Linux Unix command to determine if process is running

Question

I need a platform independent  Linux Unix OSX  shell bash command that will determine if a specific process is running  e g  mysqld  httpd    What is the simplest way command to do this

User · Answer

Putting the various suggestions together, the cleanest version I was able to come up with (without unreliable grep which triggers parts of words) is:

kill -0 $(pidof mysql) 2> /dev/null || echo "Mysql ain't runnin' message/actions"

kill -0 doesn't kill the process but checks if it exists and then returns true, if you don't have pidof on your system, store the pid when you launch the process:

$ mysql &
$ echo $! > pid_stored

then in the script:

kill -0 $(cat pid_stored) 2> /dev/null || echo "Mysql ain't runnin' message/actions"

User · Answer

None of the answers worked for me  so heres mine   process    pidof YOURPROCESSHERE tr -d   n    if    -z    process          then   echo  Process is not running   else   echo  Process is running   fi   Explanation    tr -d   n    This removes the carriage return created by the terminal   The rest can be explained by this post

User · Answer

This approach can be used in case commands  ps    pidof  and rest are not available  I personally use procfs very frequently in my tools scripts programs      egrep -m1   mysqld  httpd    proc  0-9   status   cut -d    -f3   Little explanation what is going on    -m1 - stop process on first match  mysqld  httpd   - grep will match lines which ended on mysqld OR httpd  proc  0-9   - bash will match line which started with any number cut - just split the output by delimiter     and extract field 3

User · Answer

The following shell function  being only based on POSIX standard commands and options should work on most  if not any  Unix and linux system     isPidRunning       cmd       PATH   getconf PATH   export PATH     ps -e -o pid  -o comm          awk   2           1         2        1      print  1  2           -n   cmd     amp  amp      printf   s is running n s n n    1    cmd         printf   s is not running n n   1     -n   cmd            isPidRunning httpd httpd is running 586  usr apache bin httpd 588  usr apache bin httpd    isPidRunning ksh ksh is running 5230 ksh    isPidRunning bash bash is not running   Note that it will choke when passed the dubious  0   command name and will also fail to identify processes having an embedded space in their names   Note too that the most upvoted and accepted solution demands non portable ps options and gratuitously uses a shell that is  despite its popularity  not guaranteed to be present on every Unix Linux machine  bash

User · Answer

While pidof and pgrep are great tools for determining what s running  they are both  unfortunately  unavailable on some operating systems  A definite fail safe would be to use the following  ps cax   grep command  The output on Gentoo Linux    14484          S      0 00 apache2 14667          S      0 00 apache2 19620          Sl     0 00 apache2 21132          Ss     0 04 apache2   The output on OS X    42582       Z      0 00 00  smbclient  46529       Z      0 00 00  smbclient  46539       Z      0 00 00  smbclient  46547       Z      0 00 00  smbclient  46586       Z      0 00 00  smbclient  46594       Z      0 00 00  smbclient    On both Linux and OS X  grep returns an exit code so it s easy to check if the process was found or not      bin bash ps cax   grep httpd  gt   dev null if      -eq 0    then   echo  Process is running   else   echo  Process is not running   fi     Furthermore  if you would like the list of PIDs  you could easily grep for those as well   ps cax   grep httpd   grep -o        0-9     Whose output is the same on Linux and OS X   3519 3521 3523 3524  The output of the following is an empty string  making this approach safe for processes that are not running  echo ps cax   grep aasdfasdf   grep -o        0-9     This approach is suitable for writing a simple empty string test  then even iterating through the discovered PIDs      bin bash PROCESS  1 PIDS  ps cax   grep  PROCESS   grep -o        0-9     if   -z   PIDS     then   echo  Process not running   1 gt  amp 2   exit 1 else   for PID in  PIDS  do     echo  PID   done fi   You can test it by saving it to a file  named  running   with execute permissions  chmod  x running  and executing it with a parameter    running  httpd      bin bash ps cax   grep httpd if      -eq 0    then   echo  Process is running   else   echo  Process is not running   fi     WARNING     Please keep in mind that you re simply parsing the output of ps ax which means that  as seen in the Linux output  it is not simply matching on processes  but also the arguments passed to that program  I highly recommend being as specific as possible when using this method  e g    running  mysql  will also match  mysqld  processes   I highly recommend using which to check against a full path where possible     References   http   linux about com od commands l blcmdl1 ps htm  http   linux about com od commands l blcmdl1 grep htm

User · Answer

Here is my version  Features    checks for exact program name  first argument of the function   search for  mysql  will not match running  mysqld  searches program arguments  second argument of the function    script      bin bash     1 - cmd    2 - args   return  0 - no error  running  1 - error  not running function isRunning         for i in   pidof  1   do         cat  proc  i cmdline   tr   000        grep -F -e   2  1 gt  amp 2 gt   dev null         if      -eq 0    then             return 0         fi     done     return 1    isRunning java  -Djava util logging config file logging properties  if      -ne 0    then     echo  not running  starting     fi

