r)∧(q→r) and (p∨q)→r are logically equivalent  2- show that (p → r) ∨ (q → r) and (p ∧ q) → r are logically equivalent  without truth table .


Strangely, I've never heard Ext functors referred to by any other name, and so I'm not sure what "Ext" actually means. The only thing I can think of that "Ext" might stand for is "Exterior", which makes a little bit of sense. Does anybody know the meaning and/or history of the term?

The names of the derived functors $\operatorname{Tor}$ and $\operatorname{Ext}$ seem quite cryptic to me. Does anyone know what these abbreviations stand for? I would be glad if someone could tell me where these names come from.


When we drop a stone in a pond, we see waves of water spreading over a distance.   Often did I see the geometry of the waves, it is mostly circular.   So no matter how the geometry of the stone is varied the waves seemed to me, a circular one.   Taking an irregular shaped middle sized stone and dropping in the water we see the phenomenon of circular waves spreading out, why is it that we always see circular one? If it's not always the case, please guide me so. Thanks in advance!

I have had a question since childhood.  Why do we always get circular waves (ripples) in water even when we throw irregularly shaped object in it?


I faced a problem with one very interesting series: $\sum_{n=1}^\infty \frac{1}{n^3\sin{\pi\sqrt{2}n}}$ I know that the answer is $-\frac{13\pi^3}{360\sqrt{2}}$, but I couldn’t get it. At first I have tried the fraction decomposition of the function $\frac{1}{\sin{\pi\sqrt{2}n}}$, but when I’ve done this I faced a new series that I can’t handle $\sum_{n=1}^\infty \sum_{k=1}^\infty \frac{(-1)^k}{n^2(2n^2-k^2)}$ Next try was to just apply the residue theorem to first or second series, but I didn’t get anything good. At last I’ve tried to find some function whose residues will be members of the series(just like you can do with this series $\sum_{n=1}^\infty \frac{1}{(\sinh{\pi n})^2}$) So, any ideas or approaches will be appreciated! Especially some tricky methods, because I believe that this value can be obtained without “deep math”.

I need to compute $$\sum_{n=1}^{+\infty} \frac{1}{n^3\sin(n\pi\sqrt{2})}.$$ This an exercice of "Amar and Matheron, complex analysis". I proved the convergence and now to compute the sum, I follow the hint of the book which is : Consider integrals of the form $$\int_{\gamma}\frac{dz}{z^3[\sin(\pi z)\sin(\sqrt{2}-1)\pi z]}$$ for a well-chosen $\gamma.$ I know this a residue theorem application but it seems a bit hard to have the good idea. I also tried with a summation factor. Any help will be greatly appreciated.


I want to upgrade my ubuntu 17.10 to 18.04 from terminal of ubuntu.  I've tried using commands  sudo apt-get update  sudo apt-get upgrade  sudo apt-get dist-upgrade  All the above commands executed successfully. But when I checked it using the command.  sudo lsb_release -a But it didnt work.

When I attempt to upgrade Ubuntu from 17.10 to 18.04, the Update Manger says "Your computer is up-to-date."  Why isn't it detecting the new release?


I have just started with programming and had a question regarding main function , i read somewhere that we declare main function with a int data type and use and integer with the return statement, why can we not declare main function with a string data type and use a string as a return?  string main(){ return "hello";}   why is this code invalid ?  i have tried running this code in codeblocks and got an error  error:   'string' does not name a type| ||=== Build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|

What is the correct (most efficient) way to define the main() function in C and C++ — int main() or void main() — and why? And how about the arguments? If int main() then return 1 or return 0?  There are numerous duplicates of this question, including:       — For C++, with a very good answer indeed.     Related:


I have my class as:  public class Element {     int number, group, period;     String symbol, name;     double weight;         public Element(int number, String symbol, String name, int group, int period, double weight) {         this.number = number;         this.symbol = symbol;         this.name = name;         this.group = group;         this.period = period;         this.weight = weight;     }   I need to do a Comparator class that will first sort the Element by the group then if its in the same group sort by number. My code for that is:  class GroupComparator implements Comparator<Element> {     @Override     public int compare(Element a, Element b) {         return a.group < b.group ? -1 : a.group == b.group ? a.number-b.number : 1;     } }   I'm not sure how to formulate it to make it work.

