HP-UX 11i June 2004 Release Notes

5
[] The contents are optional in formats and command descriptions. If the
contents are a list separated by |, you must choose one of the items.
{} The contents are required in formats and command descriptions. If the
contents are a list separated by |, you must choose one of the items.
... The preceding element may be repeated an arbitrary number of times.
| Separates items in a list of choices.