Start the system shell process:

Write a command into the system shell process:

Read the command output:

Check whether the process is running or not:

Write an exit command into the shell process:

Verify the program has actually finished:

The right way to call StartProcess for a program plus its arguments is using a list:

Calling StartProcess with the command and arguments in a single string is not allowed:

Also, calling StartProcess with the program arguments as arguments for StartProcess is not allowed:

Special symbols like ~ and * are not converted using shell expansion, because StartProcess skips the shell:

Shell commands like dir, echo cannot be called directly on Windows because they are not binaries (however, they work on Unix systems because they are Unix binaries):

Some commands might need to be called using absolute paths:

Create an interactive console in the Wolfram Language. To test this example, first evaluate the cells. Then type any valid shell command in the input box and click the Go button:

Start a new WolframKernel process for parallel computation:

Make the kernel process do a long computation and quit:

Read the process output whenever it finishes:

Read any messages sent to the error stream: