Python GetHostId.py getting sys.argv[1] IndexError: list index out of range

Question

i am working on a python script to be a multi tool for getting DNS information on servers in a enterprise env. so far the script i have is using python 3.5. i am using argparse for creating command line options, which i am trying to create an if/ elif / else statement which contains the different selections. the main error message i am getting is:

./GetHostName.py
Traceback (most recent call last):
  File "./GetHostName.py", line 34, in <module>
    remoteServer = sys.argv[1]
IndexError: list index out of range

that is when the command is run by itself. when it is run with a host name at the end ./GetHostName.py hostName it gives this message:

GetHostName.py: error: unrecognized arguments: hostName 

I didn't put real name of server for security issues.... When i use the argparse options say like the -f option for getting the FQDN, it gives this response...

./GetHostName.py -f hostName
3
-f

from the way it appears, it is taking the -f as input for the server name, when it should only be the input for argparse input. i have tried everything to fix it that i can think of. i have encased the main code body in a main function, that didn't work so i removed it. i use the try: statement and exception statements. that didn't work. i am wondering if there is something just basically wrong with my programming logic at this point...

this here is the code from the script:

#!C:\Bin\Python35\python.exe
# 

# import libraries
import sys, os
import argparse as ap
import socket

# Command Line interface setup


def argParse():
    #Command Line arg parse
    parser=ap.ArgumentParser(description='A tool to get a remote servers DNS information.')
    parser.add_argument("-a", "--address", default="fqdn", help="Gets IP address from host name.")
    parser.add_argument("-f", "--fqdn", default="fqdn", help="Gets the FQDN address of server.")
    parser.add_argument("-d", "--addrinfo", default="fqdn", help="Gets the FQDN address of server.")
    parser.add_argument("-l", "--local", default="fqdn", help="Gets info on local host.")
    parser.add_argument("-Pr", "--proto",  default="fqdn", help="Translate an Internet protocol name to a constant suitable for passing as the (optional) third argument to the socket() function.")
    parser.add_argument("-n", "--nameinfo", default="fqdn", help="Gets name and port on remote host.")
    parser.add_argument("-Sn", "--servbyname", default="fqdn", help="Translate an Internet service name and protocol name to a port number for that service.")
    parser.add_argument("-Sp", "--servbyport",  default="fqdn", help="Translate an Internet port number and protocol name to a service name for that service.")
    parser.add_argument("-t", "--timeout", default="fqdn", help="Return the default timeout in seconds for new socket objects.")
    parser.add_argument("-v", "--verbose",  default="fqdn", help="Increase output verbosity")
    return parser.parse_args()
    #remoteServer = input().strip().split()

args=argParse()




if args.fqdn:
    remoteServer = sys.argv[1]
    print (len(sys.argv))
    remoteServerIP = socket.getfqdn(remoteServer)
    print (remoteServerIP)

elif args.address:
    remoteServer = sys.argv[2]
    print (len(sys.argv))
    remoteServerIP = socket.gethostbyname(remoteServer)
    print (remoteServerIP)

elif args.addrinfo:
    remoteServer = sys.argv[3]
    print (len(sys.argv))
    remoteServerIP = socket.getaddrinfo(remoteServer)
    print (remoteServerIP)

elif args.local:
    remoteServer = sys.argv[4]
    print (len(sys.argv))
    remoteServerIP = socket.gethostname()
    print (remoteServerIP)  

 elif args.proto:
    remoteServer = sys.argv[5]
    print (len(sys.argv))
    remoteServerIP = socket.getprotobyname(remoteServer)
    print (remoteServerIP)

elif args.servbyname:
    remoteServer = sys.argv[6]
    print (len(sys.argv))
    remoteServerIP = socket.getservbyname(remoteServer)
    print (remoteServerIP)

elif args.servbyport:
    remoteServer = sys.argv[7]
    print (len(sys.argv))
    remoteServerIP = socket.getservbyport(remoteServer)
    print (remoteServerIP)

elif args.timeout:
    remoteServer = sys.argv[8]
    print (len(sys.argv))
    remoteServerIP = socket.getdefaulttimeout(remoteServer)
    print (remoteServerIP)

elif args.verbose:
    remoteServer = sys.argv[9]
    print (len(sys.argv))
    remoteServerIP = socket.gethostbyaddr(remoteServer)
    print (remoteServerIP)

else:
    args.nameinfo
    remoteServer = sys.argv[10]
    print (len(sys.argv))
    remoteServerIP = socket.getnameinfo(remoteServer)
    print (remoteServerIP)

any help would be appreciated. please note that when i run a script with just this in it, it works just fine:

#!C:\Bin\Python35\python.exe
#
import sys, os
import argparse
import socket

# Command Line interface setup
def main():
        remoteServer = sys.argv[1]
        remoteServerIP = socket.gethostbyaddr(remoteServer)
        print (remoteServerIP)

if __name__ == '__main__':
    main()

thanks in advance. -Betzelel

PS the code may look out of format, due to having to copy and paste into this blog, and manually putting 4 spaces on to each line to get it to show up as code lol.

Answer 1

I've had this problem long time ago. To fix this I've changed

parser.add_argument("-a", "--address", default="fqdn", help="Gets IP address from host name.")

in

parser.add_argument("-a", "--address", default="fqdn", help="Gets IP address from host name.", dest=ipfromhostname)

So for getting the value from -a you have to change

remoteServer = sys.argv[1]

in

remoteServer = args.ipfromhostname

where ipfromhostname is the dest value.

EDIT:

You have to do this operation for every parser.add_argument