Tutorial by Examples: st

Exit status 0: success Exit status other than 0: failure To test on the exit status of a command: if command;then echo 'success' else echo 'failure' fi

You can do things like this: [[ $s = 'something' ]] && echo 'matched' || echo "didn't match" [[ $s == 'something' ]] && echo 'matched' || echo "didn't match" [[ $s != 'something' ]] && echo "didn't match" || echo "matched" [[ $s -eq...

A heredoc uses the limitstring to determine when to stop consuming input. The terminating limitstring must Be at the start of a line. Be the only text on the line Note: If you use <<- the limitstring can be prefixed with tabs \t Correct: cat <<limitstring line 1 line 2 limit...

Press controlr and type a pattern. For example, if you recently executed man 5 crontab, you can find it quickly by starting to type "crontab". The prompt will change like this: (reverse-i-search)`cr': man 5 crontab The `cr' there is the string I typed so far. This is an incremental s...

If you need to add custom headers to your volley requests, you can't do this after initialisation, as the headers are saved in a private variable. Instead, you need to override the getHeaders() method of Request.class as such: new JsonObjectRequest(REQUEST_METHOD, REQUEST_URL, REQUEST_BODY, RESP_L...

Use $this to refer to the current object. Use self to refer to the current class. In other words, use $this->member for non-static members, use self::$member for static members. In the example below, sayHello() and sayGoodbye() are using self and $this difference can be observed here. cl...

You can create temporary files which has a visible name on the file system which can be accessed via the name property. The file can, on unix systems, be configured to delete on closure (set by delete param, default is True) or can be reopened later. The following will create and open a named temp...

OVERVIEW cocos2d-x is an open source, cross-platform game engine. It allows developers to code in C++, Lua and Javascript deployment into iOS, Android, Windows Phone, Mac OS X, Windows Desktop and Linux. PREREQUISITES Build Requirements Mac OS X 10.7+, Xcode 4.6+ Windows 7+, VS 2012+ Ubunt...

To produce nested JSON object, you need to simply add one JSON object to another: JSONObject mainObject = new JSONObject(); // Host object JSONObject requestObject = new JSONObject(); // Included object try { requestObject.put("lastname", lastname); reques...

Bootstrap's grid system has 12 units known as Columns that can be used to layout content horizontally across the viewport. The reason for a 12-unit grid (instead of 10, 16, etc..) is that 12 evenly divides into 6 (halves), 4 (quarters) and 3 (thirds). This makes adapting to a variety of layouts muc...

HTML and Form Builder is not a core component since Laravel 5, so we need to install it separately: composer require laravelcollective/html "~5.0" Finally in config/app.php we need to register the service provider, and the facades aliases like this: 'providers' => [ // ... ...

Padding Remember, members of a struct are usually padded to ensure they are aligned on their natural boundary: struct t { int a, b, c, d; // a is at offset 0, b at 4, c at 8, d at 0ch char e; // e is at 10h short f; // f is at 12h (naturally aligned) lo...

Python will implicitly convert any object to a Boolean value for testing, so use it wherever possible. # Good examples, using implicit truth testing if attr: # do something if not attr: # do something # Bad examples, using specific types if attr == 1: # do something if att...

Sometimes, you may have a list structure that looks like this: Animal Listing Table NameTypeDescriptionTitleString (Text)Name of the animalAgeNumberHow old the animal isValueCurrencyValue of the animalTypeLookup (Animal Types Table)Lookup Field (Gives dropdown of choices from Animal Types Table) ...

To get First object: MyModel.objects.first() To get last objects: MyModel.objects.last() Using Filter First object: MyModel.objects.filter(name='simple').first() Using Filter Last object: MyModel.objects.filter(name='simple').last()

Web applications often require static files like CSS or JavaScript files. To use static files in a Flask application, create a folder called static in your package or next to your module and it will be available at /static on the application. An example project structure for using templates is as f...

In an enum it is possible to define a specific behavior for a particular constant of the enum which overrides the default behavior of the enum, this technique is known as constant specific body. Suppose three piano students - John, Ben and Luke - are defined in an enum named PianoClass, as follows:...

A typeglob *foo holds references to the contents of global variables with that name: $foo, @foo, $foo, &foo, etc. You can access it like an hash and assign to manipulate the symbol tables directly (evil!). use v5.10; # necessary for say our $foo = "foo"; our $bar; say ref *foo{SCAL...

Swift let sampleText = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderi...

$ mkdir hello-world $ cd hello-world $ tns create hello-world --ng $ tns platform add android #You can only add ios on an OSX machine Then ensure you have a device connected or an emulator running (if you don't, the default emulator should start or an error will be raised. I would recommend ge...