File Encodings in Vim

    By default, You need to guide Vim to decode double-byte encodings like GBK and Big5. The default Vim configuration only works well with Unicode encodings including utf-8, utf-16, utf-16be etc..Edit your .vimrc file, add line like:

set fileencodings=ucs-bom,utf-8,gbk,big5,latin1

    Now Vim is able to detect and decode GBK and Big5 encodings automatically. And according my experience, Vim respects utf-16 and utf-16be files only they have BOM byes. Otherwise, these files are wrongly decoded. In this case, you may want to manually reopen the file using a correct encoding. The Vim command like:

:e ++enc=<your_encoding>

    And Vim does not store BOM when saving by default. To enable/disable BOM saving, use:

:set bomb
:set nobomb

    I've attached a series of text files to learn the usage. These text file all contains string "123你好", but saved in different encodings. Let's list their code points first:

	1	2	3	你	好
GBK	0x31	0x32	0x33	0xc4e3	0xbac3
Big5	0x31	0x32	0x33	0xa741	0xa66e
Unicode	0x31	0x32	0x33	0x4f60	0x597d
UTF-8 encoded	0x31	0x32	0x33	0xe4bda0	0xe5a5bd

    And our hexdump's here, note the byte order:

# hexdump -C test_gbk.txt
00000000  31 32 33 c4 e3 ba c3                              |123....|
00000007
# hexdump -C test_big5.txt
00000000  31 32 33 a7 41 a6 6e                              |123.A.n|
00000007
# hexdump -C test_ucs2be.txt
00000000  00 31 00 32 00 33 4f 60  59 7d                    |.1.2.3O`Y}|
0000000a
# hexdump -C test_ucs2be_bom.txt
00000000  fe ff 00 31 00 32 00 33  4f 60 59 7d              |...1.2.3O`Y}|
0000000c
# hexdump -C test_ucs2le.txt
00000000  31 00 32 00 33 00 60 4f  7d 59                    |1.2.3.`O}Y|
0000000a
# hexdump -C test_ucs2le_bom.txt
00000000  ff fe 31 00 32 00 33 00  60 4f 7d 59              |..1.2.3.`O}Y|
0000000c
# hexdump -C test_utf8.txt
00000000  31 32 33 e4 bd a0 e5 a5  bd                       |123......|
00000009
# hexdump -C test_utf8_bom.txt
00000000  ef bb bf 31 32 33 e4 bd  a0 e5 a5 bd              |...123......|
0000000c

    My test text files are here. More info:

:help encoding
:help fileencoding
:help fileencodings
:help encoding-names
:help bomb