import "github.com/juju/cmd/v4"
var DefaultFormatters = map[string]Formatter{
"smart": FormatSmart,
"yaml": FormatYaml,
"json": FormatJson,
}DefaultFormatters holds the formatters that can be specified with the --format flag.
var ErrNoPath = errors.New("path not set")var ErrSilent = errors.New("cmd: error out silently")ErrSilent can be returned from Run to signal that Main should exit with code 1 without producing error output.
var FormatJson = json.MarshalFormatJson marshals value to a json-formatted []byte.
func CheckEmpty(args []string) errorCheckEmpty is a utility function that returns an error if args is not empty.
func FormatSmart(value interface{}) ([]byte, error)FormatSmart marshals value into a []byte according to the following rules:
* string: untouched
* bool: converted to `True` or `False` (to match pyjuju)
* int or float: converted to sensible strings
* []string: joined by `\n`s into a single string
* anything else: delegate to FormatYaml
func FormatYaml(value interface{}) ([]byte, error)FormatYaml marshals value to a yaml-formatted []byte, unless value is nil.
func IsErrSilent(err error) boolIsErrSilent returns whether the error should be logged from cmd.Main.
func IsRcPassthroughError(err error) boolIsRcPassthroughError returns whether the error is an RcPassthroughError.
func Main(c Command, ctx *Context, args []string) intMain runs the given Command in the supplied Context with the given arguments, which should not include the command name. It returns a code suitable for passing to os.Exit.
func NewCommandLogWriter(name string, out, err io.Writer) loggo.WriterNewCommandLogWriter creates a loggo writer for registration by the callers of a command. This way the logged output can also be displayed otherwise, e.g. on the screen.
func NewRcPassthroughError(code int) errorNewRcPassthroughError creates an error that will have the code used at the return code from the cmd.Main function rather than the default of 1 if there is an error.
func ParseAliasFile(aliasFilename string) map[string][]stringParseAliasFile will read the specified file and convert the content to a map of names to the command line arguments they relate to. The function will always return a valid map, even if it is empty.
func ZeroOrOneArgs(args []string) (string, error)ZeroOrOneArgs checks to see that there are zero or one args, and returns the value of the arg if provided, or the empty string if not.
type AppendStringsValue []stringAppendStringsValue implements gnuflag.Value for a value that can be set multiple times, and it appends each value to the slice.
func NewAppendStringsValue(target *[]string) *AppendStringsValueNewAppendStringsValue is used to create the type passed into the gnuflag.FlagSet Var function. f.Var(cmd.NewAppendStringsValue(&someMember), "name", "help")
func (v *AppendStringsValue) Set(s string) errorImplements gnuflag.Value Set.
func (v *AppendStringsValue) String() stringImplements gnuflag.Value String.
type Command interface {
// IsSuperCommand returns true if the command is a super command.
IsSuperCommand() bool
// Info returns information about the Command.
Info() *Info
// SetFlags adds command specific flags to the flag set.
SetFlags(f *gnuflag.FlagSet)
// Init initializes the Command before running.
Init(args []string) error
// Run will execute the Command as directed by the options and positional
// arguments passed to Init.
Run(ctx *Context) error
// AllowInterspersedFlags returns whether the command allows flag
// arguments to be interspersed with non-flag arguments.
AllowInterspersedFlags() bool
}Command is implemented by types that interpret command-line arguments.
type CommandBase struct{}CommandBase provides the default implementation for SetFlags, Init, and Help.
func (c *CommandBase) AllowInterspersedFlags() boolAllowInterspersedFlags returns true by default. Some subcommands may want to override this.
func (c *CommandBase) Init(args []string) errorInit in the simplest case makes sure there are no args.
func (c *CommandBase) IsSuperCommand() boolIsSuperCommand implements Command.IsSuperCommand
func (c *CommandBase) SetFlags(f *gnuflag.FlagSet)SetFlags does nothing in the simplest case.
type Context struct {
Dir string
Env map[string]string
Stdin io.Reader
Stdout io.Writer
Stderr io.Writer
// contains filtered or unexported fields
}Context represents the run context of a Command. Command implementations should interpret file names relative to Dir (see AbsPath below), and print output and errors to Stdout and Stderr respectively.
func DefaultContext() (*Context, error)DefaultContext returns a Context suitable for use in non-hosted situations.
func (ctx *Context) AbsPath(path string) stringAbsPath returns an absolute representation of path, with relative paths interpreted as relative to ctx.Dir.
