Tutorial by Examples: is

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...

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...

Things you need A paid Apple Developer Program Membership A valid App ID and identifier for you app (like com.example.MyApp) which is not used before anywhere Access to developer.apple.com and Member Center An iOS Device to test (as Push Notifications don't work on Simulator) Enabling t...

Registers: 8 bit: A, B, C, D, E, H, L, F, I, R, 16 bit: SP, PC, IX, IY, and shadows of some 8b registers: A', B', C', D', E', H', L' and F'. Most of the 8 bit registers can be used also in pairs as 16 bit registers: AF, BC, DE and HL. SP is stack pointer, marking the bottom of stack memory (used b...

In order to determine some simple statistics of a value in a column of a table, you can use an aggregate function. If your individuals table is: NameAgeAllie17Amanda14Alana20 You could write this statement to get the minimum, maximum and average value: SELECT min(age), max(age), avg(age) FROM i...

The maximum number of remembered commands: ~> $ echo $HISTSIZE 1000

You can place named arguments in any order you want. Sample Method: public static string Sample(string left, string right) { return string.Join("-",left,right); } Call Sample: Console.WriteLine (Sample(left:"A",right:"B")); Console.WriteLine (Sample(right...

foreach varlist1 list1 ?varlist2 list2 ...? body foreach is a powerful control structure that allows looping over a list or multiple lists. set alpha [list a b c d e f] foreach {key} $alpha { puts "key: $key" } Multiple variable names may be specified. set alphaindexes [list a ...

The revert command allows discarding unwanted uncommitted changes. Reverting changes to a single file. hg revert example.c Reverting all changes. This will discard all changes not just the current directory. hg revert --all hg will output which files were reverted. reverting exa...

To list files and folders inside current directory, we use ls command: user@host:/$ ls bin boot cdrom dev etc home initrd.img lib lib64 lost+found media mnt opt proc root run sbin srv sys tmp usr var vmlinuz ls prints folder structure in simple view, color coded by type....

Invented by John McCarthy around 1958, Lisp (List Processor) has continued to grow into an entire family of languages. Since StackOverflow is more about practical programming problems, typically problems will involve actual Lisp dialects or derived languages and their implementations. Problems that...

public class NullableTypesExample { static int? _testValue; public static void Main() { if(_testValue == null) Console.WriteLine("null"); else Console.WriteLine(_testValue.ToString()); } } Output: null

Without timezone, with microseconds from datetime import datetime datetime.now().isoformat() # Out: '2016-07-31T23:08:20.886783' With timezone, with microseconds from datetime import datetime from dateutil.tz import tzlocal datetime.now(tzlocal()).isoformat() # Out: '2016-07-31T23:09:4...

GNU Emacs uses a special format for documentation: info. The Common Lisp standard has been converted to the Texinfo format, which can be used to create documentation browsable with the info reader in GNU Emacs. See here: dpans2texi.el converts the TeX sources of the draft ANSI Common Lisp standard...

ODS (on-disk structure) version is a number representing version of the database low-level data layout structure (ODS). When a new feature is added to Firebird it might or might not require the structure of database pages or system tables (database metadata) to change. If it does, the ODS version mu...

For some use cases, you can use the using syntax to help define a custom scope. For example, you can define the following class to execute code in a specific culture. public class CultureContext : IDisposable { private readonly CultureInfo originalCulture; public CultureContext(string ...

For example, in the sentence: That cake is extremely nice. The rules of the English language would make cake a noun, extremely an adverb that modifies the adjective nice, and through this analysis the meaning could be understood. However, this analysis is dependent on us recognising that the...

The elapsedMillis library provides a class with the same name that keeps track of the time that passed since it was created or set to a certain value: #include <elapsedMillis.h> #define OUTPIN LED_BUILTIN #define PERIOD 500 elapsedMillis ledTime; bool ledState = false; void setup...

This is very close to an example from the arduino docs: // set constants for blinking the built-in LED at 1 Hz #define OUTPIN LED_BUILTIN #define PERIOD 500 // this is in milliseconds int ledState = LOW; // millis() returns an unsigned long so we'll use that to keep track of time unsigned...

#include <elapsedMillis.h> void setup() { Serial.begin(115200); elapsedMillis msTimer; elapsedMicros usTimer; long int dt = 500; delay(dt); long int us = usTimer; long int ms = msTimer; Serial.print("delay(");Serial.print(dt);Serial.println(") to...