Re: displaying top cpu using process

["Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxxxxxxxxx>]

On Apr 7,  4:33pm, Dominik Vogt wrote:
} Subject: displaying top cpu using process
}
}   ps gives me complete control over the output format, but I can't
}   make it give me the CPU percentage.  Although the 'C' output
}   modifier is documented as 
} 
}     "use raw CPU time for %CPU instead of decaying average"
} 
}   I always get the decaying average.

I can't even get my "ps" to accept the C modifier.  It keeps interpreting
it as the "selection by command name" option, and telling me that only
root is allowed to do that.

}     top -b -n 1 | sed '<script>'
} 
}   But then, this only works if the terminal window from which top
}   was started has enough lines. [...]  To get the full output I
}   have to detach top from the terminal.  

That's odd; on RH6.2, for me, "top -b -n 1" produces a lot more lines
of output than the height of the terminal.  (procps-2.0.6-5)  However,
try fooling it by stuffing the LINES and COLUMNS environment variables.

}   In other words, I need one process that generates the data and one
}   that writes it into the terminal window. There are several ways to
}   do this, but the best solution seems to be a coprocess (because the
}   coprocess is killed if the terminal window that runs the script is
}   closed).

A coprocess is overkill.  Just use the parameter assignment and a pipe:

topcpu {
  local p=0 pid user pri ni size rss share stat lib cpu mem time command
  LINES=10 COLUMNS=200 top d 2 c b n 43200 |
  while read pid user pri ni size rss share stat lib cpu mem time command
  do
    [[ $pid == PID ]] && { p=1; continue }
    (( p )) && { print $pid $cpu% $command; p=0 }
  done
}

43200 iterations of 2 sec is 24 hours.

} Can anybody think of a better solution (that does not include
} writing any C code)?

Presumably it's possible to compute the CPU percentages by reading from
/proc/<->/stat plus the cpu line from /proc/stat, but I don't know the
algorithm top uses.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

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