Adding data to a message with msgappend

This command adds data to the end of a message. It accepts a -cvtnull option such as msginsert.

For example:

Input: msgappend message5 ", for example"

Input: msgget message5
Output: some data, for example

Input: msgappend -cvtnull _ message5 ", with_a NULL"

Input: msgget message5
Output: some data, for example, with

Input: msgget -cvtnull X message5
Output: some data, for example, withXa NULL