func (ctx *Context) GetStderr() io.WriterGetStderr satisfies environs.BootstrapContext
func (ctx *Context) GetStdin() io.ReaderGetStdin satisfies environs.BootstrapContext
func (ctx *Context) GetStdout() io.WriterGetStdout satisfies environs.BootstrapContext
func (ctx *Context) Getenv(key string) stringGetenv looks up an environment variable in the context. It mirrors os.Getenv. An empty string is returned if the key is not set.
func (ctx *Context) Infof(format string, params ...interface{})Infof will write the formatted string to Stderr if quiet is false, but if quiet is true the message is logged.
func (ctx *Context) InterruptNotify(c chan<- os.Signal)InterruptNotify satisfies environs.BootstrapContext
func (ctx *Context) Setenv(key, value string) errorSetenv sets an environment variable in the context. It mirrors os.Setenv.
func (ctx *Context) StopInterruptNotify(c chan<- os.Signal)StopInterruptNotify satisfies environs.BootstrapContext
func (ctx *Context) Verbosef(format string, params ...interface{})Verbosef will write the formatted string to Stderr if the verbose is true, and to the logger if not.
type DeprecationCheck interface {
// Deprecated aliases emit a warning when executed. If the command is
// deprecated, the second return value recommends what to use instead.
Deprecated() (bool, string)
// Obsolete aliases are not actually registered. The purpose of this
// is to allow code to indicate ahead of time some way to determine
// that the command should stop working.
Obsolete() bool
}DeprecationCheck is used to provide callbacks to determine if a command is deprecated or obsolete.
type FileVar struct {
// Path is the path to the file.
Path string
// StdinMarkers are the Path values that should be interpreted as
// stdin. If it is empty then stdin is not supported.
StdinMarkers []string
}FileVar represents a path to a file.
func (f FileVar) IsStdin() boolIsStdin determines whether or not the path represents stdin.
func (f *FileVar) Open(ctx *Context) (io.ReadCloser, error)Open opens the file.
func (f *FileVar) Read(ctx *Context) ([]byte, error)Read returns the contents of the file.
func (f *FileVar) Set(v string) errorSet stores the chosen path name in f.Path.
func (f *FileVar) SetStdin(markers ...string)SetStdin sets StdinMarkers to the provided strings. If none are provided then the default of "-" is used.
func (f *FileVar) String() stringString returns the path to the file.
type Formatter func(value interface{}) ([]byte, error)Formatter converts an arbitrary object into a []byte.
type Info struct {
// Name is the Command's name.
Name string
// Args describes the command's expected positional arguments.
Args string
// Purpose is a short explanation of the Command's purpose.
Purpose string
// Doc is the long documentation for the Command.
Doc string
// Aliases are other names for the Command.
Aliases []string
}Info holds some of the usage documentation of a Command.
func (i *Info) Help(f *gnuflag.FlagSet) []byteHelp renders i's content, along with documentation for any flags defined in f. It calls f.SetOutput(ioutil.Discard).
type Log struct {
// If DefaultConfig is set, it will be used for the
// default logging configuration.
DefaultConfig string
Path string
Verbose bool
Quiet bool
Debug bool
ShowLog bool
Config string
Factory WriterFactory
}Log supplies the necessary functionality for Commands that wish to set up logging.
func (l *Log) AddFlags(f *gnuflag.FlagSet)AddFlags adds appropriate flags to f.
func (l *Log) GetLogWriter(target io.Writer) loggo.WriterGetLogWriter returns a logging writer for the specified target.
func (log *Log) Start(ctx *Context) errorStart starts logging using the given Context.
type MissingCallback func(ctx *Context, subcommand string, args []string) errorMissingCallback defines a function that will be used by the SuperCommand if the requested subcommand isn't found.
type Output struct {
// contains filtered or unexported fields
}Output is responsible for interpreting output-related command line flags and writing a value to a file or to stdout as directed.
func (c *Output) AddFlags(f *gnuflag.FlagSet, defaultFormatter string, formatters map[string]Formatter)AddFlags injects the --format and --output command line flags into f.
func (c *Output) Name() stringfunc (c *Output) Write(ctx *Context, value interface{}) (err error)Write formats and outputs the value as directed by the --format and --output command line flags.
type RcPassthroughError struct {
Code int
}RcPassthroughError indicates that a Juju plugin command exited with a non-zero exit code. This error is used to exit with the return code.
func (e *RcPassthroughError) Error() stringError implements error.
