Incomplete Arena Specifiers

In general, you do not need to completely specify an arena. Missing components are assigned default values or are filled in from the current focus. The only requirement is that the meaning of each part of the specifier cannot be ambiguous. Here is how the CLI fills in missing pieces:

• If you do not use a width, the CLI uses the width from the current focus.
   
• If you do not use a PID, the CLI uses the PID from the current focus.
   
• If you set the focus to a list, there is no longer a default arena. This means that you must explicitly name a width and a PID. You can, however, omit the TID. (If you omit the TID, the CLI defaults to <.)

  You can type a PID without typing a TID. If you omit the TID, the CLI uses its default of "<", where "<" indicates the lowest numbered worker thread in the process. If, however, the arena explicitly names a thread group, < means the lowest numbered member of the thread group.

  The CLI does not use the TID from the current focus, since the TID is a process-relative value.

• A dot typed before or after the number lets the CLI know if you are specifying a process or a thread. For example, "1." is clearly a PID, while ".7" is clearly a TID.

  If you type a number without typing a period, the CLI interprets the number as being a PID.

• If the width is t, you can omit the dot. For instance, t7 refers to thread 7.
   
• If you enter a width and do not specify a PID or TID, the CLI uses the PID and TID from the current focus.

  If you use a letter as a group specifier, the CLI obtains the rest of the arena specifier from the default focus.

• You can use a group ID or tag followed by a "/". The CLI obtains the rest of the arena from the default focus.