I'm looking at a handful of files on my system with setuid permission on my system, by running:  sudo find / -perm -4000   I noticed that /bin/ping shows up on the list.  Can anyone explain why ping requires setuid permission?
Ping is a a program owned by root with the user id bit set.  $ ls -l `which ping` -rwsr-xr-x 1 root root 35752 Nov  4  2011 /bin/ping   As I understand it, if a user runs the ping process, then the effective user id will change from the real user id (i.e. the user id of the person who launched the process) to the user id root. However when I try this and look at the output of ps to see if the ping process is running as the root user, I still get the real user id showing.  ps -e -o user,ruser,euser,cmd,args | grep ping sashan   sashan   sashan   ping -i 10 -c 1000 www.goog ping -i 10 -c 1000 www.google.com
How to correctly use the present perfect tense This  states that:  When you use the present perfect tense you have to be talking about a period of time that you still consider to be going on. For example, if it’s still morning, you can say, &quot;I’ve shaved this morning.&quot; If it is afternoon or evening, all of a sudden &quot;I’ve shaved this morning&quot; sounds really weird.  &quot;I've shaved this morning&quot; sounds more like past perfect, and indication of specific time (in the morning) makes this sentence incorrect.  Am  I spot on? Then what is the difference between the construct of past perfect, present perfect and future perfect? Is it possible to check out subdirectories of a repository in Git?  Imagine I am setting up a new WordPress installation. I will create two new directories for my plugin and theme customization:   wordpress/wp-content/plugins/myplugins/  wordpress/wp-content/themes/mytheme/   I want to maintain these directories via Git. In Subversion, I would accomplish this by having trunk/myplugins/ and trunk/mytheme/ directories and checking out subdirectories. Does Git have a way to accomplish the same task using a single repository?  I could just be missing the boat on some Git paradigm, as a long time SVN user with little exposure to Git.  Edit:  storing different content is an interesting way to handle this. Violation of linearity assumption in Logistic Regression I built a logistic model with 7 continuous independent variable and 8 categorical (dummy) variables in R. I tested for the linearity assumption using the Box Tidwell test and all my variables show high significance.  I am wondering now, if the assumption is violated what it would mean for the coefficient estimates and if I still can run the model with caution.   I read about the approach of using regression splines but I am confused how I would determine those and interpret the model then. How can I start Hoard of the Dragon Queen with 4th level characters? I'm pretty new to DM'ing and was just wondering if there would be a way to start the hoard of the dragon queen adventure with a group of 4th level characters?  There don't really seem to be any modules for that level range yet.  We just finished a short module that took our party to level 4, but id really like to play through this adventure because it seems awesome. Also I couldn't really find any other ones that start around that level so rather than re-roll characters we'll just start a little of the way in. Terminal flashes on empty backspace with Yosemite Since using Yosemite, I've had the annoying problem of my current Terminal window flashing when backspacing on an empty line. I know on previous versions of OS X this flashing was not default, and could be toggled in accessibility settings, but I cannot find the same setting and I'm dying to get this turned off. Any known ways to get rid of it? In the search results of stackexchange.com/search?q=*, allow people to click on a tag and go to that website with the tag page open.   For example,  shows me this:        But clicking on the hovered-on tag takes me to  and the panda.   Instead, it should take me to    The math.SE URL is already there in  /#question-summary-608993 &gt; div.summary &gt; div.started.fr &gt; a #question-summary-608993 &gt; div.hot-question-site-icon &gt; a Springer llncs TOC not working I can't get the TOC to work. I remember it worked before, but there was something I did (unfortunately I can't remember what it was), and after that the TOC just stopped working.  Here is a part from my document:  \documentclass[deutsch]{llncs}  \usepackage{graphicx} \usepackage[labelformat=empty]{caption} \usepackage{subcaption} \captionsetup{compatibility=false}  \bibliographystyle{unsrt}  \pagestyle{headings} \begin{document}  \sffamily  \begin{titlepage}     %Some stuff here \end{titlepage}  \thispagestyle{headings} \tableofcontents \newpage %more stuff here blablabla \section{test} \subsection{test2} \end{document} I'm looking for an example of a finitely generated module with submodules that are not finitely generated.  I've found  dealing with group (i.e. an example of a finitely generated group with subgroups that are not finitely generated). But I can't figure out whether that question do help to this one.  