When on, use temp files for shell commands. When off use a pipe. When using a pipe is not possible temp files are used anyway. Currently a pipe is only supported on Unix and MS-Windows 2K and later. You can check it with: > :if has("filterpipe") < The advantage of using a pipe is that nobody can read the temp file and the 'shell' command does not need to support redirection. The advantage of using a temp file is that the file type and encoding can be detected. The |FilterReadPre|, |FilterReadPost| and |FilterWritePre|, |FilterWritePost| autocommands event are not triggered when 'shelltemp' is off. The system() function does not respect this option and always uses temp files. NOTE: This option is set to the Vim default value when 'compatible' is reset.