I have a python script in which I need to invoke a shell command. The shell command can accept its input from either a file or stdin.
In my script, the input is stored in a variable. What is the proper way to invoke the command? If it matters, the shell command produces no output.
I know I could write the variable's content into a file and invoke the command with the file as argument but that seems inelegant. Surely, there's a better way.
Can someone tell me what it is? Thanks.
You can use the subprocess module.
import subprocess
process = subprocess.Popen(["Mycommand", "with", "arguments"], stdin=subprocess.PIPE)
process.communicate("My text")
communicate() is a one-off method. To do that repeatedly, I copied some code from its implementation that handled stdin in a separate thread.process.stdin.write, but as palvarez89 mentioned, that is not the preferred way. The OP mentioned trying to write the variable's content into a file and invoke the command with the file as argument. If it were a problem to use a one-off method, that would not have been suggested.Refer to How do I pass a string into subprocess.Popen (using the stdin argument)?
For python 3.5+ (3.6+ for encoding), you can use input:
from subprocess import check_output
output = check_output(["cat","-b"],
input="-foo\n-bar\n-foobar", encoding='ascii')
print(output)
