Tutorial by Examples: l

Variable substitutions should only be used inside double quotes. calculation='2 * 3' echo "$calculation" # prints 2 * 3 echo $calculation # prints 2, the list of files in the current directory, and 3 echo "$(($calculation))" # prints 6 Outside of doubl...

All the examples in this paragraph print the line !"#$&'()*;<=>? @[\]^`{|}~ A backslash quotes the next character, i.e. the next character is interpreted literally. The one exception is a newline: backslash-newline expands to the empty string. echo \!\"\#\$\&\'\(\)\*\;\...

The above type handler can be installed into SqlMapper using the AddTypeHandler method. SqlMapper.AddTypeHandler<IHtmlString>(new IHtmlStringTypeHandler()); Type inference allows you to omit the generic type parameter: SqlMapper.AddTypeHandler(new IHtmlStringTypeHandler()); There's als...

The ^ operator will perform a binary XOR in which a binary 1 is copied if and only if it is the value of exactly one operand. Another way of stating this is that the result is 1 only if the operands are different. Examples include: # 0 ^ 0 = 0 # 0 ^ 1 = 1 # 1 ^ 0 = 1 # 1 ^ 1 = 0 # 60 = 0b1111...

The << operator will perform a bitwise "left shift," where the left operand's value is moved left by the number of bits given by the right operand. # 2 = 0b10 2 << 2 # Out: 8 # 8 = 0b1000 bin(2 << 2) # Out: 0b1000 Performing a left bit shift of 1 is equivalent ...

if [[ $file1 -ef $file2 ]]; then echo "$file1 and $file2 are the same file" fi “Same file” means that modifying one of the files in place affects the other. Two files can be the same even if they have different names, for example if they are hard links, or if they are symbolic links...

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...

Numerical comparisons use the -eq operators and friends if [[ $num1 -eq $num2 ]]; then echo "$num1 == $num2" fi if [[ $num1 -le $num2 ]]; then echo "$num1 <= $num2" fi There are six numeric operators: -eq equal -ne not equal -le less or equal -lt less than ...

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...

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 ...

The zero value of a map is nil and has a length of 0. var m map[string]string fmt.Println(m == nil) // true fmt.Println(len(m) ==0) // true A nil map has no keys nor can keys be added. A nil map behaves like an empty map if read from but causes a runtime panic if written to. var m map[string]...

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...

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...

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

You shouldn't call NSLog without a literal format string like this: NSLog(variable); // Dangerous code! If the variable is not an NSString, the program will crash, because NSLog expects an NSString. If the variable is an NSString, it will work unless your string contains a %. NSLog will pars...

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...

When two margins are touching each other vertically, they are collapsed. When two margins touch horizontally, they do not collapse. Example of adjacent vertical margins: Consider the following styles and markup: div{ margin: 10px; } <div> some content </div> <div&gt...

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...