+
+/* Returns the current working directory as a malloc()'d string, or a null
+ * pointer if the current working directory cannot be determined. */
+char *
+get_cwd(void)
+{
+ long int path_max;
+ size_t size;
+
+ /* Get maximum path length or at least a reasonable estimate. */
+ path_max = pathconf(".", _PC_PATH_MAX);
+ size = (path_max < 0 ? 1024
+ : path_max > 10240 ? 10240
+ : path_max);
+
+ /* Get current working directory. */
+ for (;;) {
+ char *buf = xmalloc(size);
+ if (getcwd(buf, size)) {
+ return xrealloc(buf, strlen(buf) + 1);
+ } else {
+ int error = errno;
+ free(buf);
+ if (error != ERANGE) {
+ VLOG_WARN("getcwd failed (%s)", strerror(error));
+ return NULL;
+ }
+ size *= 2;
+ }
+ }
+}
+
+/* Returns the directory name portion of 'file_name' as a malloc()'d string,
+ * similar to the POSIX dirname() function but thread-safe. */
+char *
+dir_name(const char *file_name)
+{
+ size_t len = strlen(file_name);
+ while (len > 0 && file_name[len - 1] == '/') {
+ len--;
+ }
+ while (len > 0 && file_name[len - 1] != '/') {
+ len--;
+ }
+ while (len > 0 && file_name[len - 1] == '/') {
+ len--;
+ }
+ if (!len) {
+ return xstrdup((file_name[0] == '/'
+ && file_name[1] == '/'
+ && file_name[2] != '/') ? "//"
+ : file_name[0] == '/' ? "/"
+ : ".");
+ } else {
+ return xmemdup0(file_name, len);
+ }
+}
+
+/* If 'file_name' starts with '/', returns a copy of 'file_name'. Otherwise,
+ * returns an absolute path to 'file_name' considering it relative to 'dir',
+ * which itself must be absolute. 'dir' may be null or the empty string, in
+ * which case the current working directory is used.
+ *
+ * Returns a null pointer if 'dir' is null and getcwd() fails. */
+char *
+abs_file_name(const char *dir, const char *file_name)
+{
+ if (file_name[0] == '/') {
+ return xstrdup(file_name);
+ } else if (dir && dir[0]) {
+ char *separator = dir[strlen(dir) - 1] == '/' ? "" : "/";
+ return xasprintf("%s%s%s", dir, separator, file_name);
+ } else {
+ char *cwd = get_cwd();
+ if (cwd) {
+ char *abs_name = xasprintf("%s/%s", cwd, file_name);
+ free(cwd);
+ return abs_name;
+ } else {
+ return NULL;
+ }
+ }
+}
+
+
+/* Pass a value to this function if it is marked with
+ * __attribute__((warn_unused_result)) and you genuinely want to ignore
+ * its return value. (Note that every scalar type can be implicitly
+ * converted to bool.) */
+void ignore(bool x OVS_UNUSED) { }