lfc_python(3)							 Python Reference						     lfc_python(3)

NAME

       lfc - Python interface to the LFC
       lfcthr - Thread enabled version of Python interface to the LFC

SYNOPSIS

       import lfc

       import lfcthr
       lfcthr.init()

DESCRIPTION

       The  lfc  module  permits  you to access the LFC client interface from python programs. The lfc module is a swig wrapping of the standard C
       interface.  For detailed descriptions of each function see the individual man page of each function.

       The lfcthr module is a version of the lfc module supporting multi-threaded Python clients. Its usage is similar to the  usage  of  the  lfc
       module except the obligatory initialisation call lfcthr.init() in the main program before threads are started.

       There  follows  a  series  of  examples of how to use selected functions and how to retrieve the information returned by them: Examples are
       finding the GUID of an existing entry, listing the replicas of a given GUID and setting and  retrieving	the  comment  associated  with	an
       entry.

EXAMPLE

       #!/usr/bin/python

       import sys
       import lfc

       """
       # stat an existing entry in the LFC and print the GUID
       """

       name = "/grid/dteam/my.test"

       stat = lfc.lfc_filestatg()
       res = lfc.lfc_statg(name,"",stat)

       if res == 0:
	  guid = stat.guid
	  print "The GUID for " + name + " is " + guid
       else:
	  err_num = lfc.cvar.serrno
	  err_string = lfc.sstrerror(err_num)
	  print "There was an error while looking for " + name + ": Error " + str(err_num) 
		 + " (" + err_string + ")"
	  sys.exit(1)

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # list the replicas of a given entry, starting from the GUID
       """

       guid = "6a3164e0-a4d7-4abe-9f76-e3b8882735d1"

       listp = lfc.lfc_list()
       flag = lfc.CNS_LIST_BEGIN

       print "Listing replicas for GUID " + guid

       num_replicas=0

       while(1):
	  res = lfc.lfc_listreplica("",guid,flag,listp)
	  flag = lfc.CNS_LIST_CONTINUE

	  if res == None:
	     break
	  else:
	     rep_name = res.sfn
	     print "Replica: " + rep_name
	     num_replicas = num_replicas + 1

       lfc.lfc_listreplica("",guid,lfc.CNS_LIST_END,listp)
       print "Found " + str(num_replicas) + " replica(s)"

EXAMPLE

       #!/usr/bin/python

       import sys
       import lfc
       import re

       """
       # setting and retrieving a comment on a file
       """

       file = "/grid/dteam/my.test"

       comment = "MyComment"
       res = lfc.lfc_setcomment(file,comment)

       if res != 0:
	  err_num = lfc.cvar.serrno
	  err_string = lfc.sstrerror(err_num)
	  print "Problem while setting comment for " + file + ": Error " + str(err_num) 
		 + " (" + err_string + ")"
	  sys.exit(1)

       buffer=""
       for i in range(0,lfc.CA_MAXCOMMENTLEN+1):
	 buffer=buffer + " "

       res = lfc.lfc_getcomment(file,buffer)

       if res != 0:
	  err_num = lfc.cvar.serrno
	  err_string = lfc.sstrerror(err_num)
	  print "Problem while reading the comment for " + file + ": Error " + str(err_num) 
		 + " (" + err_string + ")"
	  sys.exit(1)

       r = re.compile("(.*?) ", re.DOTALL)
       comment = r.findall(buffer)[0]

       print "Read back comment " + comment

EXAMPLE

       #!/usr/bin/python

       """
       # Using the lfc_readdirxr method
       """

       import sys
       import lfc

       name = "/grid/dteam/my.test"

       dir = lfc.lfc_opendirg(name,"")
       if (dir == None) or (dir == 0):
	       err_num = lfc.cvar.serrno
	       err_string = lfc.sstrerror(err_num)
	       print "Error while looking for " + name + ": Error " + str(err_num) 
		      + " (" + err_string + ")"
	       sys.exit(1)

       while 1:
	       read_pt = lfc.lfc_readdirxr(dir,"")
	       if (read_pt == None) or (read_pt == 0):
		       break
	       entry, list = read_pt
	       print entry.d_name
	       try:
		       for i in range(len(list)):
			       print " ==> %s" % list[i].sfn
	       except TypeError, x:
		       print " ==> None"

       lfc.lfc_closedir(dir)