type StringsValue []stringStringsValue implements gnuflag.Value for a comma separated list of strings. This allows flags to be created where the target is []string, and the caller is after comma separated values.
func NewStringsValue(defaultValue []string, target *[]string) *StringsValueNewStringsValue is used to create the type passed into the gnuflag.FlagSet Var function. f.Var(cmd.NewStringsValue(defaultValue, &someMember), "name", "help")
func (v *StringsValue) Set(s string) errorImplements gnuflag.Value Set.
func (v *StringsValue) String() stringImplements gnuflag.Value String.
type SuperCommand struct {
CommandBase
Name string
Purpose string
Doc string
Log *Log
Aliases []string
// contains filtered or unexported fields
}SuperCommand is a Command that selects a subcommand and assumes its properties; any command line arguments that were not used in selecting the subcommand are passed down to it, and to Run a SuperCommand is to run its selected subcommand.
func NewSuperCommand(params SuperCommandParams) *SuperCommandNewSuperCommand creates and initializes a new SuperCommand, and returns
the fully initialized structure.
func (c *SuperCommand) AddHelpTopic(name, short, long string, aliases ...string)AddHelpTopic adds a new help topic with the description being the short param, and the full text being the long param. The description is shown in 'help topics', and the full text is shown when the command 'help ' is called.
func (c *SuperCommand) AddHelpTopicCallback(name, short string, longCallback func() string)AddHelpTopicCallback adds a new help topic with the description being the short param, and the full text being defined by the callback function.
func (c *SuperCommand) AllowInterspersedFlags() boolFor a SuperCommand, we want to parse the args with allowIntersperse=false. This will mean that the args may contain other options that haven't been defined yet, and that only options that relate to the SuperCommand itself can come prior to the subcommand name.
func (c *SuperCommand) Info() *InfoInfo returns a description of the currently selected subcommand, or of the SuperCommand itself if no subcommand has been specified.
func (c *SuperCommand) Init(args []string) errorInit initializes the command for running.
func (c *SuperCommand) IsSuperCommand() boolIsSuperCommand implements Command.IsSuperCommand
func (c *SuperCommand) Register(subcmd Command)Register makes a subcommand available for use on the command line. The command will be available via its own name, and via any supplied aliases.
func (c *SuperCommand) RegisterAlias(name, forName string, check DeprecationCheck)RegisterAlias makes an existing subcommand available under another name.
If check is supplied, and the result of the Obsolete call is true,
then the alias is not registered.
func (c *SuperCommand) RegisterDeprecated(subcmd Command, check DeprecationCheck)RegisterDeprecated makes a subcommand available for use on the command line if it is not obsolete. It inserts the command with the specified DeprecationCheck so that a warning is displayed if the command is deprecated.
func (c *SuperCommand) RegisterSuperAlias(name, super, forName string, check DeprecationCheck)RegisterSuperAlias makes a subcommand of a registered supercommand
available under another name. This is useful when the command structure is
being refactored. If check is supplied, and the result of the Obsolete
call is true, then the alias is not registered.
func (c *SuperCommand) Run(ctx *Context) errorRun executes the subcommand that was selected in Init.
func (c *SuperCommand) SetCommonFlags(f *gnuflag.FlagSet)SetCommonFlags creates a new "commonflags" flagset, whose flags are shared with the argument f; this enables us to add non-global flags to f, which do not carry into subcommands.
func (c *SuperCommand) SetFlags(f *gnuflag.FlagSet)SetFlags adds the options that apply to all commands, particularly those due to logging.
type SuperCommandParams struct {
// UsagePrefix should be set when the SuperCommand is
// actually a subcommand of some other SuperCommand;
// if NotifyRun is called, it name will be prefixed accordingly,
// unless UsagePrefix is identical to Name.
UsagePrefix string
// Notify, if not nil, is called when the SuperCommand
// is about to run a sub-command.
NotifyRun func(cmdName string)
Name string
Purpose string
Doc string
Log *Log
MissingCallback MissingCallback
Aliases []string
Version string
// UserAliasesFilename refers to the location of a file that contains
// name = cmd [args...]
// values, that is used to change default behaviour of commands in order
// to add flags, or provide short cuts to longer commands.
UserAliasesFilename string
}SuperCommandParams provides a way to have default parameter to the
NewSuperCommand call.
type UnrecognizedCommand struct {
Name string
}func (e *UnrecognizedCommand) Error() stringtype WriterFactory interface {
NewWriter(target io.Writer) loggo.Writer
}WriterFactory defines the single method to create a new logging writer for a specified output target.
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