Using the built-in FileIO Tasks

FireWorks comes with several built-in tasks for performing file I/O (writing, moving, and deleting files).


The FileWriteTask is a simple way to write files (a more powerful version based on templating is the TemplateWriterTask).

Required parameters

  • files_to_write: ([{filename:(str), contents:(str)}]) - this is a list of dictionaries. each dictionary must have a filename (string) and contents (str). The contents are written to the corresponding filename.

Optional parameters

  • dest: (str) - the directory in which to write all the files (default is current working directory)


The FileDeleteTask lets you delete one or more files.

Required parameters

  • files_to_delete: ([(str)]) - a list of Strings corresponding to the filenames to delete

Optional parameters

  • dest: (str) - the directory in which to delete all the files (default is current working directory)


The FileTransferTask is a built-in FireTask for moving and copying files, perhaps to a remote server. Its usage is straightforward:

  • a files key that contains a list of files to move or copy
  • additional options control how directory names are interpreted, how to perform the move/copy, and what to do in case of errors

An example of a Firework that copies two files, file1.txt and file2.txt, to the home directory looks as follows:

  - _fw_name: FileTransferTask
    - src: file1.txt
      dest: ~/file1.txt
    - src: file2.txt
      dest: ~/file2.txt
    mode: copy

In Python code, the same task would be defined as:

firetask1 = FileTransferTask({'files': [{'src': 'file1.txt', 'dest': '~/file1.txt'}, {'src': 'file2.txt', 'dest': '~/file2.txt'}], 'mode': 'copy'})

The files parameter must be specified, and is an array of dictionaries with src and dest keys. The default mode of operation is to move files from the source to destination; by changing the mode to copy, we will copy the files instead. Note that you can put as many files (or directories) in the files list as you want; the same mode will be applied to all of them. If you want to move some files and copy others, you’d need to include two different ``FileTransferTask``s in your Firework.

A more compact representation for File Transfers can be given if several files are being moved/copied to the same directory:

  - _fw_name: FileTransferTask
    dest: dest_dir
    - file1.txt
    - file2.txt
    mode: copy

In Python code, this representation would be defined as:

firetask1 = FileTransferTask({'files': ['file1.txt', 'file2.txt'], 'dest':'dest_dir', 'mode': 'copy'})

An example of the FileTransferTask in action is given in the FireTask tutorial.

FileTransferTask Options

Below are the various options that can be set for the FileTransferTask.


The potential values are:

  • move - move a file or directory
  • copy - copy a file/dir (including permissions) but do not include metadata
  • copy2 - copy a file/dir (including permissions); also include metadata
  • copytree - recursively copy an entire directory copy
  • copyfile - copy the contents of a file into another file (no metadata)
  • rtransfer - do a remote transfer (this is covered later in this doc)


With the exception of rtransfer, FileTransferTask is using Python’s shutil module to do the move/copy. You can read more about these modes in `Python’s *shutil* docs <`_.


Either True or False (default=*False*). If True, a failed move/copy will just cause FileTransferTask to move to the next file in the files list. If False, a failed move/copy will raise an error.


Either True or False (default=*True*). If False, the src and dest of files are taken literally. If True, the src and dest interpret environment variables and shortcuts like ~ and .


In remote transfer mode, some shortcuts like . and ~ are not interpreted for the destination. However, environment variables will still be interpreted if shell_interpret is True.

Remote Transfers

Remote transfers are handled via SFTP using the paramiko Python library (make sure you’ve installed it via pip install paramiko). To do a remote transfer, you set files as before but:

  • You’ll first need to configure passwordless login via ssh between the two machines that are transferring files
  • Set the mode of transfer to rtransfer (see previous section)
  • You must set an additional option called server to the remote server hostname or IP
  • Make sure the dest doesn’t contain symbols that can’t properly be interpreted on the local machine, like ~ or .
  • If you are using a non-standard keyfile location (e.g., not something like ~/.ssh/, you need to set the key_filename option to the location of your key filename.

If all this is configured properly, you should be able to transfer files to a remote machine via FileTransferTask. Some potential hiccups:

  • You require a password to SSH between machines and haven’t configured passwordless SSH.
  • You are using a non-standard SSH port
  • Your known_hosts file is not located in ~/.ssh/known_hosts

The _use_global_spec option

By default, the parameters for the FileTransferTask should be defined within the _task section of the spec corresponding to the FileTransferTask, not as a root key of the spec. If you’d like to instead specify the parameters in the root of the spec, you can set _use_global_spec to True within the _task section. Note that _use_global_spec can simplify querying and communication of parameters between FireWorks but can cause problems if you have multiple FileTransferTasks within the same Firework.


The CompressDir task allows you to compress each file in the current directory (e.g., via gzip).

Required parameters


Optional parameters

  • compression: (str) - choose between “gz” (default) and “bz2” compression modes
  • dest: (str) - destination location
  • ignore_errors: (bool) - whether to ignore errors


The ArchiveDir task allows you to archive the current working directory into a single file.

Required parameters

  • base_name: (str) the full file path of the output archive file
  • format: (str) “zip”, “tar”, “bztar” or “gztar”

Optional parameters

  • format: (str) - choose between “zip”, “tar”, “bztar” or “gztar” (default).