Run bash script as daemon

Question

I have a script  which runs my PHP script each X times      bin bash while true  do  usr bin php -f   my-script php echo  Waiting     sleep 3 done   How can I start it as daemon

User · Answer

Another cool trick is to run functions or subshells in background, not always feasible though

name(){
  echo "Do something"
  sleep 1
}

# put a function in the background
name &
#Example taken from here
#https://bash.cyberciti.biz/guide/Putting_functions_in_background

Running a subshell in the background

(echo "started"; sleep 15; echo "stopped") &

User · Answer

A Daemon is just program that runs as a background process  rather than being under the direct control of an interactive user      The below bash code is for Debian systems - Ubuntu  Linux Mint distros and so on   The simple way   The simple way would be to edit your  etc rc local file and then just have your script run from there  i e  everytime you boot up the system    sudo nano  etc rc local   Add the following and save    For a BASH script  bin sh TheNameOfYourScript sh  gt   dev null  amp    The better way to do this would be to create a Daemon via Upstart   sudo nano  etc init TheNameOfYourDaemon conf   add the following   description  My Daemon Job  author  Your Name  start on runlevel  2345       pre-start script   echo    date   My Daemon Starting   gt  gt   var log TheNameOfYourDaemonJobLog log end script  exec  bin sh TheNameOfYourScript sh  gt   dev null  amp    Save this   Confirm that it looks ok   init-checkconf  etc init TheNameOfYourDaemon conf   Now reboot the machine   sudo reboot   Now when you boot up your system  you can see the log file stating that your Daemon is running   cat   var log TheNameOfYourDaemonJobLog log    bull  Now you may start stop restart get the status of your Daemon via   restart  this will stop  then start a service  sudo service TheNameOfYourDaemonrestart restart   start  this will start a service  if it s not running  sudo service TheNameOfYourDaemonstart start   stop  this will stop a service  if it s running  sudo service TheNameOfYourDaemonstop stop   status  this will display the status of a service  sudo service TheNameOfYourDaemonstatus status

User · Answer

To run it as a full daemon from a shell  you ll need to use setsid and redirect its output  You can redirect the output to a logfile  or to  dev null to discard it  Assuming your script is called myscript sh  use the following command   setsid myscript sh  gt  dev null 2 gt  amp 1  lt   dev null  amp    This will completely detach the process from your current shell  stdin  stdout and stderr   If you want to keep the output in a logfile  replace the first  dev null with your  path to logfile   You have to redirect the output  otherwise it will not run as a true daemon  it will depend on your shell to read and write output

User · Answer

You can go to  etc init d  - you will see a daemon template called skeleton   You can duplicate it and then enter your script under the start function

User · Answer

Some commentors already stated that answers to your question will not work for all distributions  Since you did not include CentOS in the question but only in the tags  I d like to post here the topics one has to understand in order to have a control over his her proceeding regardless of the distribution    what is the init daemon  optional  what is the inittab file   etc inittab   what does the inittab file do in your distro  e g  does it actually run all scripts in  etc init d      For your problem  one could start the script on sysinit by adding this line in  etc inittab and make it respawn in case it terminates     start and respawn after termination ttyS0  respawn  bin sh  path to my script sh   The script has to be made executable in advance of course   chmod  x  path to my script sh   Hope this helps

[linux] Run bash script as daemon

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