Filtering notifications

You can filter PPS notifications based on the names of attributes, the values of attributes, or a combination of the two.

To filter notifications, use the following syntax:

f=attrspec{+attrspec}...

where attrspec is an attribute specification consisting of either an attribute's name or an expression specifying an attribute's value. If you want to be notified when the attribute is deleted, add a minus sign (-) before its name:

f=-attr

The syntax for specifying an attribute's value is:

attroperatorvalue

where attr is the attribute's name, operator is the operator used to determine the threshold for triggering notifications, and value is the value to compare to.

Supported operators are:

<, <=, >, >=, =, ==, and != for integers. Integer values must be in the range of a long long; otherwise they're treated as strings.
=, ==, and != for strings. Note that = and == are synonymous. String values can include the + character, but only by escaping it with \.

If you specify only an attribute's name, PPS notifies you of any updates where an attribute with that name is set. If you specify a name, operator, and value, PPS notifies you of any updates where the named attribute is set to a value that matches the given operator and value expression.

In both full and delta modes, the file descriptor will get notifications if any of the attribute specifications match:

In full mode, the entire object is returned.
In delta mode, only the specified attributes are returned. Changes to other attributes are filtered out.

In the following examples, the name of the object being opened is "objname":

/pps/objname?delta,f=attr1+attr2 — return change notifications for only the attributes named "attr1" and "attr2"
/pps/objname?delta,f=attr1<37 — return change notifications for only the attribute named "attr1" when its value is less than 37
/pps/objname?f=attr2<0+attr2>100 — return change notifications for the entire object when the attribute "attr2" has an integer value less than 0 or greater than 100
/pps/objname?delta,f=attr1=a\+b — return change notifications only for the attribute "attr1" when it has a string value of "a+b"
/pps/objname?delta,f=attr1+attr2<10 — return change notifications only for the attribute "attr1" (for any change) and attribute "attr2" when it has an integer value less than 10.