13.5. Module os

os module provides operating system dependent functionality. You can import it using the following import statement.

>>> import os

getuid() function returns the current process's effective user's id.

>>> os.getuid()
500

getpid() returns the current process's id. getppid() returns the parent process's id.

>>> os.getpid()
16150
>>> os.getppid()
14847

uname() returns different information identifying the operating system, in Linux it returns details you can get from the uname command. The returned object is a tuple, (sysname, nodename, release, version, machine)

>>> os.uname()
('Linux', 'd80', '2.6.34.7-56.fc13.i686.PAE', '#1 SMP Wed Sep 15 03:27:15 UTC 2010', 'i686')

getcwd()returns the current working directory. chdir(path) changes the current working directory to path. In the example we first see the current directory which is my home directory and change the current directory to /tmp and then again checking the current directory.

>>> os.getcwd()
'/home/kushal'
>>> os.chdir('/tmp')
>>> os.getcwd()
'/tmp'

So let us use another function provided by the os module and create our own function to list all files and directories in any given directory.

def view_dir(path='.'):
    """
    This function prints all files and directories in the given directory.

    :args path: Path to the directory, default is current directory
    """
    names = os.listdir(path)
    names.sort()
    for name in names:
        print name,

>>> view_dir('/')
.readahead bin boot dev etc home junk lib lib64 lost+found media mnt opt proc root run sbin srv sys tmp usr var