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# Installation
### Module Dependencies
* argparse (if Python version is <= 2.6)
* netattr
* netifaces
#### Note
As long as your `setuptools` installation is reasonably up to date, `setup.py` will take care of installing any required dependencies.
### 1. Clone the cidrchk git repository
```
git clone https://github.com/jhunkeler/cidrchk.git
```
### 2. Install the script
```
cd cidrchk
sudo python setup.py install
```
If you are unable to install `cidrchk` as root, please use the following notation instead:
```
python setup.py install --user
```
# What is cidrchk?
`cidrchk` is a simple Python script with only one purpose: To inform a user whether or not their computer is connected to a particular network.
# How do I use it?
Let's assume you depend on autofs to automatically mount NFS directories at-will.
However, when you are off-site or not connected to your institution's VPN, you quickly realize attempting to access these data areas causes significant delays (i.e. a *five minute* default timeout)
Consider the following **.cshrc** example:
```
setenv PATH ${HOME}/bin:${PATH}
setenv MYDATA /remote/data1
alias badidea "cd ${MYDATA}"
```
What happens if you attempt to execute your favorite alias?
```
$ badidea
[ no output, waiting for autofs to timeout ]
```
Whoops! Things didn't go as planned, so let's take a look at the same **.cshrc** example using `cidrchk`:
```
setenv PATH ${HOME}/bin:${PATH}
setenv MYDATA /remote/data1
set _OFFSITE = `cidrchk 10.0.0.0/20 66.55.32.0/20 >/dev/null`
setenv OFFSITE ${status}
unset _OFFSITE
alias badidea "cd ${MYDATA}"
if ( ${OFFSITE} ) then
unalias badidea
endif
```
In the above example the following is *true*:
If 10.0.0.0/20 represents your institution's VPN address space and 66.55.32.0/20 represents your company's local intranet, and your home IP was 192.168.1.101, cidrchk returned a non-zero value indicating your computer was "off-site".
Furthermore, if your computer's IP address was 66.55.45.10 (i.e. you are in your cubicle), cidrchk would return zero indicating your computer was "on-site".
## Other Possibilities
Issuing `-v` to cidrchk will echo the return value to the console, resulting in slightly cleaner code:
```
setenv OFFSITE `cidrchk -v 10.0.0.0/20 66.55.32.0/20`
if ( ${OFFSITE} ) then
# do something clever to prevent personal hardship
endif
```
The downside to parsing a string rather than an integer is logical operators will not work as expected. `${OFFSITE} > "0"` is not the same as evaluating `${OFFSITE} > 0`.
## What about BASH?
The required notation is nearly identical to TCSH:
```
_OFFSITE=$(cidrchk 10.0.0.0/20 66.55.32.0/20 >/dev/null)
export OFFSITE=$?
if (( ${OFFSITE} )); then
#do something clever to prevent personal hardship
fi
```
# Options
```
usage: cidrchk [-h] [--ignore IGNORE] [--debug] [--verbose] cidr [cidr ...]
Detects whether or not any ethernet devices match to a defined CIDR range.
positional arguments:
cidr IP range(s) to detect
optional arguments:
-h, --help show this help message and exit
--ignore IGNORE, -i IGNORE
IP range(s) to ignore (Default: link-local and
localhost)
--debug, -d
--verbose, -v
```
# Bug Reporting
Submit bug reports via this project's issue tracker: https://github.com/jhunkeler/cidrchk/issues
Please remember to include your computer's operating system, the name of the shell you executed cidrchk from, the output of `cidrchk -d`, and any relevant code snippets you may have.
|
