Using cffi to call functions of shared library from python - c

Question

I am calling some c-sdk from python code. This python code is running as lambda on greengrass. I am using cffi to call the function of shared so from python. My lambda (python code) is running as gcc_user but when i print the user in my C code, it prints something like: T� Pp.
Below is the C code that i am using to print the user info:
char* username[10];
getlogin_r(username, 10);
printf("current user in c program ");
for(index = 0;index<10; index++)
{
printf("%c",username[index]);
}
printf("\n");
Below is the python code that i am using call the shared lib (C code):
import cffi
import _cffi_backend
from sys import exit, platform
import boto3
from multiprocessing import Process
import sys, os
import logging
import getpass
def StartVideoStreaming(channelName):
ffi = cffi.FFI()
cdef_from_file = None
header = '/home/admin/alprwebrtcdemo/amazon-kinesis-video-streams-webrtc-sdk-c/samples/kvsWebRTCClientMasterGstreamer.h'
try:
with open(header, 'r') as libtestcffi_header:
cdef_from_file = libtestcffi_header.read()
except FileNotFoundError:
print('Unable to find "%s"' % header)
exit(2)
except IOError:
print('Unable to open "%s"' % header)
exit(3)
finally:
if cdef_from_file == '':
print('File "%s" is empty' % header)
exit(1)
ffi.cdef(cdef_from_file)
lib_extension = ''
if platform.startswith('freebsd') or platform.startswith('linux'):
lib_extension = 'so'
elif platform.startswith('win'):
lib_extension = 'dll'
CLibTC = ffi.dlopen('/home/admin/alprwebrtcdemo/amazon-kinesis-video-streams-webrtc-sdk-c/build/liblibkvsWebrtcClientMasterGstSample.' + lib_extension)
arg_0 = "arg0".encode('utf-8')
arg_1 = channelName.encode('utf-8')
argv_keepalive = [ffi.new("char[]", arg_0),
ffi.new("char[]", arg_1)]
argv = ffi.new("char *[]", argv_keepalive)
session = boto3.Session()
logging.info("user in process: {}".format(getpass.getuser()))
credentials = session.get_credentials()
accountKeyID = credentials.access_key
accountSecret = credentials.secret_key
sessionToken = credentials.token
logging.info("ID: {}, secret: {}, session: {}".format(accountKeyID, accountSecret, sessionToken))
arg1 = accountKeyID.encode('utf-8')
arg2 = accountSecret.encode('utf-8')
arg3 = sessionToken.encode('utf-8')
CLibTC.start(2,argv,arg1,arg2,arg3)
print('Everything is fine!!!')
def main():
logging.info("XDG_CACHE_HOME env variable value: {}".format(os.environ.get(HOME)))
logging.info("user in python: {}".format(getpass.getuser()))
sys.path.insert(0,'')
p1 = Process(target=StartVideoStreaming, args=('channeltest666',))
p1.start()
p1.join()
Is there a way to call c lib from python and force it to run as gcc_user? According to me it should have been running as gcc_user at first place because its just a function call from python code.

Answer 1

It should be char username [10], without the *. Maybe there are other problems too but try to fix that first.