Starting from version 1.4.0, Call Prefix Filter can save the filter rules to a CSV file. This feature facilitates backup and transfer purposes.

The CSV format is documented for users who are interested to edit the CSV file at their PC.

CSV file format

Each line should consists of 4 fields in the following order.

1. Action
2. Country code
3. Prefix
4. Exact number

All keywords are expected to be in lower case.

The app handles well both the Win10-style CRLF and Android-style LF text format.

The first text line serves a file signature for a Call Prefix Filter CSV file. The 4 fields contains 4 keywords as follows.

• action,c_code,prefix,exact

Action

The action field specifies the action associated with the number prefix. It can be:

• block
• allow

If the field is left blank, the app takes it as a "block" entry.

Country code & Prefix

The prefix fields specifies the number prefix to be processed.

The following characters are allowed:

• +1234567890*# ,.;-(/)N

It is advised to use only the number digits and the plus sign. The other characters are never noticed in Android incoming call number.

Either country code or prefix can be left blank. If both fields are left blank, the app thinks it is an invalid entry.

The country code & prefix combined is used as a rule identifier in the app.

When a CSV file is imported, the app checks for duplicate in rule identifiers. When a text line has the same identifier as a previous line, the early rule will be over-written by the newer rule.

Exact number

The exact number field specifies whether the prefix be taken as an exact number. It can be:

• true
• false

If the field is left blank, the app takes it as a "false" entry.