Cryptocode package question, protocol with 4 players
TikZ or cryptocode package for cryptographic protocol diagrams
Delete all but the most recent n file for each group of files that share the same prefix in a directory My question is a bit different from some older questions simply asking for "deleting all but the most recent n files in a directory".  I have a directory that contains different 'groups' of files where each group of files share some arbitrary prefix and each group has at least one file. I do not know these prefixes in advance and I do not know how many groups there are.  EDIT: actually, I know something about the file names, that is they all follow the pattern prefix-some_digits-some_digits.tar.bz2. The only thing matters here is the prefix part, and we can assume that within each prefix there is no digit or dash.  I want to do the following in a bash script:   Go through the given directory, identify all existing 'groups', and for each group of files, delete all but the most recent n files of the group only. If there are less than n files for a group, do nothing for that group, i.e. do not delete any file for that group.   What is a robust and safe way of doing the above in bash? Could you please explain the commands step-by-step? What is $48\div2(9+3)$? There is a huge debate on the internet on the value of $48\div2(9+3)$. I believe the answer $2$ as I believe it is part of the bracket operation in BEDMAS.  yields the same answer. I also believe that if $48\div2\times(9+3)$ was asked it would be $288$ which Mathway agrees with as well. However,  says it is $288$ either way. A friend of mine (who is better at math) told me that there is no such thing as 'implicit multiplication', only shorthand so that is in fact done after the division (going left to right, not necessarily because division occurs before multiplication. But he didn't explicitly give a reason) What is the answer and why? Schengen Visa four years- 90 days stay I have been granted multiple entry Schengen Visa valid for 4 years with the duration of stay of 90 days. Does it mean only 90 days of stay in total during a 4 years period?  I'll be travelling to Schengen Area in September for 25 days, then after 2 month or so I will travel again for 30 days. Similarly, I'll be traveling to the Schengen Area in the future depending on the business meetings.  How will I know, that how many days are left? On what basis the calculations are done?  Also, please explain the "90/180" rule. How to use grep on column? I want to apply grep on particular column in column command.  myfile.txt  3,ST,ST01,3,3,856 3,ST,ST02,4,9,0234 6,N1,N101,2,3,ST 6,N1,N102,1,60,Comcast 6,N1,N103,1,2,92   My Command:  column -s, -t &lt; myfile.txt | grep -w "ST"   Here I want to only grep the pattern ST in 2nd column. How to do this ?  Expected Result:  3       ST            ST01              3            3            856 3       ST            ST02              4            9            0234 Unable to mount /dev/loop0 during install Best Fake Proofs? (A M.SE April Fools Day collection) Is starting a group with 5 newbies (DM included) possible? Some friends and I want to start playing D&amp;D (5e), but none of us, DM included (not me) have played before to any great extent. The DM and I have some cursory experience with 4e, but have never been able to play to any great extent. Is this advisable, or should we play with existing groups first? We live in a relatively remote area, making it hard to find experienced players. Let $G$ a group with normal subgroups $M,N$ such that $M\cap N=\{e\}$. Show that if $G$ is generated by $M\cup N$ then $G\cong M \times N$. How do RAM and processor speed affect overall performance on Android? Since Android can be installed on wide range of devices, I'm wondering how important RAM and the CPU speed are to the performance of a device.  There are always tradeoffs when something is increased and another one decreased!  Is more RAM or a faster processor better for general browsing and less mulititasking?  What if I'm interested in gaming or doing lots of things at once?  Will more RAM make up for a slower processor or vice-versa? I use a very custom style (not mine) and very frequently I get a heading  on the bottom of a page and the next paragraph on the top of the next page. Sometimes this paragraph may be a list or similar. The same is true for listings and the listing description.   Is there a general way how I can adjust the "badness" of these events? Or can I adjust when a section heading would be on the last, say, 3cm of a page it should go to the next page? Or can I say, if a *listing description" is on the top 3cm of a page pull 5 more listing lines from the last page onto this page?   