realpath,readlink -f: coreutils compat, closes 11021

function                                             old     new   delta
xmalloc_realpath_coreutils                             -     121    +121

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/xreadlink.c

@@ -122,3 +122,33 @@ char* FAST_FUNC xmalloc_realpath(const char *path)
 	return xstrdup(realpath(path, buf));
 #endif
 }
+
+char* FAST_FUNC xmalloc_realpath_coreutils(const char *path)
+{
+	char *buf;
+
+	errno = 0;
+	buf = xmalloc_realpath(path);
+	/*
+	 * There is one case when "readlink -f" and
+	 * "realpath" from coreutils succeed,
+	 * even though file does not exist, such as:
+	 *     /tmp/file_does_not_exist
+	 * (the directory must exist).
+	 */
+	if (!buf && errno == ENOENT) {
+		char *last_slash = strrchr(path, '/');
+		if (last_slash) {
+			*last_slash++ = '\0';
+			buf = xmalloc_realpath(path);
+			if (buf) {
+				unsigned len = strlen(buf);
+                                buf = xrealloc(buf, len + strlen(last_slash) + 2);
+				buf[len++] = '/';
+				strcpy(buf + len, last_slash);
+			}
+		}
+	}
+
+	return buf;
+}