Write a python program for creating virtual file system on Linux environment.

virtualfs.py

1:  import shelve  
2:  import os,sys  
3:  fs=shelve.open('myfilesystem.fs', writeback=True)  
4:  current_dir=[]  
5:  def install(fs):  
6:    uname=raw_input("Enter user name : ")  
7:    fs[""]={"System":{},"Users":{uname:{}}}  
8:  def current_dictionary():  
9:    """Displays dictionary containing the files in the current directory"""  
10:    d=fs[""]  
11:    for key in current_dir:  
12:      d=d[key]  
13:    return d  
14:  def ls(args):  
15:    print 'Contents of directory are : '"/"+"/".join(current_dir)+':'  
16:    for i in current_dictionary():  
17:      print i  
18:  def cd(args):  
19:    if len(args)!=1:  
20:      print "Usage: cd <directory>"  
21:      return  
22:    if args[0]=="..":  
23:      if len(current_dir)==0:  
24:        print "Sorry!!! Cannot go above root"  
25:      else:  
26:        current_dir.pop()  
27:    elif args[0] not in current_dictionary():  
28:      print "Directory "+ args[0]+" not found"  
29:    else:  
30:      current_dir.append(args[0])  
31:  def mkdir(args):  
32:    if len(args)!=1:  
33:      print "Usage: mkdir <directory>"  
34:      return  
35:    d=current_dictionary()[args[0]]={}  
36:    print "Directory created..."  
37:    fs.sync()  
38:  def rmdir(args):  
39:    if len(args)!=1:  
40:      print "Usage: rmdir <directory>"  
41:      return  
42:    elif args[0] not in current_dictionary():  
43:      print "Directory "+ args[0]+" not found"  
44:    else:  
45:      d=current_dictionary()  
46:      print d  
47:      for key1 in d:  
48:        if (key1==args[0]):  
49:          del d[key1]  
50:          print "Directory removed..."  
51:          fs.sync()  
52:          break  
53:  COMMANDS = {'ls' : ls,'cd' : cd, 'mkdir' : mkdir, 'rmdir' : rmdir}  
54:  install(fs)  
55:  while True:  
56:    raw=raw_input('>')  
57:    cmd=raw.split()[0]  
58:    if cmd in COMMANDS:  
59:      COMMANDS[cmd](raw.split()[1:])  
60:  raw_input('Press the enter key to close the filesystem.........')