This command allows a file to be downloaded before the action begins. You do not need a matching continue if statement for the file to be downloaded and checked in advance. This command is preferred over the download command.

To easily create prefetch commands, the make-prefetch utility can be used.

Version Platforms
8.0.584.0 AIX, HP-UX, Mac, Red Hat, SUSE, Solaris, Windows
8.1.535.0 Debian, Ubuntu


prefetch <name> sha1:<sha1> size:<size> <url> [sha256:<sha256>]


  • name is the file name for the download.
  • sha1 is the SHA-1 of the file.
  • size is the size of the file in bytes.
  • url is the url of the file.
  • sha256 is an optional SHA-256 of the file.

The name must be a simple filename, without special characters or path delimiters. If the name violates any of the following rules, the download command will fail:

  • Name must be 32 characters or less.
  • Name must only be composed of ASCII characters a-z, A-Z, 0-9, -, _, and non-leading periods.


Prefetch a picture of Hodor.

prefetch hodor.jpg sha1:ce842e0af799f2ba476511c8fbfdc3bf89612dd0 size:57656 sha256:74f69205a016a3896290eae03627e15e8dfeba812a631b5e0afca140722a322b

Prefetch and run a different patch depending on whether the operating system is Windows XP.

if {name of operating system = "WinXP"}
prefetch patch.exe sha1:92c643875dda80022b3ce3f1ad580f62704b754f size:813160
prefetch patch.exe sha1:c964d4fd345b6e5fd73c2235ec75079b34e9b3d2 size:845416
wait __Download\patch.exe