Hey everyone! I'm new to this, and I had a little mix-up today while trying to open some text files named `[2,3,5,7].txt` using the `open` command on Debian (which links to `xdg-open`). Instead of running `for num in 2 3 5 7; do open $num.txt; done;`, I accidentally typed `for num in 2 3 5 7; do open $num; done;`. This caused Chrome to open tabs for the IP addresses `0.0.0.[2,3,5,7]`! I received a warning about potential malware, so I closed the tabs right away. I'm curious, why does `xdg-open` interpret the digits as IP addresses, and is there any risk of malware since Chrome didn't actually load those pages?
3 Answers
IP addresses can be represented in different forms. Besides the standard dotted-decimal format, IPv4 can also be expressed as a single 32-bit integer. So, when Chrome receives `2`, it correctly interprets it as `0.0.0.2`. As for why your browser was called in the first place, that depends on how your system is configured. Just to ease your mind about the malware risk: addresses from that block aren’t public, so you should be safe!
The `0.0.0.X` addresses usually don’t reach the internet; they’re likely local to your machine. You can check if those addresses route back to your PC using the command `ip route get 0.0.0.[2 3 5 7]`. Chrome probably tried to fetch a "site" but failed to get SSL info or a valid domain, which made it suspicious. If those IPs route back to you, something might be hosting a local server, but that's kind of rare for such low-number IPs. Just run that command when you get a chance to check it out!
For future reference, if you want to avoid this issue, you can use brace expansion like this: `open {2,3,5,7}.txt`. It’ll do what you need in bash! But just a heads up, it still only invokes `open` once for all those files, so that's a solid way to go.
Oh wow, I totally forgot about brace expansion! Thank you! But will that only call `open` once? I might just create a small wrapper script to avoid these kinds of mishaps.
Thanks for the helpful explanation! I’ll definitely give that command a try when I’m home. I suspected there was nothing on the other end since those IPs are reserved.