Like communicate, but validates the output of the process as UTF-8, and returns it as a regular NUL terminated string.
On error, stdout_buf and stderr_buf will be set to undefined values and should not be used.
| this | |
| stdin_buf |
data to send to the stdin of the subprocess, or null |
| cancellable | |
| stdout_buf |
data read from the subprocess stdout |
| stderr_buf |
data read from the subprocess stderr |