Gosh - A pluggable interactive shell written Go
Gosh (or Go shell) is a framework that uses Go's plugin system to create
for building interactive console-based shell programs. A gosh shell is
comprised of a collection of Go plugins which implement one or more commands.
When gosh starts, it searches directory ./plugins for available shared object
files that implement command plugins.
Getting started
Pre-requisites
- Go 1.8 or above
- Linux
- Mac OSX
Gosh makes it easy to create shell programs. First, download or clone this
repository. For a quick start, run the following:
go run shell/gosh.go
This will produce the following output:
888
888
888
.d88b. .d88b. .d8888b 88888b.
d88P"88bd88""88b88K 888 "88b
888 888888 888"Y8888b.888 888
Y88b 888Y88..88P X88888 888
"Y88888 "Y88P" 88888P'888 888
888
Y8b d88P
"Y88P"
No commands found
After the splashscreen is displayed, gosh informs you that no commands found, as expected. Next,
exit the gosh shell (Ctrl-C) and let us compile the example plugins that comes with the source code.
go build -buildmode=plugin -o plugins/sys_command.so plugins/syscmd.go
The previous command will compile plugins/syscmd.go and outputs shared object
plugins/sys_command.so, as a Go plugin file. Verify the shared object file was created:
> ls -lh plugins/
total 3.2M
-rw-rw-r-- 1 4.5K Mar 19 18:23 syscmd.go
-rw-rw-r-- 1 3.2M Mar 19 19:14 sys_command.so
-rw-rw-r-- 1 1.4K Mar 19 18:23 testcmd.go
Now, when gosh is restarted, it will dynamically load the commands implemented in the shared object file:
> go run shell/gosh.go
...
Loaded 4 command(s)...
Type help for available commands
gosh>
As indicated, typing help lists all available commands in the shell:
gosh> help
help: prints help information for other commands.
Available commands
------------------
prompt: sets a new shell prompt
sys: sets a new shell prompt
help: prints help information for other commands.
exit: exits the interactive shell immediately
Use "help <command-name>" for detail about the specified command
A command
A Gosh Command is represented by type api/Command:
type Command interface {
Name() string
Usage() string
ShortDesc() string
LongDesc() string
Exec(context.Context, []string) (context.Context, error)
}
The Gosh framework searches for Go plugin files in the ./plugins directory. Each package plugin must
export a variable named Commands which is of type :
type Commands interface {
...
Registry() map[string]Command
}
Type Commands type returns a list of Command via the Registry().
The following shows example command file plugins/testcmd.go. It implements
two commands via types helloCmd and goodbyeCmd. The commands are exported via type testCmds using
method Registry():
package main
import (
"context"
"fmt"
"io"
"github.com/vladimirvivien/gosh/api"
)
type helloCmd string
func (t helloCmd) Name() string { return string(t) }
func (t helloCmd) Usage() string { return `hello` }
func (t helloCmd) ShortDesc() string { return `prints greeting "hello there"` }
func (t helloCmd) LongDesc() string { return t.ShortDesc() }
func (t helloCmd) Exec(ctx context.Context, args []string) (context.Context, error) {
out := ctx.Value("gosh.stdout").(io.Writer)
fmt.Fprintln(out, "hello there")
return ctx, nil
}
type goodbyeCmd string
func (t goodbyeCmd) Name() string { return string(t) }
func (t goodbyeCmd) Usage() string { return t.Name() }
func (t goodbyeCmd) ShortDesc() string { return `prints message "bye bye"` }
func (t goodbyeCmd) LongDesc() string { return t.ShortDesc() }
func (t goodbyeCmd) Exec(ctx context.Context, args []string) (context.Context, error) {
out := ctx.Value("gosh.stdout").(io.Writer)
fmt.Fprintln(out, "bye bye")
return ctx, nil
}
// command module
type testCmds struct{}
func (t *testCmds) Init(ctx context.Context) error {
out := ctx.Value("gosh.stdout").(io.Writer)
fmt.Fprintln(out, "test module loaded OK")
return nil
}
func (t *testCmds) Registry() map[string]api.Command {
return map[string]api.Command{
"hello": helloCmd("hello"),
"goodbye": goodbyeCmd("goodbye"),
}
}
var Commands testCmds
License
MIT