Assume you have some objects which have several fields they can be compared by:  public class Person {      private String firstName;     private String lastName;     private String age;      /* Constructors */      /* Methods */  }   So in this example, when you ask if:  a.compareTo(b) > 0   you might be asking if a's last name comes before b's, or if a is older than b, etc...  What is the cleanest way to enable multiple comparison between these kinds of objects without adding unnecessary clutter or overhead?   java.lang.Comparable interface allows comparison by one field only Adding numerous compare methods (i.e. compareByFirstName(), compareByAge(), etc...) is cluttered in my opinion.   So what is the best way to go about this?


Let $T: \mathbb{R}^4 \to \mathbb{R}^4$ be any linear transformation. Then how can I show that $T$ has a proper non zero invariant subspace.  If $T$ has an eigen value then it is clear but if not then I can't solve it. Please help me. Thanks.

Could any one just tell me a sketch of the proof of the followings?  $1$. If $n>1$, does every linear transformation on $\mathbb{R}^n$ have an invariant subspaces of dimension $2$?  $2$ Is there a vector space $V$ and a linear transformation $T$ on $V$ such that it has exactly $3$ invariant subspace?  Thank you!


Is "Which is the longest river in the world?" correct OR "What is the longest river in the world?" OR are both of these correct?  Please explain with reasons. Thanks!

Most of the time one or the other feels better, but every so often, "which" vs. "what" trips me up.   So, what's the exact difference and when should you use one or the other?


Can a character intentionally fail their save to disbelieve against a Shadow Conjuration spell that is mimicking a summoning spell to gain the full benefit of any healing that a summoned creature might grant, even if they are fully aware that the creature summoned is an illusion?

If one uses Shadow Evocation on a willing ally (e.g. Telekinetic Charge) can they choose not to disbelieve? Shadow Evocation  Nondamaging effects have normal effects except against those who disbelieve them. Against disbelievers, they have no effect.  Disbelief  Creatures encountering an illusion usually do not receive saving throws to recognize it as illusory until they study it carefully or interact with it in some fashion. A successful saving throw against an illusion reveals it to be false, but a figment or phantasm remains as a translucent outline. A failed saving throw indicates that a character fails to notice something is amiss. A character faced with proof that an illusion isn't real needs no saving throw. If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.  (my emphasis) Voluntarily Giving up a Saving Throw  A creature can voluntarily forego a saving throw and willingly accept a spell's result. Even a character with a special resistance to magic can suppress this quality.  If I understand the above correctly,  If the ally believes the caster actually cast Telekinetic Charge, it seems they get a save which they could forgoe and so be guaranteed the benefit of the spell. >> We're good here. If the ally knows the caster didn't cast Telekinetic Charge, (say because of a high Spellcraft check or because she knows the caster's spell list) they have proof that the illusion isn't real and so need no saving throw. >> Even though she "needs no saving throw", can she still choose to forego the save and be effected by the spell?  In other words, I think the question boils down to: Does one always have a choice not disbelieve an illusion, even when one has proof that it's not real?


What this code does is to identify the row of the array based on the input (Date) and return the values associated with the input date. However, this for loop is not working as it does not respect the if condition and always returns the last row of the array. function viewData() {    var ss = SpreadsheetApp.getActiveSpreadsheet();   var formSS = ss.getSheetByName("Overall Cashflow"); //Data entry Sheet   var datasheet = ss.getSheetByName("Cashflow Tracker Data"); //Data Sheet   var data = datasheet.getDataRange().getValues();   var date = formSS.getRange("H5").getDisplayValue();      for (var i = 0; i < data.length; i++){          if (data[i][0] == date) {            break;          }         var oldinflow = data[i][1];         var oldoutflow = data[i][2];    }       formSS.getRange("H8").setValue(oldinflow);   formSS.getRange("H11").setValue(oldoutflow); }

Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.


I was reading a science magazine and it claimed that  disproves all of Newtonian physics. I was highly skeptical because all we have been learning at school is Newtonian physics and we haven't even touched on relativity yet. Does that mean that the school is teaching me things that in reality are not true?  Additionally, by "all of Newtonian physics" does that include Newton's 3 laws of motion? Gravity?   The magazine also mentioned that quantum physics is also somehow disproving these previously held "theories".  Support would be appreciated.

