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gorhill 2013-08-30 08:05:01 -04:00
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@ -4,12 +4,12 @@ Cron expression parser in Go language (golang).
Given a cron expression and a time stamp, you can get the next time stamp which satisfy the cron expression. Given a cron expression and a time stamp, you can get the next time stamp which satisfy the cron expression.
In another project, I decided to use Cron syntax to encode scheduling information. Thus this standalone library to parse and execute cron expressions. In another project, I decided to use Cron syntax to encode scheduling information. Thus this standalone library to parse and apply time stamps to cron expressions.
Implementation Implementation
-------------- --------------
The reference documentation for this implementation is found at The reference documentation for this implementation is found at
https://en.wikipedia.org/wiki/Cron#CRON_expression, which I copy/pasted here (laziness) with modifications where this implementation differs: https://en.wikipedia.org/wiki/Cron#CRON_expression, which I copy/pasted here (laziness!) with modifications where this implementation differs:
Field name Mandatory? Allowed values Allowed special characters Field name Mandatory? Allowed values Allowed special characters
---------- ---------- -------------- -------------------------- ---------- ---------- -------------- --------------------------
@ -64,7 +64,7 @@ Predefined cron expressions
Other details Other details
------------- -------------
* If only six field are present, a `0` second field is prepended, that is, `* * * * * 2013` internally become `0 * * * * * 2013`. * If only six fields are present, a `0` second field is prepended, that is, `* * * * * 2013` internally become `0 * * * * * 2013`.
* If only five fields are present, a `0` second field is prepended and a wildcard year field is appended, that is, `* * * * *` internally become `0 * * * * * *`. * If only five fields are present, a `0` second field is prepended and a wildcard year field is appended, that is, `* * * * *` internally become `0 * * * * * *`.
* Domain for day-of-week field is [0-7] instead of [0-6], 7 being Sunday (like 0). This to comply with http://linux.die.net/man/5/crontab#. * Domain for day-of-week field is [0-7] instead of [0-6], 7 being Sunday (like 0). This to comply with http://linux.die.net/man/5/crontab#.
* As of now, the behavior of the code is undetermined if a malformed cron expression is supplied * As of now, the behavior of the code is undetermined if a malformed cron expression is supplied
@ -91,8 +91,9 @@ to create a `CronExpression` object once and keep a copy of it for reuse:
cronexpr := cronexpression.NewCronExpression("0 0 29 2 *") cronexpr := cronexpression.NewCronExpression("0 0 29 2 *")
nextTime := cronexpr.NextTime(time.Now()) nextTime := cronexpr.NextTime(time.Now())
...
Use `cronexpression.NoMatch()` to find out whether a valid time was returned. For exemple, Use `cronexpression.NoMatch()` to find out whether a valid time was returned. For example,
cronexpression.NoMatch(cronexpression.NextTimeFromCronString("* * * * * 1980", time.Now())) cronexpression.NoMatch(cronexpression.NextTimeFromCronString("* * * * * 1980", time.Now()))