+int get_process_uid(pid_t pid, uid_t *uid) {
+ char *p;
+ FILE *f;
+ int r;
+
+ assert(uid);
+
+ if (pid == 0)
+ return getuid();
+
+ if (asprintf(&p, "/proc/%lu/status", (unsigned long) pid) < 0)
+ return -ENOMEM;
+
+ f = fopen(p, "re");
+ free(p);
+
+ if (!f)
+ return -errno;
+
+ while (!feof(f)) {
+ char line[LINE_MAX], *l;
+
+ if (!fgets(line, sizeof(line), f)) {
+ if (feof(f))
+ break;
+
+ r = -errno;
+ goto finish;
+ }
+
+ l = strstrip(line);
+
+ if (startswith(l, "Uid:")) {
+ l += 4;
+ l += strspn(l, WHITESPACE);
+
+ l[strcspn(l, WHITESPACE)] = 0;
+
+ r = parse_uid(l, uid);
+ goto finish;
+ }
+ }
+
+ r = -EIO;
+
+finish:
+ fclose(f);
+
+ return r;
+}
+