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getlinks method
       """

       result, list = lfc.lfc_getlinks("/grid/dteam/antotests/extratests/dir2/f105", "")
       print result
       print len(list)
       if (result == 0):
	    for i in list:
		 print i.path

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getreplica method
       """

       result, list = lfc.lfc_getreplica("/grid/dteam/antotests/extratests/dir2/f105", "", "")
       print result
       print len(list)
       if (result == 0):
	    for i in list:
		 print i.host
		 print i.sfn

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getacl and lfc_setacl methods to add a user ACL
       """

       nentries, acls_list = lfc.lfc_getacl("/grid/dteam/tests_sophie3", lfc.CA_MAXACLENTRIES)

       print nentries
       print len(acls_list)

       for i in acls_list:
	       print i.a_type
	       print i.a_id
	       print i.a_perm

       # When adding a first ACL for a given user, you also need to add the mask
       # When adding the second user ACL, it is not necessary anymore

       acl_user = lfc.lfc_acl()
       acl_mask = lfc.lfc_acl()

       acl_user.a_type=2	# 2 corresponds to CNS_ACL_USER
       acl_user.a_id=18701	# user id
       acl_user.a_perm=5

       acl_mask.a_type=5	# 5 corresponds to CNS_ACL_MASK
       acl_mask.a_id=0		     # no user id specified
       acl_mask.a_perm=5

       acls_list.append(acl_user)
       acls_list.append(acl_mask)

       res = lfc.lfc_setacl("/grid/dteam/tests_sophie3", acls_list)

       if res == 0:
	       print "OK"
       else:
	       err_num = lfc.cvar.serrno
	       err_string = lfc.sstrerror(err_num)
	       print "There was an error : Error " + str(err_num) + " (" + err_string + ")"
	       sys.exit(1)

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getacl and lfc_setacl methods to remove a user ACL
       """

       nentries, acls_list = lfc.lfc_getacl("/grid/dteam/tests_sophie3", lfc.CA_MAXACLENTRIES)

       # Note : you cannot remove the owner ACL (i.e. for CNS_ACL_USER_OBJ type) if ACLs
       # ====== for other users exist. Ff all the other user ACLs are deleted, the owner
       # ====== ACL is automatically removed.

       for i in acls_list:
	       print i.a_type
	       print i.a_id
	       print i.a_perm

       del acls_list[1]    # delete a given user ACL from the list of ACLs

       res = lfc.lfc_setacl("/grid/dteam/tests_sophie3", acls_list)

       if res == 0:
	       print "OK"
       else:
	       err_num = lfc.cvar.serrno
	       err_string = lfc.sstrerror(err_num)
	       print "There was an error : Error " + str(err_num) + " (" + err_string + ")"
	       sys.exit(1)

EXAMPLE

       #!/usr/bin/env python
       import lfcthr
       import os
       from threading import Thread

       class slave(Thread):

	  def __init__ (self):
	     Thread.__init__(self)

	  def run(self):
	       ....
	       result = lfcthr.lfc_getreplica("", guid, "")
	       ....
	       return

       if __name__ == '__main__':

	   os.environ['LFC_HOST'] = 'my_lfc.cern.ch'

	   #	 Threaded library initialisation
	   lfcthr.init()

	   ....
	   #	 Start up of threads
	   for i in xrange(totalNumberOfSlaves):
	       slv = slave(i)
	       slv.start()

	   ....

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getusrmap method
       """

       result, list = lfc.lfc_getusrmap()
       print result
       print len(list)
       if (result == 0):
	    for i in list:
		 print i.userid + " " + i.username

EXAMPLE

       #!/usr/bin/python

       import lfc

       """
       # Using the lfc_getgrpmap method
       """

       result, list = lfc.lfc_getgrpmap()
       print result
       print len(list)
       if (result == 0):
	    for i in list:
		 print i.gid + " " + i.groupname

KNOWN BUGS

       The  current  interface to the lfc_getcomment(3), lfc_getcwd(3), lfc_readlink(3), lfc_seterrbuf(3) requires the passing of str object which
       is modified to contain the result (in a similar way to the C functions, which accept a buffer).	However this breaks  the  immutability	of
       python str. This will be changed in the future.

SEE ALSO

       LFC C interface man pages

LFC
					       $Date: 2010-02-04 13:08:39 +0100 (Thu, 04 Feb 2010) $				     lfc_python(3)