GitHub - bobg/subcmd (original) (raw)

Subcmd - command-line interfaces with subcommands and flags

This is subcmd, a Go package for writing command-line programs that require flag parsing and that have “subcommands” that also require flag parsing.

Use it when you want your program to parse command lines that look like this:

command -globalopt subcommand -subopt1 FOO -subopt2 ARG1 ARG2

Subcommands may have sub-subcommands and so on. Subcommands may also be implemented as separate executables.

This is a layer on top of the standard Go flag package.

Usage

import ( "context" "database/sql" "flag"

"github.com/bobg/subcmd/v2" )

func main() { // Parse global flags normally. dbname := flag.String("db", "", "database connection string") flag.Parse()

db, err := sql.Open(dbdriver, *dbname) if err != nil { ... }

// Stash global options in a top-level command object. c := command{db: db}

// Run the subcommand given in the remainder of the command line. err = subcmd.Run(context.Background(), c, flag.Args()) if err != nil { ... } }

// The top-level command object. type command struct { db *sql.DB }

// To be used in subcmd.Run above, command must implement this method. func (c command) Subcmds() subcmd.Map { return subcmd.Commands( // The "list" subcommand takes one flag, -reverse. "list", c.list, "list employees", subcmd.Params( "-reverse", subcmd.Bool, false, "reverse order of list", ),

// The "add" subcommand takes no flags but one positional argument.
"add", c.add, "add new employee", subcmd.Params(
  "name", subcmd.String, "", "employee name",
)

) }

// Implementation of the "list" subcommand. // The value of the -reverse flag is passed as an argument. func (c command) list(ctx context.Context, reverse bool, _ []string) error { query := "SELECT name FROM employees ORDER BY name" if reverse { query += " DESC" } rows, err := c.db.QueryContext(ctx, query) if err != nil { ... } defer rows.Close() for rows.Next() { ... } return rows.Err() }

// Implementation of the "add" subcommand. func (c command) add(ctx context.Context, name string, _ []string) error { _, err := c.db.ExecContext(ctx, "INSERT INTO employees (name) VALUES ($1)", name) return err }