9.3.4 Completion Options

When completing file names, certain file names are usually ignored. The variable completion-ignored-extensions contains a list of strings; a file name ending in any of those strings is ignored as a completion candidate. The standard value of this variable has several elements including ".o", ".elc", ".dvi" and "~". The effect is that, for example, ‘foo’ can complete to ‘foo.c’ even though ‘foo.o’ exists as well. However, if all the possible completions end in “ignored” strings, then they are not ignored. Displaying a list of possible completions disregards completion-ignored-extensions; it shows them all.

If an element of completion-ignored-extensions ends in a slash (‘/’), it's a subdirectory name; then that directory and its contents are ignored. Elements of completion-ignored-extensions which do not end in a slash are ordinary file names, and do not apply to names of directories.

If completion-auto-help is set to nil, the completion commands never display a list of possibilities; you must type ? to display the list.

Partial Completion mode implements a more powerful kind of completion that can complete multiple words in parallel. For example, it can complete the command name abbreviation p-b into print-buffer if no other command starts with two words whose initials are ‘p’ and ‘b’.

To enable this mode, use M-x partial-completion-mode, or customize the variable partial-completion-mode. This mode binds special partial completion commands to <TAB>, <SPC>, <RET>, and ? in the minibuffer. The usual completion commands are available on M-<TAB> (or C-M-i), M-<SPC>, M-<RET> and M-?.

Partial completion of directories in file names uses ‘*’ to indicate the places for completion; thus, ‘/u*/b*/f*’ might complete to ‘/usr/bin/foo’. For remote files, partial completion enables completion of methods, user names and host names. See section Remote Files.

Partial Completion mode also extends find-file so that ‘<include>’ looks for the file named include in the directories in the path PC-include-file-path. If you set PC-disable-includes to non-nil, this feature is disabled.

Icomplete mode presents a constantly-updated display that tells you what completions are available for the text you've entered so far. The command to enable or disable this minor mode is M-x icomplete-mode.