test -f "$name" || touch "$name"  So I use this command to test if the file already exists but the problem now is if the file is a copy, my script continue in the same file, while I just want the script to end after it already exists with the text "this file already exists" end script.
I wrote a simple backup script which back ups my stuff on a remote server, everything is working great but I'd like to have some sort of report like "backup successful or not".  this is my script   # backup CHECK date1=`date +"%d.%m.%y - %H.%M"` host=`hostname` twdate=`date +"%d.%m"` performtw=`ls -la|grep "tw"|grep "$twdate" &gt; tmp1.txt` echo $performtw if cat tmp1.txt|grep "tw" then echo backup successfull printf "tw backup success!" | mail -s "tw backup check $date1 repor$ rm tmp1.txt else echo backup failure printf "sitename backup failure!" | mail -s "site backup check $date1 repor$ rm tmp1.txt fi exit   But this isn't working really well and I ask you if there's some simpler and more powerful way to do it? Basically it just needs to check if file exists with the name starting xyz and was created at date xyz.
In the book "Jurassic Park" does the Lysine Contingency actually get explained? I was watching the movie recently and noticed that one of the characters (very) briefly mentions a safety they built into the system should any of the dinosaurs escape. They called it the Lysine Contingency saying that all the dinos have been genetically modified to depend heavily on lysine in their diet, so if any of them escape they wouldn't be able to survive without the food supplements that the park gives them.   Why doesn't the story end right there? Does the Michael Crichton book actually explain this in depth? Waiting for a file to be created in C# Reverse DNS - how to correctly configure for SMTP delivery I started a new service and we need to send emails to our customers (new account confirms, etc).   My server is known as prod01.bidrodeo.com and resolves to 97.107.134.38 .  For reverse DNS, 97.107.134.38 resolves to prod01.bidrodeo.com . However, all our email addresses are in the form of user@bidrodeo.com. Should I make the reverse DNS point to bidrodeo.com instead?   My emails are getting delayed or rejected by certain systems and i am not sure if my reverse DNS is not set up correctly. Is it safe to put hot food in the fridge? I heard that putting really warm food in the fridge right after cooking it is not the right thing to do. It might cause bacterial growth? Is this true? Tag score calculation wrong in Android App pgfplots fillbetween with multiple curves register_nav_menus() won't register menus Please help with menu registeration:  I have followed this guide (http://codex.wordpress.org/Navigation_Menus) step by step.  Added the following code to functions.php:  function register_my_menus() {   register_nav_menus(     array('header-menu' =&gt; __( 'Header Menu' ) )   ); }  add_action( 'init', 'register_my_menus' );   But the guide says that this will make the menu appear in the Appearance -> Menus admin screen in the "Theme Locations" box as "Header Menu".  When I go to Appearance -> Menus everything is greyed out and there is no option of "Theme Locations" Why does gulp.src not like being passed an array of complete paths to files? When can an autonomous system be written using a Hamiltonian? Do not show the score for users during primaries I believe that showing the post score for nomination posts during primaries is a bad idea.  When I loaded the primaries page during the election, the first thing I saw was a post voted -1. This immediately colored my impression of the post. Reading his post didn't indeed make me wish he was a moderator, but at the same point I couldn't bring myself to click on the down arrow. He wasn't an awesome candidate, but he wasn't a -2 score candidate either. Actually, I kinda wanted to sympathy upvote instead.  I want to judge by myself whether a candidate is worth or not my +1. For some of those people I don't have an opinion already, and I want to form one on my own. I don't want game theory to kick in, I don't want to be tricked into sympathy upvotes.  Having those numbers in large print as the first thing I see about them honestly prevents me from doing so. I'd rather have their avatar there.     Some people on chat do not agree with me;  I imagine they'll post explaining why I want to be aware of their opinion while forming my own.      