Add --print-next-match-and-exit and --format

README.md

@@ -4,15 +4,19 @@ A tiny tool that waits until a given cron expression would trigger, and then jus
 
 ![image](doc/screenshot.png)
 
-## Example
-
+## Examples
 
 ```sh
 $ wait-for-cron-expression-match "*/5 * * * *"
 [wait-for-cron-expression-match] 2020/07/10 11:59:29.965045 waiting 30.035156s until next match (2020-07-10T12:00:00+02:00) of cron expression ["*/5 * * * *"]
 [wait-for-cron-expression-match] 2020/07/10 12:00:00.966919 done
 ```
 
+```sh
+$ wait-for-cron-expression-match -print-next-match-and-exit "*/3 * * * *"
+2020-07-10T12:48:00+02:00
+```
+
 ## Contents
 
 - [Get it](#get-it)
@@ -36,6 +40,10 @@ wait-for-cron-expression-match [OPTIONS] [CRON_EXPRESSION [CRON_EXPRESSIONS...]]
 Usage of wait-for-cron-expression-match:
   -dots
     	Print dots to stdout while waiting
+  -format string
+    	Timestamp format (default "2006-01-02T15:04:05Z07:00")
+  -print-next-match-and-exit
+    	Only print the timestamp of the next expression match and exit (without waiting)
   -q	(alias for -quiet)
   -quiet
     	Suppress all output

README.template.md

@@ -4,15 +4,19 @@ A tiny tool that waits until a given cron expression would trigger, and then jus
 
 ![image](doc/screenshot.png)
 
-## Example
-
+## Examples
 
 ```sh
 $ ${APP} "*/5 * * * *"
 [${APP}] 2020/07/10 11:59:29.965045 waiting 30.035156s until next match (2020-07-10T12:00:00+02:00) of cron expression ["*/5 * * * *"]
 [${APP}] 2020/07/10 12:00:00.966919 done
 ```
 
+```sh
+$ ${APP} -print-next-match-and-exit "*/3 * * * *"
+2020-07-10T12:48:00+02:00
+```
+
 ## Contents
 
 - [Get it](#get-it)

main.go

@@ -11,8 +11,10 @@ import (
 )
 
 var config struct {
-	Quiet     bool
-	PrintDots bool
+	Quiet                     bool
+	PrintDots                 bool
+	PrintNextTimestampAndExit bool
+	TimestampFormat           string
 
 	cronExpressions    []string
 	schedules          []cron.Schedule
@@ -24,6 +26,9 @@ var app = "wait-for-cron-expression-match"
 func init() {
 	log.SetFlags(log.Ltime | log.Ldate | log.Lmicroseconds)
 	log.SetPrefix(fmt.Sprintf("[%s] ", app))
+	config.TimestampFormat = time.RFC3339
+	flag.BoolVar(&config.PrintNextTimestampAndExit, "print-next-match-and-exit", config.PrintNextTimestampAndExit, "Only print the timestamp of the next expression match and exit (without waiting)")
+	flag.StringVar(&config.TimestampFormat, "format", config.TimestampFormat, "Timestamp format")
 	flag.BoolVar(&config.Quiet, "quiet", config.Quiet, "Suppress all output")
 	flag.BoolVar(&config.Quiet, "q", config.Quiet, "(alias for -quiet)")
 	flag.BoolVar(&config.PrintDots, "dots", config.PrintDots, "Print dots to stdout while waiting")
@@ -60,6 +65,10 @@ func main() {
 			next = nextNew
 		}
 	}
+	if config.PrintNextTimestampAndExit {
+		fmt.Println(next.Format(config.TimestampFormat))
+		return
+	}
 	delta := next.Sub(now)
 	if delta < tickInterval {
 		tickInterval = delta