Running Flows

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.

For convenience, flowc, the flow compiler, compiles the flow, then uses flowrcli to run it for you (unless you specify otherwise). So that is the easiest way to run a flow and is used below.

If you have run make or make install_flow then you will have flowc and flowrcli installed on your system. Be sure they are in your $PATH so that can be invoked directly.

Then you can run flows easily using flowc.

If you do not wish to install flowc then you can run it using cargo from the root of the project directory by substituting cargo run -p flowc -- for flowcin the examples below.

User's terminal Current Working Directory should be the root directory of the flow project

Compiling flowstdlib if you have used cargo install to install flowstdlib

If you have not compiled the project from source using make, then it's probable that flowstdlib has not been compiled to WASM. However, there should be a flowstdlib binary on your system. This should be run, passing it the path to the flowstdlib source folder (the root, not src inside it) in order to compile it.

This will take considerable time, and leave the compiled WASM files in $HOME/.flow/flib/flowstdlib

Finding Libraries

In order for flowc and flowrcli to be able to find library functions, the (default) directory where the flowstdlib is built by default ($HOME/.flow/lib) is searched

Directories to add to the library search path to help find libraries used can be passed to flowc via one or more instances of the -L, --libdir <LIB_DIR|BASE_URL> Option (see below for an example).

Full List of flowc Options

See the next section flowc for a description of the command line arguments it accepts.

Example Invocations

  • flowc -C flowr/src/bin/flowrcli flowr/examples/fibonacci

    uses the context_functions provided by flowrcli and run the flow whose root flow is defined in ./flowr/examples/fibonacci/root.toml. Do not pass in any arguments to the flow.

    • You should get a fibonacci series output to the terminal,

  • echo "Hello" | flowc -C flowr/src/bin/flowrcli flowr/examples/reverse-echo - This example reads from STDIN so we echo in some text.

    • You may see some output like:

      Testing /Users/andrew/workspace/flow/flowr/examples/reverse-echo/reverse/Cargo.toml WASM Project Compiling /Users/andrew/workspace/flow/flowr/examples/reverse-echo/reverse/Cargo.toml WASM project

      the first time this example is run as the provided function is tested and compiled to WASM, followed by

      olleH

      which is the input string "Hello" reversed.

  • flowc -C flowr/src/bin/flowrcli flowr/examples/fibonacci - You should get a fibonacci series output to the terminal

  • flowc -C flowr/src/bin/flowrcli flowr/examples/sequence 10 - as previous examples except that after the source_url a flow_argument of "10" is passed in

    • A short sequence of numbers (2, 5, 8) and a string will be printed. The "10" represents the maximum of the sequence.

Running a flow from the web

As stated, the source_url can be a Url to a web resource, or a flow definition hosted on a web server.

Example running a flow from the web

We can use a flow that is part of the flow project, where the flow definition is hosted on the web by GitHub:

flowc -C flowr/src/bin/flowrcli "https://raw.githubusercontent.com/andrewdavidmackenzie/flow/master/flowcore/tests/test-flows/hello-world/root.toml"

That will pull the flow definition content from the web, compile it and run it, producing the expected output:

Hello World!