I have done the follow:   chown'd it to a group chmod 775 usermod   this is the status of the permission drwxrwxr-x  3 root www-data 4096 Mar 22 23:11 html  The groups my user is in ubuntu : ubuntu adm dialout cdrom floppy sudo audio dip www-data video plugdev netdev lxd  But if I do touch test it just gives me a permission denied. Am I missing something.  As for a little background, I'm running a Ubuntu server on AWS. I'm also trying to give my apache user writing permission in the html folder.
I changed permissions of a file (chmod g+w testfile) and running ls -l testfile gives:  -rwxrwxr-x 1 user1 user1 0 2011-01-24 20:36 testfile   I then added a user to that group ("/etc/group" has user1:x:1000:user2 line), but am failing to edit that file as user2. Why is this so?
I would like to change a file extension from *.txt to *.text. I tried using the basename command, but I'm having trouble on changing more than one file.  Here's my code:  files=`ls -1 *.txt`  for x in $files do     mv $x "`basename $files .txt`.text" done   I'm getting this error:  basename: too many arguments Try basename --help' for more information Is the distribution of an Ito diffusion at time t absolutely continuous wrt Lebesgue measure? How to mount PCIe SSD from MacBook Air in another computer I got this SSD out of an Apple laptop that's broken from liquid damage.  What is this connection called and how do I mount this storage device to retrieve data from it? It looks like PCIe. Does Apple sell a part to mount this via USB adapter or something? Is there any analytics information that moderators can access for individual questions? How can I check for Python version in a program that uses new language features? If I have a Python script that requires at least a particular version of Python, what is the correct way to fail gracefully when an earlier version of Python is used to launch the script?  How do I get control early enough to issue an error message and exit?  For example, I have a program that uses the ternery operator (new in 2.5) and "with" blocks (new in 2.6).  I wrote a simple little interpreter-version checker routine which is the first thing the script would call ... except it doesn't get that far. Instead, the script fails during python compilation, before my routines are even called. Thus the user of the script sees some very obscure synax error tracebacks - which pretty much require an expert to deduce that it is simply the case of running the wrong version of Python.  I know how to check the version of Python. The issue is that some syntax is illegal in older versions of Python. Consider this program:  import sys if sys.version_info &lt; (2, 4):     raise "must use python 2.5 or greater" else:     # syntax error in 2.4, ok in 2.5     x = 1 if True else 2     print x   When run under 2.4, I want this result  $ ~/bin/python2.4 tern.py  must use python 2.5 or greater   and not this result:  $ ~/bin/python2.4 tern.py    File "tern.py", line 5     x = 1 if True else 2            ^ SyntaxError: invalid syntax   (Channeling for a coworker.) Is a diode needed for this simple mini solenoid circuit? Is my C1/D visa valid for transit in the US, if I want to go on a vacation to Mexico? I am a beginner in learning selenium Webdriver. I am not able to understand how page object and factory models works and how it can be beneficial?    Kindly help me explain it with detailed explanation. Where can I ask questions about the computer problems I have been facing?  Current problems I am facing with my computers:   Windows 7 errors random "Blue screens of Death" computer randomly freezing up Xfire challenges JavaScript hard refresh of current page load() method deprecated? Celebrating the same new year several times over? Determine wether the differential equation is stable or not for the following conditions:  $x'''(0) = x''(0) = x'(0) = x(0) =0$  $\frac{d^3x(t)}{dt^3}+\frac{d^2x(t)}{dt^2}+4\frac{dx(t)}{dt}+4x(t) = e^t(H(t)-H(t-3))$  Now, I got that the solution to this differential equation reduces x(t) by use of Laplace Transforms, however, how do I determine whether or not it is stable?  $x(t) = 0.1e^{-t} + 0.1e^t - 0.1\sin(2t) + 0.1e^3 (\sin(2(t-3)) + e^{-t+3}-e^{t-3})*H(t-3)$  Now I first thought I would look at it graphically and I used Matlab software to get a plot as shown below:    And from the plot above it clearly appears to diverge (though this is not a proof).  Anyone have an idea as to an elegant proof to show the solution is unstable?  Anyone help would be greatly appreciated! In general, in most places, it is said that using TeX defaults is the best. However, TeX does provide things like \, and \quad etc. When one should use them? Both in general and in math mode in particular. I  here on MSO today, but it was found to have been asked .  I'm not concerned by this (better to be found by more than one user) but, I noticed that the wording in the closure statement is factually incorrect:    No it doesn't have an answer - Not even a sniff of one!  This statement, logically, should be factually accurate and reflect the existence of answers and include singular/plural references to them - or at a minimum use language that covers both scenarios.  Edit: As a result of my question,  and the bug in question has been remedied, but this question still remains valid. What is a "loop device" when mounting? How did the English language come to this?       The play was awful.     Is the complete opposite of     The play was awesome.   But if you break it down to awe followed by ful or some, it doesn't make sense at all. Can someone shed a light on this?  Is there a rule to this, or is it one of those things you need to just memorize? What to do when you find a bad link in an answer? If a link has gone stale in an answer, what is the correct way to report this in the SO universe?  e.g. Jon's first link in    I have added a comment but not found the correct link yet. Flattening a shallow list in Python Why would var be a bad thing?