# NHS Number command line interface
A National Health Service (NHS) Number is a unique number allocated in a shared
numbering scheme to registered users of the three public health services in
England, Wales, and the Isle of Man.
This tool is a command line interface that parses each standard input line into
an NHS number, then validates the check digit is correct.
* If the line is a valid NHS number, then print it.
* If the line is an invalid NHS Number, or is unparseable, then print an error message.
* If the line is blank, then skip it.
References:
* [National Health Service (NHS)](https://en.wikipedia.org/wiki/National_Health_Service)
* [NHS Number](https://en.wikipedia.org/wiki/NHS_number)
## Examples
Suppose you have a text file `input.txt` that contains one NNS Number per line,
and some may be valid or invalid:
```txt
999 123 4560
999 123 4561
```
If you use Linux or macOS, then here's how to parse each line and validate it:
```sh
If you use Windows, then here's how to parse each line and validate it:
```sh
The commmand prints the valid NHS Number to stdout:
```stdout
999 123 4560
```
The commmand prints the invalid NHS Number to stderr:
```stderr
Error invalid line 1. Error: validate check digit failed. NHS Number: 999 123 4561
```
## Releases
You can build a release for your own platform:
```sh
cargo build --release
```
You can download a prebuilt release for Windows:
* Windows with GNU: <target/x86_64-pc-windows-gnu/release/nhs-number-cli.exe>
We aim to add more prebuilt releases soon.