Did Einstein completely prove Newton wrong? If so, why we apply Newtonian mechanics even today? Because Newton said that time is absolute and Einstein suggested it ?   So, if fundamentals are conflicting, how can both of them be true at a time?


When I tried to access StackOverflow.com I got the following message:     This site is currently in read-only mode; we’ll return with full functionality soon.   Mainly what is the maintenance the Stack Exchange Team is doing ?

As a signed in user when I click on "Ask a Question" (which goes to the page ) I get an "Oops! Something Bad Happened!" error.   I've had an SO account for quite a while, sign in using a Google account, have always been able to ask questions before, have good karma/score, and I'm on Chrome/OS X 33.0.1750.146     We apologize for any inconvenience, but an unexpected error occurred   while you were browsing our site.      It’s not you, it’s us. This is our fault.      Detailed information about this error has automatically been recorded   and we have been notified.      Yes, we do look at every error. We even try to fix some of them.      It’s not strictly necessary, but if you’d like to give us additional   information about this error, do so at our feedback site,   .


I read this story a long time ago - it might have been part of a longer book all set in the same universe (a la I, Robot). I remember it very vividly, but I can't find the name of the  story or author now.  The basic plot of the story is that humans have colonized Mars, but it's just the beginning of colonization, maybe 1 or 2 generations of children have been born on Mars. The limiting factor on Mars is the lack of water, and there's a custom where if you go to someone's house, you bring water with you (like bringing wine, I think). They currently get all their water from Earth, but there is some political opposition to this - people thinking that Mars will take all the water from Earth (the Martians make the point that some absurdly small fraction of the ocean like 0.00000001% will cover their water needs for a century, but politicians are making a big deal of it).  In the end, to avoid their dependence upon Earth's water supplies, some Martian colonists take an incredibly risky mission to the Asteroid belt and bring back a frozen water asteroid, showing that they can get their own water if they need.  I'm fairly certain this is not anything too obscure, so presumably someone will get this one quick. Thanks!

I remember reading a story about humans colonizing Mars.  It was from the point of view of a pilot and I think he and others were mining asteroids to use the materials on Mars.  I do remember they used water vapor for thrusters.  Someone on Earth was using the Mars colonists as scapegoats and behaving like the Late Senator McCarthy.  He kept referring to them as "Water wasters" and said they were demanding water from Earth and would use up all the water and humans would have to ration water and so on.  In truth, the amount of water they were using (I think from Martian polar caps) was quite small and they were no threat -- the politician was just using them as a focus so he could build his career.  Rather than take him on politically, they sent an expedition out to Saturn, grabbed a large chunk of ice from Saturn's rings, brought it back, and I think they crashed it on Mars, talking about how it would serve their needs for decades or more.  I can't remember if there was more, such as figuring that one effect of that much water on Mars (as it changed into liquid form) would help with terraforming or not.  But I remember the point was that they could not longer be used as a scapegoat by the politician.  The recent talk of asteroid mining has me thinking of this, but I can't remember the author's name or the title.


Suppose I have a phone book java desktop application which  uses peoples name,address,phone numbers etc stored in a database.database server used is mysql and persistence using hibernate framework.Then how am i suppose to deliver this application to so called customer who has no at all programming knowlewdge??  PS:i have used eclipse as my IDE.

Java is one of my programming languages of choice.  I always run into the problem though of distributing my application to end-users.  Giving a user a JAR is not always as user friendly as I would like and using Java WebStart requires that I maintain a web server.  What's the best way to distribute a Java application?  What if the Java application needs to install artifacts to the user's computer?  Are there any good Java installation/packaging systems out there?


I'm trying really hard here to get an arcpy equivalent for ARCGIS' ModelBuilder's Iterate Feature Selection. I need to export the individual polygon rows in a feature class as new feature classes.  Any help?

I have a feature class with over 2,000 features, and I need to make them all individual feature classes based on a field.   Is there a way to do this?


How to soften edges of texture, 'rounding' it? The actual problem is to soften edges of QR code width width n pixels, like . I need some simple algorithm without heavy calculations, or at least some ready made libraries in Java/C++.

How do you implement the fastest possible  algorithm?  I am going to implement it in Java, so  solutions are ruled out. My application, , is cross platform, so I don't want .


