85 lines
1.4 KiB
Markdown
85 lines
1.4 KiB
Markdown
---
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tags:
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- Programming_Languages
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- shell
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- automation
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---
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# Cron
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## `cronie`
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In Arch Linux I use `cronie` for cron jobs. (There is no cron service installed by default). Install `cronie` and then enable it in systemd with:
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```bash
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systemctrl enable --now cronie.service
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```
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## Commands
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### List cron jobs
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```
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crontab -l
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```
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### Open cron file
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```
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crontab -e
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```
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### Check cron log
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```bash
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journalctl | grep CRON
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# Different distros have different loggers
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```
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## Syntax
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````bash
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m h d mon dow command
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# minute, hour, day of month, day of week, bash script/args
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# 0-59, 0-23, 1-31, 1-12, 0-6
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````
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**Examples**
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Run on the hour every hour
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````
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0 * * * * mysqlcheck --all-databases --check-only-changed --silent
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````
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At 01:42 every day:
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````
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42 1 * * * mysqlcheck --all-databases --check-only-changed --silent
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````
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Every half hour:
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```
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0,30 * * * * ${HOME}/bash_scripts/automate_commit.sh
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```
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**Shorthands**
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* `@reboot` – Run once, at startup
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* `@yearly` – Run once a year, “0 0 1 1 \*”.\</>
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* `@annually` – same as @yearly
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* `@monthly` – Run once a month, “0 0 1 * \*”
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* `@weekly` – Run once a week, “0 0 * * 0”
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* `@daily` – Run once a day, “0 0 * * \*”
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* `@midnight` – same as @daily
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* `@hourly` – Run once an hour, “0 * * * \*”
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**Examples**
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````
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@hourly mysqlcheck --all-databases --check-only-changed --silent
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````
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**View the logs**
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````bash
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sudo grep crontab syslog
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````
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