I know that there is no difference in 0022 and 022 referring to . I have file 1.c, with permissions 0066. But when I change the mode of file 1.c to 1066, and then when I check the permissions of file with ls -l, it effects the permissions.  Each time different permission bits are changing with change in this first digit. What actually it signifies?  [vm4 ~]# ls -l 1.c ----rw-rw- 1 root root 10 Dec 23 22:48 1.c [vm4 ~]# chmod 1066 1.c [vm4 ~]# ls -l 1.c ----rw-rwT 1 root root 10 Dec 23 22:48 1.c [vm4 ~]# chmod 2066 1.c [vm4 ~]# ls -l 1.c ----rwSrw- 1 root root 10 Dec 23 22:48 1.c [vm4 ~]# chmod 5066 1.c [vm4 ~]# ls -l 1.c ---Srw-rwT 1 root root 10 Dec 23 22:48 1.c
I've never really got how chmod worked up until today. I followed a tutorial that explained a big deal to me.   For example, I've read that you've got three different permission groups:   owner (u) group (g) everyone (o)   Based on these three groups, I now know that:   If the file is owned by the user, the user permissions determine the access. If the group of the file is the same as the user's group, the group permission determine the access. If the user is not the file owner, and is not in the group, then the other permission is used.   I've also learned that you've got the following permissions:   read (r) write (w) execute (x)   I created a directory to test my newly acquired knowledge:  mkdir test   Then I did some tests:  chmod u+rwx test/ # drwx------ chmod g+rx test/ # drwxr-x--- chmod u-x test/ # drw-r-x---   After fooling around for some time I think I finally got the hang of chmod and the way you set permission using this command.    But...  I still have a few questions:   What does the d at the start stand for? What's the name and use of the containing slot and what other values can it hold? How can I set and unset it? What is the value for this d? (As you only have 7=4+2+1 7=4+2+1 7=4+2+1) Why do people sometimes use 0777 instead of 777 to set their permissions?   But as I shouldn't be asking multiple questions, I'll try to ask it in one question.  In UNIX based system such as all Linux distributions, concerning the permissions, what does the first part (d) stand for and what's the use for this part of the permissions?
I have several covariates in my calculation for a model, and not all of them are statistically significant.  Should I remove those that are not?  This question discusses the phenomenon, but does not answer my question:   There is nothing in the answer to that question that suggests that non-significant covariates be taken out, though, so right now I am inclined to believe that they should stay in.  Before even reading that answer, I was thinking the same since a covariate can still explain some of the variance (and thus help the model) without necessarily explaining an amount beyond some threshold (the significance threshold, which I see as not applicable to covariates).  There is another question somewhere on CV for which the answer seems to imply that covariates should be kept in regardless of significance, but it is not clear on that.  (I want to link to that question, but I was not able to track it down again just now.)  So...   Should covariates that do not show as statistically significant be kept in the calculation for the model?  (I have edited this question to clarify that covariates are never in the model output by the calculation anyway.)  To add complication, what if the covariates are statistically significant for some subsets of the data (subsets which have to be processed separately).  I would default to keeping such a covariate, otherwise either different models would have to be used or you would have a statistically significant covariate missing in one of the cases.  If you also have an answer for this split case, though, please mention it. Let $F$ be a field. Why does $F[x]$ have infinitely many irreducible elements?   For the case F has characteristic 0  Then x-a is irreducible for all a $\in F$ since x satisfies no non-trivial relations in F.  Obviously this argument fails for a finite field since there are only finitely many a to choose from.  So how may I construct irreducible polynomials in a finite field?  I figure it must involve higher powers of x, maybe $x^n-a$ ? Title says it all, I don't see confirmation in  and a cursory google search seemed to say assume no and speculate about the pokemon bank. Add a new repository to software sources How to Measure Luck vs Skill in Games? "Unanswered" question sort order on profile pages To help users keep track of (and hopefully get answers to) unanswered questions, it would be useful to have an "unanswered" sort order on a user's profile page.  It would order the list of questions with unanswered questions first.   This would be in addition to the "recent," "views," "newest," and "votes" sort orders. What does "all the more" mean and how is it used? Here is a sample context:     As you might expect, the framework also provides some convenience   classes to make the task of writing custom validators all the more agreeable.   (Emphasis added.) What do bookcases do for enchanting? I was amused by the expression "Paid a penny and only farted" (related by @FumbleFingers), which suggested a similar Japanese saying: 大山鳴動鼠一匹 - "Find only a small mouse coming out after hearing rumblings and experiencing shaking of the big mountain."  It’s humorous. I chuckled when I read it, and I wrote to the author that I love it.  With that said, the word "fart" reminds me of another Japanese proverb, 百日の説法屁一つ- "A fart ruins 100 days of sermons by the priest", which means that a small mistake (the sound of a fart in front of the congregation) brings all his efforts to naught.  