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usage.go
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/
usage.go
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package main
import (
"bytes"
"flag"
"fmt"
"io"
"text/tabwriter"
)
func optionTable(w io.Writer, rows [][]string) {
tw := tabwriter.NewWriter(w, 2, 4, 2, ' ', 0)
for _, row := range rows {
for i, cell := range row {
if i > 0 {
tw.Write([]byte("\t"))
}
tw.Write([]byte(cell))
}
tw.Write([]byte("\n"))
}
tw.Flush()
}
func usageFor(fs *flag.FlagSet, usage string) func() {
return func() {
var b bytes.Buffer
b.WriteString("Usage:\n " + usage + "\n")
var options [][]string
fs.VisitAll(func(f *flag.Flag) {
var dash = "-"
if len(f.Name) > 1 {
dash = "--"
}
var opt = " " + dash + f.Name
if f.DefValue != "false" {
opt += "=" + f.DefValue
}
options = append(options, []string{opt, f.Usage})
})
if len(options) > 0 {
b.WriteString("\nOptions:\n")
optionTable(&b, options)
}
fmt.Println(b.String())
}
}