Re: [Chicken-users] [Chicken-hackers] CHICKEN 4.9.0rc1 is available

[John Cowan]

Mario Domenech Goulart scripsit:

> Getting the current work directory is surprisingly hard (maybe not that
> surprising).  There's $PWD, the pwd shell builtin and the pwd executable
> file (usually /bin/pwd or /usr/bin/pwd).  

You can't count on the shell built-in existing; it's a bashism.  As for
/bin/pwd, it turns out it has options:  /bin/pwd -L does sanity checks
on $PWD and outputs it if it looks sane (if not, it falls back to its
internal algorithm), whereas /bin/pwd -P ignores $PWD.  The default is -L.
I doubt if one Unix programmer in ten thousand knows about these.

Some Unixes have a syscall to retrieve the current directory.  If not,
the canonical algorithm is to stat "." to find out its device number
and i-number, and then cd to ".." and search the new current
directory for a name whose i-number matches the one we had before.
Repeat until we reach the root (i-number 2).

-- 
John Cowan          http://www.ccil.org/~cowan        address@hidden
There are three kinds of people in the world:
those who can count, and those who can't.