Code:

#!/usr/bin/env python
import RPi.GPIO as GPIO
import sys
import os
import time
GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.OUT)

def relayon():
        GPIO.output(4, GPIO.LOW)
        time.sleep(60)
        GPIO.output(4, GPIO.HIGH)

#filename=str(sys.argv[1])
complete_filename="/home/pi/proc1.py"
sms_file=open(complete_filename,"r")
message=sms_file.read(160)
if (message.find("poweron")!= -1): (relayon)
elif (message.find("poweroff") != -1):
     GPIO.output(4, GPIO.LOW)

Error: (or lack there of)

pi@raspberrypi:~ $ sudo python proc1.py
proc1.py:9: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  GPIO.setup(4, GPIO.OUT)
pi@raspberrypi:~ $