+@item
+This function is missing on some platforms:
+Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 11 2011-11.
+@item
+This function requires linking with @code{-lutil} on some platforms:
+glibc 2.3.6, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8.
+It is available without link options on other platforms:
+MacOS X 10.5, OSF/1 5.1, Cygwin, Interix 3.5.