On 2014-12-29 14:01, Gil Dawson wrote:
I'm having a little problem understanding the Unix terminology.
You may find Chapter 2 of the freely available book "The Linux Command
Line" ( http://linuxcommand.org/tlcl.php ) to be helpful. Although this
book is about Linux, not MacOS X, both are based on Unix.
This paragraph has me stumped.
'...if the filenames ... begin with "/"'
--I cannot imagine how a filename could begin with "/".
Does the author possibly mean /pathname/?
A pathname might begin with either a "/" or a "~", would it not?
Configuration and log files are files, whereas pathnames can point to
anything. So although it may be confusing, I think that "filename" is
the correct terminology here. The filename may be just the name of a
file without any directory component, or it may include a relative
directory component or an absolute directory component. Examples:
Simple filename: extra-stuff.conf (look for the file
"extra-stuff.conf" inside the current directory)
With relative directory: my-stuff/extra-stuff.conf (look for the file
"extra-stuff.conf" inside the directory "my-stuff" which in turn is in
the current directory"). Note that this is the same as
./my-stuff/extra-stuff.conf
Another example with a relative directory:
../../another-place/extra-stuff.conf (go up two directory levels from
the current directory, then into the directory "another-place" and then
the file is extra-stuff.conf).
Absolute directory component: /private/etc/apache2/extra-stuff.conf
"If the filenames do *not* begin with "/", ...
"/private/var/log/apache2/foo_log"
--This is an example of a filename that does not begin with
"/", right?
I don't get it. I see "/" at the beginning of everything.
What would be an example of a filename that /does/ begin with "/"?
/private/var/log/apache2/foo_log" *does* begin with "/". You're trying
to make too much of a distinction between pathnames and filenames.
"/usr//private/..."
-- What is the meaning of "//" in this context?
It has no meaning, extra slashes between directory components are
ignored. This lets scripts and other programs construct filenames
without having to detect and remove extraneous slashes; if a script
always adds a slash, it will be there when needed and won't cause
problems if it is not needed. The following are all equivalent:
/usr/private
/usr//private
/usr/private/
/////usr/////private/////
For more reading, see
http://teaching.idallen.com/cst8207/12f/notes/160_pathnames.html
--
Mark Montague
m...@catseye.org
