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From: pfalstad@phoenix.Princeton.EDU (Paul John Falstad)
Newsgroups: comp.unix.programmer
Subject: Re: getting the current working directory
Message-ID: <5195@idunno.Princeton.EDU>
Date: 11 Jan 91 08:10:37 GMT
References: <42380@ut-emx.uucp>
Sender: news@idunno.Princeton.EDU
Distribution: usa
Organization: Princeton University, Princeton, New Jersey
Lines: 76

In article <42380@ut-emx.uucp> pefv700@perv.pe.utexas.edu writes:
>According to my SunOS man page on getwd(3), getwd(buf) will put the absolute
>path of the current working directory in buf UNLESS there is an error, in
>which case buf contains some message.  The problem is, you don't know if you
>got the directory name or the message.

Yes, you do.  If there is an error, getwd returns NULL.  Otherwise it
returns the address of the buffer.

Here is a version of getwd I wrote for zsh.  I'd be interested in what
people think of it.  I needed a version that didn't fork(), and was
having problems with the Sun getwd().

char *getwd(void)
{
static char buf0[MAXPATHLEN];
char buf3[MAXPATHLEN],*buf2 = buf0+1;
struct stat sbuf;
struct direct *de;
DIR *dir;
ino_t ino = -1;
dev_t dev = -1;

	buf2[0] = '\0';
	buf0[0] = '/';
	for(;;) {
		if (stat(".",&sbuf) < 0) {
			chdir(buf0);
			return NULL;
			}
		ino = sbuf.st_ino;
		dev = sbuf.st_dev;
		if (stat("..",&sbuf) < 0) {
			chdir(buf0);
			return NULL;
			}
		if (sbuf.st_ino == ino && sbuf.st_dev == dev) { /* we're done */
			chdir(buf0);
			return strdup(buf0);
			}
		dir = opendir("..");
		if (!dir) {
			chdir(buf0);
			return NULL;
			}
		chdir("..");
		readdir(dir); readdir(dir);
		while (de = readdir(dir))
			if (de->d_fileno == ino) { /* find file with matching inode */
				lstat(de->d_name,&sbuf);
				if (sbuf.st_dev == dev)
					goto match;
				}
		rewinddir(dir);
		readdir(dir); readdir(dir);
		while (de = readdir(dir)) {
			lstat(de->d_name,&sbuf);
			if (sbuf.st_dev == dev) /* find file with matching device # */
				goto match;
			}
		closedir(dir);
		return NULL;
match:
		strcpy(buf3,de->d_name);
		if (*buf2)
			strcat(buf3,"/");
		strcat(buf3,buf2);
		strcpy(buf2,buf3);
		closedir(dir);
		}
}

--
Paul Falstad, pfalstad@phoenix.princeton.edu PLink:HYPNOS GEnie:P.FALSTAD
"We could nuke Baghdad into glass, wipe it with Windex, tie fatback on
our feet and go skating." - Air Force Times columnist Fred Reed