Consider the group $C_2\times C_2=\{x^2=y^2=1, xy=yx\}$.  Then, any automorphism of $C_2\times C_2$, say $\phi$, must map $x$ to something of the same order, so $x$ can be mapped to $x$, $y$, or $xy$.  Consider the case when $\phi(x)=y$.  Then, I want to say what $\phi$ does to the other elements of $C_2\times C_2$.  What would be the best way of going about this?  I know that $\phi(e)=e$ where $e$ is the identity element, but what would happen to $\phi(y)$ or $\phi(xy)$?  Could we say anything?  What about the case then when $\phi(x)=xy$ or $\phi(x)=x$?
Show $\operatorname{Aut}(C_2 \times C_2)$ is isomorphic to $D_6$ (the group with $x^3=1$, $y^2=1$ and $xy=yx^2$).  I'm not really sure how to express the elements of $\operatorname{Aut}(C_2 \times C_2)$. Would it be sufficient to show the elements of $\operatorname{Aut}(C_2 \times C_2)$, find their order and show they bijectively map to every element of $D_6$ and satisfy $xy=yx^2$?
What does this cryptic Bash command mean? What will happen when Winter Bash is over? Tomorrow (January 2nd 2019) is the day that Winter Bash will be gone.  So I am thinking: Will there be some sort of a final ranking page anywhere?  It would be nice so I don't need to keep going to  every day to see my rank.  If there isn't going to be anything like that, what should I do to see my final rank on Winter Bash? Is $\mathbb{Q}(\sqrt{2}) \cong \mathbb{Q}(\sqrt{3})$? Could someone with experience in using these exercise typesetting packages please offer a quick compare and contrast of these packages to help me choose?  Packages under consideration are:         Having read briefly the documentation, they all seem to do the same thing generally, so could you please focus on the differences?  Some differences will not be obvious until I've learnt and used all the different packages but I want to better appreciate the differences now, a priori. Keeping the time stamp when syncing with Ubuntu One? Can I rent a camper in the US/Canada with a European B license? We are considering a holiday in North America with a camper. I have a European driver's license (B) which allows me to drive personal cars up to 3500 kg, although I can imagine that an average camper easily weighs more.  Does my license qualify me to drive a camper? If not, can I take an American/Canadian driver's test which would allow me to drive a camper? I have just bought a Nikon 50mm f/1.8D prime lens.  I took this picture (leg of my glasses frame on a mouse, and a LED desk lamp is on top of it) : f1.8, 1/80s, ISO 200   The purple fringing is right in the middle of the picture. Does it happen very often to this lens? How do you take profit from stock trading while keeping capital invested? Video produced from images only plays in VLC but no other players After seeing a question regarding the acquisition of Data's cat Spot, the point was brought up that Data's  midway through the series.  My question is, how? I have thought up two possibilities (see below to my own answer) but I'm wondering if there aren't possibly others that might fit better. Exhibit A- Spot the Younger  Exhibit B- Spot the Older Start + Gerund vs Start + Infinitive: is there a subtle tense difference? Is there a subtle difference between these fragments:  Jack walked over to the car, opened the door, and started to look for the aspirin vial in the glove compartment. Jill looked on skeptically. Jack walked over to the car, opened the door, and started looking for  the aspirin vial in the glove compartment. Jill looked on skeptically. Is a 2-hour transit time enough to catch a connecting flight in Muscat airport? Both flights are with Oman Air I am flying from Dubai to India with Oman Air with a layover of 2 hours at Muscat airport. Is 2 hours enough for me to catch my connecting flight from Muscat to New Delhi? My flight from Dubai to Muscat as well as the connecting flight from Muscat to New Delhi are with Oman Air. Do I need to re-check in my luggage? Am I taking a risk or should I take an earlier flight from Dubai to get more layover time to be on the safer side? Undefined Symbol ___gxx_personality_v0 on link Cool Text Highlighting in LaTeX How exactly do I install Minecraft Mods and what is Forge? Deleting files from Remote FTP-Server older than x days i've got a remote FTP server where i store some backups via cronjob.  The Problem is that i only got a little amount of space so im doing incremental backups. I want to keep the backups about 14 days.  I don't have any other access to the server except FTP and i don't now how to delete files older than x days. Every file got a name with a date in it  yxzNamezxy-date-y-m-d.tar.bz2 (datev-20100111.tar.bz2(   Hope to get some help here.  Cheers and thanks for the hopefully coming answeres,  Dennis  /Edit  I'm trying to use the curl thing which is mantioned in an answere with this part of code  curl ftp://$FTP_SERVER --user $FTP_USER:$FTP_PASS --list-only &gt; files.tmp declare -a aFiles let iCount=0 exec &lt; files.tmp while read sLine do         aFiles[$iCount]=$sLine         ((iCount++)) done  echo -e "\n Files: \n\n\n" echo ${aFiles[@]}  echo -e "\nfor ...\n\n\n" for sFile in $aFiles do         echo -e "\nFile:" $sFile done   but the secound loop doesn't give me more than 1 filename  Cheers,  Dennis SingleEmailMessage sending isn't working when called from Unit Test I have the following code:      public class OrderRequestCreationEmails {     public static void sendMail()     {          Messaging.reserveSingleEmailCapacity(2);         Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();         String[] toAddresses = new String[] {'dgriff@varonis.com'};           mail.setToAddresses(toAddresses);          mail.setReplyTo('dgriff@varonis.com');          mail.setSenderDisplayName('Mail Test');          mail.setSubject('Success! Mail Sent');          mail.setBccSender(false);         mail.setPlainTextBody('BODY');          Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });     } }   I tried to call this function from a test as such: (I know its not an actual test, its just to see if I receive a mail).  @isTest private class CreationEmailsTest {     @isTest private static void sendMailTest() {         OrderRequestCreationEmails.sendMail();     } }   And I haven't received the mail, no idea why?  It's an example I took from the salesforce developer guide. couldn't find any answers online...  FYI - deliverability in the sandbox is turned on, and test deliverability works What is the correct way to punctuate the end of a sentence before a quote that directly supports the statement? I assume either a colon or a semicolon, but I have no idea which is correct.  For example:     Waldo is a better hide-and-seek player than Clem; "Waldo was   the winner of the past ten annual hiding awards" (Where's Waldo 13).      Waldo is a better hide-and-seek player than Clem:  "Waldo was   the winner of the past ten annual hiding awards" (Where's Waldo 13).   (Excuse the silly example, but I didn't have a better one.) Maximum weight an average bicycle can carry? Search a specific word and copy line to another Sheet