Black Hat Bash - Bash Scripting for Hackers and Pentesters (Early Access) (Dolev Farhi, Nick Aleks)

This script assigns the first positional argument to the variable

TARGET. Notice, also, that the argument ${0} is assigned to the

SCRIPT_NAME variable. This argument contains the script’s name

(in this case, ping_with_arguments.sh).

To run this script, use the following commands:

$ chmod u+x ping_with_arguments.sh

$./ping_with_arguments.sh nostarch.com

Running the script ping_with_arguments.sh...

Pinging the target nostarch.com...

PING nostarch.com (104.20.120.46) 56(84) bytes of data.

64 bytes from 104.20.120.46 (104.20.120.46): icmp_seq=1 ttl=57 time=6.89 ms

64 bytes from 104.20.120.46 (104.20.120.46): icmp_seq=2 ttl=57 time=4.16 ms

--snip--

Listing 1-18

Passing arguments to a script

This script will perform a ping command against the domain

nostarch.com passed to it on the command line. The value was

assigned to the $1 variable; if we passed another argument, it would

get assigned to the second variable, $2. Use CTRL+C to exit this

script, as ping may run indefinitely on some operating systems.

This script is available at https://github.com/dolevf/Black-Hat-

Bash/blob/master/ch01/ping_with_arguments.sh.

What if you wanted to access all arguments? You can do so

using the variable $@. Also, using $#, you can get the total number

of arguments passed. The following script demonstrates how this

works:

#!/bin/bash

echo "The arguments are: $@"

echo "The total number of arguments are: $#"

Save this script to a file named show_args.sh and run it as

follows:

$ chmod u+x show_args.sh

$ ./show_args.sh "hello" "world"

The arguments are: hello world

The total number of arguments are: 2

Table 1-7 summarizes the variables related to positional

arguments.