# [ `fxtools fix` ]
## Summary
This command will replace all nucleotides not matching: `[ACTGNactgn]`
with the missing nucleotide `N`.
### Parameters
Default will write to stdout, but you can provide an output file with the `-o` flag.
## Usage
```bash
fxtools fix \
-i <input_fastx> \
-o <output_fastx>
```