2.2. Command Line Tool#

A command-line tool is a type of Process object that can be run by itself or as a Workflow step. It is a wrapper for a command like ls, echo, tar, etc. The command-line tool is defined in the baseCommand attribute of the command-line tool CWL document.

A CWL command-line tool must also have inputs and outputs. The following example contains a minimal example of a CWL command-line tool for the echo Linux command, using inputs and outputs.

digraph G { compound=true; rankdir="LR"; fontname="Verdana"; fontsize="10"; graph [splines=ortho]; node [fontname="Verdana", fontsize="10", shape=box]; edge [fontname="Verdana", fontsize="10"]; subgraph cluster_0 { command[style="filled" label=<<FONT FACE='sans-serif;'>echo</FONT>>]; label="baseCommand"; fill=gray; } inputs -> command [lhead=cluster_0]; command -> outputs [ltail=cluster_0]; }

CWL command-line tool.#

cwlVersion: v1.2
class: CommandLineTool

baseCommand: echo

stdout: output.txt

    type: string
    inputBinding: {}
    type: string
      glob: output.txt
      loadContents: true
      outputEval: $(self[0].contents)


The example above uses a simplified form to define inputs and outputs. You will learn more about in the Inputs and in the Outputs sections.