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SEARCH KEYWORD -- Trap



  Gracefully exiting from console programs in Ruby


Imagine you write a CLI program or a Rake task which loops through some data performing some work on it. You run it and then you remembered something. You’d love to kill the process with ctrl-c, but that will raise an exception somewhere in the loop. What you want is for the iteration to complete and then you want the program to quit. You could handle the Interrupt exception or add some conditions. But how about a cleaner and reusable way? No problem - you can trap signals, which mean...

   Ruby,Exit,Command window,Console,Graceful     2012-03-14 13:42:16


  A trap in PDOStatement::bindParam


First, let's check out below codes: <?php $dbh = new PDO('mysql:host=localhost;dbname=test', "test"); $query = <<prepare($query); $bind_params = array(':username' => "laruence", ':password' => "weibo"); foreach( $bind_params as $key => $value ){ $statement->bindParam($key, $value); } $statement->execute(); What is the SQL executed finally? Is there any problem with above codes? Many people may think the query executed is : INSERT INTO `user` (`username`, `password...

   PHP,Trap,bindParam     2013-08-29 10:48:55


  Useful Bash Scripts


Many people hack together shell scripts quickly to do simple tasks, but these soon take on a life of their own. Unfortunately shell scripts are full of subtle effects which result in scripts failing in unusual ways. It's possible to write scripts which minimise these problems. In this article, I explain several techniques for writing robust bash scripts. Use set -u ...

   Linux,Shell,Bash,Command,Robust     2012-01-15 10:28:00


  Writing robust shellling scripts


Many people hack together shell scripts quickly to do simple tasks, but these soon take on a life of their own. Unfortunately shell scripts are full of subtle effects which result in scripts failing in unusual ways. It's possible to write scripts which minimise these problems. In this article, I explain several techniques for writing robust bash scripts. Use set -u ...

   Robust,Shell script,Set,Commands     2012-03-19 13:25:26


  A Python assignment trap


Python has no assignment, it only has reference. Assume, we have following code snippet: >>> values = [0, 1, 2] >>> values[1] = values >>> values [0, [...], 2] Why the result is not [0, [0, 1, 2], 2], instead it goes into an infinite loop? To understand this, we need to understand some basics about Python. Python has no variables, it only has labels. When we run: values = [0, 1, 2] Python will first create a list object [0,1,2], then it labels it as values. If we later...

   Python,Assignment,Trap,Shallow copy     2013-07-19 22:08:36


  How Integers Should Work (In Systems Programming Languages)


My last post outlined some of the possibilities for integer semantics in programming languages, and asked which option was correct. This post contains my answers. Just to be clear: I want practical solutions, but I’m not very interested by historical issues or backwards compatibility with any existing language, and particularly not with C and C++. We’ll start with: Premise 1: Operations on default integer types return the mathematically correct result or else trap. This is the same pre...

   Number,Algorithm,System,Embedded system     2011-12-05 12:48:41


  ARE YOU LIKE ME? OR DO YOU HAVE DISCIPLINE?


If you are anything like me, you've started more things than you have finished. We're innately curious about the things around us and inspired when we come across people who have mastered their trade. We see people create cool and beautiful things and think, "Man, that looks easy, if I put in a little time I can do that in no time." What follows is a few days or weeks of focused and dedicated learning. During this time we make some progress, but not much. In fact, the progress that we do ma...

   Work,Learning,Effort,Detail,Complexity     2011-10-25 10:27:28


  Do designers need code?


So many problems in software occur because programmers and designers don't communicate well all the time. Why don't more designers learn to code themselves or have engineers build abstractions better suited to them? People's minds work in different ways, they can process thoughts differently, solve problems in completely different but equally valid ways. It's a mistake to assume everyone should possess the same skill set.  Also not everyone should be a full stack engineer although full stac...

   Design,Coding     2014-01-07 06:22:52


  Let 's write some front end codes


I've seen a lot of arguments that there is no much technical value writing web portal, I think that the vast majority of good programmers will try many different things. The low level development and machine learning are not the only technologies which are  full of wisdom and challenges, I wrote web site for a few years, it is difficult to say that this is my initial interest, although I touched on other technologies as well, I still feel building website is challenging. Front end developme...

   Front end development, JavaScript,CSS     2013-01-22 04:00:24


  A trap about PHP random number


The method to get random number in PHP is very simple, we only need to use rand() function. int rand ( int $min , int $max ) One function call can return the random number in a specified range. But in fact, the random number in computer is actually pseudorandomness, generally to increase the randomness, we may set a random seed before calling rand(). void srand ([ int $seed ] ) According to other language features, we should pass a time value as a parameter to the srand() function, generally...

   PHP,rand,srand,mt_rand     2013-06-07 09:10:10