Show parameter name in usage message of flag

Flag package provides features about command-line flag parsing. It includes a usage message of course. For example, it shows them as following.

package main

import (
    "flag"
    "os"
)

func main() {
    var importFile string
    var config bool
    var number int

    flags := flag.NewFlagSet("mycmd", flag.ExitOnError)
    flags.StringVar(&importFile, "import", "", "import file.")
    flags.BoolVar(&config, "c", false, "edit config.")
    flags.IntVar(&number, "n", 0, "number of executions.")

    flags.Parse(os.Args[1:])
}

$ ./mycmd --help
Usage of mycmd:
  -c    edit config.
  -import string
        import file.
  -n int
        number of executions.

This build automatically. The parameter name uses the flag's type. But sometimes want to customize parameter name.
For example, in the example above, I would like to use file as an argument to -import and number as an argument to -n(Because that is surely more natural ;)).

This can specify from usage argument xxVar methods. If includes a back-quoted name in usage, it uses for the parameter name.

package main

import (
    "flag"
    "os"
)

func main() {
    var importFile string
    var config bool
    var number int

    flags := flag.NewFlagSet("mycmd", flag.ExitOnError)
    flags.StringVar(&importFile, "import", "", "Import `file`.")
    flags.BoolVar(&config, "c", false, "Edit config.")
    flags.IntVar(&number, "n", 0, "`Number` of executions.")

    flags.Parse(os.Args[1:])
}

$ ./mycmd --help 
Usage of mycmd:
  -c    edit config.
  -import file
        import file.
  -n number
        number of executions.

I didn't know long about this. This describes in the doc of PrintDefaults func.

I hope this helps someone.

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Show parameter name in usage message of flag

y-yagi

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