Question

In Bash I’m trying to get the process with most %CPU. Once i get it, i’m using awk to evaluate if the process must be killed or just change it’s nice. Once i get the process, here’s what i’m trying to do :

awk -v awkmax="$CPU_MAX" '
{ 
  if( $3 > awkmax && $4 < 15 ) { 
    system("renice "$4"+5 -p "$1"")
  } 
  else if ( $3 > awkmax && $4 == 15 ) { 
    system("kill -9 "$1"")
    print "The process $1 has been killed.\n" 
  } 
}'

where $3 is pcpu, $4 is the nice value and $1 is the pid.

My problem is here:

system("renice "$4"+5 -p "$1"")

it doesn’t work because of the "$4"+5, which is the actual nice of the process plus 5.

How can i pass that value to renice?

Answer 1

You have some quoting issues, the first system call should be:

system("renice " $4 + 5 " -p " $1)

And the second:

system("kill -9 " $1)

Space is the string concatenation operator in awk.

A note on kill -9: it’s better to start with less severe signals before resorting to -9, as this doesn’t let the process do any cleaning up after it self, IIRC, start with SIGHUP (-1), then SIGINT (-2), then SIGTERM (-15), if none of these makes the process quit, then use SIGKILL (-9).