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# Installation
* Clone the `cidrchk` git repository
* `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. For example, on your "work" laptop, you depend on autofs to automatically mount NFS directories. However, when you are off-site or not connected to your institution's VPN, you quickly realize attempting to access these data areas will cause significantly long delays (i.e. the *five minute* default timeout period)
# 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
```
# How do I use it?
Consider the following **.cshrc** example:
```
setenv PATH $HOME/bin:${PATH}
setenv MYDATA /remote/data1
alias badidea "cd ${MYDATA}"
```
What happens if you, out of habit, 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".
Inversely, 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 Possiblities
Issuing `-v` to `cidrchk` will echo the return value to the console, resulting in slightly more cleaner code:
```
setenv OFFSITE `cidrchk -v 10.0.0.0/24 66.55.32.0/20`
if ( ${OFFSITE} ) then
# do something clever to prevent personal hardship
endif
```
## How do I use BASH with cidrchk?
The notation required for `cidrchk` to use BASH is nearly identical to TCSH:
```
_OFFSITE=$(cidrchk 10.0.0.0/24 66.55.32.0/20 >/dev/null)
export OFFSITE=$?
if (( ${OFFSITE} )); then
#do something clever to prevent personal hardship
fi
```
# Bug Reporting
Submit bug reports via this project's issue tracker: https://bitbucket.org/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.
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