This article is from a FAQ concerning SCO operating
systems. While some of the information may be applicable to any OS,
or any Unix or Linux OS, it may be specific to SCO Xenix, Open
This is an old article about SCO Unix and is only left here for historical purposes.
There is lots of Linux, Mac OS X and general Unix info elsewhere on
this site: Search this site is the best
way to find anything.
If you are getting this from some program you are running in
background or from cron, it's because it can't write to your
terminal- either because it doesn't have a tty to write to (cron)
or because it's detached or otherwise blocked.
(/dev/tty is a special file that always is the controlling
terminal- even when standard input and standard output have been
A common program that writes to /dev/tty is cpio: if it needs
another volume (tape or floppy is full), it writes to /dev/tty
asking you to give it the name of another device it can write on.
Therefore, cpio scripts put into background can generate this kind
If you are getting this at the command line, the permissions on
/dev or /dev/tty itself may be wrong.
Stuart J. Browne noted:
If you want to see the actual message (and you
are using OSR5+) try adding the "-P0,1" flag to CPIO, ie: