1 files changed, 38 insertions, 0 deletions
diff --git a/sys/fio/fnullfile.x b/sys/fio/fnullfile.x
new file mode 100644
index 00000000..4080a03b
--- /dev/null
+++ b/sys/fio/fnullfile.x
@@ -0,0 +1,38 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+# FNULLFILE -- Determine if the named file is the null file.
+
+bool procedure fnullfile (fname)
+
+char	fname[ARB]		# null file candidate
+
+pointer	sp, osfn
+bool	first_time, bval
+char	nullpath[SZ_FNAME]
+int	strmatch()
+bool	streq()
+
+data	first_time /true/
+string	nullfile "dev$null"
+
+begin
+	# Some simple, fast tests first.
+	if (streq (fname, nullfile))
+	    return (true)
+	else if (strmatch (fname, "{null}") == 0)
+	    return (false)
+
+	call smark (sp)
+	call salloc (osfn, SZ_PATHNAME, TY_CHAR)
+
+	if (first_time) {
+	    call fpathname (nullfile, nullpath, SZ_FNAME)
+	    first_time = false
+	}
+
+	call fpathname (fname, Memc[osfn], SZ_PATHNAME)
+	bval = streq (Memc[osfn], nullpath)
+
+	call sfree (sp)
+	return (bval)
+end