And I actually want to find a more "module-like" example rather than an example derived from a 'strange' group.  Can you please help? Thank you! What are copy elision and return value optimization? Can Cycles use multiple UV layers? How to add user to a group from Mac OS X command line? trying to add a user to a group from the command line but can't figure out how?   Specifically this is on Mac OS X Server 10.5.8  like to add user to 'admin' and 'wheel' groups Recommendations for Numerical Analysis texts? I'm in a numerical analysis course right now and it's pretty rigorous but I'm enjoying it a lot. I took a lower level course before that was more oriented towards implementation of numerical methods, so it's not my first time with the material.  Anyway, my professor wrote his own course notes and they're fantastic but I wanted some reference material since I'm currently outlining my own notes. Just wondering what the big ones out there are  edit: I would say I'm at an advanced undergraduate level Upgrade or replace a Wubi installation? I've got Windows 7 with Wubi 11.10 installed. I would like to upgrade to 12.04 but I'm not sure what the best path would be.  I'm not skilled enough to use Ubuntu all the time, and my iPhone requires me to run some Windows version for the damn iTunes software. I would love to run Windows XP but I can't figure out how to install it via USB -- my computer has no cd drive.  I'd like to run Windows XP and Wubi 12.04 on top of that. Or, perhaps, Ubuntu 12.04 natively and Windows XP alongside of that. So I guess I have 2 questions:   (lazy) Should I upgrade my Wubi from inside Ubuntu, or should I remove Wubi 11.10 from within Windows and install a brand new Wubi 12.04? (proper) How can I install Windows XP and Ubuntu 12.04 alongside each other?   Update: I am going to create a separate question post about the above #2 question... I realize it's wrong to ask two questions in one post when they are that different. When I dock my Windows 7 laptop, I want it to prefer the wired ethernet connection over WiFi.  This is a pretty straightforward thing to do on my Mac - I just reorder my network preferences, and it "does the right thing." I just can't figure out how to achieve the same thing on my Win7 laptop.  So, when I'm docked, it connects to WiFi, and then fails to connect to servers on the local wired network. How do I fix this? how to replace multiple strings together in Oracle I have a string coming from a table like "can no pay{1},as your payment{2}due on {3}". I want to replace {1} with some value , {2} with some value and {3} with some value .  Is it Possible to replace all 3 in one replace function ? or is there any way I can directly write query and get replaced value ?   I want to replace these strings in Oracle stored procedure the original string is coming from one of my table I am just doing select on that table   and then I want to replace {1},{2},{3} values from that string to the other value that I have from another table Want to install Ubuntu on Chromebook Copy/duplicate database without using mysqldump Is it necessary to dispose System.Timers.Timer if you use one in your application? I am using System.Timers.Timer class in one of the classes in my application. I know that Timer class has Dispose method inherited from the parent Component class that implements IDisposable interface. Instances of the class below are created many times during my application lifecycle; each of them has an instance of Timer class that generates Elapsed events continuously during the class's lifecycle. Should I implement IDisposable interface in the class that uses Timer class to dispose the timer object? (I have seen code that doesn't do this at all). I am afraid that some unmanaged resources will not be freed if I use the class below like this:  SomeClass someClass = new SomeClass(); someClass.DoSomething(); someClass = null;   The class:  using System.Timers;  public class SomeClass {     private Timer m_timer;      public SomeClass()     {                    m_timer = new Timer();         m_timer.Interval = 1000;         m_timer.Elapsed += new ElapsedEventHandler(m_timer_Elapsed);         m_timer.AutoReset = false;         m_timer.Start();                            }      public void DoSomething()     {      }      private void m_timer_Elapsed(object sender, ElapsedEventArgs e)     {         try         {             //Do some task         }         catch (Exception ex)         {             //Ignore         }         finally         {             if (m_timer != null)             {                 //Restart the timer                 m_timer.Enabled = true;             }         }     } } How to read a line from the console in C? What is the simplest way to read a full line in a C console program The text entered might have a variable length and we can't make any assumption about its content. Produce an explicit bijection between rationals and naturals?