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I have seen a crontab record in system.

0-55/5 * * * *   root  <command>

I read the crontab -e example files and I know the first position stands for minute. But I cannot figure out the meaning of / (slash) there. Could anyone explain the meaning to me?

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/ is a forward slash. \ is a backslash. Forward slashes lean forward. Backslashes lean backwards. – jw013 Feb 18 '12 at 8:25
man 5 crontab has explanations too. – Mat Feb 18 '12 at 8:29
@jw013 thanks for correcting! @Mat Thanks. Buy the way, how to go to next page with man? I read through man crontab and through it was the end. – steveyang Feb 18 '12 at 8:35
@yangchenyun, it's not the next page. It's another section. man crontab brings up the first entry for crontab, which is for the crontab command in section 1. Towards the end of that manpage, it says SEE ALSO crontab(5). That tells you that you can use man 5 crontab to read the crontab entry in section 5, which describes the format of the crontab file. – cjm Feb 18 '12 at 9:17
@cjm Thanks for this information. I was always wondering about those (3) thing in the SEE ALSO section! – steveyang Feb 18 '12 at 13:21
up vote 15 down vote accepted

The forward slash is used in conjunction with ranges to specify step values.

0-55/5 * * * * means your command will be executed every five minutes (0, 5, 10, 15, ..., 55).

0-55/5 is the same as */5.

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By the way, a shorter way to say that is */5. – Warren Young Feb 21 '12 at 15:15
what about */31 on the minute field. Does it means the scrip will on on 0 and 31 or 1 and 31? – Daniel Shen May 25 '15 at 4:24
@DanielShen It would run on 0 and 31 on every hour. – Ville Apr 14 at 5:41

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