Tutorial by Examples: t

if [[ -r $filename ]]; then echo "$filename is a readable file" fi if [[ -w $filename ]]; then echo "$filename is a writable file" fi if [[ -x $filename ]]; then echo "$filename is an executable file" fi These tests take permissions and ownership into a...

String comparison uses the == operator between quoted strings. The != operator negates the comparison. if [[ "$string1" == "$string2" ]]; then echo "\$string1 and \$string2 are identical" fi if [[ "$string1" != "$string2" ]]; then echo &quot...

The -e conditional operator tests whether a file exists (including all file types: directories, etc.). if [[ -e $filename ]]; then echo "$filename exists" fi There are tests for specific file types as well. if [[ -f $filename ]]; then echo "$filename is a regular file&quot...

In helloJohn.sh: #!/bin/bash greet() { local name="$1" echo "Hello, $name" } greet "John Doe" # running above script $ bash helloJohn.sh Hello, John Doe If you don't modify the argument in any way, there is no need to copy it to a local variabl...

Gradients are new image types, added in CSS3. As an image, gradients are set with the background-image property, or the background shorthand. There are two types of gradient functions, linear and radial. Each type has a non-repeating variant and a repeating variant: linear-gradient() repeating-...

Some regular expression flavors allow named capture groups. Instead of by a numerical index you can refer to these groups by name in subsequent code, i.e. in backreferences, in the replace pattern as well as in the following lines of the program. Numerical indexes change as the number or arrangemen...

A description list (or definition list, as it was called before HTML5) can be created with the dl element. It consists of name-value groups, where the name is given in the dt element, and the value is given in the dd element. <dl> <dt>name 1</dt> <dd>value for 1</dd...

You define a map using the keyword map, followed by the types of its keys and its values: // Keys are ints, values are ints. var m1 map[int]int // initialized to nil // Keys are strings, values are ints. var m2 map[string]int // initialized to nil Maps are reference types, and once defined ...

One can declare and initialize a map in a single statement using a composite literal. Using automatic type Short variable declaration: mapIntInt := map[int]int{10: 100, 20: 100, 30: 1000} mapIntString := map[int]string{10: "foo", 20: "bar", 30: "baz"} mapStringInt :...

import fmt people := map[string]int{ "john": 30, "jane": 29, "mark": 11, } for key, value := range people { fmt.Println("Name:", key, "Age:", value) } Note that when iterating over a map with a range loop, the iteration order i...

people := map[string]int{ "john": 30, "jane": 29, "mark": 11, } for key, _ := range people { fmt.Println("Name:", key) } If you are just looking for the keys, since they are the first value, you can simply drop the underscore: for key := r...

The delete built-in function removes the element with the specified key from a map. people := map[string]int{"john": 30, "jane": 29} fmt.Println(people) // map[john:30 jane:29] delete(people, "john") fmt.Println(people) // map[jane:29] If the map is nil or ther...

Go programs end when the main function ends, therefore it is common practice to wait for all goroutines to finish. A common solution for this is to use a sync.WaitGroup object. package main import ( "fmt" "sync" ) var wg sync.WaitGroup // 1 func routine(i int...

slice = append(slice, "hello", "world")

A useful tool in Java Concurrency is ThreadLocal – this allows you to have a variable that will be unique to a given thread. Thus, if the same code runs in different threads, these executions will not share the value, but instead each thread has its own variable that is local to the thread. For exa...

To create a first-level (<h1>) header, use the equal sign (=) in a line under your text: All About Dogs ============== All About Dogs Use hyphens (-) for second-level (<h2>) headers: The Debut Novel --------------- The Debut Novel The line below the header can be of a...

We can illustrate this problem with the following pseudo-code function foo() { global $bob; $bob->doSomething(); } Your first question here is an obvious one Where did $bob come from? Are you confused? Good. You've just learned why globals are confusing and considered a bad p...

Bool is a Boolean type with two possible values: true and false. let aTrueBool = true let aFalseBool = false Bools are used in control-flow statements as conditions. The if statement uses a Boolean condition to determine which block of code to run: func test(_ someBoolean: Bool) { if som...

The prefix ! operator returns the logical negation of its argument. That is, !true returns false, and !false returns true. print(!true) // prints "false" print(!false) // prints "true" func test(_ someBoolean: Bool) { if !someBoolean { print("someBoolean ...

Creating immutable arrays: NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; // Using the array literal syntax: NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; ...