It can’t happen in big Western churches. But it could well happen in a small wooden temple where a priest would preach to 30 – 50 provincial followers. Can you imagine how the proud priest being called 'the venerable' would be embarrased when his loud fart is heard by all his followers during his serious sermon and they start to giggle here and there in the hall?  We also have a similar saying" 九仞の功を一簣に欠く, which literally means "Collapse a 9- meter sand tower with the last pile of sand."  What is the English equivalent of the saying "A fart ruins 100 days of sermons by the priest (bishop): a small mistake depreciates the value of (vitiates) all labor and effort to naught," preferably in such a humorous way? Uninstalling Homebrew messed up git I uninstalled Homebrew using .  After running the above commands, I can't find .bashrc and .bash_profle. All files are gone from Documents , Desktop and Downloads :'(  When I do git status on /Users/ava it shows:  # On branch master # Untracked files: #   (use "git add &lt;file&gt;..." to include in what will be committed)  ... all the files which are in /Users/ava   history   113  cd `brew --prefix`   114  rm -rf Cellar   115  brew prune   116  rm `git ls-files`   117  rm -r Library/Homebrew Library/Aliases Library/Formula Library/Contributions   118  rm -rf .git   119  rm -rf ~/Library/Caches/Homebrew   120  sudo chown -R $USER:admin /usr/local   121  ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"   122  brew doctor   What just happened? Class method differences in Python: bound, unbound and static What is the difference between the following class methods?  Is it that one is static and the other is not?  class Test(object):   def method_one(self):     print "Called method_one"    def method_two():     print "Called method_two"  a_test = Test() a_test.method_one() a_test.method_two() Problem with PDO MySQL For the last couple of days I've been getting the following error:     Fatal error: Undefined class constant 'MYSQL_ATTR_USE_BUFFERED_QUERY' in /home/mydomain/public_html/drupal/includes/database/mysql/database.inc on line 46   This comes after my Hosting did an upgrade and PHP is now version 5.2.17.  From what they have told me, I think I have to enable a PDO MySQL extension in php.ini.  The problem is I'm on a shared hosting and I don't have access to the file; also, my Hosting said they can't change it either.  My info.php shows:     PDO      PDO support enabled      PDO drivers sqlite, sqlite2        pdo_sqlite      PDO Driver for SQLite 3.x enabled      PECL Module version (bundled) 1.0.1 $Id: pdo_sqlite.c 293036 2010-01-03 09:23:27Z   sebastian $      SQLite Library 3.3.7     I tried modifying the .htaccess file and/or adding my own php.ini file to the root directory per some suggestions I found, but nothing I've tried has worked yet.  Can anyone please suggest what else I could do?  EDIT:  Once again I asked the Hosting to enable PDO_MySQL extension and their answer was that they could not, that cPanel (to which they migrated from Plesk, causing this whole problem) had this extension disabled by default and changing it would affect their servers.  Their solution?  That I would change my programming to adjust to these new features, which I wouldn't even know how to go about.  Are they right requesting that I do this? Is there any other way? Does a non-EU Spouse of a UK national need a visa to visit the Schengen area? I am a British national resident in the UK. My wife is Jordanian, resident in the UK with me. She has a UK biometric residency permit. We were married in the UK and the marriage is registered in the UK.   Does my wife need visas to travel with me on holiday in France and Spain? I understand from EU Directives that she does not. Would we be able to leave the UK by ferry to France if my wife does not have a French visa but can prove that she is married to me and resident in the UK? If visas are necessary but the French or Spanish consulates were NOT to grant the visas, would this be in contravention of EU Directives/Law? If the answer to question 3 is "Yes, it would be unlawful", what action can one take to get the visas? If someone else is booking international ticket for me using his credit or debit card, does he need to be present physically at the time of check-in?   Suppose I am coming back from Singapore to my home country and my ticket is booked by my friend for me, who lives in my home country. Do airlines in Singapore ask for the person to be present physically to check in? What does the helpful flag mean? I don't see "Helpful" in the list of things I can do when I press the flag link.   In my profile page I saw "6 helpful flags."  How do I earn these flags?  May I make them on other peoples' posts or comments?   This is what I am talking about: What exactly is flash sync speed and should it be a factor in a buying decision? How can I list all user names and/or home directories? I want to list all the users dirs on the machine.Usually, I will do:  ls -l /home   But I use it in a script that will be deployed on others machines and maybe on that machines they don't call it home (e.g. myHome). So I want to generalize it to ls -l ~. But it just lists my users home dirs instead of all users home dirs name (basically I want to get a list of the users names on the machine). How can I generalize it? Usually I use the package mhchem for writing chemical formulas, but until now I was not able to find a solution for writing crystals such as Nd^{3+}:YAG properly with this package. When simply writing   \ce{Nd^{3+}:YAG}   it results in an error. My current alternative solution is to write it as   \ce{Nd^{3+}}:\ce{YAG}   Is there a more elegant way to do that? Splicing a list of arguments into a function with Sequence IMAP: how to move a message from one folder to another (using the IMAP commands, not with the assistance of any other mail package)