//
// SPDX-License-Identifier: Apache-2.0
-// package cmd defines a RunFunc type, representing a process that can
-// be invoked from a command line.
+// package cmd helps define reusable functions that can be exposed as
+// [subcommands of] command line programs.
package cmd
import (
+ "flag"
"fmt"
"io"
+ "io/ioutil"
+ "path/filepath"
+ "regexp"
+ "runtime"
+ "sort"
+ "strings"
)
-// A RunFunc runs a command with the given args, and returns an exit
-// code.
-type RunFunc func(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int
+type Handler interface {
+ RunCommand(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int
+}
+
+type HandlerFunc func(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int
+
+func (f HandlerFunc) RunCommand(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+ return f(prog, args, stdin, stdout, stderr)
+}
+
+type Version string
-// Multi returns a command that looks up its first argument in m, and
-// runs the resulting RunFunc with the remaining args.
+func (v Version) RunCommand(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+ prog = regexp.MustCompile(` -*version$`).ReplaceAllLiteralString(prog, "")
+ fmt.Fprintf(stdout, "%s %s (%s)\n", prog, v, runtime.Version())
+ return 0
+}
+
+// Multi is a Handler that looks up its first argument in a map, and
+// invokes the resulting Handler with the remaining args.
//
// Example:
//
-// os.Exit(Multi(map[string]RunFunc{
-// "foobar": func(prog string, args []string) int {
+// os.Exit(Multi(map[string]Handler{
+// "foobar": HandlerFunc(func(prog string, args []string) int {
// fmt.Println(args[0])
// return 2
-// },
+// }),
// })("/usr/bin/multi", []string{"foobar", "baz"}))
//
// ...prints "baz" and exits 2.
-func Multi(m map[string]RunFunc) RunFunc {
- return func(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
- if len(args) < 1 {
- fmt.Fprintf(stderr, "usage: %s command [args]", prog)
- return 2
+type Multi map[string]Handler
+
+func (m Multi) RunCommand(prog string, args []string, stdin io.Reader, stdout, stderr io.Writer) int {
+ _, basename := filepath.Split(prog)
+ basename = strings.TrimPrefix(basename, "arvados-")
+ basename = strings.TrimPrefix(basename, "crunch-")
+ if cmd, ok := m[basename]; ok {
+ return cmd.RunCommand(prog, args, stdin, stdout, stderr)
+ } else if len(args) < 1 {
+ fmt.Fprintf(stderr, "usage: %s command [args]\n", prog)
+ m.Usage(stderr)
+ return 2
+ } else if cmd, ok = m[args[0]]; ok {
+ return cmd.RunCommand(prog+" "+args[0], args[1:], stdin, stdout, stderr)
+ } else {
+ fmt.Fprintf(stderr, "%s: unrecognized command %q\n", prog, args[0])
+ m.Usage(stderr)
+ return 2
+ }
+}
+
+func (m Multi) Usage(stderr io.Writer) {
+ fmt.Fprintf(stderr, "\nAvailable commands:\n")
+ m.listSubcommands(stderr, "")
+}
+
+func (m Multi) listSubcommands(out io.Writer, prefix string) {
+ var subcommands []string
+ for sc := range m {
+ if strings.HasPrefix(sc, "-") {
+ // Some subcommands have alternate versions
+ // like "--version" for compatibility. Don't
+ // clutter the subcommand summary with those.
+ continue
}
- if cmd, ok := m[args[0]]; !ok {
- fmt.Fprintf(stderr, "unrecognized command %q", args[0])
- return 2
- } else {
- return cmd(prog+" "+args[0], args[1:], stdin, stdout, stderr)
+ subcommands = append(subcommands, sc)
+ }
+ sort.Strings(subcommands)
+ for _, sc := range subcommands {
+ switch cmd := m[sc].(type) {
+ case Multi:
+ cmd.listSubcommands(out, prefix+sc+" ")
+ default:
+ fmt.Fprintf(out, " %s%s\n", prefix, sc)
}
}
}
+
+type FlagSet interface {
+ Init(string, flag.ErrorHandling)
+ Args() []string
+ NArg() int
+ Parse([]string) error
+ SetOutput(io.Writer)
+ PrintDefaults()
+}
+
+// SubcommandToFront silently parses args using flagset, and returns a
+// copy of args with the first non-flag argument moved to the
+// front. If parsing fails or consumes all of args, args is returned
+// unchanged.
+//
+// SubcommandToFront invokes methods on flagset that have side
+// effects, including Parse. In typical usage, flagset will not used
+// for anything else after being passed to SubcommandToFront.
+func SubcommandToFront(args []string, flagset FlagSet) []string {
+ flagset.Init("", flag.ContinueOnError)
+ flagset.SetOutput(ioutil.Discard)
+ if err := flagset.Parse(args); err != nil || flagset.NArg() == 0 {
+ // No subcommand found.
+ return args
+ }
+ // Move subcommand to the front.
+ flagargs := len(args) - flagset.NArg()
+ newargs := make([]string, len(args))
+ newargs[0] = args[flagargs]
+ copy(newargs[1:flagargs+1], args[:flagargs])
+ copy(newargs[flagargs+1:], args[flagargs+1:])
+ return newargs
+}
projects / arvados.git / blobdiff