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32.8.2 Functions for Killing

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 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.

— Command: kill-region start end &optional region

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.

— User Option: kill-read-only-ok

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.

— Command: copy-region-as-kill start end &optional region

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.