Show that$$ \int_{0}^{+\infty}\frac{1}{x^x}{\rm d}x<2 $$

There was a friend asking me how to prove  $$\int_0^\infty x^{-x}\,dx<2$$  Mathematica showed that its approximate value is 1.99546, so I think it isn't easy to solve it, can you provide me some ideas about this question?


The idea of my PS1 configuration is to show some extended info like Mercurial or Git repo status, command execution time, etc. The prompt is split by two lines because it produces too many characters to fit into a single line. Here is my PS1 in my .bashrc (not sure if the entire source code is necessary here):  function prompt_status {         local color_app="\e[1;38;5;214m"         local color_branch="\e[1;38;5;32m"         local color_revision="\e[0;38;5;64m"         if git rev-parse --is-inside-work-tree &> /dev/null; then                 local branch="$(git rev-parse --abbrev-ref HEAD | tr -d '\n')"                 local revision="$(git rev-parse HEAD | tr -d '\n')"                 echo -ne $color_app"git "$color_branch"$branch "$color_revision"($revision)"         elif hg status &> /dev/null; then                 local branch="$(hg branch | tr -d '\n')"                 local revision_number="$(hg identify -n | tr -d '\n')"                 local revision="$(hg parent --template '{node}' | tr -d '\n')"                 echo -ne $color_app"hg "$color_branch"$branch "$color_revision"($revision_number:$revision)"         else                 return         fi         echo -e " \e[0m" }  function prompt_return_value {         RET=$?         if [[ $RET -eq 0 ]]; then                 echo -ne "" #echo -ne "\e[32m$RET\e[0m"         else                 echo -ne "\e[1;37;41m$RET\e[0m "         fi }  function timer_start {         timer=${timer:-$SECONDS} }  function timer_stop {         seconds_elapsed=$(($SECONDS - $timer))         unset timer }  function prompt_seconds_elapsed {         local c;         local t=${seconds_elapsed}s         if [ $seconds_elapsed -ge 60 ]; then                 c=196                 t=$(format_seconds $seconds_elapsed)         elif [ $seconds_elapsed -ge 20 ]; then                 c=214         elif [ $seconds_elapsed -ge 10 ]; then                 c=100         elif [ $seconds_elapsed -ge 5 ]; then                 c=34         elif [ $seconds_elapsed -ge 1 ]; then                 c=22         else                 return         fi         echo -ne "\e[0;38;5;${c}m${t} \e[0m" }  function format_seconds {         ((h=${1}/3600))         ((m=(${1}%3600)/60))         ((s=${1}%60))         printf "%02d:%02d:%02d\n" $h $m $s }  trap 'timer_start' DEBUG PROMPT_COMMAND=timer_stop  export PS1="\n\e[1;38;5;106m\u@\h \e[0;38;5;136m\w\[\e[0m\]\n\$(prompt_return_value)\$(prompt_seconds_elapsed)\$(prompt_status)\$ "   The problem is that the prompt looks broken when a terminal window has small width. This is what I get for 80 columns:  username@some-very-long-hostname ~/tmp/d 06a14b06cac) $ 9866c9d0d26d2b27063a89ee1c330   It's like wrapped at the 2nd line causing total mess (see the $ sign in the middle). It works almost perfectly for a larger terminal column number, say 120:  username@some-very-long-hostname ~/tmp/d hg default (0:69866c9d0d26d2b27063a89ee1c3306a14b06cac) $   Also I noticed that add more text to the end of the terminal line causes an issue that's very similar to the effects described for 80 columns above. The question is: does bash handle new lines or "too long" incorrectly for PS1?  Thanks.    UPDATE  This question is not an exact duplicate of  . After some discussion with @AdamKatz, it seems that zero-length output escapes \[ and '] work only when they are literally put in the PS1 string, but they does not seem to work when returned from a function causing to appear unescaped on terminal.

Often when I start looking at history of commands some of the characters from a command displayed aren't erased, for example:  What's happening:  prompt$ some_command prompt$ some_commanother_command   What should have happened:  prompt$ some_command prompt$ another_command   I can't erase those characters and bash ignores them when executing the command. They also disappear when a new prompt is being displayed (after pressing Enter for example).  I asked other people who work on Linux at my workplace and they said that they have that problem sometimes too, but they didn't have an idea on how solve that issue.  I have Ubuntu 11.10 and I'm using guake. Here is my PS1:  \e[0;31m\u \A ${PWD##*/}\e[0;32m$(parse_git_branch)\e[0;31m$\e[m   where parse_git_branch is  parse_git_branch () {     git name-rev HEAD 2> /dev/null | sed 's#HEAD\ \(.*\)# (\1)#' }   As far as I know my colleagues have that problem even with less "fancy" PS1.


