Wait for a process to finish

Question

Is there any builtin feature in Bash to wait for a process to finish   The wait command only allows one to wait for child processes to finish  I would like to know if there is any way to wait for any process to finish before proceeding in any script   A mechanical way to do this is as follows but I would like to know if there is any builtin feature in Bash   while ps -p  cat  PID FILE   gt   dev null  do sleep 1  done

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I found  kill -0  does not work if the process is owned by root  or other   so I used pgrep and came up with   while pgrep -u root process name  gt   dev null  do sleep 1  done   This would have the disadvantage of probably matching zombie processes

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Had the same issue  I solved the issue killing the process and then waiting for each process to finish using the PROC filesystem   while   -e  proc   pid     do sleep 0 1  done

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On a system like OSX you might not have pgrep so you can try this appraoch  when looking for processes by name   while ps axg   grep process name   gt   dev null  do sleep 1  done   The   symbol at the end of the process name ensures that grep matches only process name to the end of line in the ps output and not itself

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There s no builtin   Use kill -0 in a loop for a workable solution   anywait         for pid in       do         while kill -0   pid   do             sleep 0 5         done     done     Or as a simpler oneliner for easy one time usage   while kill -0 PIDS 2 gt   dev null  do sleep 1  done    As noted by several commentators  if you want to wait for processes that you do not have the privilege to send signals to  you have find some other way to detect if the process is running to replace the kill -0  pid call   On Linux  test -d   proc  pid  works  on other systems you might have to use pgrep  if available  or something like ps   grep    pid

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From the bash manpage      wait  n                Wait for each specified process and return its termination  status           Each  n  may be a process ID or a job specification  if a           job spec is given  all processes  in  that  job s  pipeline  are           waited  for   If n is not given  all currently active child processes           are waited for  and the return  status  is  zero    If  n           specifies  a  non-existent  process or job  the return status is           127   Otherwise  the return status is the  exit  status  of  the           last process or job waited for

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Rauno Palosaari s solution for Timeout in Seconds Darwin  is an excellent workaround for a UNIX-like OS that does not have GNU tail  it is not specific to Darwin    But  depending on the age of the UNIX-like operating system  the command-line offered is more complex than necessary  and can fail   lsof -p  pid  r 1m s -t   grep -qm1   date -v   timeout S   s 2 gt  dev null    echo INF    On at least one old UNIX  the lsof argument  r 1m s fails  even for a superuser    lsof  can t read kernel name list    The m s is an output format specification   A simpler post-processor does not require it   For example  the following command waits on PID 5959 for up to five seconds   lsof -p 5959  r 1   awk         if  T    gt   5    exit 1        In this example  if PID 5959 exits of its own accord before the five seconds elapses       is 0   If not      returns 1 after five seconds   It may be worth expressly noting that in  r 1  the 1 is the poll interval  in seconds   so it may be changed to suit the situation

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Use inotifywait to monitor some file that gets closed  when your process terminates  Example  on Linux    yourproc  gt logfile log  amp  disown inotifywait -q -e close logfile log   -e specifies the event to wait for  -q means minimal output only on termination  In this case it will be   logfile log CLOSE WRITE CLOSE   A single wait command can be used to wait for multiple processes   yourproc1  gt logfile1 log  amp  disown yourproc2  gt logfile2 log  amp  disown yourproc3  gt logfile3 log  amp  disown inotifywait -q -e close logfile1 log logfile2 log logfile3 log   The output string of inotifywait will tell you  which process terminated  This only works with  real  files  not with something in  proc

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FreeBSD and Solaris have this handy pwait 1  utility  which does exactly  what you want   I believe  other modern OSes also have the necessary system calls too  MacOS  for example  implements BSD s kqueue   but not all make it available from command-line

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This bash script loop ends if the process does not exist  or it s a zombie   PID  lt pid to watch gt  while s  ps -p  PID -o s    amp  amp       s   amp  amp    s      Z      do     sleep 1 done   EDIT  The above script was given below  by Rockallite  Thanks   My orignal answer below works for Linux  relying on procfs i e   proc   I don t know its portability   while      -d  proc  PID    amp  amp    -z  grep zombie  proc  PID status        do     sleep 1 done   It s not limited to shell  but OS s themselves do not have system calls to watch non-child process termination

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Fedora Cent Os same trouble when used yum install and interrupt it with Ctrl Z  Use this command  sudo cat  var cache dnf  pid  if there any pid  you can manually remove it  sudo nano  var cache dnf  pid  crtl x followed by Y and Enter to exit nano editor  you can use any editor you want to open   If after  delete some tmp files that may still be there  sudo systemd-tmpfiles --remove dnf conf

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To wait for any process to finish  Linux   tail --pid  pid -f  dev null   Darwin  requires that  pid has open files    lsof -p  pid  r 1  amp  gt  dev null   With timeout  seconds   Linux   timeout  timeout tail --pid  pid -f  dev null   Darwin  requires that  pid has open files    lsof -p  pid  r 1m s -t   grep -qm1   date -v   timeout S   s 2 gt  dev null    echo INF

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Okay  so it seems the answer is -- no  there is no built in tool   After setting  proc sys kernel yama ptrace scope to 0  it is possible to use the strace program  Further switches can be used to make it silent  so that it really waits passively   strace -qqe    -p  lt PID gt

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Blocking solution  Use the wait in a loop  for waiting for terminate all processes   function anywait          for pid in          do         wait  pid         echo  Process  pid terminated      done     echo  All processes terminated      This function will exits immediately  when all processes was terminated  This is the most efficient solution   Non-blocking solution  Use the kill -0 in a loop  for waiting for terminate all processes   do anything between checks   function anywait w status         for pid in          do         while kill -0   pid          do             echo  Process  pid still running                 sleep 1         done     done     echo  All processes terminated      The reaction time decreased to sleep time  because have to prevent high CPU usage   A realistic usage   Waiting for terminate all processes   inform user about all running PIDs   function anywait w status2         while true     do         alive pids            for pid in              do             kill -0   pid  2 gt  dev null                    amp  amp  alive pids    pid           done          if      alive pids     -eq 0           then             break         fi          echo  Process es  still running      alive pids              sleep 1     done     echo  All processes terminated      Notes  These functions getting PIDs via arguments by    as BASH array

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All these solutions are tested in Ubuntu 14 04   Solution 1  by using ps command    Just to add up to Pierz answer  I would suggest   while ps axg   grep -vw grep   grep -w process name  gt   dev null  do sleep 1  done   In this case  grep -vw grep ensures that grep matches only process name and not grep itself  It has the advantage of supporting the cases where the process name is not at the end of a line at ps axg   Solution 2  by using top command and process name    while      awk   12   process name   print  0    lt  top -n 1 -b       do sleep 1  done   Replace process name with the process name that appears in top -n 1 -b  Please keep the quotation marks   To see the list of processes that you wait for them to be finished  you can run   while     do p   awk   12   process name   print  0    lt  top -n 1 -b        b       break  echo  p  sleep 1  done   Solution 3  by using top command and process ID    while      awk   1   process id   print  0    lt  top -n 1 -b       do sleep 1  done   Replace process id with the process ID of your program

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There is no builtin feature to wait for any process to finish   You could send kill -0 to any PID found  so you don t get puzzled by zombies and stuff that will still be visible in ps  while still retrieving the PID list using ps

[bash] Wait for a process to finish

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