Get Golang flags as byte array - arrays

Question

I am using flag package to read all the parameters I am passing to my Golang program. The problem is that if I pass an argument such as "\x41BC", it is not read as a 3 byte array (with chars 'A', 'B' and 'C'), but as a 6 byte array ('\', 'x', '4', '1', 'B', 'C').
If it could be useful to answer, I am reading that string using:
flag.StringVar(&param, "param", "", "the param with hex chars")
Is there a way to avoid this?
Thanks in advance!

Answer 1

"\x41BC" is a quoted string. The flag package does not do any unquoting, it will just hand you over the arguments that were specified when starting your application. You can use the strconv.Unquote() and strconv.UnquoteChar() functions to unquote them.
One thing you should be aware of is that strconv.Unquote() can only unquote strings that are in quotes (e.g. start and end with a quote char " or a back quote char `), so we have to manually append that.
See this example:
s := `\x41BC`
fmt.Println(s)
s2, err := strconv.Unquote(`"` + s + `"`)
if err != nil {
panic(err)
}
fmt.Println(s2)
Output (try it on the Go Playground):
\x41BC
ABC
So if you want to be able to provide quoted strings as command line arguments and still have the unquoted values, you have to unquote them with strconv.Unquote() after calling flag.Parse(), for example:
var param string
flag.StringVar(&param, "param", "", "the param with hex chars")
flag.Parse()
var err error
param, err = strconv.Unquote(`"` + param + `"`)
if err != nil {
panic(err) // handle error
}
// param now contains the unquoted argument value