I am having following code section  Security Centre uses following technologies \newline  \subsection{Intelligent threat intelligence}  \newline It looks for bad actors by using    I get error there is no line here to end. I want to know how can I introduce gap of a line in my pages so that I can generated things with space in between text.I know if in microsoft word I press enter key it generates a new line I want something similar in this.

I would like to have my whole document showing a blank line (or space) between paragraphs and no indentation. I know how to do it line by line, but is there a way to change that with just one or a few lines at the beginning of the document? Like a package you can install, or a new command?


Background - I am drawing polygons of counties over a 17th century map that I have georeferenced. I have a number of issues with this version of GIS which I haven't experienced with past versions. When I try to draw a polygon the shape keeps closing after 3 vertexes have been applied. The only way I have found to get round this is to draw a square of vertexes over the whole county and then keep adding vertexes to draw in the polygon which is very time-consuming.

I am drawing polygons of counties over a 17th Century map that I have georeferenced. I have an issue with this version of ArcMap which I haven't experienced with past versions. The shape keeps closing after 3 vertexes have been applied.  The only way I have found to get round this is to draw a square of vertexes over the whole county and then keep adding vertexes to draw in the polygon which is very time consuming. How can I avoid this happening?


How can we describe the enteries of a matrix by just knowing the determinant of it?

Prove that if $A$ is a square matrix with integer entries and $\det(A) = \pm 1$, then $A^{-1}$ contains all integer entries.  I'm really thrown off by this one, its unlike all the examples I've seen.. I just dont know where to start... how can I begin to prove this?


In The Last Jedi we have the First Order tracking the Resistance through hyperspace, and this is treated as brand new cutting edge technology previously thought to be impossible.  But in the Star Wars Rebels episode "Gathering Forces" (S1 E09), we also have the Empire tracking the crew of the Ghost through hyperspace, via a tracking device that they attached to the ship. The crew of the Ghost does not seem particularly stunned that this tracking technology exists. This is decades before the events of TLJ.  Is this the same technology? If so, why are Finn and Rose so shocked by it in TLJ? is there an in-universe explanation?

In TLJ, a big deal is made about how the First Order is able to track the Resistance (lead) ship     through hyperspace.   Everyone seems surprised that this is possible.     Rose and Finn comment that the tracking mechanism must be similar to other, pre-existing tracking mechanisms, which is why they know what to destroy, but they don't seem to know where this new ability comes from.   Is it ever made clear how the First Order is doing this? Or is it just "new technology"?


I need to know the limit of this sequence:   $\lim (a^n +b^n)^{1/n}$ for $a,b>0$   I suppose that this limits will be in function of a and b, but how I can solve it?

I'm having some difficulty with this proof. Could you help me?     Let $a,b>0$ and $c_n = (a^n + b^n)^{1/n}$. Show that $$\lim_{n\to \infty}c_n = \max \{a,b\}.$$   Thank you.


I'm trying to figure out how to make a script that will be able to send commands to a screen that will execute within whatever the screen is doing. Is this possible, and if so, how is it done? I've already tried screen -X etc, and it is not executing the commands.

I'm trying to run a minecraft server on my unRAID server.  The server will run in the shell, and then sit there waiting for input. To stop it, I need to type 'stop' and press enter, and then it'll save the world and gracefully exit, and I'm back in the shell. That all works if I run it via telnetting into the NAS box, but I want to run it directly on the box.   this is what I previously had as a first attempt:  #define USER_SCRIPT_LABEL Start Minecraft server #define USER_SCRIPT_DESCR Start minecraft server. needs sde2 mounted first cd /mnt/disk/sde2/MCunraid screen -d -m -S minecraft /usr/lib/java/bin/java -Xincgc -Xmx1024M -jar CraftBukkit.jar   MCunraid is the folder where I have the Craftbukkit.jar and all the world files etc. If I type that screen line in directly, the screen does setup detached and the server launches. If I execute that line from within the script it doesn't seem to set up a screen  for stopping the server, I need to 'type' in STOP and then press enter. My approach was  screen -S minecraft -X stuff "stop $(echo -ne '\r')"   to send to screen 'minecraft' the text s-t-o-p and a carriage return. But that doesn't work, even if I type it directly onto the command line. But if I 'screen -r' I can get to the screen with the server running, then type 'stop' and it shuts down properly.  The server runs well if I telnet in and do it manually, just need to run it without being connected from my remote computer.


