It is frequently useful to post-process the fields in some way. Padding, limiting, cutting off parts and suppressing certain values can be achieved by using tilde modifiers. A typical tilde spec might look like ‘%~(cut 3)~(ignore "0")y’.
These are the valid modifiers:
Here's an example:
Let's take an example. The ‘%o’ spec in the summary mode lines will return a date in compact ISO8601 format—‘19960809T230410’. This is quite a mouthful, so we want to shave off the century number and the time, leaving us with a six-character date. That would be ‘%~(cut-left 2)~(max-right 6)~(pad 6)o’. (Cutting is done before maxing, and we need the padding to ensure that the date is never less than 6 characters to make it look nice in columns.)
Ignoring is done first; then cutting; then maxing; and then as the very last operation, padding.