Tell if a folder/file is hidden in Mac OS X

According to the ls man page, you should be able -O option combined with the -l option to view flags with ls. For example:

ls -Ol foo.txt
-rw-r--r-- 1 harry staff - 0 18 Aug 19:11 foo.txt
chflags hidden foo.txt
ls -Ol foo.txt
-rw-r--r-- 1 harry staff hidden 0 18 Aug 19:11 foo.txt
chflags nohidden foo.txt
ls -Ol foo.txt
-rw-r--r-- 1 harry staff - 0 18 Aug 19:11 foo.txt

Edit: Just to give a more specific solution to what the OP wanted (see comments below): To see if a folder is hidden or not, we can pass the -a option to ls to view the folder itself. We can then pipe the output into sed -n 2p (thanks Stack Overflow) to get the required line of that output. An example:

mkdir foo
chflags hidden foo
ls -aOl foo | sed -n 2p
drwxr-xr-x@ 2 harry staff hidden 68 18 Aug 19:11 .

Edit 2: For a command that should work regardless of whether it's a file or a folder, we need to do something slightly more hacky.

The needed line of output from ls -al varies depending on whether the thing is a file or folder, as folders show a total count, whereas files do not. To get around this, we can grep for the character r. This should be in ~all of all files/folders (nearly all should have at least one read permission), but not in the totals line.

As the line we want to get then becomes the first line, we can use head -n 1 to get the first line (alternative, if you prefer sed, sed -n 1p could be used).

So, for example with a directory:

mkdir foo
chflags hidden foo
ls -aOl foo | grep r | head -n 1
drwxr-xr-x@ 2 harry staff hidden 68 18 Aug 19:11 .

and with a file:

touch foo.txt
chflags hidden foo.txt
ls -aOl foo.txt | grep r | head -n 1
-rw-r--r-- 1 harry staff hidden 0 18 Aug 19:11 foo.txt

Edit 3: See Tyilo's answer below for a nicer way than grepping for r :)

Found the solution here: How can I make ls show information about the directory specified only, not info about its sub-files or folder contents?

Which basically is ls -ldO foo and then you just append | awk '{ print $5 }' to make it display the information.