Next: Compatibility Mode, Up: Implementation Differences [Contents][Index]
GNU
troff operates in
safer mode
by default;
to mitigate risks from untrusted input documents,
it disables the
cf,
pi,
and
sy
requests.
GNU
troff’s
-U
option enables “unsafe mode”,
restoring their function and enabling additional extension requests,
open,
opena,
and pso.
Recall Host System Service Access.