It is possible to have whitespace between the -e command line option and its parameter.
Note that the groff program supports a GROFF_ENCODING environment variable which is eventually expanded to option -k.
Note that U+FEFF not at the start of the input data actually is emitted; it has then the meaning of a `zero width no-break space' character - something not needed normally in groff.
For these reasons, preconv supports the coding tag convention (with some restrictions) as used by GNU Emacs and XEmacs (and probably other programs too).
Coding tags in GNU Emacs and XEmacs are stored in so-called File Variables. preconv recognizes the following syntax form which must be put into a troff comment in the first or second line.
-*- tag1: value1; tag2: value2; ... -*-
The only relevant tag for preconv is `coding' which can take the values listed below. Here an example line which tells Emacs to edit a file in troff mode, and to use latin2 as its encoding.
.\" -*- mode: troff; coding: latin-2 -*-
The following list gives all MIME coding tags (either lowercase or uppercase) supported by preconv; this list is hard-coded in the source.
big5, cp1047, euc-jp, euc-kr, gb2312, iso-8859-1, iso-8859-2, iso-8859-5, iso-8859-7, iso-8859-9, iso-8859-13, iso-8859-15, koi8-r, us-ascii, utf-8, utf-16, utf-16be, utf-16le
In addition, the following hard-coded list of other tags is recognized which eventually map to values from the list above.
ascii, chinese-big5, chinese-euc, chinese-iso-8bit, cn-big5, cn-gb, cn-gb-2312, cp878, csascii, csisolatin1, cyrillic-iso-8bit, cyrillic-koi8, euc-china, euc-cn, euc-japan, euc-japan-1990, euc-korea, greek-iso-8bit, iso-10646/utf8, iso-10646/utf-8, iso-latin-1, iso-latin-2, iso-latin-5, iso-latin-7, iso-latin-9, japanese-euc, japanese-iso-8bit, jis8, koi8, korean-euc, korean-iso-8bit, latin-0, latin1, latin-1, latin-2, latin-5, latin-7, latin-9, mule-utf-8, mule-utf-16, mule-utf-16be, mule-utf-16-be, mule-utf-16be-with-signature, mule-utf-16le, mule-utf-16-le, mule-utf-16le-with-signature, utf8, utf-16-be, utf-16-be-with-signature, utf-16be-with-signature, utf-16-le, utf-16-le-with-signature, utf-16le-with-signature
Those tags are taken from GNU Emacs and XEmacs, together with some aliases. Trailing `-dos', `-unix', and `-mac' suffixes of coding tags (which give the end-of-line convention used in the file) are stripped off before the comparison with the above tags happens.