elisp: The Region
30.8 The Region
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The text between point and the mark is known as “the region”. Various
functions operate on text delimited by point and the mark, but only
those functions specifically related to the region itself are described
here.
The next two functions signal an error if the mark does not point
anywhere. If Transient Mark mode is enabled and ‘mark-even-if-inactive’
is ‘nil’, they also signal an error if the mark is inactive.
-- Function: region-beginning
This function returns the position of the beginning of the region
(as an integer). This is the position of either point or the mark,
whichever is smaller.
-- Function: region-end
This function returns the position of the end of the region (as an
integer). This is the position of either point or the mark,
whichever is larger.
Instead of using ‘region-beginning’ and ‘region-end’, a command
designed to operate on a region should normally use ‘interactive’ with
the ‘r’ specification to find the beginning and end of the region. This
lets other Lisp programs specify the bounds explicitly as arguments.
Interactive Codes.
-- Function: use-region-p
This function returns ‘t’ if Transient Mark mode is enabled, the
mark is active, and there is a valid region in the buffer. This
function is intended to be used by commands that operate on the
region, instead of on text near point, when the mark is active.
A region is valid if it has a non-zero size, or if the user option
‘use-empty-active-region’ is non-‘nil’ (by default, it is ‘nil’).
The function ‘region-active-p’ is similar to ‘use-region-p’, but
considers all regions as valid. In most cases, you should not use
‘region-active-p’, since if the region is empty it is often more
appropriate to operate on point.
Info Catalog
elisp: The Mark
elisp: Markers