Tutorial by Examples: t

In addition to cursor movements using the arrow keys, Home, End, Page up, and Page down, emacs defines a number of keystrokes that can move the cursor over smaller or larger pieces of text: By character: Backward character: C-b Forward character: C-f By word Backward word: M-b (i.e. Alt b...

One of the use cases of callback URLs is OAuth. Let us do this with an Instagram Login: If the user enters their credentials and clicks the Login button, Instagram will validate the credentials and return an access_token. We need that access_token in our app. For our app to be able to listen to suc...

X-Macros can be used for code generation, by writing repetitive code: iterate over a list to do some tasks, or to declare a set of constants, objects or functions. Here we use X-macros to declare an enum containing 4 commands and a map of their names as strings Then we can print the string values ...

Enums contains only constants and can be compared directly with ==. So, only reference check is needed, no need to use .equals method. Moreover, if .equals used incorrectly, may raise the NullPointerException while that's not the case with == check. enum Day { GOOD, AVERAGE, WORST; } publi...

The Standard (10.4) states: Member functions can be called from a constructor (or destructor) of an abstract class; the effect of making a virtual call (10.3) to a pure virtual function directly or indirectly for the object being created (or destroyed) from such a constructor (or destructor) is u...

Insertion sort is a very simple, stable, in-place sorting algorithm. It performs well on small sequences but it is much less efficient on large lists. At every step, the algorithms considers the i-th element of the given sequence, moving it to the left until it is in the correct position. Graphica...

Installation Volley JCenter Gradle Import //in your project's app level build.gradle compile 'com.android.volley:volley:1.0.0' Create a subclass of Application public class AppController extends Application { public static final String TAG = AppController.class .getSimpleN...

.set-colors(@type) when (@type = error) { @base-color: #d9534f; background: @base-color; color: contrast(@base-color, lighten(@base-color, 25%), darken(@base-color, 25%)); border: 1px solid contrast(@base-color, lighten(@base-color, 25%), darken(@base-color, 25%)); } .set-colors(@type)...

There are two common ways to list all processes on a system. Both list all processes running by all users, though they differ in the format they output (the reason for the differences are historical). ps -ef # lists all processes ps aux # lists all processes in alternative format (BSD) Thi...

VariableDetails$* / $@Function/script positional parameters (arguments). Expand as follows:$* and $@ are the same as $1 $2 ... (note that it generally makes no sense to leave those unquoted)"$*" is the same as "$1 $2 ..." 1 "$@" is the same as "$1" "$2&qu...

The default editor that will be involked by any scripts or programs, usually vi or emacs. ~> $ echo $EDITOR vi

The hostname assigned to the system during startup. ~> $ echo $HOSTNAME mybox.mydomain.com

This variable identifies the hardware, it can be useful in determining which binaries to execute: ~> $ echo $HOSTTYPE x86_64

Similar to $HOSTTYPE above, this also includes information about the OS as well as hardware ~> $ echo $MACHTYPE x86_64-redhat-linux-gnu

Returns information about the type of OS running on the machine, eg. ~> $ echo $OSTYPE linux-gnu

The search path for finding binaries for commands. Common examples include /usr/bin and /usr/local/bin. When a user or script attempts to run a command, the paths in $PATH are searched in order to find a matching file with execute permission. The directories in $PATH are separated by a : character...

A readonly list of the options bash is supplied on startup to control its behaviour: ~> $ echo $SHELLOPTS braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor

Positional parameters passed to the script from either the command line or a function: #!/bin/bash # $n is the n'th positional parameter echo "$1" echo "$2" echo "$3" The output of the above is: ~> $ ./testscript.sh firstarg secondarg thirdarg firstarg sec...

LINQ provides a built-in function for checking the equality of two IEnumerables, and that function can be used on arrays. The SequenceEqual function will return true if the arrays have the same length and the values in corresponding indices are equal, and false otherwise. int[] arr1 = { 3, 5, 7 };...

Consider this example function to check if a host is up: is_alive() { ping -c1 "$1" &> /dev/null } This function sends a single ping to the host specified by the first function parameter. The output and error output of ping are both redirected to /dev/null, so the functi...