cmd

A library to create shell-like command processors, slightly inspired by the Python cmd/cmd2 package

Installation

$ go get github.com/gobs/cmd

Documentation

http://godoc.org/github.com/gobs/cmd

Example

import "github.com/gobs/cmd"

// return true to stop command loop
func Exit(line string) (stop bool) {
      fmt.Println("goodbye!")
      return true
}
  
// change the prompt
func (cmd *Cmd) SetPrompt(line string) (stop bool) {
      cmd.Prompt = line
      return
}

// initialize Cmd structure
commander := &cmd.Cmd{Prompt: "> ",}
commander.Init()

// add inline method
commander.Add(cmd.Command{
      "ls",
      `list stuff`,
      func(line string) (stop bool) {
          fmt.Println("listing stuff")
          return
  }})

// add another command
commander.Add(cmd.Command{
      Name: "prompt",
      Help: `Set prompt`,
      Call: commander.SetPrompt
      })

// and one more
commander.Add(cmd.Command{
      "exit",
      `terminate example`,
      Exit
  })

// start command loop
commander.CmdLoop()

Available commands

The command processor predefines a few useful commands, including function definitions and conditionals.

Use the help command to see the list of available commands.

Function definition is similart to bash functions:

function test {
    echo Function name: $0
    echo Number of arguments: $#
    echo First argument: $1
    echo All arguments: $*
}

but you can also define a very short function (one-liner):

function oneliner echo "very short function"

Variables can be set/listed using the var command:

> var catch 22

> var catch
    catch: 22

> echo $catch
    22

To unset/remove a variable use:

> var -r catch
> var -rm catch
> var --remove catch

note that currently only "string" values are supported (i.e. var x 1 is the same as `var x "1"1)

Conditional flow with if and else commands:

if (condition) {
    # true path
} else {
    # false path
}

The else block is optional:

if (condition) {
    # only the truth
}

And the short test:

if (condition) echo "yes!"

Conditions:

The simplest condition is the "non empty argument":

if true echo "yes, it's true"

But if you are using a variable you need to quote it:

if "$nonempty" echo "nonempty is not empty"

All other conditionals are in the form: (cond arguments...):

(z $var)        # $var is empty

(n $var)        # $var is not empty

(t $var)        # $var is true (true, 1, not-empty var)

(f $var)        # $var is false (false, 0, empty empty)

(eq $var val)   # $var == val

(ne $var val)   # $var != val

(gt $var val)   # $var > val

(gte $var val)  # $var >= val

(lt $var val)   # $var < val

(lte $var val)  # $var <= val

(startswith $var val) # $var starts with val
(endswith $var val)   # $var ends with val
(contains $var val)   # $var contains val

Conditions can also be negated with the "!" operator:

if !true echo "not true"
if !(contains $var val) echo val not in $var

As for variables, for now only string comparisons are supported.