HP R4.2 - Manual (Page 632)

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Summary of Commands spStatus
UCS 1000 R4.2 Administration 585-313-507 Issue 3 April 2000 593
Mailbox Information — Index, Empty, Full
The mailbox information is rudimentary information about activity within each
mailbox. It does not tell you how many letters have been sent via each
mailbox. However, it does tell you whether the mailbox is empty (1st Empty
== 1st Full) and if the values are changing from one display to the next, you
know mail is passing through that mailbox. Keep in mind that mailbox 1, from
the PC, is now reserved by the kernel and is used by the ioctl() form of mail
sending for all processes other than the limited number of processes that
directly own mailboxes.
In iterative mode, only those lines whose values have changed since the list
display are listed. On decimal entries, the delta value since the last time is
also printed.