Many shell programs can be controlled entirely with arguments and piping data in. Let's say you are trying to do something in Python which a program will already do for you; it would be great if there was an easy way to face off the shell.
subprocess can be used for this. Below is an example which uses echo to generate output on stdout which is then used as stdin for cat.
import subprocess echoproc = subprocess.Popen(['echo', 'echo is sending this text to stdout'], \ stdout=subprocess.PIPE) catproc = subprocess.Popen(['cat'], \ stdin=echoproc.stdout, \ stdout=subprocess.PIPE, \ stderr=subprocess.PIPE) stdout, stderr = catproc.communicate() print(b"stdout: " + stdout) print(b"stderr: " + stderr)
Note that stdout and stderr are a
bytes type (rather than