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# isBinaryFile
Detects if a file is binary in Node.js using ✨promises✨. Similar to [Perl's `-B` switch](http://stackoverflow.com/questions/899206/how-does-perl-know-a-file-is-binary), in that:
- it reads the first few thousand bytes of a file
- checks for a `null` byte; if it's found, it's binary
- flags non-ASCII characters. After a certain number of "weird" characters, the file is flagged as binary
Much of the logic is pretty much ported from [ag](https://github.com/ggreer/the_silver_searcher).
Note: if the file doesn't exist or is a directory, an error is thrown.
## Installation
```
npm install isbinaryfile
```
## Usage
Returns `Promise<boolean>` (or just `boolean` for `*Sync`). `true` if the file is binary, `false` otherwise.
### isBinaryFile(filepath)
* `filepath` - a `string` indicating the path to the file.
### isBinaryFile(bytes[, size])
* `bytes` - a `Buffer` of the file's contents.
* `size` - an optional `number` indicating the file size.
### isBinaryFileSync(filepath)
* `filepath` - a `string` indicating the path to the file.
### isBinaryFileSync(bytes[, size])
* `bytes` - a `Buffer` of the file's contents.
* `size` - an optional `number` indicating the file size.
### Examples
Here's an arbitrary usage:
```javascript
const isBinaryFile = require("isbinaryfile").isBinaryFile;
const fs = require("fs");
const filename = "fixtures/pdf.pdf";
const data = fs.readFileSync(filename);
const stat = fs.lstatSync(filename);
isBinaryFile(data, stat.size).then((result) => {
if (result) {
console.log("It is binary!")
}
else {
console.log("No it is not.")
}
});
const isBinaryFileSync = require("isbinaryfile").isBinaryFileSync;
const bytes = fs.readFileSync(filename);
const size = fs.lstatSync(filename).size;
console.log(isBinaryFileSync(bytes, size)); // true or false
```
## Testing
Run `npm install`, then run `npm test`.
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