I have a bunch of files and I want to rename them using regular expressions.  I want to do this in a Linux Command line. I have the files report1.txt report2.txt report3.txt  How can I rename these so that they state myreport1.txt myreport2.txt myreport3.txt  Please let me know, I've searched the internet and they have many complex examples.
Rename all the files within a folder with prefix “Unix_” i.e. suppose a folder has two files a.txt and b.pdf than they both should be renamed from a single command to Unix_a.txt and Unix_b.pdf
R stem and leaf values Proof of an equality involving cosine $\sqrt{2 + \sqrt{2 + \cdots + \sqrt{2 + \sqrt{2}}}}\ =\ 2\cos (\pi/2^{n+1})$ so I stumbled upon this equation/formula, and I have no idea how to prove it. I don't know how should I approach it: $$ \sqrt{2 + \sqrt{2 + \cdots + \sqrt{2 + \sqrt{\vphantom{\large A}2\,}\,}\,}\,}\ =\ 2\cos\left(\vphantom{\Large A}\pi \over 2^{n + 1}\right) $$  where $n\in\mathbb N$ and the square root sign appears $n$-times.  I thought about using sequences and limits, to express the LHS as a recurrence relation but I didn't get anywhere.  edit: Solved, thanks for your answers and comments. Why can't I capture my first Pokemon? I'm trying to just catch my first Pokemon and I can't for some reason. From what I've read I should be able to see the three basic Pokemon to choose from and catch one but I can't see them.  I can only see three pulsing circles and the app appears to be stuck on map view. I've tried clicking or walking over the circles but nothing happens.   Any suggestion on how to fix this? What's the meaning "them" here? I've confused about the word "them" in the middle of the sentence:     They know all about them   Westovers in Idaho.   Could you please tell me what the meaning of "them" here is?     Does it mean "they know about the oils which are made by Westovers in Idaho"?   The full text is here:      Dad had always said he wanted to build a room the size of a cruise ship   but I’d never thought he’d have the money. I looked to Mother for an   explanation but it was Dad who answered. The business was a roaring   success, he explained. Essential oils were popular, and Mother had the best   on the market. “Our oils are so good,” he said, “we’ve started eating into the   profits of the large corporate producers. They know all about them   Westovers in Idaho.”   Educated by Tara Westover How to set up Dolphin as default file manager? How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression? For example here is the sum of $\cos$ series:  $$\sum_{k=0}^{n-1}\cos (a+k \cdot d) =\frac{\sin(n \times \frac{d}{2})}{\sin ( \frac{d}{2} )} \times \cos \biggl( \frac{ 2 a + (n-1)\cdot d}{2}\biggr)$$  There is a slight difference in case of $\sin$, which is: $$\sum_{k=0}^{n-1}\sin (a+k \cdot d) =\frac{\sin(n \times \frac{d}{2})}{\sin ( \frac{d}{2} )} \times \sin\biggl( \frac{2  a + (n-1)\cdot d}{2}\biggr)$$   How do we prove the above two identities? I use the Stack Exchange sites very often to find solutions to problems and help me with decision-making.  In some sites I have asked question and received answers, and I have more than 15 reputation. On Stack Overflow I have always found answers to my questions and never needed to post a question (avoiding duplicate questions). However, I would like to vote for the answers that helped me but I do not have the ability to do that, due to low reputation.  Posting a question or answering an answer on each site seems like the only way to get enough reputation.  Since I have no input to give in these areas unless they will be counted as duplications, many answers that I have already used are missing my vote.  I suggest to take into account all of the reputations from all Stack Exchange sites for voting, or thinking about a different way to allow votes. How to search inside files on Windows 7? In Windows XP we can search for files that contain a defined keyword (inside all files types).  Windows 7 can look inside files for a keyword, but only for text files. (*.doc, *.txt, *.inf, ...), not (*.conf, *.dat, *.*, ...).   don't contain any filter I can use for this.  How is this possible? Insert distinct data into Combobox List Define a mathematical set Todo comments:Not include and left align? I have an idea or subject that should have a Q&amp;A, and want to propose a new site. How can I do this?  Related: How to only append to clipboard (but not overwrite current data)? I have a rather large file, I need to copy the entire contents somewhere, but when I scroll down the page all the data I have selected becomes unselected. I could just copy and paste block by block, but I would find it much easier as there is a lot of data, to just be able to append the contents to the end of the current clipboard data. Is that possible?  That is so that I can have a keyboard shortcut which will enable me to copy this to the clipboard:  I am some nice new text.   When this is what is already there:  I am the old text.   And have it look like this when pasted:  I am the old text. I am some nice new text.   So there are 3 things that I would really like from this (I would have 3 separate keyboard shortcuts to do this):   Append the data to the end of the clipboard and have it put in a RETURN before it (as shown in the example above). Append the data to the end of the clipboard but have it so that there is not RETURN before it so that it would continue on on the same line initially. Have all this but so that the data is put at the beginning of the clipboard before all the data which is currently there.   I am running Ubuntu GNOME 16.04 with GNOME 3.20. variable-sized "such that" pipe Passing an array as a function parameter in JavaScript Why are date-based hats awarded too early? country code TLD vs second level ccTLD I'm really worried about professionalism.  My site would be something like http://mywebsite.uy instead of http://mywebsite.com.uy.  What do you think about this practice? What should I have in mind at the moment of choosing one? I install virtualBox on Ubuntu 16.04, but after install and create new virtual Host shows this error:     Kernel driver not installed (rc=-1908)      The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please install virtualbox-dkms package and load the kernel module by executing  modprobe vboxdrv       as root. If it is available in your distribution, you should install the     DKMS package first. This package keeps track of Linux kernel changes and   recompiles the vboxdrv kernel module if necessary.  where: suplibOsInit what: 3 VERR_VM_DRIVER_NOT_INSTALLED (-1908) - The support driver is not installed. On linux, open returned ENOENT.     How to address this modprobe vboxdrv error? Who are the diamond moderators, and what is their role? Some people have a diamond after their username (e.g. )    What special privileges do diamond moderators have? How can I become a diamond moderator? Who are the diamond moderators?  How many are there?      For more information, see  in the .     Note: not to confuse with certain Stack Exchange employees, for example  members or "community managers", who often have diamonds as well, but are not ordinary moderators. Show that the boundary of a set equals the boundary of its complement $\newcommand{\bdy}{\operatorname{bdy}}$  I'm trying to show that $\bdy(A) = \bdy(A^c)$.  I know that $\bdy(A) = \operatorname{closure} A \setminus \operatorname{int}(A) = (\operatorname{int}(A^c))^c \setminus \operatorname{int}(A)$, but I don't know where to go from there.  Any help or hints would be very much appreciated.