How can I make a bash command run periodically?

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I want to execute a script and have it run a command every x minutes.

Also any general advice on any resources for learning bash scripting could be really cool. I use Linux for my personal development work, so bash scripts are not totally foreign to me, I just haven't written any of my own from scratch.

How to Run or Repeat a Linux Command Every X Seconds Forever, You can use watch command, watch is used to run any designated command at while true; do <your_command>; sleep <interval_in_seconds>; done task for the cron daemon which allows for running periodic commands. If you are new to bash scripting, you can check our guide about bash loops here. In case this is the first time you hear about the "sleep" command, it is used to delay something for a specified amount of time. In scripts, you can use it to tell your script to run command 1, wait for 10 seconds and then run command 2.

In addition to @sputnick's answer, there is also watch. From the man page:

Execute a program periodically, showing output full screen

By default this is every 2 seconds. watch is useful for tailing logs, for example.

bash - Repeat a command every x interval of time in terminal?, Simply enabling job control in the subshell by starting the script using means that it will inherit all the file descriptors from the parent shell. Instead, lets interpret "periodically" as "every time I press Enter to execute a new command". can put the main part of the script in PROMPT_COMMAND instead. The watch command is appropriate in your case, i would use a terminal multiplexer (e.g. tmux, screen, etc.) and then run the command using . watch -n 5 ./script.sh In that case even if you close the terminal or ssh connection to the machine the script would still be running.

How can we schedule to run a command in background periodically , When I first started using Linux, it was like being tossed into the deep end of While cron lets you schedule commands to run periodically, at lets you in to the server, instead I could write a short script that collects data from� Just to clarify want I really want to do, actually I want to run a Python program P periodically until I give some command to stop it. And just in case that P happens to be running while I'm giving out the stop command, I want it to finish the current run first, and then not to run ever since.

I want to execute the script and have it run a command every {time interval}

cron (https://en.wikipedia.org/wiki/Cron) was designed for this purpose. If you run man cron or man crontab you will find instructions for how to use it.

any general advice on any resources for learning bash scripting could be really cool. I use Linux for my personal development work, so bash scripts are not totally foreign to me, I just haven't written any of my own from scratch.

If you are comfortable working with bash, I recommend reading through the bash manpage first (man bash) -- there are lots of cool tidbits.

Schedule One-Time Commands with the UNIX at Tool, I do not have previlage to use crontab -e to run my script. Is there other way to periodically run my script? Basically I need to run it once a week. How can I run a script in Linux operating system using command line options? By default, the shell script will not run. You need to set execute permission for your shell script. To execute or run script type the following command: chmod +x script-name-here OR chmod 0755 script.sh Next, use the ls command to view permission on the script:

Avoiding Time Drift

Here's what I do to remove the time it takes for the command to run and still stay on schedule:

#One-liner to execute a command every 600 seconds avoiding time drift
#Runs the command at each multiple of :10 minutes

while sleep $(echo 600-`date "+%s"`%600 | bc); do ls; done

This will drift off by no more than one second. Then it will snap back in sync with the clock. If you need something with less than 1 second drift and your sleep command supports floating point numbers, try adding including nanoseconds in the calculation like this

while sleep $(echo 6-`date "+%s.%N"`%6 | bc); do date '+%FT%T.%N'; done

How to run the shell script periodically without using Crontab , This iterates ten times executing command each time - it can be a pipe or a series of commands separated by ; or && . You can use the $i variable to know which� You can use watch command, watch is used to run any designated command at regular intervals. Open Terminal and type: watch -n x <your command> change x to be the time in seconds you want. For more help using the watch command and its options, run man watch or visit this Link.

How to run a command multiple times, using bash shell?, the_main_thing is the command or script you want to run periodically. The purpose of [[ $0 = /* ]] && script=$0 || script=$PWD/$0 is to get the� Unix & Linux: How can I run a command which will survive terminal close? The Question: Sometimes I want to start a process and forget about it. If I start it from the command line, like this

Scheduling jobs in UNIX without cron (Example), For example, some tasks (including regularly recurring tasks) need to run I have no time to spare in the evenings to run commands and scripts that have to And I don't want to have to get up at oh-dark-hundred to start a� RELATED: How to Use Pipes on Linux. Using at with Files of Commands. You can also store a sequence of commands in a file, and then pass it to at. This can be a plain text file of commands—it doesn’t have to be an executable script. You can use the -f (file) option in the following way to pass a filename to at: at now + 5 minutes -f clean.txt

How to use cron in Linux, The software utility cron is a time-based job scheduler in Unix-like computer operating systems. Users that set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, given and do not inherently increase over time, with the exception of periodically�

Comments
  • Did you look at cron?
  • As for your request for resources, the bash-hackers wiki has a well-tended list of resources, which is explicitly pruned to avoid guides that are not careful to avoid classic pitfalls.
  • Crontab is here the better choise, especially if you want to run this "forever" (a long time).
  • Good question :) +1 to compensate
  • I don't know about better and worse choices. They both have their pros and cons. One downside of the cron approach is you can get multiple instances of the command running at the same time. That cannot happen with the foreground while loop example.
  • Really depends of what you want to do. The while loop will get out of sync (with whatever). If you have to be time acurate the loop wouldn' t work (at least not that easy).
  • Cron is of course what should have been obvious to me at the beginning. This is a process that will run once every fifteen or thirty minutes and will only take seconds to complete.
  • It's important to point out that watch is nonstandard and doesn't exist on most non-GNU systems (including Macs) by default.
  • This is clever! This actually removes the runtime of the command. It could, however use some improvements.
  • I would implement the following update. This removes all overhead which is the result of calling echo date and bc : t=$SECONDS; while true; do cmd; sleep $(((t+=6) - SECONDS)); done. The variable SECONDS is a bash internal variable. You can see that the drift is minimal if you replace cmd with date '+%FT%T.%6N'
  • @kvantour Great input! You solution still continues to drift indefinitely. But you gave me some more to consider. I have updated my solution!
  • The snapping back could be problematic with small dt