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 #1
08-31-2008
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Trick for bash scripters (check if process is running)
I have seen this question -- check if a process is running -- in a lot of forums and all seem a bit complex and unnecessary:
Checking if /proc/PID exists? ps aux | grep -E "PID|name" ? etc... There is a simpler way of doing it: sending signal 0 (zero) to the process and letting the kernel tell if the process is running. So all you have to do is kill -0 PID or killall -0 name and check the return value of kill command using $? bash Code:
kill -0 pid echo $? Code:
pid = ARGV[0]
begin
Process.kill(0, Integer(pid))
puts "#{pid} is alive!"
rescue Errno::EPERM # changed uid
puts "#{pid} has escaped my control!";
rescue Errno::ESRCH
puts "#{pid} is deceased."; # or zombied
rescue
puts "Odd; I couldn't check the status"
end
Code:
import sys
import os
try:
os.kill(int(sys.argv[1]), 0)
print "Running"
except:
print "Not running"
Code:
kill 0, $ARGV[0] or die "Not running"; print "Running\n"; Code:
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
int
main (int argc, char * argv[])
{
printf ("%s\n", !kill (atoi(argv[1]), 0) ? "Running" : "Not Running");
return 0;
}
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#2
08-31-2008
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'Advanced programming in the UNIX environment' explains the reason for having this feature. I did not see where you mention 'only works for processes that your process has permissions to signal'.
And if the shell has a kill builtin, it is possible the behaviors are different from those listed in the man page for /usr/bin/kill. kill is a builtin in the bash shell and the ksh shell. To get the man page behavior for a builtin like kill - (or for example:test or echo), you need to specify the image file like: Code:
/bin/echo /bin/kill /bin/test # /bin == /usr/bin you can use either
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#3
08-31-2008
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Quote:
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