If one of the arguments equals \-1, the corresponding value is not changed.
Regardless of what changes are made to the real UID, effective UID,
-and saved set-user-ID, the file system UID is always set to the same
+and saved set-user-ID, the filesystem UID is always set to the same
value as the (possibly new) effective UID.
Completely analogously,
.BR setresgid ()
sets the real GID, effective GID, and saved set-group-ID
-of the calling process (and always modifies the file system GID
+of the calling process (and always modifies the filesystem GID
to be the same as the effective GID),
with the same restrictions for unprivileged processes.
.SH RETURN VALUE