User · Answer

You SHOULD know the PID    Finding a process by trying to do some kind of pattern recognition on the process arguments  like pgrep  mysqld   is a strategy that is doomed to fail sooner or later  What if you have two mysqld running   Forget that approach  You MAY get it right temporarily and it MAY work for a year or two but then something happens that you haven t thought about   Only the process id  pid  is truly unique   Always store the pid when you launch something in the background  In Bash this can be done with the    Bash variable  You will save yourself SO much trouble by doing so   How to determine if process is running  by pid   So now the question becomes how to know if a pid is running   Simply do    ps -o pid  -p  lt pid gt    This is POSIX and hence portable  It will return the pid itself if the process is running or return nothing if the process is not running  Strictly speaking the command will return a single column  the pid  but since we ve given that an empty title header  the stuff immediately preceding the equals sign  and this is the only column requested then the ps command will not use header at all  Which is what we want because it makes parsing easier   This will work on Linux  BSD  Solaris  etc   Another strategy would be to test on the exit value from the above ps command  It should be zero if the process is running and non-zero if it isn t  The POSIX spec says that ps must exit  0 if an error has occurred but it is unclear to me what constitutes  an error   Therefore I m not personally using that strategy although I m pretty sure it will work as well on all Unix Linux platforms

User · Answer

This prints the number of processes whose basename is  chromium-browser    ps -e -o args    awk  BEGIN c 0    if  match  1              sub           1     Do not strip process names enclosed by square brackets   if  1  cmd  c     END print c   cmd  chromium-browser    If this prints  0   the process is not running  The command assumes process path does not contain breaking space  I have not tested this with suspended processes or zombie processes   Tested using gwak as the awk alternative in Linux   Here is a more versatile solution with some example usage      bin sh isProcessRunning     if      1-      -q     then  local quiet 1   shift else  local quiet 0  fi ps -e -o pid args    awk  BEGIN status 1    name  2  if name                sub          name     strip dirname  if process name is not enclosed by square brackets   if name  cmd  status 0  if q  exit else print  0    END exit status   cmd   1  q  quiet    process  chromium-browser   printf  Process     process    is   if isProcessRunning -q   process    then printf  running  n   else printf  not running  n   fi  printf  Listing of matching processes  PID and process name with command line arguments   n  isProcessRunning   process

User · Answer

The simpliest way is to use ps and grep   command  httpd  running  ps ax   grep -v grep   grep  command   wc -l  if   running -gt 0    then     echo  Command is running  else     echo  Command is not running  fi   If your command has some command arguments  then you can also put more  grep cmd arg1  after  grep  command  to filter out other possible processes that you are not interested in   Example  show me if any java process with supplied argument    -Djava util logging config file logging properties  is running  ps ax   grep -v grep   grep java   grep java util logging config file logging properties   wc -l

User · Answer

You should know the PID of your process   When you launch it  its PID will be recorded in the    variable  Save this PID into a file   Then you will need to check if this PID corresponds to a running process  Here s a complete skeleton script   FILE   tmp myapp pid   if   -f  FILE    then    PID   cat  FILE  else    PID 1 fi  ps -o pid  -p  PID if      -eq 0    then   echo  Process already running     else   echo  Starting process     run my app  amp    echo     gt   FILE fi   Based on the answer of peterh  The trick for knowing if a given PID is running is in the ps -o pid  -p  PID instruction

User · Answer

This should work on most flavours of Unix  BSD and Linux   PATH  usr ucb   PATH  ps aux   grep httpd   grep -v grep   Tested on    SunOS 5 10  Hence the PATH      Linux 2 6 32  CentOS  Linux 3 0 0  Ubuntu  Darwin 11 2 0 FreeBSD 9 0-STABLE Red Hat Enterprise Linux ES release 4  Red Hat Enterprise Linux Server release 5

User · Answer

Just a minor addition  if you add the -c flag to ps  you don t need to remove the line containing the grep process with grep -v afterwards  I e   ps acux   grep cron   is all the typing you ll need on a bsd-ish system  this includes MacOSX  You can leave the -u away if you need less information   On a system where the genetics of the native ps command point back to SysV  you d use  ps -e  grep cron   or  ps -el  grep cron    for a listing containing more than just pid and process name  Of course you could select the specific fields to print out using the -o  lt field field     gt  option

User · Answer

I use pgrep -l httpd but not sure it is present on any platform     Who can confirm on OSX

User · Answer

On most Linux distributions  you can use pidof 8    It will print the process ids of all running instances of specified processes  or nothing if there are no instances running   For instance  on my system  I have four instances of bashand one instance of remmina running      pidof bash remmina 6148 6147 6144 5603 21598   On other Unices  pgrep or a combination of ps and grep will achieve the same thing  as others have rightfully pointed out

[linux] Linux/Unix command to determine if process is running?

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