要设置的cron

Question

I have an already setted up cron job. Now i have a file whose cron i have to setup such that my file should run at 9:00 am,11:00am,1:00pm,5:00pm and 7:00pm

Idont have much idea about cron So can anyone please help me in setting up this cron for my file at the aboove given timings !!

Answer 1

The format for the CRON Jobs is:

minute hour dom month dow user cmd

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minute This controls what minute of the hour the command will run on, and is between '0' and '59'

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hour This controls what hour the command will run on, and is specified in the 24 hour clock, values must be between 0 and 23 (0 is midnight)

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dom This is the Day of Month, that you want the command run on, eg to run a command on the 19th of each month, the dom would be 19.

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month This is the month a specified command will run on, it may be specified numerically (0-12), or as the name of the month (eg May)

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dow This is the Day of Week that you want a command to be run on, it can also be numeric (0-7) or as the name of the day (eg sun).

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user This is the user who runs the command.

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cmd This is the command that you want run. This field may contain multiple words or spaces.

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If you don't wish to specify a value for a field, just place a * in the field.

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Here is an example of how a crontab is setup.

01 * * * * root echo "This command is run at one min past every hour"
17 8 * * * root echo "This command is run daily at 8:17 am"
17 20 * * * root echo "This command is run daily at 8:17 pm"
00 4 * * 0 root echo "This command is run at 4 am every Sunday"
* 4 * * Sun root echo "So is this"
42 4 1 * * root echo "This command is run 4:42 am every 1st of the month"
01 * 19 07 * root echo "This command is run hourly on the 19th of July"

Answer 2

Each of the positions means a specific thing:

1. Minute [0,59]
2. Hour [0,23]
3. Day of the month [1,31]
4. Month of the year [1,12]
5. Day of the week ([0,6] with 0=Sunday)

For example:

0 9,11,13,17,19 * * * /bin/whatever >> /some/log/if/you/want/it.log

In English:

Run /bin/whatever on the 0th minute of the 9th, 11th, 13th, 17th, and 19th hour of every day, of every month, each day of the week.

Answer 3

0 9,11,13,17,19 * * * something

man 5 crontab