Read-Only Buffers
=================
If a buffer is "read-only", then you cannot change its contents,
although you may change your view of the contents by scrolling and
narrowing.
Read-only buffers are used in two kinds of situations:
* A buffer visiting a write-protected file is normally read-only.
Here, the purpose is to inform the user that editing the buffer
with the aim of saving it in the file may be futile or
undesirable. The user who wants to change the buffer text despite
this can do so after clearing the read-only flag with `C-x C-q'.
* Modes such as Dired and Rmail make buffers read-only when altering
the contents with the usual editing commands would probably be a
mistake.
The special commands of these modes bind `buffer-read-only' to
`nil' (with `let') or bind `inhibit-read-only' to `t' around the
places where they themselves change the text.
- Variable: buffer-read-only
This buffer-local variable specifies whether the buffer is
read-only. The buffer is read-only if this variable is non-`nil'.
- Variable: inhibit-read-only
If this variable is non-`nil', then read-only buffers and read-only
characters may be modified. Read-only characters in a buffer are
those that have non-`nil' `read-only' properties (either text
properties or overlay properties). Note:Special Properties,
for more information about text properties. Note:Overlays, for
more information about overlays and their properties.
If `inhibit-read-only' is `t', all `read-only' character
properties have no effect. If `inhibit-read-only' is a list, then
`read-only' character properties have no effect if they are members
of the list (comparison is done with `eq').
- Command: toggle-read-only
This command changes whether the current buffer is read-only. It
is intended for interactive use; do not use it in programs. At
any given point in a program, you should know whether you want the
read-only flag on or off; so you can set `buffer-read-only'
explicitly to the proper value, `t' or `nil'.
- Function: barf-if-buffer-read-only
This function signals a `buffer-read-only' error if the current
buffer is read-only. Note:Interactive Call, for another way to
signal an error if the current buffer is read-only.