Common operations on Posix pathnames.

Instead of importing this module directly, import os and refer to
this module as os.path.  The "os.path" name is an alias for this
module on Posix systems; on other systems (e.g. Mac, Windows),
os.path provides the same operations in a manner specific to that
platform, and is an alias to another module (e.g. macpath, ntpath).

Some of this can actually be useful on non-Posix systems too, e.g.
for manipulation of the pathname component of URLs.

listdir(path) -> list_of_strings

Return a list containing the names of the entries in the directory.

    path: path of directory to list

The list is in arbitrary order.  It does not include the special
entries '.' and '..' even if they are present in the directory.

remove(path)

Remove a file (same as unlink(path)).

system(command) -> exit_status

Execute the command (a string) in a subshell.

unlink(path)

Remove a file (same as remove(path)).

getcwd() -> path

Return a string representing the current working directory.

mkdir(path [, mode=0777])

Create a directory.

No Document.

chdir(path)

Change the current working directory to the specified path.

makedirs(path [, mode=0777])

Super-mkdir; create a leaf directory and all intermediate ones.
Works like mkdir, except that any intermediate path segment (not
just the rightmost) will be created if it does not exist.  This is
recursive.

close(fd)

Close a file descriptor (for low level IO).

stat(path) -> stat result

Perform a stat system call on the given path.

rename(old, new)

Rename a file or directory.

Directory tree generator.

For each directory in the directory tree rooted at top (including top
itself, but excluding '.' and '..'), yields a 3-tuple

    dirpath, dirnames, filenames

dirpath is a string, the path to the directory.  dirnames is a list of
the names of the subdirectories in dirpath (excluding '.' and '..').
filenames is a list of the names of the non-directory files in dirpath.(more...)

rmdir(path)

Remove a directory.

access(path, mode) -> True if granted, False otherwise

Use the real uid/gid to test for access to a path.  Note that most
operations will use the effective uid/gid, therefore this routine can
be used in a suid/sgid environment to test if the invoking user has the
specified access to the path.  The mode argument can be F_OK to test
existence, or the inclusive-OR of R_OK, W_OK, and X_OK.

popen(command [, mode='r' [, bufsize]]) -> pipe

Open a pipe to/from a command returning a file object.

getpid() -> pid

Return the current process id

chmod(path, mode)

Change the access permissions of a file.

Get an environment variable, return None if it doesn't exist.
The optional second argument can specify an alternate default.