How to get process ID of background process

Question

I start a background process from my shell script  and I would like to kill this process when my script finishes   How to get the PID of this process from my shell script  As far as I can see variable    contains the PID of the current script  not the background process

User · Answer

You might also be able to use pstree   pstree -p user   This typically gives a text representation of all the processes for the  user  and the -p option gives the process-id  It does not depend  as far as I understand  on having the processes be owned by the current shell  It also shows forks

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this is what I have done  Check it out  hope it can help      bin bash     So something to show  echo  UNO   gt   UNO txt echo  DOS   gt   DOS txt     Initialize Pid List dPidLst        Generate background processes tail -f UNO txt amp  dPidLst   dPidLst     tail -f DOS txt amp  dPidLst   dPidLst         Report process IDs echo PID    echo dPidLst  dPidLst     Show process on current shell ps -f     Start killing background processes from list for dPid in  dPidLst do         echo killing  dPid  Process is still there          ps   grep  dPid         kill  dPid         ps   grep  dPid         echo Just ran    ps    command   dPid must not show again  done   Then just run it as    bgkill sh with proper permissions of course  root umsstd22  P       bgkill sh PID 23757 dPidLst  23758 23759 UNO DOS UID        PID  PPID  C STIME TTY          TIME CMD root      3937  3935  0 11 07 pts 5    00 00 00 -bash root     23757  3937  0 11 55 pts 5    00 00 00  bin bash   bgkill sh root     23758 23757  0 11 55 pts 5    00 00 00 tail -f UNO txt root     23759 23757  0 11 55 pts 5    00 00 00 tail -f DOS txt root     23760 23757  0 11 55 pts 5    00 00 00 ps -f killing 23758  Process is still there  23758 pts 5    00 00 00 tail   bgkill sh  line 24  23758 Terminated              tail -f UNO txt Just ran  ps  command  23758 must not show again  killing 23759  Process is still there  23759 pts 5    00 00 00 tail   bgkill sh  line 24  23759 Terminated              tail -f DOS txt Just ran  ps  command  23759 must not show again  root umsstd22  P     ps -f UID        PID  PPID  C STIME TTY          TIME CMD root      3937  3935  0 11 07 pts 5    00 00 00 -bash root     24200  3937  0 11 56 pts 5    00 00 00 ps -f

User · Answer

pgrep can get you all of the child PIDs of a parent process   As mentioned earlier    is the current scripts PID   So  if you want a script that cleans up after itself  this should do the trick    trap  kill    pgrep -P      tr   n         SIGINT SIGTERM EXIT

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An even simpler way to kill all child process of a bash script   pkill -P      The -P flag works the same way with pkill and pgrep - it gets child processes  only with pkill the child processes get killed and with pgrep child PIDs are printed to stdout

User · Answer

is the current script s pid    is the pid of the last background process   Here s a sample transcript from a bash session   1 refers to the ordinal number of background process as seen from jobs      echo    3748    sleep 100  amp   1  192    echo    192    kill  1   1    Terminated              sleep 100

User · Answer

You need to save the PID of the background process at the time you start it   foo  amp  FOO PID      do other stuff kill  FOO PID   You cannot use job control  since that is an interactive feature and tied to a controlling terminal  A script will not necessarily have a terminal attached at all so job control will not necessarily be available

User · Answer

You can use the jobs -l command to get to a particular jobL   Z  1    Stopped                 guard  my mac workspace r  jobs -l  1   46841 Suspended  18           guard   In this case  46841 is the PID   From help jobs      -l   Report the process group ID and working directory of the jobs    jobs -p is another option which shows just the PIDs

[linux] How to get process ID of background process?

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