Regardless of the discussion here, if you do prefer to hide the scores as you vote, here's the jQuery oneliner that does just that:  $(".vote-count-post").hide() This is my first time posting on Math exchange. I have been self-teaching myself Mathematics and recently started learning some Algebra. I was posed the following questions, in which I would like to answer before I proceed, but having some trouble finding proper solutions. So the format will be question, and my answer.      What name do we give an element $a \in \mathbb{Z}_n$ that has a multiplicative inverse?   A modular multiplicative inverse of an integer $a$ is an integer $x$ such that $ax \cong 1 (\mod m)$. This means that the remainder after dividing $ax$ by integer $m$ is equal to $1$.      Give an example, for some $n \in \mathbb{N}$, of an element of $\mathbb{Z}_n$, that does not have a multiplicative inverse?   This question is throwing me off because - does the $n$ we speak of matter for both $n \in \mathbb{N}$ and $\mathbb{Z}_n$ ot solely $n$? My guess here would be $0$ because we cannot have an inverse of $0$.      Prove that multiplicative inverse are unique; an element $a \in \mathbb{Z}_n$ cannot have two multiplicative inverses.    Suppose that an element $a\in\mathbb{Z}_n$ has an inverse $a'$. Next, suppose that $a^*$ is also an inverse of $a$. Then, $a'$ is a solution to $a \cdot_n x=1$, and similarly $a^*$ has a solution to $a \cdot_n x=1$.   Lemma: Suppose $a'$ is multiplicative inverse of $a$ in $\mathbb{Z}_n$, then for any $b \in \mathbb{Z}_n$ the equation $a \cdot_n x=b$ has a unique solution, such that $x = a' \cdot_n b$.   By Lemma, equation $a \cdot_n x = 1$ has a unique solution, namely $x=a'=a^*$. Therefore, an element $a\in \mathbb{Z}_n$ cannot have two multiplicative inverses.    Thank you for the help. I would love any constructive feedback for these. If you can help me elaborate on some ideas, that would be really helpful also.  Thank you very much! What is the difference between a linear and a circular polarizer? What is integration by parts, really? Integration by parts comes up a lot - for instance, it appears in the definition of a weak derivative / distributional derivative, or as a tool that one can use to turn information about higher derivatives of a function into information about an integral of that function. Concrete examples of this latter category include: proving that $f \in C^2(S^1)$ implies that the Fourier series of $f$ converges absolutely and uniformly, and the Taylor series expansion with the integral formula for remainder.  However, I don't feel like I really understand what integration by parts is really doing. To me, it is just an algebraic trick that follows from the fundamental theorem of calculus and the product rule. Is there some more conceptual way to think about it?  How do you think about this useful idea? Using ArcGIS 10.0, is it possible to reorder the fields in a file geodatabase, and have the order persisted to the database?  We considered exporting to XML, and writing a parser to change the field order, then re-creating a new database from the XML. This seems like a laborious process.  Another idea is to import the existing field definitionss into Excel, re-order them, export to CSV, then write a Python script to create these fields in a new Geodatabase. Does a script like this exist, before we write it from scratch?  Unfortunately the ArcGIS Diagrammer doesn't seem to support field re-ordering.  Are there any scripts or hacks we could use to simplify this process? Are the Night's Watch still required? What does “” exactly mean in “echo  temp.txt”? Applying an ellipsis to multiline text How to space columns evenly in a table with multicolumns? Why on average does each bootstrap sample contain roughly two thirds of observations? Difference between $\Delta$, $d$ and $\delta$ I have read the thread regarding , but it does not answer my question.  I am confused about the notation for change in Physics. In Mathematics, $\delta$ and $\Delta$ essentially refer to the same thing, i.e., change. This means that $\Delta x = x_1 - x_2 = \delta x$. The difference between $\delta$ and $d$ is also clear and distinct in differential calculus. We know that $\frac{dy}{dx}$ is always an operator and not a fraction, whereas $\frac{\delta y}{\delta x}$ is an infinitesimal change.   In Physics, however, the distinction is not as clear. Can anyone offer a clearer picture?