Expand wildcards and the following special keywords in {expr}. 'wildignorecase' applies. If {list} is given and it is |TRUE|, a List will be returned. Otherwise the result is a String and when there are several matches, they are separated by characters. [Note: in version 5.0 a space was used, which caused problems when a file name contains a space] If the expansion fails, the result is an empty string. A name for a non-existing file is not included, unless {expr} does not start with '%', '#' or '<', see below. When {expr} starts with '%', '#' or '<', the expansion is done like for the |cmdline-special| variables with their associated modifiers. Here is a short overview: % current file name # alternate file name #n alternate file name n file name under the cursor autocmd file name autocmd buffer number (as a String!) autocmd matched name C expression under the cursor sourced script file or function name sourced script line number or function line number script file line number, also when in a function "123_" where "123" is the current script ID || call stack word under the cursor WORD under the cursor the {clientid} of the last received message |server2client()| Modifiers: :p expand to full path :h head (last path component removed) :t tail (last path component only) :r root (one extension removed) :e extension only Example: :let &tags = expand("%:p:h") . "/tags" Note that when expanding a string that starts with '%', '#' or '<', any following text is ignored. This does NOT work: :let doesntwork = expand("%:h.bak") Use this: :let doeswork = expand("%:h") . ".bak" Also note that expanding "" and others only returns the referenced file name without further expansion. If "" is "/.cshrc", you need to do another expand() to have the "/" expanded into the path of the home directory: :echo expand(expand("")) There cannot be white space between the variables and the following modifier. The |fnamemodify()| function can be used to modify normal file names. When using '%' or '#', and the current or alternate file name is not defined, an empty string is used. Using "%:p" in a buffer with no name, results in the current directory, with a '/' added. When {expr} does not start with '%', '#' or '<', it is expanded like a file name is expanded on the command line. 'suffixes' and 'wildignore' are used, unless the optional {nosuf} argument is given and it is |TRUE|. Names for non-existing files are included. The "" item can be used to search in a directory tree. For example, to find all "README" files in the current directory and below: :echo expand(" /README") expand() can also be used to expand variables and environment variables that are only known in a shell. But this can be slow, because a shell may be used to do the expansion. See |expr-env-expand|. The expanded variable is still handled like a list of file names. When an environment variable cannot be expanded, it is left unchanged. Thus ":echo expand('$FOOBAR')" results in "$FOOBAR". See |glob()| for finding existing files. See |system()| for getting the raw output of an external command. Can also be used as a |method|: Getpattern()->expand()