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`onPrompt`

Events triggered by changes in state of the interactive shell

Description

onPrompt events are triggered by changes in state of the interactive shell (often referred to as readline). Those states are defined in the interrupts section below.

Usage

event onPrompt name=(before|return|after|command-completion|abort|eof) { code block }

!event onPrompt name[.before|.return|.after|.command-completion|.abort|.eof]

Valid Interrupts

abort Triggered if ctrl+c pressed while in the interactive prompt
after Triggered after user has written a command into the interactive prompt and then hit enter
before Triggered before readline displays the interactive prompt
command-completion Triggered after a command has completed. Also passes it’s exit number via STDIN. A cheaper alternative to onCommandCompletion event
eof Triggered if ctrl+d pressed while in the interactive prompt
return Triggered when return is pressed while cursor is still on same line as prompt

Payload

The following payload is passed to the function via stdin:

{
    "Name": "",
    "Interrupt": {
        "Name": "",
        "Operation": "",
        "CmdLine": "",
        "ExitNum": -1
    }
}

Name

This is the namespaced name – ie the name and operation.

Interrupt/Name

This is the name you specified when defining the event.

Interrupt/Operation

This is the interrupt you specified when defining the event.

Valid interrupt operation values are specified below.

Interrupt/CmdLine

This is the command line executed, ie what you typed into the readline prompt.

Please note this is only populated if the interrupt is after or command-completion.

Interrupt/ExitNum

This is the exit number for the command line that is executed.

Please note this is only populated if the interrupt is command-completion otherwise it defaults to -1.

Event Return

This event doesn’t have any $EVENT_RETURN parameters.

Examples

Interrupt ‘before’

event onPrompt example=before {
    out "This will appear before your command prompt"
}

Interrupt ‘after’

event onPrompt example=after {
    out "This will appear after you've hit [enter] on your command prompt"
    out "...but before the command executes"
}

Echo the command line

» event onPrompt echo=after { -> set event; out $event.Interrupt.CmdLine }
» echo hello world
echo hello world
hello world

Detail

Standard out and error

Stdout and stderr are both written to the terminal. So this event can be used to provide multiple additional lines to the prompt since readline only supports one line for the prompt itself and three extra lines for the hint text.

Order of execution

Interrupts are run in alphabetical order. So an event named “alfa” would run before an event named “zulu”. If you are writing multiple events and the order of execution matters, then you can prefix the names with a number, eg 10_jump

Namespacing

This event is namespaced as $(NAME).$(OPERATION).

For example, if an event in onPrompt was defined as example=eof then its namespace would be example.eof and thus a subsequent event with the same name but different operation, eg example=abort, would not overwrite the former event defined against the interrupt eof.

The reason for this namespacing is because you might legitimately want the same name for different operations (eg a smart prompt that has elements triggered from different interrupts).

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