I was trying to install viber using .deb package : dpkg --install viber.deb and got the following error : Selecting previously unselected package viber. (Reading database ... 373332 files and directories currently installed.) Preparing to unpack viber.deb ... Unpacking viber (12.0.0.7) ... dpkg: dependency problems prevent configuration of viber:  viber depends on libssl1.0.0; however:   Package libssl1.0.0:amd64 is not installed.  dpkg: error processing package viber (--install):  dependency problems - leaving unconfigured Processing triggers for gnome-menus (3.32.0-1ubuntu1) ... Processing triggers for desktop-file-utils (0.23-4ubuntu1) ... Processing triggers for mime-support (3.60ubuntu1) ... Processing triggers for bamfdaemon (0.5.3+18.04.20180207.2-0ubuntu1) ... Rebuilding /usr/share/applications/bamf-2.index... Processing triggers for hicolor-icon-theme (0.17-2) ... Errors were encountered while processing:  viber  Since then I haven't been able to do anything using apt. I always get: sudo apt install viber                     Reading package lists... Done Building dependency tree        Reading state information... Done viber is already the newest version (12.0.0.7). You might want to run 'apt --fix-broken install' to correct these. The following packages have unmet dependencies:  viber : Depends: libssl1.0.0 but it is not installable E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).  The problem is, when I try: apt --fix-broken install  I get: Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages will be REMOVED:   viber 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. 1 not fully installed or removed. After this operation, 346 GB disk space will be freed. Do you want to continue? [Y/n]  Is it normal that it says my whole disk space is going to be freed? Otherwise what should I do to fix this?

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


I've got a test script that repeatedly builds a library under different configurations. It also tee's the output for postmortem failures:  $MAKE" static dynamic cryptest.exe 2>&1 | tee -a "$TEST_RESULTS" if [ "$?" -ne "0" ]; then     echo "ERROR: failed to make cryptest.exe" | tee -a "$TEST_RESULTS" fi   The script is not working as intended because the test is capturing tee's return code, and not make's return code.  I looked at the man pages for tee(1), but I don't see an option to have it restore a return code.  How can I capture the return code from make before tee smashes it?

I have two processes foo and bar, connected with a pipe:  $ foo | bar   bar always exits 0; I'm interested in the exit code of foo. Is there any way to get at it?


I just update, but, I don't want to restart the computer, 'cause it may not reboot

My /boot partition is nearly full and I get a warning every time I reboot my system. I already deleted old kernel packages (linux-headers...), actually I did that to install a newer kernel version that came with the automatic updates.  After installing that new version, the partition is nearly full again. So what else can I delete? Are there some other files associated to the old kernel images?  Here is a list of files that are on my /boot partition:  :~$ ls /boot/ abi-2.6.31-21-generic         lost+found abi-2.6.32-25-generic         memtest86+.bin abi-2.6.38-10-generic         memtest86+_multiboot.bin abi-2.6.38-11-generic         System.map-2.6.31-21-generic abi-2.6.38-12-generic         System.map-2.6.32-25-generic abi-2.6.38-8-generic          System.map-2.6.38-10-generic abi-3.0.0-12-generic          System.map-2.6.38-11-generic abi-3.0.0-13-generic          System.map-2.6.38-12-generic abi-3.0.0-14-generic          System.map-2.6.38-8-generic boot                          System.map-3.0.0-12-generic config-2.6.31-21-generic      System.map-3.0.0-13-generic config-2.6.32-25-generic      System.map-3.0.0-14-generic config-2.6.38-10-generic      vmcoreinfo-2.6.31-21-generic config-2.6.38-11-generic      vmcoreinfo-2.6.32-25-generic config-2.6.38-12-generic      vmcoreinfo-2.6.38-10-generic config-2.6.38-8-generic       vmcoreinfo-2.6.38-11-generic config-3.0.0-12-generic       vmcoreinfo-2.6.38-12-generic config-3.0.0-13-generic       vmcoreinfo-2.6.38-8-generic config-3.0.0-14-generic       vmcoreinfo-3.0.0-12-generic extlinux                      vmcoreinfo-3.0.0-13-generic grub                          vmcoreinfo-3.0.0-14-generic initrd.img-2.6.31-21-generic  vmlinuz-2.6.31-21-generic initrd.img-2.6.32-25-generic  vmlinuz-2.6.32-25-generic initrd.img-2.6.38-10-generic  vmlinuz-2.6.38-10-generic initrd.img-2.6.38-11-generic  vmlinuz-2.6.38-11-generic initrd.img-2.6.38-12-generic  vmlinuz-2.6.38-12-generic initrd.img-2.6.38-8-generic   vmlinuz-2.6.38-8-generic initrd.img-3.0.0-12-generic   vmlinuz-3.0.0-12-generic initrd.img-3.0.0-13-generic   vmlinuz-3.0.0-13-generic initrd.img-3.0.0-14-generic   vmlinuz-3.0.0-14-generic   Currently, I'm using the 3.0.0-14-generic kernel.


