Tutorial by Examples: d

If it's not already done in php.ini, error reporting can be set dynamically and should be set to allow most errors to be shown: Syntax int error_reporting ([ int $level ] ) Examples // should always be used prior to 5.4 error_reporting(E_ALL); // -1 will show every possible error, even whe...

try/catch try..catch blocks can be used to control the flow of a program where Exceptions may be thrown. They can be caught and handled gracefully rather than letting PHP stop when one is encountered: try { // Do a bunch of things... throw new Exception('My test exception!'); } catch (E...

Usually, you have to use git add or git rm to add changes to the index before you can git commit them. Pass the -a or --all option to automatically add every change (to tracked files) to the index, including removals: git commit -a If you would like to also add a commit message you would do: g...

Perl tries to do what you mean: print "Hello World\n"; The two tricky bits are the semicolon at the end of the line and the \n, which adds a newline (line feed). If you have a relatively new version of perl, you can use say instead of print to have the carriage return added automatical...

An unordered list can be created with the <ul> tag and each list item can be created with the <li> tag as shown by the example below: <ul> <li>Item</li> <li>Another Item</li> <li>Yet Another Item</li> </ul> This will produce a...

An ordered list can be created with the <ol> tag and each list item can be created with the <li> tag as in the example below: <ol> <li>Item</li> <li>Another Item</li> <li>Yet Another Item</li> </ol> This will produce a numbere...

One common pitfall when using dictionaries is to access a non-existent key. This typically results in a KeyError exception mydict = {} mydict['not there'] Traceback (most recent call last): File "<stdin>", line 1, in <module> KeyError: 'not there' One way to avoid...

Right after you install Git, the first thing you should do is set your username and email address. From a shell, type: git config --global user.name "Mr. Bean" git config --global user.email [email protected] git config is the command to get or set options --global means that the ...

Creating jobs To create an job, just append a single & after the command: $ sleep 10 & [1] 20024 You can also make a running process a job by pressing Ctrl + z: $ sleep 10 ^Z [1]+ Stopped sleep 10 Background and foreground a process To bring the Process to the f...

The function rand() can be used to generate a pseudo-random integer value between 0 and RAND_MAX (0 and RAND_MAX included). srand(int) is used to seed the pseudo-random number generator. Each time rand() is seeded wih the same seed, it must produce the same sequence of values. It should only be see...

Here's a standalone random number generator that doesn't rely on rand() or similar library functions. Why would you want such a thing? Maybe you don't trust your platform's builtin random number generator, or maybe you want a reproducible source of randomness independent of any particular library ...

> redirect the standard output (aka STDOUT) of the current command into a file or another descriptor. These examples write the output of the ls command into the file file.txt ls >file.txt > file.txt ls The target file is created if it doesn't exists, otherwise this file is truncated. ...

< reads from its right argument and writes to its left argument. To write a file into STDIN we should read /tmp/a_file and write into STDIN i.e 0</tmp/a_file Note: Internal file descriptor defaults to 0 (STDIN) for < $ echo "b" > /tmp/list.txt $ echo "a" >> ...

File descriptors like 0 and 1 are pointers. We change what file descriptors point to with redirection. >/dev/null means 1 points to /dev/null. First we point 1 (STDOUT) to /dev/null then point 2 (STDERR) to whatever 1 points to. # STDERR is redirect to STDOUT: redirected to /dev/null, # effect...

2 is STDERR. $ echo_to_stderr 2>/dev/null # echos nothing Definitions: echo_to_stderr is a command that writes "stderr" to STDERR echo_to_stderr () { echo stderr >&2 } $ echo_to_stderr stderr

Truncate > Create specified file if it does not exist. Truncate (remove file's content) Write to file $ echo "first line" > /tmp/lines $ echo "second line" > /tmp/lines $ cat /tmp/lines second line Append >> Create specified file if it does not e...

It's possible to extent native elements, but their descendants don't get to have their own tag names. Instead, the is attribute is used to specify which subclass an element is supposed to use. For example, here's an extension of the <img> element which logs a message to the console when it's l...

Browse to File > New > Solution to bring you up the new project dialog Select Single View App and press Next Configure your app by setting your app name and organization ID, and press Next: Set your Project name and Solution name, or leave as the default name. Click Create to create...

A simple two-column layout consists of two fixed-width, floated elements. Note that the sidebar and content area are not the same height in this example. This is one of the tricky parts with multi-column layouts using floats, and requires workarounds to make multiple columns appear to be the same he...

Events fired on DOM elements don't just affect the element they're targeting. Any of the target's ancestors in the DOM may also have a chance to react to the event. Consider the following document: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> </hea...