select-safe-coding-systemfrom to &optional default-coding-system accept-default-p file
This function selects a coding system for encoding specified text, asking the user to choose if necessary. Normally the specified text is the text in the current buffer between from and to. If from is a string, the string specifies the text to encode, and to is ignored.
If the specified text includes raw bytes (see Text Representations),
raw-text for its encoding.
If default-coding-system is non-
nil, that is the first
coding system to try; if that can handle the text,
select-safe-coding-system returns that coding system. It can
also be a list of coding systems; then the function tries each of them
one by one. After trying all of them, it next tries the current
buffer’s value of buffer-file-coding-system (if it is not
undecided), then the default value of
buffer-file-coding-system and finally the user’s most
preferred coding system, which the user can set using the command
prefer-coding-system (see Recognizing
Coding Systems in The GNU Emacs Manual).
If one of those coding systems can safely encode all the specified
select-safe-coding-system chooses it and returns it.
Otherwise, it asks the user to choose from a list of coding systems
which can encode all the text, and returns the user’s choice.
default-coding-system can also be a list whose first element is
t and whose other elements are coding systems. Then, if no coding
system in the list can handle the text,
queries the user immediately, without trying any of the three
alternatives described above.
The optional argument accept-default-p, if non-
should be a function to determine whether a coding system selected
without user interaction is acceptable.
calls this function with one argument, the base coding system of the
selected coding system. If accept-default-p returns
select-safe-coding-system rejects the silently selected coding
system, and asks the user to select a coding system from a list of
If the variable select-safe-coding-system-accept-default-p is
nil, it should be a function taking a single argument.
It is used in place of accept-default-p, overriding any
value supplied for this argument.
As a final step, before returning the chosen coding system,
select-safe-coding-system checks whether that coding system is
consistent with what would be selected if the contents of the region
were read from a file. (If not, this could lead to data corruption in
a file subsequently re-visited and edited.) Normally,
buffer-file-name as the
file for this purpose, but if file is non-
nil, it uses
that file instead (this can be relevant for
similar functions). If it detects an apparent inconsistency,
select-safe-coding-system queries the user before selecting the
Here are two functions you can use to let the user specify a coding system, with completion. See Completion.
read-coding-systemprompt &optional default
This function reads a coding system using the minibuffer, prompting with string prompt, and returns the coding system name as a symbol. If the user enters null input, default specifies which coding system to return. It should be a symbol or a string.
This function reads a coding system using the minibuffer, prompting with string prompt, and returns the coding system name as a symbol. If the user tries to enter null input, it asks the user to try again. See Coding Systems.