I installed mysql server and want to install the mysql client using following code:  apt-get install mysql-client   but I got following error message:  E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   It looks like the file locked and permission, if it is the case, it does not ask me for a password.  Your help and information is great appreciated.  Regards,  Inung

I get this error whenever I try to install programs using the terminal:  home@ubuntu:~$ apt-get install myunity E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   Also I'm unable to install updates using the terminal.


The cake was baked.   Is the word baked considered a predicate adjective? Would the word baked also be a past participle written in passive voice? I am just trying to figure this out.

How can you tell when a participle is being used as an adjective?  I feel completely lost trying to guess. Just as a completely arbitrary example   For every dedicated scientist patiently recording atmospheric pressure and wind speed while shivering at high altitudes, there is a carnival barker with a bevy of pretty girls willing to dangle from a basket or parachute down to earth.


In absorption spectrum, we pass white light through the sample of gas or liquid which is to be examined. The electrons in those atoms will will absorb particular wavelengths from the white light and will get excited to a higher energy level. The wavelength which are absorbed by the electrons won't appear in the screen and hence dark lines should be observed in a coloured background if the light is further passed through a prism or a diffraction grating. In this way and absorption spectrum is obtained in which dark lines appear in a coloured background. But we know that electrons don't like to stay in higher energy level. They typically stay there for a time that is of the order of $10^{-8} s$. So they will jump back to the ground level either by one transition or by multiple transitions and thus they will the emit the energy in the form of photons. If they come back to the ground level in one transition they will emit photon which has the exact wavelength of a photon that they absorbed. Thus we won't say see dark lines in a coloured background as the electron emitted the photon of the exact same wavelength with it absorb which we see as dark lines in a coloured background, right?

My teacher told me that in an atom (assume hydrogen), as soon as the single electron absorbs a photon with the right amount of energy, it jumps up to another energy level, and instantly falls back down to the initial one, releasing a photon with the same wavelength as the one it absorbed. So, if I place a source of white light, and in front of it a sample of hydrogen, and then a prism, according to what I have read so far, the screen should show an absorption spectrum, but why would it? Since the electrons are falling back down in all the hydrogen atoms almost instantaneously, they should give out the specific wavelengths of light which form the emission spectrum, which, I think, would combine with the previous one (absorption spectrum) to give a continuous spectrum? TL;DR: If a sample of hydrogen atoms is excited by white light, why don't the electrons getting excited and coming down instantly give absorption and emission spectrums respectively, which would combine to give a continuous spectrum? **NOTE:**I would have the same question regarding emission spectrums, but I assume all the atoms in the discharge tube would be excited (so no room for further absorption and production of an absorption spectrum), which would give out just the emission spectrum of hydrogen.


I have a repo that is forked, call this myFork.  The repo that I forked from, call it upstream.   I set up the upstream repo using this:   On myFork, I have 2 branches: master and myDevelop.  For master, it is used to track changes to upstream/master.  How do I setup so that myDevelop to track upstream/develop only?  To expand the question further, how do I:   set xyz branch on myFork to set abc branch on upstream?

I know how to make a new branch that tracks remote branches, but how do I make an existing branch track a remote branch?  I know I can just edit the .git/config file, but it seems there should be an easier way.