The style I use does not use standard structure tags and environments. But lets call them section, subsection, listing and I will try to migrate them to my lingo. Persist sort/filter selections I have a directory that contains the following:  x.pdf y.zip z.mp3 a.pdf   I want to delete all files apart from x.pdf and a.pdf. How do I do this from the terminal? There are no subdirectories so no need for any recursion. How to prove this binomial identity $\sum_{r=0}^n {r {n \choose r}} = n2^{n-1}$? I am trying to prove this binomial identity $\sum_{r=0}^n {r {n \choose r}} = n2^{n-1}$ but am not able to think something except induction,which is of-course not necessary (I think) here, so I am inquisitive to prove this in a more general way.  The left side of an identity occurs while solving another problem (concerning binomial theorem) so I am more interested in deriving the right side from the left side, else I have to remember it now onward.  EDIT: I am more interested in an algebraic proof rather than combinatorial argument or something involving calculus (however I liked  and  solution), hence I am removing the combinatorics tag. Is there any difference between Present Perfect and Present Perfect Continuous? So today I woke up and noticed new item in inventory which was a booster pack containing 3 cards from L4D 2. From what I see on market these booster packs are new (graph only shows up to 19 of June). No matter the game it seems to always contain 3 cards. There are two actions I can do with it: unpack or sell. There is fancy animation when you unpack the booster ;)    I'm not exactly sure why I got it, I have few guesses:   I got new badge, power player - this could give me a booster? Because of new badge I reached level 10 - maybe every couple levels there are gifts? It just dropped randomly for everyone?   Maybe together we could rule out above guesses. It's also interesting from the point of market, to estimate how many boosters are there. With some games they seem to be more valuable than 3 cards separately, but that maybe only initial confusion. The iOS-app should provide (at least) the same features as the site and the ability to edit your profile is not so unimportant.  In my opinion, the user should be able to change the every single info-field in his profile (including, but not limited to nickname, description, profile picture) by pressing an "Edit" button which should be located somewhere on his or her profile view. $\sqrt{c+\sqrt{c+\sqrt{c+\cdots}}}$, or the limit of the sequence $x_{n+1} = \sqrt{c+x_n}$ (Fitzpatrick Advanced Calculus 2e, Sec. 2.4 #12)  For $c \gt 0$, consider the quadratic equation $x^2 - x - c = 0, x &gt; 0$.  Define the sequence $\{x_n\}$ recursively by fixing $|x_1| \lt c$ and then, if $n$ is an index for which $x_n$ has been defined, defining  $$x_{n+1} = \sqrt{c+x_n}$$  Prove that the sequence $\{x_n\}$ converges monotonically to the solution of the above equation.  Note: The answers below might assume $x_1 \gt 0$, but they still work, as we have $x_3 \gt 0$.    This is being repurposed in an effort to cut down on duplicates, see here: .  and here: . How to open and convert CHM documents? I have some documents that are in a .chm format. I wondered if there is a file format that can be easier to navigate, supported and of equal file size in Ubuntu?  If there is, I would like to start converting all those books and probably using them with less hassle on all my Ubuntu PCs and my Android phone. In the comment field on StackOverflow (and other StackExchange sites as well, I presume) you're required to write 15 characters for the server to accept your post. If a shorter post is submitted, an information message states that the comment is too short. That is all good.  However, below the comment field is a counter, which counts up to 15 and then down from however many characters you're allowed to type minus fifteen. This counter doesn't always act the same as the actual validation: if I pad my message with whitespace, the validation notices and still says the message is too short, but the counter does not notice, and counts as usual.  Suggested fix: make the character counter trim the message before it counts, so the two messages say the same thing. How specific does "beast you have seen" have to be for Wild Shape? Starting at 2nd level, you can use your action to magically assume the   shape of a beast that you have seen before.   This doesn't say anything about the gender or age of the beast, so can a druid change into a female bear if he has only seen male bears? Can he change into a bear cub if he has only seen adult bears? What about hens/roosters/chickens, which look quite a bit different? Or does the gender of the animal shape just match the gender of druid?