Have you ever been in need to execute some commands scheduled via a crontab, every let’s say 5 seconds?, naturally this is not possible with crontab, however adding a small shell script to loop and execute a command or commands every 5 seconds and setting it up to execute once in a minute through crontab makes this possible.
Here is an example shell script that does execute commands every 5 seconds:
#!/bin/bash
command1_to_exec='/bin/ls';
command2_to_exec='/bin/pwd';
for i in $(echo 1 2 3 4 5 6 7 8 9 10 11); do
sleep 5;
$command1_to_exec; $command2_to_exec;
done
This script will issue a sleep every 5 seconds and execute the two commands defined as $command1_to_exec and $command2_to_exec
Copy paste the script to a file or fetch exec_every_5_secs_cmds.sh from here
The script can easily be modified to execute on any seconds interval delay, the record to put on cron to use with this script should look something like:
# echo '* * * * * /path/to/exec_every_5_secs_cmds.sh' | crontab -
Where of course /path/to/exec_every_5_secs_cmds.sh needs to be modified to a proper script name and path location.
Another way to do the on a number of seconds program / command schedule without using cron at all is setting up an endless loop to run/refresh via /etc/inittab with a number of predefined commands inside. An example endless loop script to run via inittab would look something like:
while [ 1 ]; do
/bin/ls
sleep 5;
done
To run the above sample never ending script using inittab, one needs to add to the end of inittab, some line like:
mine:234:respawn:/path/to/script_name.sh
A quick way to add the line from consone would be with echo:
echo 'mine:234:respawn:/path/to/script' >> /etc/inittab
Of course the proper paths, should be put in:
Then to load up the newly added inittab line, inittab needs to be reloaded with cmd:
# init q
I've also red, some other methods suggested to run programs on a periodic seconds basis using just cron, what I found in stackoverflow.com's as a thread proposed as a solution is:
* * * * * /foo/bar/your_script
* * * * * sleep 15; /foo/bar/your_script
* * * * * sleep 30; /foo/bar/your_script
* * * * * sleep 45; /foo/bar/your_script
One guy, even suggested a shorted way with cron:
0/15 * * * * * /path/to/my/script
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