Which standard permissions are valid under macOS Catalina for the folder / Users?

I've done a very stupid thing and, welp …

chmod 755 /Users

I was trying to google, but apparently I can not find any information about what permissions this folder should have. You are worried about damaging the system while trying to fix a security issue. So maybe there is a way to automatically correct permissions for some default values?

Before you respond, Disk Utility does not have a First Aid section, only the First Aid button, which runs the first-aid script on the selected drive.

Visa – Can I get a new ESTA while I still have a valid one?

I was in the US for 6 weeks earlier this year. I plan to return for another 6 weeks with the same ESTA visa in March next year to look for a job. This would bring me to the full length of the ESTA visa.

I am worried that 6 weeks will not be enough to find a job and wonder if it is possible to apply for a completely new 90-day visa even though I have a current visa.

Does anyone have any knowledge about it? Would it be risky to do something?

Usa – Visa in Passport has expired, my i-20 is valid and I am switching from Bachelor to Master. Does the rule of automatic re-validation apply to me?

I think you should be fine. The automatic renewal also applies if the category of non-immigrants changes. Therefore, changing the I-20 details should not be a problem.

See 22 CFR 41.112 (d) (1) (ii):

(d) Automatic renewal of validity at the ports of entry.

(1) If the requirements of paragraph (d) (2) of this Section are fully met, the following provisions shall apply to non-immigrant foreigners applying for readmission in ports of entry:

(i) The period of validity of an expired non-immigrant visa issued in accordance with INA 101 (a) (15) may be automatically extended until the date of the request for readmission. and

(ii) In cases where the original non-immigration classification of a foreigner has been changed by the DHS to another non-immigration classification, the validity of an expired or non-expired non-immigration visa may be automatically extended until the date of the application for readmission. and the visa can be converted into this modified classification as needed.

(2) The provisions in paragraph (d) (1) of this section apply only to foreigners without a migration background who:

(i) is in possession of an I-94 (Arrival-Departure Record), duly endorsed by the DHS, stating that the period of first-time admittance or extension has not yet expired, or in the case of a qualified person F or J students or exchange visitors or The accompanying spouse or the child of such a foreigner has an up-to-date Form I-20 (certificate of admission for non-immigrant students) or an IAP-66 (Exchanges Authorization Certificate) issued by the school The student owns the DHS or the sponsor of the exchange program that the alien from the DHS was allowed to attend, authorized and approved by the issuing school official or sponsor of the program to indicate the time period for the initial admission or renewal of the approved stay DHS;

(ii) Request readmission after an absence of not more than 30 days, exclusively in adjacent area or in the case of a student or exchange visitor or accompanying spouse or child who meets the requirements of paragraph (d) (2) (i) of this After an absence of not more than 30 days in adjacent territory or on adjacent islands other than Cuba;

(iii) has retained the status of non-immigrant and wishes to resume;

(iv) request readmission within the approved time limit for initial authorization or extension of stay;

(v) is in possession of a valid passport;

(vi) does not require approval under INA 212 (d) (3); and

(vii) did not apply for a new visa abroad.

(3) The provisions of paragraphs (d) (1) and (d) (2) of this Section shall not apply to nationals of countries designated in the Ministry's annual report to the Congress entitled Patterns of Global Terrorism as Supporters of Terrorism are.

(Emphasis added)

See also 8 CFR 214.1 (b) (1) (iv), which is specific to the I-20 requirement for F-1 students:

(b) readmission of non-immigrants in accordance with Section 101 (a) (15) (F), (J), (M) or (Q) (ii) to complete non-elapsed periods of prior reception or extension of stay,

(1) Section 101 (a) (15) (F). The inspecting immigration officer must re-allow for the period of status under § 214.2 (f) (5) (iii) all non-immigrant foreigners whose non-immigrant visa is automatically revalidated in accordance with 22 CFR 41.125 (f) and who request readmission pursuant to § 101 (a) (15) (F) of the law, if the alien:

(i) is allowed;

(ii) requests readmission following an absence from the United States of America not exceeding 30 days, exclusively in adjacent or adjacent islands;

(iii) is in possession of a valid passport, unless the latter is exempted from the obligation to present a passport; and

(iv) Present or is the accompanying spouse or accompanying child of a foreigner presenting to the alien an Arrival / Departure Log, Form I-94 (see § 1.4), issued in connection with the previous admittance or previous residency, which Form of the foreigner I-20 identity card and either:

(A) A duly confirmed page 4 of Form I-20A-B, if the information on the last Form I-20A of the student has not changed materially since the first issue of the form. or

(B) A new Form I-20A-B, if the information on the last Form I-20A of the student has changed since the first issue of the form.

