1 files changed, 38 insertions, 0 deletions
diff --git a/sys/etc/xisatty.x b/sys/etc/xisatty.x
new file mode 100644
index 00000000..177bec67
--- /dev/null
+++ b/sys/etc/xisatty.x
@@ -0,0 +1,38 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<clset.h>
+include	<fset.h>
+
+# XISATTY -- Test if the given file is a terminal.
+
+int procedure xisatty (fd)
+
+int	fd			# file descriptor of candidate device
+int	epa, epa_tt, epa_ty
+extern	zgettt(), zgetty()
+int	fstati(), clstati()
+
+begin
+	# If we are a connected subprocess, the referenced file is a standard
+	# stream, and i/o has not been redirected, assume that the file behaves
+	# as a terminal.
+
+	if (clstati(CL_PRTYPE) == PR_CONNECTED)
+	    if (fd == STDIN || fd == STDOUT || fd == STDERR)
+		if (fstati (fd, F_REDIR) == NO)
+		    return (YES)
+		else
+		    return (NO)
+
+	# Otherwise, the use of the terminal driver tells us if the file is
+	# open on a terminal device.
+
+	epa = fstati (fd, F_DEVICE)
+	call zlocpr (zgettt, epa_tt)
+	call zlocpr (zgetty, epa_ty)
+
+	if (epa == epa_tt || epa == epa_ty)
+	    return (YES)
+	else
+	    return (NO)
+end