the c++ programming language and school
The Definitive C++ Book Guide and List
As I understand this, firewalls (assuming default settings) deny all incoming traffic that has no prior corresponding outgoing traffic.  Based on  and , reverse SSH tunneling can be used to get around pesky firewall restrictions.  I would like to execute shell commands on a remote machine. The remote machine has its own firewall and is behind an additional firewall (router). It has an IP address like 192.168.1.126 (or something similar). I am not behind a firewall and I know the remote machine's IP address as seen from the Internet (not the 192.168.1.126 address). Additionally, I can ask someone to execute ssh (something) as root on the remote machine first.  Could anyone explain me, step by step, how reverse SSH tunneling works to get around the firewalls (local and remote machines' firewalls and the additional firewall between them)?  What is the role of the switches (-R, -f, -L, -N)? Why is $\langle \textbf R \rangle =Tr \rho R$ here $\rho$ is the state density matrix I can't play Pokemon GO! What's wrong? Add days to JavaScript Date Uncommitted work pending in unit test with trigger and queueable callout I have an after insert trigger that invokes queueable Apex which makes a callout.  The trigger and callout work fine in the UI and I don't get any errors in normal operation.  However, my unit test keeps failing with the "uncommitted work pending" error despite all my attempts to separate the callout.  I've used a testVisible variable to disable the callout from the trigger so that I can invoke the queueable job explicitly in a startTest/stopTest block after the DML that fires the trigger.  I've pored over the callout class to make sure it's not doing any DML beforehand.  Anyway, if it was doing DML, I should get the uncommitted work pending errors in the UI, right?  I've tried API version 37 and version 41 but the unit test still fails.   I've had a case open with Salesforce premier support for 6 weeks now but haven't made any progress.  Any suggestions?  The unit test:  @isTest static void testCallout() {     // Disable the callout while setting up data.     CCx_EHR_CMCT_Services.isQueueSendEnabled = false;      // Set up the data and execute the DML.     / ...     insert act;      // Set up the http mock     // ...      // Now enable and execute the callout     Test.startTest();     CCx_EHR_CMCT_Services.isQueueSendEnabled = true;     Test.setMock(HttpCalloutMock.class, mock);     System.enqueueJob(new QueueSendToRedox(new List&lt;ActivityHL__c&gt;{act}, desk)));     Test.stopTest();  }   Trigger:  trigger HL_ActivityHL_c on ActivityHL__c (before insert, before update, after insert) {     if (Trigger.isAfter) {         if (Trigger.isInsert) {             CCx_ClientDataDomain.sendEHRClinicalComm(Trigger.new);         }     } }   Trigger handler class:  public without sharing class CCx_ClientDataDomain {     public static void sendEHRClinicalComm(List&lt;ActivityHL__c&gt; triggerNew) {     // do some processing here.     // ...     // then queue the callout job.     System.enqueueJob(new CCx_EHR_CMCT_Services.QueueSendToRedox(             deskActivities.get((Id) desk.getDeskId()), desk));     } }   Queueable job class with callout method:  public with sharing class CCx_EHR_CMCT_Services {     // isQueueSendEnabled is an attempted workaround for unit tests     @testVisible     private static Boolean isQueueSendEnabled = true;      public class QueueSendToRedox implements Queueable, Database.AllowsCallouts {         private List&lt;ActivityHL__c&gt; activities;         private CCx_DeskHierarchySelector.Desk desk;         private Boolean isEnabled;          public QueueSendToRedox(List&lt;ActivityHL__c&gt; activities, CCx_DeskHierarchySelector.Desk desk) {             this.activities = activities;             this.desk = desk;             this.isEnabled = isQueueSendEnabled;         }          public void execute (QueueableContext context) {             if(this.isEnabled) sendClinicalCommToRedox(activities, desk);         }     }      public static void sendClinicalCommToRedox(List&lt;ActivityHL__c&gt; activities, CCx_DeskHierarchySelector.Desk desk) {         // Set up data for the callout.  No DML actions are executed before the callout.         HttpRequest req = buildRequest();         // ...          // Callout         Http http = new Http();         HttpResponse resp = http.send(req);     } } Usage of singular or plural SI base units when written in both symbol as well as name I have multiple doubts related to the usage of singular or plural SI base units when written in both symbol as well as name.  I have framed this question under two parts, namely, Part (a) and Part (b). Each part has three sentences which I have written on the basis of my understanding.  Please answer these 6 sentences/questions.   Part (a):   says that while using prefix for e.g., centi as in centimeter, it is   l = 75 cm long.(correct) l = 75 cms long. (wrong)    Does this rule is used for all SI prefixes (having powers of 10)? In this regard, we should be saying, or writing that, "how many cm are there in one metre?" (while saying we should say centimter or centimetres?) Please strike-through the wrong SI unit in the following sentences.  