My good friend Greg was asking about how to store data to files onboard a MikroTik device so I thought I’d elaborate here with some information and examples.
Before we get started, some things to note:
- While you can fetch and read the contents of any file, you are limited to working with 4096 character files as this is a limitation on the amount of information that can be contained in a string variable in RouterOS at this time.
- When creating new files in RouterOS via terminal the extension .txt will be appended to anything that doesn’t already have .txt at the end.
- You can work with newlines \n\r as delimeters (which is super helpful when downloading something list of IP addresses from somewhere)
The basic commands for working with a file, using variables in place of static content or file names:
1. To create a new file
/file print file=$filename
2. To read an existing file
:set $filedata [/file get $filename contents]
3. To write to an existing file
/file set $filename contents=$newdata
4. To append to an existing file
/file set $filename contents=([get $filename contents] . $newdata)
