Name of the errorfile for the :make command (see :make_makeprg) and the :grep command. When it is empty, an internally generated temp file will be used. When "##" is included, it is replaced by a number to make the name unique. This makes sure that the ":make" command doesn't overwrite an existing file. NOT used for the ":cf" command. See 'errorfile' for that. Environment variables are expanded :set_env. See option-backslash about including spaces and backslashes. This option cannot be set from a modeline or in the sandbox, for security reasons.

(default: "")

not available when compiled without the +quickfix feature