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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

$Date$ LFC