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)