kill-region is the usual subroutine for killing text. Any
command that calls this function is a kill command (and should
probably have ‘kill’ in its name). kill-region puts the
newly killed text in a new element at the beginning of the kill ring or
adds it to the most recent element. It determines automatically (using
last-command) whether the previous command was a kill command,
and if so appends the killed text to the most recent entry.
The commands described below can filter the killed text before they
save it in the kill ring. They call filter-buffer-substring
(see Examining Buffer Contents) to perform the filtering. By default,
there’s no filtering, but major and minor modes and hook functions can
set up filtering, so that text saved in the kill ring is different
from what was in the buffer.
This function kills the stretch of text between start and
end; but if the optional argument region is
non-nil, it ignores start and end, and kills the
text in the current region instead. The text is deleted but saved in
the kill ring, along with its text properties. The value is always
nil.
In an interactive call, start and end are point and
the mark, and region is always non-nil, so the command
always kills the text in the current region.
If the buffer or text is read-only, kill-region modifies the kill
ring just the same, then signals an error without modifying the buffer.
This is convenient because it lets the user use a series of kill
commands to copy text from a read-only buffer into the kill ring.
If this option is non-nil, kill-region does not signal an
error if the buffer or text is read-only. Instead, it simply returns,
updating the kill ring but not changing the buffer.
This function saves the stretch of text between start and
end on the kill ring (including text properties), but does not
delete the text from the buffer. However, if the optional argument
region is non-nil, the function ignores start and
end, and saves the current region instead. It always returns
nil.
In an interactive call, start and end are point and
the mark, and region is always non-nil, so the command
always saves the text in the current region.
The command does not set this-command to kill-region, so a
subsequent kill command does not append to the same kill ring entry.