AC_CHECK_FUNCS(seteuid setresuid setegid setresgid chroot bzero strerror)
AC_CHECK_FUNCS(vsyslog setlinebuf mktime ftruncate chsize rename)
AC_CHECK_FUNCS(waitpid strlcpy strlcat initgroups memmove strdup)
-AC_CHECK_FUNCS(pread pwrite strndup strcasestr strtok_r mkdtemp)
+AC_CHECK_FUNCS(pread pwrite strndup strcasestr strtok_r mkdtemp dup2)
AC_CHECK_FUNCS(isatty)
AC_HAVE_DECL(setresuid, [#include <unistd.h>])
AC_HAVE_DECL(setresgid, [#include <unistd.h>])