Running flows with flowrcli

In order to run a flow, it must first be compiled. Then a "flow runner" such as flowrcli can be used to run the compiled flow manifest).

Flow runners in general and flowrcli run the compiled flow manifest (by default named manifest.json).

In order to compile a flow definition down to a flow manifest that can be run, you use flowc as usual, with the addition of the -c, --compile option. This compiles the flow but does not invoke flowrcli to run it.

Then flowrcli as described below can be used to run the compiled flow.

This section describes command line arguments that can be supplied to flowrcli and what they are useful for.

Getting help for flowrcli

Use -h, --help (e.g. flowc -h or cargo run -p flowc -- -h) to print out help for the usage of flowc.

This will print something like this:

Usage: flowr [OPTIONS] [flow-manifest] [flow_args]...

  [flow-manifest]  the file path of the 'flow' manifest file
  [flow_args]...   A list of arguments to pass to the flow.

  -d, --debugger                     Enable the debugger when running a flow
  -m, --metrics                      Calculate metrics during flow execution and print them out when done
  -n, --native                       Link with native (not WASM) version of flowstdlib
  -s, --server                       Launch flowr with a coordinator only, no client
  -c, --client <port>                Launch flowr with a client only, no coordinator, to connect to a flowr coordinator
  -C, --context                      Execute only 'context' (not general) jobs in the coordinator
  -j, --jobs <MAX_JOBS>              Set maximum number of jobs that can be running in parallel)
  -L, --libdir <LIB_DIR|BASE_URL>    Add a directory or base Url to the Library Search path
  -t, --threads <THREADS>            Set number of threads to use to execute jobs (min: 1, default: cores available)
  -v, --verbosity <VERBOSITY_LEVEL>  Set verbosity level for output (trace, debug, info, warn, default: error)
  -h, --help                         Print help information
  -V, --version                      Print version information

Similarly to flowc, in order to locate libraries used in flow execution, flowrcli needs to know where to locate them. As for flowc, you can rely on the default ($HOME/.flow/lib), modified using the $FLOW_LIB_PATH environment variable, or using one or more instance of the -L, --libdir <LIB_DIR|BASE_URL> option.


After the Options you can supply an optional field for where to load the root flow from. This can be a relative or absolute path when no Url scheme is used, an absolute path if the file:// scheme is used or a web resources if either the http or https scheme is used.

  • If no argument is supplied, it assumes the current directory as the argument, and continues as below
  • If it's a directory then it attempts to load "root.toml" from within the directory
  • If it's a file then it attempts to load the root flow from that file


Any arguments after flow-manifest are assumed to be arguments for the flow itself. When it starts executing it can retrieve the value of these parameters using context functions.

Example Invocations

For each of these examples, there is first a flowc line showing how the flow can be compiled. This will leave a compiled manifest.json flow manifest alongside the flow's root definition file. That manifest is then run using flowrcli

  • flowc -C flowr/src/bin/flowrcli -c flowr/examples/fibonacci - compile the fibonacci example only
  • flowrcli flowr/examples/fibonacci - run the pre-compiled fibonacci example flow manifest
    • You should get a fibonacci series output to the terminal,
  • flowc -C flowr/src/bin/flowrcli -c flowr/examples/sequence - compile the flow only, do not run it
  • flowrcli flowr/examples/sequence 10 - run the compiled flow, a short sequence of numbers (2, 5, 8) and a string will be printed. The "10" represents the maximum of the sequence.
  • flowrcli flowr/examples/sequence/manifest.json 10 - run the compiled flow, specifying the full path to the manifest.json file


Similar to flowrcli that interacts with the terminal and the file system for IO, flowrgui is another runner for flows, but with a Graphical User Interface (GUI). It displays STDIO and STDERR on the UI, shows images written to visually and tracks writes to files during execution.

Most (but not all) of the same command line options as flowrcli are supported, and help can be see using:

flowrgui --help