Crontab scheduled task

Crontab (scheduled task operation)

Edit command: crontab-e

View command: crontab-l

# For details see man 4 crontabs

# Example of job definition:

#.-minute (0-59)

# |.-hour (0-23)

# | |.-day of month (1-31)

# |.-month (1-12) OR jan,feb,mar,apr...

# |.-day of week (0-6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat

# |

# * user-name command to be executed

The format is as follows:

Minute hour day month week user-name command

Minute--- minutes (0-59)

Hour- hours (0-23)

Day- date (1-31)

Month--- month (January-December)

Week---- week (0-6) / / 0 represents Sunday

In addition to numbers, there are several special symbols, namely "*", "/" and "-", * represents all the numbers in the range of values, "/" represents each, "* / 5" means every five units, "-" represents from a number to a number, "," separate several discrete numbers. Here are a few examples:

Example:

1 * / tmp/test.sh

Indicates that the script is executed at the first minute of each hour

2 3 * / tmp/test.sh

Indicates that the script is executed at 3: 02 every day

1 1 * * 0 / tmp/test.sh

Represents the execution of the script at 01:01 every week

1 1 1 * / tmp/test.sh

Represents the execution of the script at 01:01 every month

It is easier to make the mistake of doing the first minute of each hour once per minute. Note the difference between the two:

1 * / tmp/test.sh

Indicates that the script is executed at the first minute of each hour

* / 1 * / tmp/test.sh

Represents the execution of the script every minute

So keep in mind the difference brought about by the symbol "/" here.

The usage of "-":

0 10 * * 1-3 / tmp/test.sh

It means to execute the script at 10:00 every Monday through Wednesday morning.

0 10 * 1, 3, 5 / tmp/test.sh

It means to execute the script at 10:00 on Monday, Wednesday and Friday every week.