Incoming command-line arguments are expanded using a template pattern. Workloads often have a common form and only a small part of the shell command need be different.

Braces, {}, are used in all cases. Empty braces will substitute the full incoming argument line. Use one of the below patterns as a shorthand notation for many common scenarios.

The -t/--template argument is used by the client command to expand templates just prior to execution. The cluster command simply forwards this argument to all clients.

In some situations it may be useful to expand a template with the submit command. These are expanded prior to scheduling as the actual args for the task.

Filepath Operations#

Shell commands often operate on filepaths. In such cases, it may be useful to manipulate these paths. Instead of using a shell interpolation (see below), use one of the available shorthand notations listed here.


Expand to immediate parent directory of given file. E.g., /some/path/to/file.h5 translates to /some/path/to.


Expand to second parent directory of given file. E.g., /some/path/to/file.h5 translates to /some/path.


The basename of the given file. E.g., /some/path/to/file.h5 translates to file.h5.


The basename of the given file without its file type extension. E.g., /some/path/to/file.h5 translates to file.


The full path of the given file without the extension. This is useful for targeting adjacent files with a different extension. E.g., /some/path/to/file.h5 translates to /some/path/to/file.


The file type extension for the given file. E.g., /some/path/to/file.h5 translates to .h5.


The file type extension for the given file without the leading dot. E.g., /some/path/to/file.h5 translates to h5.

Argument Slicing#

Command-line inputs are understood as individual arguments delimited by whitespace. Slice into the argument vector using the {[]} notation. Arguments follow zero-based indexing. Negative index values are counting backwards from the end.

Select with a singular value.


The first argument.


The second argument.


The last argument.

Select a range with a start and stop value, non-inclusive of the stop value. Including a leading or trailing colon implies the default value (inclusive).


The second and third argument.


The first four arguments.


The last two arguments.

Include a third value as a step (or sometimes referred to as stride). Leaving out the start and step value implies starting from the first element (inclusive).


Every second argument starting from the first.


Every odd argument.

Slicing notation

This notation with a start, stop, and step value is identical to Python-style slicing syntax.

Shell Expansion#

General purpose shell commands can be expanded with the {% %} notation. The incoming command-line args can be substituted with an @.

{% basename @ %}

Equivalent to {/}.

{% mktemp -d %}

Create temporary directory and insert its path.

Lambda Expressions#

Arbitrary Python expressions can be expanded with the {= =} notation. The input argument can be used within the expression with the variable x.

Exposed standard library modules include os, os.path as path, math and datetime as dt.

Incoming arguments are intelligently coerced into the expected type. E.g., 2 will be an integer, 4.67 a float, null and none will be a Python None, and true/false will be the appropriate boolean value.

{= x * math.pi =}

Multiply the incoming argument (expected to be a float) by Pi.

{= dt.datetime.fromtimestamp(x) =}

Convert incoming POSIX timestamp to ISO format.