Filters

Use filters to examine specific rows in a large volume of data. The data that is returned by the debugging commands can be refined to select only the relevant data.

Data is filtered in the Event Stream Processor, before it is sent out.

The esp_client command exf performs filtering as follows:

exf {kind} [ {stream} [ {object} ] ] {expr}

The names of the stream and object are optional, similar to the command ex. There is an added argument containing the filter expression. The filter expression references a pre-defined variable, similar to the breakpoint filter expressions containing the current row. This expression compares the row with the expression and decides if the row should be returned. Whenever the filter expression returns true (non-0, non-NULL), the record is returned to the user and displays.

The rules for the defined variables are:

If all rows in the returned data set are of the same type, they are wrapped in a single variable row.
If the data kind contains rows of mixed types (the input or history data), multiple variables are defined, with names matching the XML tags printed for these records. Only one variable, matching the type of the current record, contains a value. All others are set to NULL.