My weight is 70 kg / kgs,  or My weight is 70 kilogram / kilograms.   Part (b):  and the page next to above web link says, we should write:  2.6 m/s, or 2.6 metres per second.   In this regard, we should say, or write:   Its speed is 0.26 metres per second.  This pipe is 0.75 metres long. How many cm are there in 2 metres? How to get text under mouse in any open window How to open a serial port by friendly name? Could a ship warp into Borg cube and destroy it? During the Wolf-359 incident, 39 starships were destroyed, and 11,000 people were killed or assimilated.  Why didn’t one of the smaller ships warp into that one Borg cube? Doesn’t warping into it destroy anything?  Even if it just warps through without touching, one could program the navicom to self destruct while the ship is in the middle of Borg cube. You are here, but where's here? I find the .youarehere a styling for the main navigation links causes the text to be a little difficult to read on the also-blue header background. Could we give it a little bit of background colour or something else that would provide more contrast?  For example:    which is the product of the following CSS*:  .nav ul li {     margin: -2px 10px 0 0;     padding: 5px; }  .nav ul li.youarehere {     background-color: rgba(0, 80, 112, 0.25);     border-radius: 5px; }  .nav ul li.youarehere a {     color: #A1E9FF; }   *For bonus points, also reduce the line height for the codeblocks! What does 'apt-get install update' do? I saw this snippet in some installation instructions:  $ apt-get install update   I know what apt-get install XXXX does and I know what apt-get update does, but I can't find any info on what this combined statement does. What does it do? What is the function represented by the power series $$ \sum_{k=2}^\infty\frac{x^k}{k(k-1)}\quad? $$  It looks like $\dfrac1{1-x}$ but I don't know. How to Search for Files Recursively into Subdirectories I am trying to look for all XML files in a particular directory and all sub-directories (recursively) inside it.  ls -R *.xml is only listing files in the current directory. I am quite sure, the sub-folders themselves have several .xml files, but none are showing up.  Is this a configuration issue? Cannot create PostGIS extension with Ubuntu 18.04 What is the trajectory of a photon moving through a vacuum? Since electromagnetic energy is carried by photons and moves in forms of waves, does it mean that a single photon when propagating through space doesn't follow the straight path but instead always moves up and down, up and down like a wave. If so another question arises the speed of propagation of light in vacuum is fixed meaning that it will always take the same amount of time for it to travel from point A to point B, but if a photon always moves up and down it will also mean that it travels longer distance than the distance between A and B and so it ill travel faster than light propagates, is it even possible, could you please clarify these concepts for me? What class of Devil Fruit does the Gomu Gomu no Mi come under? Considering the three types of Devil Fruits that has been explained are 1. Paramecia Type - where the user can get super human abilities and change their body parts into weapons, etc. 2. Zoan type - where the use can turn into a particular animal and inherit its abilities 3. Logia Type - where the user's body inherits a particular element and the body becomes like air which cannot be touched or damaged by non Haki users.  So what exactly is the type of Gomu Gomu no Mi? It cannot be Zoan or Logia. It's very close to a Paramecia but still doesn't have a logical explanation to be of Paramecia type! So is it some special type of Devil Fruit? Is having a skills bar chart on a resume a good idea? linear dependence proof using subsets How to change the disk space left warning in Windows 7? my disk has over 100GB of free space, but the usage bar in Computer is displayed in red, as if it reached a low space limit. It looks like Windows applies the same 10% or 15% hard disk space value for low space warnings, regardless of if the disk is 50GB in size or 1.5TB, which is not very smart and obsolete for most recent computers.  Is there a Registry key or some place I can change this percentage so the usage bar displays in green, not red?  The hibernation and page files are already reserved (5GB together), so surely the low space warning for a 1.5TB disk should be 5-10GB, not 150GB or more. The way Windows 7 computes the low space limit seems pretty dumb, not much Intellisense there.  This is not a high priority issue, but it makes the Computer applet look pretty stupid and it's irritating every day to see that 100GB of free space is putting my computer in the red. It would also be nice to be able to edit this low limit percentage in Computer/Manage/Storage/Disk Management or directly in the disk properties ("Tools" tab). Limit of $\prod\limits_{k=2}^n\frac{k^3-1}{k^3+1}$ Calculate $$\lim_{n \to \infty} \frac{2^3-1}{2^3+1}\times \frac{3^3-1}{3^3+1}\times \cdots \times\frac{n^3-1}{n^3+1}$$ No idea how to even start.