iconv: conversions from `en_US.utf8' and to `ru_RU.utf8' are not supported
could be improved, e.g.,
iconv: conversions from `en_US.utf8' and to `ru_RU.utf8' is pointless
iconv: conversions from `en_US.utf8' and to `ru_RU.utf8' will not modify your data
iconv translates character encoding. While it may recognize the name of a locale, there is a difference between encoding and locale:
- encoding lists all of the available character codes in a character set, with reference to the appearance of the characters (referred to as glyphs).
- locale tells how the characters in a given encoding are used, e.g., which are printable, which are not, which are used for special cases such as decimal separators. It also deals with things that are not related to character sets, such as the names for the days of the week.
Since both locales
ru_RS.utf8 use the same encoding,
iconv has nothing to do. Since it cannot guess what you might be trying to do, it tells you that the conversion is "not supported".
iconv does support is conversions between different encodings. For instance, in your list
do not use UTF-8 encoding. Those are used for character sets with fewer than 256 characters; UTF-8 is used for Unicode, with many more than 256 characters.
As for what is the correct command to use, that depends on what the actual encoding of your input file is (it might be UTF-8, it might be ISO-8859-1), and whether you want the output to be UTF-8 (no problem) or one of the other encodings (less likely, and involving some loss of information).