```
#!/usr/local/bin/python3
import sys
def print_factorial( user_val ):
if( user_val < 1 ):
return( 1 )
else:
return( print_factorial( user_val - 1 ) * user_val )
if( __name__ == "__main__" ):
if( len( sys.argv ) == 2 ):
print( print_factorial( int ( sys.argv[ 1 ] ) ) )
else:
sys.stderr.write( "usage: %s <integer>\n" % sys.argv[ 0 ] )
exit( 0 )
```
