Arguments

Command Line Interface

The command for generating Apache access logs:

$python3.4 $Visor_HOME/src/fake_log_gen/fake_log_gen.py -m access -o outputfile

The command for generating Apache error logs:

$python3.4 $Visor_HOME/src/fake_log_gen/fake_log_gen.py -m error -o outputfile

argparse

The Python argparse module provides a convenient way of writing command-line interfaces. It can save you a lot of trouble of dealing with sys.argv, and can automatically generate help messages.

$ python3.4 ../src/fake_log_gen/fake_log_gen.py -h

usage: fake_log_gen.py [-h] [-o O] [-m M]

optional arguments:
  -h, --help  show this help message and exit
  -o O        fake logfile
  -m M        log mode

Create Parser

Import the Python argparse module and instantiate a parser:

parser = argparse.ArgumentParser()

Add Arguments

For now, there are 2 arguments for our generator program:

• The output file
• The log mode (access log or error log)

parser.add_argument("-o", help="fake logfile")
parser.add_argument("-m", help="log mode")

The explanation after the help will be utilized by the -h messages.

Parse the Arguments

Parse the arguments via parse_args() method:

args = parser.parse_args()

parse_args() just illustrate how the program will access the arguments. Usually called with no arguments, ArgumentParser will automatically determine the command-line arguments from sys.argv.

Access the Arguments

Now, we are capable to access the parsed arguments:

mode = args.m

Pay attention that when use the . notation to access arguments, don't need to add the - before the argument name. Here, use args.m instead of args.-m.