How to run URL from cronjob at specific time in Linux

Cron allows Linux users to run commands or scripts at a given date and time.

Here I’m going to explain how to setup cron job in Linux in which you want to run URL at specific date-time.

Each user has its own crontab file in Linux. Crontab files can be found in /var/spool folder with file names as username. crontab command is used to add, edit, install, uninstall or list cron jobs.
So to create or edit cron job enter following command:
```
crontab –e
```

Above command will open a crontab file, if exists, otherwise an empty file for creating a new crontab.

Following is syntax for setting cron jobs using crontab file:
```
1 2 3 4 5 /path/to/command arg1 arg2
```

First 5 options are for date-time setup:

Example: Following script will run given URLS daily at 2 AM

0 2 * * * curl -s "https://example.com/notification_scirpt?group=1" > /dev/null 2>&1

0 2 * * * curl -s " https://example.com/notification_scirpt?group=2" > /dev/null 2>&1

After adding above lines save file. Command to save a file in VIM editor iswq!.

Linux will automatically install new crontab changes.

Above commands will run curl by fetching the URL’s.
It will be executed daily at 2 AM.
You can also pass query parameters in URL (group in the above example) like normal curl request.
–s option is used to make curl silent so that no output generated.

/dev/null and 2>&1 are explained below:

> is for redirect
/dev/null is a black hole where any data sent, will be discarded
2 is the file descriptor for Standard Error
> is for redirect
& is the symbol for file descriptor (without it, the following 1 would be considered a filename)
1 is the file descriptor for Standard Out. Therefore >/dev/null 2>&1 is redirecting the output of your program to /dev/null. Include both the Standard Error and Standard Out.