Programming Practices – How do I best handle valid but impossible input?

For example, suppose you write in a language that is OO rather than functional first.

Runtime checks

Hard to read code? Why? You can start the method by saying that certain values ​​are invalid. That should make reading / understanding easier.

Validation is another concern anyway. You should know where it starts and where it ends, redesigning your code to make it easy to see and improve readability. In fact, if the code for validating the input is so complicated that it is difficult to read, this is an indication that you should extract the validation to another method.

I understand that there are some situations where it is not obvious how this can be achieved without compromising on efficiency. For example, validating a list could mean going through it. And then iterate again to actually use it … If you have a solution like Linq or something similar, you should be able to write the validation code separately from using the list, while iterating it only once. Thanks to Linq is lazily evaluated.

You may also want to avoid duplicate checks in the code's internals. You can use conditional compilations, debug assurances, code contracts, or similar solutions to perform the additional validation only in development and test environments.

Compile time checks

If you have a good code contract solution, it will be validated when you create it.

Speaking of tools that validate the code … can you get or write one? I think of a lint or something similar that could test the code requirements and be added to build the integration. I know that such a tool is not always cost effective. However, if your situation is specific and important enough, such a tool is of value.

However, it is better to express validations as part of the type system so that they are checked at compile time without the need for additional tools.

For example, you could have a guy Tand a guy ValidatedTthat can only be initialized with valid values ​​of T, Then your internal code will only accept ValidatedT (of course with a better name) to make sure that the validation has already taken place, and no matter how many methods the ValidatedT Value is passed on, the validation took place only once. This should also improve readability, as you can see clearly where you have them T and where are you ValidatedT, Not only that, but you could have ValidatedT for different situations …

I mean, when I say the guy string, What is it? A username? a product description? What? However, if I say the type UsernameThen you know what it is in the system, and you know it's a valid value.

By the way, you can still take advantage of an easier-to-read code, even if you do not need to check the compile-time when using type aliases.

Strategy – Is it a valid or acceptable practice to develop a separate page to meet the accessibility requirements?

I've recently visited some sites that either use outdated technologies (like Flash) or have a lot of complex front-end Javascript code to create UI interaction.

Some of these sites include a link or button that takes you to a page in accessibility mode that removes any unnecessary features. In addition, only content optimized for screen readers and other accessible features (such as keyboard navigation) are provided.

Given that accessibility is now so important and integrative design is slowly being integrated into many of the standard design systems, it is still considered an acceptable practice to provide a separate page to accommodate accessibility guidelines (i.e., WCAG 2.0) fulfill? Are there other reasons why this could be a better strategy / option in the current design and development culture?

Exchange Server to allow sending emails from any sender with valid SMTP authentication without delegation?

I'm using Exchange Server 2019 and really enjoy the product and security. One feature that I find great is that you can not send as a sender just because you have SMTP AUTH, unless that sender allows the SMTP authentication username to be sent on behalf of that sender. However, there are scenarios in which I send emails programmatically through REST API services for my websites and apps and use an SMTP AUTH account to allow sending through my mail server. However, the sender name may not even be on my Exchange server. For example, a person referring a friend to a product.

Is it possible to allow Exchange Server 2019 to send on behalf of the sender address as long as SMTP AUTH is reached?

Customs and entry – One-year valid B2 visa, but passport with WT / WB stamp at the airport?

You should do one of the following before the December date, which I believe is stamped or written in your passport:

  • Have your entry corrected. You have been admitted under the visa waiver program, but you should not, because you have a B-2 visa.
  • leave and return to the US.

If you are entering the US with a visa in the future, open your passport on the visa page before handing it over to the immigration officer. This reduces the likelihood of a wrong approval record.

