The following image comprises two main elements: at the top is a block of disk subsystem output from collect. Below it is a cfilt expression.
I'll explain the cfilt expression one part at a time.
| dis | in the ascii output of collect there are 2 or 3 comment lines (starting with '#') before the data for each subsystem. The first line contains the subsystem label. cfilt matches the first three characters of this label with the subsystem specifier in each expression, in this case "dis". |
|---|---|
| name=re0,re1 | this is a selection-criterion. To the left of the
equals-sign is some column-tag. To the right is a
comma-separated list of values (strings) expected in the
given column. Only the lines whose values in the given
column match values in the list will be used, and the
resulting cfilt output will be in the same
order as this list. All other lines
will be ignored. Thus the lines with the values "re0" and
"re1" will be selected, and the first value will be for
"re0", the second for "re1".
The column-tag is not case-sensitive, however the values (to the right of the equals-sign) are. That is, they must match exactly. If no selection-criterion is given, all lines are selected, and and summing is automatically turned on. |
| RKB/S+WKB/S | this is the tag-expression. It gets a bit complicated
here. The tag-expression is an arbitrary expression consisting
of constants, functions (see the manual page for a list), and
column-labels, such as "RKB/S". When the expression is
evaluated, the actual value in the column under the corresponding
column-label is substituted for the column label. So, in this
example, for "re0", "RKB/S" is 2301 and "WKB/S" is 0, so the
expression is 2301+0, or 2301.
The tag-expressions are NOT case-sensitive. |
Now I'd like to tie it all together:
For the DISK ("dis") subsystem, all lines are selected which have
the values "re0" or "re1" in the "NAME" column. For each selected
line the expression "RKB/S+WKB/S" is evaluated. The result of evaluating
an expression is written in the corresponding order to cfilt's
output. If summing were turned on (by adding a "+" to the end of the
subsystem-label (as in "dis+:name=re0,re1:RKB/S+WKB/S"), then for all
selected lines (or all lines, if no selection-criterion was given), the
results of evaluating the tag-expressions would be summed, producing
one value for each expression in the subsystem.
In this example, cfilt's output for this sample would be:
<epoch-seconds> <sample-number> 2301 2280