Shell commands

Running a shell command

There are two ways to specify the command you want to run: either with a string or a list of arguments. The two following lines are equivalent:

shell.call('cat /etc/passwd')
shell.call(('cat', '/etc/passwd'))

If you want to use bash-specific constructs such as file redirections or other, you should use the string argument:

shell.call('cat /etc/passwd > /tmp/other') # works
shell.call(('cat', '/etc/passwd', '>', '/tmp/other')) # does not

Use shell.call(), as described in the previous section.

Use shell.stdout or shell.stderr files to get the output:

p = shell.call("cat /etc/passwd")
contents = p.stdout.read()

If you want to start a command and keep interacting with it, or simply let it run in the background, use shell.run_background():

# Start a program
p = shell.background('/bin/slow-program arg0 arg1')

# Do some other stuff ...
...

# Wait for the program to end
p.wait()

Run a program and gets its output as a string:

stdout, stderr = shell.get_output('cat /etc/passwd')

or as bytes:

stdout, stderr = shell.get_output('cat /etc/passwd', text=False)

Both call() and background() return a Popen instance.