To have your entry corrected, you can introduce yourself to a delayed checkpoint. These websites are intended for persons who (among other things) believe that the documents issued in the port of entry and the corresponding endorsements require a review and possible correction:

The on-site staff for the late-time inspection is also available to review and issue the required documents to correct the errors arising from the entry documents issued on entry into the United States relating to an incorrect classification of non-immigrants, inaccurate biographical information or an incorrect approval period are appropriate. Any designated later inspection site or CBP office at an international airport should be able to help you, no matter where the actual document was issued.

Travelers are encouraged to contact locations outside an international airport as needed to make an appointment. In many cases, the location of your final destination, where the discrepancy is resolved, may not be the port of your first arrival in the US. Mail-in procedures are usually not available.

The delayed inspection bodies correct only errors made at the time of entry. You must contact the US Department of Citizenship and Immigration (USCIS) if you: wish to replace a lost, stolen or mutilated landing permission for crew members, CBP Form I-95; apply for an extension of your stay in the US; or change your immigration status. Specific information can be found on the USCIS website.

If you opt instead for a short trip to Canada, Mexico or the Caribbean, you should explicitly tell the official that you have been admitted to the VWP even though you have a valid visa. Otherwise, the officer may re-enroll you for the remainder of your initial registration, as this is the usual procedure for VWP travelers traveling to Canada, Mexico or the Caribbean.

You should also know that a 1-year visa does not entitle you to stay one year in the US. The admission period for B-2 visitors is usually six months. If you want to spend more than six months in the US, you may need to make some explanations.

Also note that your last visit to the US does not have to end before your visa expires: the admission deadline is independent. For example, if your visa was valid from 1 September 2019 to 31 August 2020, you could theoretically start a six-month stay on the 31st of August 2020. The likelihood that this is allowed depends in part on how much time you have spent in the US in the recent past.

As an example of someone who did Understand that the validity of the visa does not determine the duration of each stay. If you're still in serious trouble, you might be interested in the story of Baxter Reid. Even the journalist who reports on the linked story repeats his misunderstanding of the visa rules:

26-year-old Sydney man Baxter Reid was on a five-year visa in the US and had traveled to Canada to leave the US every six months and re-enter Canada to get his visa valid.

A visitor's visa does not entitle anyone to stay in the US for the duration of the visa, provided he leaves the country and returns every six months. On the contrary, it authorizes her to submit an entry request during the visa period. For each entry request, the immigration officer determines whether the applicant is actually a temporary visitor. Someone who spends more time in the US than outside the US is not likely to be considered a passing visitor.

If a visitor is admitted to the status B-1 or B-2, the immigration officer grants a period of six months to one year (8 CFR 214.2 (b) (1) and 8 CFR 214.2 (b) (2)). , This can be extended without leaving the country by submitting an application to USCIS. However, this option is not available to VWP visitors.

Java assignment declaration valid or invalid

Please note that in object-oriented programming every class declaration is considered as an object. This means that you must have permission to change properties in its object.

Based on your question, I'll adjust your question as follows so you can change those variables.

Change your toy class


package toyPackage;

public class Toy {
 protected int size; // this is protected and can not be accessed by other classes
 static int max; // this is private to this class. can not be accessed by other classes
 public static final int temp = 10; // this is a final value and can not be changed anymore


public class Toy {

 protected int size;
 private int max; // no need for static
 public int temp = 10; // needs to be changed.. can no longer be a constant

  Create getters and setters to access these 
  values from outside these classes 

  public int getSize(){
    return this.size;

  public void setSize(int newSize){
    this.size = newSize;

  public void setMax(int max){
    this.max = max;

Back to our experimentation package,

package experiment;

import toyPackage.*;

public class Driver {
 public static void main(String() args) {
 Toy p = new Toy();
 //p.size = 10; changes to

 // p.max = 20;

 //Toy.max = 30; // needs to be made public or use my solution below

 //Toy.temp = 40; // this is labled final and can not change anymore

Customs and immigration – Can I travel to Australia with an expired US visa but a valid Australian visitor visa from the US?

Am Indian and work in the USA. My visa extension is registered and in process at the US Consulate. The current one expired a week ago. I will still get my status on it. I am planning to travel to Australia after a week to visit my friend and back to India. I have a valid Australian visitor visa.

Does this apply to the visa status of the country?