Prefix

For the common initial substring of a word list, see the prefix function:

$prefix(word list)

It compares words case-insensitively and returns the shared beginning using the first word's spelling. Missing input or no common beginning returns an empty string. It does not modify the input variables.

Examples:

Expression	Result
`$prefix(foobar foobaz)`	`fooba`
`$prefix(foobar foobaz foobooya)`	`foob`
`$prefix(one two three)`	Empty string

A completion script can filter candidate nicknames, apply prefix() to those candidates, and insert the result into the input line. The function itself does not install a completion binding or edit the input. See onchannel, pattern, and key bindings.

Quoted-word behavior depends on xdebug dword; long candidate lists and shared prefixes can require repeated comparisons. Consult the function page for result quoting and Unicode details.

For status-line prefixes instead, see the %{1}P field in status_format. It is unrelated to common-substring calculation.

Source references

source/functions.c: prefix registration and common-prefix calculation.
source/status.c: separate status-window prefix field.