How to edit multi-gigabyte text files? Vim doesn't work =(

Ctrl-C will stop file load. If the file is small enough you may have been lucky to have loaded all the contents and just killed any post load steps. Verify that the whole file has been loaded when using this tip.

Vim can handle large files pretty well. I just edited a 3.4GB file, deleting lines, etc. Three things to keep in mind:

1. Press Ctrl-C: Vim tries to read in the whole file initially, to do things like syntax highlighting and number of lines in file, etc. Ctrl-C will cancel this enumeration (and the syntax highlighting), and it will only load what's needed to display on your screen.
2. Readonly: Vim will likely start read-only when the file is too big for it to make a . file copy to perform the edits on. I had to w! to save the file, and that's when it took the most time.
3. Go to line: Typing :115355 will take you directly to line 115355, which is much faster going in those large files. Vim seems to start scanning from the beginning every time it loads a buffer of lines, and holding down Ctrl-F to scan through the file seems to get really slow near the end of it.

Note - If your Vim instance is in readonly because you hit Ctrl-C, it is possible that Vim did not load the entire file into the buffer. If that happens, saving it will only save what is in the buffer, not the entire file. You might quickly check with a G to skip to the end to make sure all the lines in your file are there.

It may be plugins that are causing it to choke. (syntax highlighting, folds etc.)

You can run vim without plugins.

vim -u "NONE" hugefile.log

It's minimalist but it will at least give you the vi motions you are used to.

syntax off

is another obvious one. Prune your install down and source what you need. You'll find out what it's capable of and if you need to accomplish a task via other means.

If you are on *nix (and assuming you have to modify only parts of file (and rarely)), you may split the files (using the split command), edit them individually (using awk, sed, or something similar) and concatenate them after you are done.

cat file2 file3 >> file1