Written by J. Moellenkamp
on February 17, 2011
Reading time: 1 minute
Solaris English

pstop and prun

Many people know how to kill a process, but less people know that you can suspend a running process in to resume the execution later.

The test case

I wrote a small script to demonstrate both commands.

#!/usr/bin/perl
while () {
 $zeit=time();
 print "... $zeit \n";
 sleep(2);
}

It just prints the current time every 2 seconds.

jmoekamp@hivemind:~$ ./stopstart.pl
... 1297973807
... 1297973809
... 1297973811
... 1297973813
... 1297973815
... 1297973817
... 1297973819
... 1297973821
... 1297973823
... 1297973825
... 1297973827
... 1297973858
... 1297973860
... 1297973862
... 1297973864
... 1297973866
... 1297973868
... 1297973870
^C
jmoekamp@hivemind:~$

You may have recognized that there is a 31 second gap between 1297973827 and 1297973858 for script that should print out the timestamps continiously every two seconds.

What i did in a second shell?

What happened here? At 1297973827</a> i ran the following command:

jmoekamp@hivemind:~# pstop 10103
jmoekamp@hivemind:~#

When you look at the process flags, you will see that the process has been stopped:

jmoekamp@hivemind:~# pflags 10103
10103:  /usr/bin/perl ./stopstart.pl
        data model = _ILP32  flags = MSACCT|MSFORK
 /1:    flags = STOPPED|ISTOP|ASLEEP  nanosleep(0x8047a00,0x8047a08)
        why = PR_REQUESTED

A moment before that i found out the process id via

jmoekamp@hivemind:~# ps -ef | grep "stopstart.pl" | grep -v "grep"
jmoekamp 10103  9998   0 21:16:48 pts/2       0:00 /usr/bin/perl ./stopstart.pl

Then i just waited for half a minute and resumed execution with

jmoekamp@hivemind:~# prun 10103
jmoekamp@hivemind:~#

So the perl scripted resumed to print the timestamps at 1297973858. When you check the pflags again you will see, that the the STOPPED and ISTOP flags went away:

jmoekamp@hivemind:~# pflags 10103
10103:  /usr/bin/perl ./stopstart.pl
        data model = _ILP32  flags = MSACCT|MSFORK
 /1:    flags = ASLEEP  nanosleep(0x8047a00,0x8047a08)

jmoekamp@hivemind:~#

← → Top