Added version that opens a pipe to /bin/pwd.

Python/getcwd.c

-/* Quick hack to get posix.getcwd() working for pure BSD 4.3 */
+/* Two PD getcwd() implementations.
+   Author: Guido van Rossum, CWI Amsterdam, Jan 1991, <guido@cwi.nl>. */
 
-#include "sys/param.h"
-#include "errno.h"
+/* #define NO_GETWD /* Turn this on to popen pwd instead of calling getwd() */
+
+#include <stdio.h>
+#include <errno.h>
 
 extern int errno;
 
+#ifndef NO_GETWD
+
+/* Default: Version for BSD systems -- use getwd() */
+
+#include "sys/param.h"
+
 extern char *getwd();
 
 char *
@@ -32,4 +41,38 @@ getcwd(buf, size)
 	return buf;
 }
 
-/* PS: for really old systems you must popen /bin/pwd ... */
+#else
+
+/* NO_GETWD defined: Version for backward UNIXes -- popen /bin/pwd */
+
+#define PWD_CMD "/bin/pwd"
+
+char *
+getcwd(buf, size)
+	char *buf;
+	int size;
+{
+	FILE *fp;
+	char *p;
+	int sts;
+	if (size <= 0) {
+		errno = EINVAL;
+		return NULL;
+	}
+	if ((fp = popen(PWD_CMD, "r")) == NULL)
+		return NULL;
+	if (fgets(buf, size, fp) == NULL || (sts = pclose(fp)) != 0) {
+		errno = EACCES; /* Most likely error */
+		return NULL;
+	}
+	for (p = buf; *p != '\n'; p++) {
+		if (*p == '\0') {
+			errno = ERANGE;
+			return NULL;
+		}
+	}
+	*p = '\0';
+	return buf;
+}
+
+#endif