In Python I need to get the version of an external binary I need to call in my script.
Let's say that I want to use Wget in Python and I want to know its version.
I will call
os.system( "wget --version | grep Wget" )
and then I will parse the outputted string.
How to redirect the stdout of the os.command in a string in Python?
One "old" way is:
fin,fout=os.popen4("wget --version | grep Wget")
print fout.read()
The other modern way is to use a subprocess module:
import subprocess
cmd = subprocess.Popen('wget --version', shell=True, stdout=subprocess.PIPE)
for line in cmd.stdout:
if "Wget" in line:
print line
Use the subprocess module:
from subprocess import Popen, PIPE
p1 = Popen(["wget", "--version"], stdout=PIPE)
p2 = Popen(["grep", "Wget"], stdin=p1.stdout, stdout=PIPE)
output = p2.communicate()[0]
Use subprocess instead.
Subprocess.popen calls shell to parse command and runs an extra process in Python.
pipe() but in Python I saw people use subproces.popen() even there is os.pipe(). which practice is good? Although I can see subprocess.popen() is more powerful then C popen() we can explicitly send parsed command in python.If you are on *nix, I would recommend you to use commands module.
import commands
status, res = commands.getstatusoutput("wget --version | grep Wget")
print status # Should be zero in case of of success, otherwise would have an error code
print res # Contains stdout
subprocess module is preferable to using the commands module.