Excellent response, Mark! Exactly what I needed.
Thank you. --Gil On Dec 29, 2014, at 11:40 AM, Mark Montague wrote: > 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
