README
¶
cronparse
cronparse is a tool that can parse and expand cron expressions into the times that said expression will run at.
e.g.
$ cronparse */15 0 1,15 * 1-5 /usr/bin/find
minute 0 15 30 45
hour 0
day of month 1 15
month 1 2 3 4 5 6 7 8 9 10 11 12
day of week 1 2 3 4 5
command /usr/bin/find
Contents
Building
cronparse is built using Go. To build cronparse you require the Go tool, you can find how to do that for your specific system here.
Once you have installed Go, you can get up and running by cloning this repository to a location of your choice and running:
go run cmd/cronparse/main.go */15 0 1,15 * 1-5 /usr/bin/find
Alternatively if you have your $GOPATH/bin added to your $PATH you can run:
go get -u github.com/alistairjudson/cronparse/cmd/cronparse
Tests
To run the tests you can simply run:
go test ./...
Linting
This project uses golangci-lint in order to lint the project
it is configured by the .golangci.yml file.
Architecture
cronparse has a couple of stages when it comes to parsing interpreting the expression, these stages are:
Lexical Analysis
cronparse uses a finite state machine to tokenise the individual components of the input into tokens, the way that this is implemented is heavily inspired by the approach taken by Rob Pike in this talk. If you want to find out more about this, this blog post is pretty cool.
In the tokenisation stage, the values themselves are not validated, only that the syntax of the expression matches that of a component of a cron expression.
Parsing
The parsing of the cron expression is pretty lazy, it just uses some simple pattern matching in order to validate the expressions, and expand the values that they represent.
Documentation
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Index ¶
Constants ¶
This section is empty.
Variables ¶
var CronParser = Parser{ newComponentParser("minute", parse.MinuteParser.Parse), newComponentParser("hour", parse.HourParser.Parse), newComponentParser("day of month", parse.DayOfMonthParser.Parse), newComponentParser("month", parse.MonthParser.Parse), newComponentParser("day of week", parse.DayOfWeekParser.Parse), }
CronParser is a type that can parse the components of a cron expression and expand them into the values that they run on
Functions ¶
This section is empty.
Types ¶
type ComponentParser ¶
type ComponentParser struct {
Name string
Parser PartParser
}
ComponentParser is a parser for a specific portion of a cron expression
type Numberer ¶
type Numberer interface {
Numbers() []int
}
Numberer is a type that can give you the expanded cron values
type ParsedComponent ¶
ParsedComponent is the result of parsing a cron component
func (ParsedComponent) String ¶
func (p ParsedComponent) String() string
String implements fmt.Stringer and pretty prints a parsed cron component
type Parser ¶
type Parser []ComponentParser
Parser is a type that can hold multiple ComponentParsers
type PartParser ¶
PartParser is a type that can parse part of a cron expression
Source Files
Directories