findutils/m4/nullsort.m4

AC_DEFUN([jy_SORTZ],
  [AC_PATH_PROG([SORT], [sort], [sort])
  AC_MSG_CHECKING([if $SORT supports the -z option])
if test "x$cross_compiling" = xyes
then
        # We are cross-compiling, so cannot test the target's "sort".
        ac_sort_has_z=false
else
    # find out if the sort command has a working -z option.
    if $SORT -z -c < "${srcdir:-.}/m4/order-good.bin" 2>/dev/null  >/dev/null
    then
        # sort has a -z option, but we have not yet established that
        # sort thinks there is more than one input line there.   We have
        # to make sort -c do its thing with the input lines in the wrong
        # order to determine that (we can't do it in one shot because
        # if sort returns nonzero we can't tell that it wasn't just
        # complaining about this unknown -z option.
        if $SORT -z -c < "${srcdir:-.}/m4/order-bad.bin" 2>/dev/null >/dev/null
        then
                # sort likes -z but it doesn't seem to make \0
                # a delimiter.
                ac_sort_has_z=false
        else
                ac_sort_has_z=true
        fi
    else
        # Doesn't like the z option.
        ac_sort_has_z=false
    fi
fi

if test "x$cross_compiling" = xyes
then
        AC_MSG_RESULT([assume no, since we are cross compiling])
        AC_SUBST(SORT_SUPPORTS_Z,[false])
elif $ac_sort_has_z
then
        AC_MSG_RESULT([yes])
        AC_SUBST(SORT_SUPPORTS_Z,[true])
else
        AC_MSG_RESULT([no])
        AC_SUBST(SORT_SUPPORTS_Z,[false])
fi
])