selman.me
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crun: add thing
+109
+109
crun/main.go
+109
crun/main.go
···
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package main
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import (
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"fmt"
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"io"
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"os"
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"strconv"
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"strings"
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)
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func main() {
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if err := realMain(os.Args, os.Stdout); err != nil {
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fmt.Fprintln(os.Stderr, err)
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os.Exit(1)
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}
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}
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func realMain(args []string, stdout io.Writer) error {
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if len(args) != 2 {
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return fmt.Errorf("usage: %s <cron expression>", args[0])
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}
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cron := args[1]
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description, err := DescribeCron(cron)
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if err != nil {
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return err
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}
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fmt.Fprintln(stdout, description)
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return nil
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}
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func DescribeCron(cron string) (string, error) {
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fields := strings.Fields(cron)
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if len(fields) != 5 {
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return "", fmt.Errorf("cron expression should have 5 fields")
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}
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minutes := fields[0]
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hours := fields[1]
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dayOfMonth := fields[2]
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month := fields[3]
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dayOfWeek := fields[4]
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switch {
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case minutes == "*" && hours == "*" && dayOfMonth == "*" && month == "*" && dayOfWeek == "*":
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return "This runs every minute.", nil
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case minutes == "*/15" && hours == "*" && dayOfMonth == "*" && month == "*" && dayOfWeek == "*":
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return "This runs every 15 minutes.", nil
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case minutes == "0" && hours == "*" && dayOfMonth == "*" && month == "*" && dayOfWeek == "*":
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return "This runs at the start of every hour.", nil
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case minutes == "0" && hours == "*/3" && dayOfMonth == "*" && month == "*" && dayOfWeek == "*":
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return "This runs every 3 hours.", nil
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case minutes == "0" && hours == "0" && dayOfMonth == "*" && month == "*" && dayOfWeek == "*":
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return "This runs every day at midnight.", nil
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case minutes == "0" && hours == "0" && dayOfMonth == "1" && month == "*" && dayOfWeek == "*":
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return "This runs every month at midnight on the first day.", nil
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case minutes == "0" && hours == "0" && dayOfMonth == "1" && month == "1" && dayOfWeek == "*":
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return "This runs every year at midnight on January 1.", nil
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}
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// Otherwise, construct the description
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description := "This runs "
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// Minutes
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if minutes == "*" {
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description += "every minute "
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} else {
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min, _ := strconv.Atoi(minutes)
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description += fmt.Sprintf("at %d minutes past the hour ", min)
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}
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// Hours
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if hours == "*" {
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description += "of every hour "
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} else {
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hr, _ := strconv.Atoi(hours)
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description += fmt.Sprintf("at %02d:00 ", hr)
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}
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// Day of Month
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if dayOfMonth == "*" {
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description += "on every day "
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} else {
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dom, _ := strconv.Atoi(dayOfMonth)
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description += fmt.Sprintf("on the %d of the month ", dom)
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}
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// Month
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if month == "*" {
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description += "of every month "
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} else {
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m, _ := strconv.Atoi(month)
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description += fmt.Sprintf("in month %d ", m)
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}
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// Day of Week
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if dayOfWeek == "*" {
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description += "and on every day of the week."
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} else {
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dow, _ := strconv.Atoi(dayOfWeek)
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description += fmt.Sprintf("and on the %d day of the week.", dow)
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}
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return description, nil
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}