linux - Cron 语法 - 加号/减号

Question

cron 语法中行首的加号和减号是什么意思？

+ 0 9 * * * /usr/bin/curl -k http://www.example.com/cron/deactivate_users
- 10 8 * * * /usr/bin/curl -k http://example.com/cron/delete_users

Answer 1

从减号开始：

如果 crontab 中的一行以“-”开头，这将阻止 cron 将有关命令执行的信息写入 syslog。

请参阅 crontab 的联机帮助页 (5)。

Answer 2

There is no + or - */2 is there I think you have seen the above syntax somewhere where + means to add the line to curl and call deactivate_users and remove i.e - to remove delete_users or in short words to replace delete_users cronjob with the new cronjob of deactivate_users.

Thanks & Regards,
Alok Thaker

Answer 3

It (i.e. your lines starting with + or -) probably is the output of some GNU diff (or some other diff), so it is a patch file.

You may apply that patch with the patch command. Try perhaps patch < your.diff(or else patch -p0 < your.diff) where your.diff contains such lines starting with + or - (and also a few previous ones).