— Function: file-name-all-completions partial-filename directory

This function returns a list of all possible completions for files whose name starts with partial-filename in directory directory. The order of the completions is the order of the files in the directory, which is unpredictable and conveys no useful information.

The argument partial-filename must be a file name containing no directory part and no slash. The current buffer's default directory is prepended to directory, if directory is not absolute.

File names which end with any member of completion-ignored-extensions are not considered as possible completions for partial-filename unless there is no other possible completion. completion-ignored-extensions is not applied to the names of directories.

In the following example, suppose that the current default directory, ~rms/lewis, has five files whose names begin with ‘f’: foo, file~, file.c, file.c.~1~, and file.c.~2~.

          (file-name-all-completions "f" "")
               ⇒ ("foo" "file~" "file.c.~2~"
                          "file.c.~1~" "file.c")
          
          (file-name-all-completions "fo" "")
               ⇒ ("foo")

— Function: file-name-completion partial-filename directory

This function completes the file name partial-filename in directory directory. It returns the longest prefix common to all file names in directory directory that start with partial-filename.

If only one match exists and partial-filename matches it exactly, the function returns t. The function returns nil if directory directory contains no name starting with partial-filename.

File names which end with any member of completion-ignored-extensions are not considered as possible completions for partial-filename unless there is no other possible completion. completion-ignored-extensions is not applied to the names of directories.

In the following example, suppose that the current default directory has five files whose names begin with ‘f’: foo, file~, file.c, file.c.~1~, and file.c.~2~.

          (file-name-completion "fi" "")
               ⇒ "file"
          
          (file-name-completion "file.c.~1" "")
               ⇒ "file.c.~1~"
          
          (file-name-completion "file.c.~1~" "")
               ⇒ t
          
          (file-name-completion "file.c.~3" "")
               ⇒ nil

— User Option: completion-ignored-extensions

file-name-completion usually ignores file names that end in any string in this list. It does not ignore them when all the possible completions end in one of these suffixes or when a buffer showing all possible completions is displayed.

A typical value might look like this:

          completion-ignored-extensions
               ⇒ (".o" ".elc" "~" ".dvi")