My .gitignore file isn't working as expected. How do I fix it?

# Run the following command (this removes everything from the index):
git rm -r --cached .

# Then, run:
git add .

# Finally, commit your changes:
git commit -m ".gitignore is now working"

Note, this answer's source came directly from http://stackoverflow.com/questions/1139762/gitignore-file-not-ignoring.

How do I show a list of all files and directories within a specific directory, recursivley, via the command line, such that each path printed is a fully qualified one?

$ find dir_of_interest -name '*'
dir_of_interest
dir_of_interest/dir1
dir_of_interest/dir1/file1.txt
dir_of_interest/dir2
dir_of_interest/dir2/file2.txt
dir_of_interest/dir3
dir_of_interest/dir3/file3.txt

How do I reload changes I've made to Apache's configuration?

sudo /etc/init.d/apache2 reload

How do I check if a user is a member of a specific usergroup on my Mac via the command line?

dsmemberutil checkmembership -U 'user' -G 'usergroup'

Where user is the username you're interested in and usergroup is the group you want to check to see if they're in.

How do I list the users on my Mac via the command line?

dscl . -list /Users

How do I list the usergroups on my Mac via the command line?

dscl . list /groups

How do I change a directory's group (or owner) on a *nix machine?

chgrp usergroup somedir

If you want to change the directory's contents too, simply append the -R option to the chgrp command as shown below:

chgrp -R usergroup somedir

Note that somedir could also be a file (it doesn't have to be a directory). Also, if you want to change a directory's owner simply switch chgrp to chown. The options between the two commands are the same.