Outputting QR codes on the terminal

In these dark ages, a lot of software (mostly chat apps) only work on smartphones. While it’s easy to connect a USB-OTG hub to most smartphones (even my dirt-cheap Android smartphone supports this (now three years old)), having two keyboards on your desk can be kind of annoying.

While there are a bunch of possible solutions to this problem, many of these solutions do not fix the problem when you’re not on your home setup. Which is why I often just use QR codes to send URLs to my phone, and there are a lot of QR code generator sites out there.

QR code generator sites are useful because they work everywhere, but many are slow and clunky. Perhaps acceptable in a pinch, but… what if you could just generate QR codes on the terminal?

Well, some cursory googling revealed this library: https://github.com/qpliu/qrencode-go, which doesn’t have any external (non-standard library) dependencies, is short enough to skim over for malicious code, and comes with an easily adapted example. (I am reasonably confident that there is no malicious code at ad8353b4581fa11fc01a50ebf56db3833462fc13.)

Note: I very rarely use Go. Here is what I did to compile this:

$ git clone https://github.com/qpliu/qrencode-go
$ mkdir src
$ mv qrencode/ src/

$ cat > qrcodegenerator.go
package main
import (
"bytes"
"os"
"qrencode"
)
func main() {
var buf bytes.Buffer
for i, arg := range os.Args {
if i > 1 {
if err := buf.WriteByte(' '); err != nil {
panic(err)
}
}
if i > 0 {
if _, err := buf.WriteString(arg); err != nil {
panic(err)
}
}
}
grid, err := qrencode.Encode(buf.String(), qrencode.ECLevelQ)
if err != nil {
panic(err)
}
grid.TerminalOutput(os.Stdout)
}
$ GOPATH=$PWD go build qrcodegenerator.go
$ ./qrcodegenerator test
// QR CODE IS OUTPUT HERE

Note: the above code is adapted from example code in the README.md file and is therefore LGPL3.

Since Go binaries are static (that’s what I’ve heard at least), you can then move the executable anywhere you like (e.g. ~/bin) and generate QR codes anywhere. Note that they’re pretty huge, i.e. for ‘https://blog.qiqitori.com’ (26 bytes) the QR code’s width will be 62 characters. For e.g. ‘https://blog.qiqitori.com/2020/10/outputting-qr-codes-on-the-terminal/’ (this post) the width is 86 characters.

Leave a Reply

Your email address will not be published.