Parse a command line string into flags and arguments in Golang

Question

I'm looking for a package that would take a string such as -v --format "some example" -i test and parse it into a slice of strings, handling quotes, spaces, etc. properly:

-v
--format
some example
-i
test

I've checked the built-in flag package as well as other flag handling packages on Github but none of them seem to handle this particular case of parsing a raw string into tokens. Before trying to do it myself I'd rather look for a package as I'm sure there are a lot of special cases to handle.

Any suggestion?

Answer 1

For information, this is the function I've ended up creating.

It splits a command into its arguments. For example, cat -v "some file.txt", will return ["cat", "-v", "some file.txt"].

It also correctly handles escaped characters, spaces in particular. So cat -v some\ file.txt will also correctly be split into ["cat", "-v", "some file.txt"]

func parseCommandLine(command string) ([]string, error) {
    var args []string
    state := "start"
    current := ""
    quote := "\""
    escapeNext := true
    for i := 0; i < len(command); i++ {
        c := command[i]

        if state == "quotes" {
            if string(c) != quote {
                current += string(c)
            } else {
                args = append(args, current)
                current = ""
                state = "start"
            }
            continue
        }

        if (escapeNext) {
            current += string(c)
            escapeNext = false
            continue
        }

        if (c == '\\') {
            escapeNext = true
            continue
        }

        if c == '"' || c == '\'' {
            state = "quotes"
            quote = string(c)
            continue
        }

        if state == "arg" {
            if c == ' ' || c == '\t' {
                args = append(args, current)
                current = ""
                state = "start"
            } else {
                current += string(c)
            }
            continue
        }

        if c != ' ' && c != '\t' {
            state = "arg"
            current += string(c)
        }
    }

    if state == "quotes" {
        return []string{}, errors.New(fmt.Sprintf("Unclosed quote in command line: %s", command))
    }

    if current != "" {
        args = append(args, current)
    }

    return args, nil
}