This is an example for how to use Perl's IPC::Open3 to create a child process & interact with its stdout/stdin/stderr & get the return code when it exits.
The standard documentation is rather thin, and there aren't many good examples published.
See the code for details (that's the point of an example, right?) but a few points:
- unbuffered input seems necessary if you want to write to child's stdin in response to child output: the program could be simplified for some use cases (i.e. normal Perl I/O operators used) otherwise
- you must somehow decide when your blocks of input end: this could be via delimiter (e.g. newline in this example) or timeout
- if you don't need to send input to the child, you can just close the child stdin handle at the start
- catching SIGCHILD gives you the opportunity to throw an error if interrupted (you can lose input otherwise)
- handling interruption properly is hard (maybe impossible?) - this example doesn't do this