5 POSIX specification: @url{http://www.opengroup.org/susv3xsh/coshl.html}
9 Portability problems fixed by Gnulib:
13 Portability problems not fixed by Gnulib:
16 This function is missing on some platforms:
17 FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, HP-UX 11, IRIX 6.5, Solaris 9, Cygwin, BeOS.