'fileformat' ('ff' for short) controls the way that Vim handles different line-ending sequences. Vim recognizes three file formats: unix, dos, and mac. Each of these file formats differs in the line-ending character sequences used on disk. Unix uses a LF (line feed; ^J or 0x0A), Mac uses a CR (carriage return; ^M or 0x0D), and Dos uses CRLF (^M^J or 0x0D0A).
Assuming that the fileformat has been properly detected (see below), it is very simple to convert to a different format. Simply set 'ff' to the desired format name; for example, if you are editing a dos file and want to convert to unix, just do :set ff=unix. That's it. The next time the file is written, unix line ends will be used. Things are a little tougher when your file has different ending sequences on different lines; this situation is discussed below.
As absolon was kind enough to point out in #vim, you can do mass conversion from the shell like so:
vim +"argdo set ff=<format>" +wqa <files>
This will set 'fileformat' for each file in the argument list, then quit, saving all files.
See :help argdo and :help -c if you need more detail on what this does and why.
When reading a file, Vim tries to detect the proper fileformat. The way it does this is controlled by the 'fileformats' ('ffs') option. 'ffs' contains a comma separated list of the formats to try. Each platform has its own default value for 'ffs':
Basically, Vim tries to find a line-ending sequence which appears at the end of every line, and then uses that for 'ff'. This process can get fooled in two ways:
When 'ff' is not detected correctly, you will usually see part or all of the line ending sequences in the editor window. Here is a short illustration of what you see when a mismatch happens.
| File contents | Line 1 Line 2 |
|---|---|
| unix line-ends, ff=mac | Line 1^JLine 2^J |
| unix line-ends, ff=dos | Line 1 Line 2 |
| dos line-ends, ff=unix | Line 1^M Line 2^M |
| dos line-ends, ff=mac | Line 1 ^JLine 2 ^J |
| mac line-ends, ff=unix | Line 1^MLine 2^M |
| mac line-ends, ff=dos | Line 1^MLine 2^M |
If your file has consistent line endings throughout, but you have had a 'ff' detection problem, the best fix is to force Vim to use the correct format with the :e command:
:e ++ff=mac
If you have extra leading or trailing characters (^M in unix or ^J in mac), use :%s/\r// to remove them. If you have long lines (mac line-ends with ff=dos or unix, unix line ends with ff=mac), use :%s/\r/\r/g to replace the wrong line-ends with the correct line-ends. If you are curious, the reasoning behind this methodology appears below.
:substitute can be tricky when dealing with CR and NL. The problem stems from the fact that Vim uses NL in memory to represent a Nul character (see :help NL-used-for-Nul). The result of this is that unexpected things tend to happen when you try to modify line-endings using :s. Vim help says that \r matches CR and \n matches an end-of-line. In fact, when you use :s, \r will match CR or LF, depending on the fileformat! Basically, it matches whichever control character (^M or ^J) you see in the editor window. Furthermore, in the replace pattern, \n will expand to a LF, which then gets interpreted as... a Nul! (see :help sub-replace-special). Fortunately, when \r is used in the replace pattern, it is interpreted as a line-end, which will then display (and get written) as desired.
Article by Tofer. Questions? Comments? Contact me in #vim or send gmail to chagnon.
Thanks Tofer, great article! Here's a vim tip that implements the display of non-native fileformat in the statusline.
-- GrantBow
Excellent article. Forcing the file format (:e ++ff=mac) did the trick for me. I knew it was a mac-file, but ff=mac never seemed to change anything. I've been looking for this solution quite a while now ... Thanks-- cmasc