[SOLVED] background process log shows big gaps in message timestamps

Issue

I started a long running job under nohup in the background over a weekend. When looking at the output after it finished, I noticed that there were large gaps between the timestamps of some log messages. Some gaps were as long as 10 hrs. I had no way of finding out what was going on with my job at that time.

I ran it on a standard Red hat linux server machine at work.

Is this behavior caused by nohup command ? If not what could be possible causes ?

One such long running job was as the script below -

#!/bin/bash

while true
do
    echo "`date`  `top -n 1 -b | grep progname`"
done

And here one such gap from the log -

Mon May 26 04:29:42 PDT 2014  27685 user    18   0 2883m 2.8g 1732 S  0.0  3.9  29:05.54 progname
Tue May 27 03:20:35 PDT 2014  27685 user    18   0 3371m 3.3g 1732 S  0.0  4.6  34:23.21 progname

Solution

Ok.

pid is a variable that is the pid of the process you want to monitor-- Try this for starters (Courtesy of S Chazelas):

export pid=$(ps -ef | grep progname | awk '{$print $2}')
while rss=$(ps -o rss= -p "${pid}") 
do
  printf '%d %s\n' "$rss"  "$(date)"
  sleep 60; 
done > t.lis
# 
echo "Done $(date)" >> t.lis

rss is the resident set size (memory allocated to the process) in pages.

getconf PAGESIZE 

will show how many bytes are in a page of memory.

Answered By - jim mcnamara

Answer Checked By - Marilyn (WPSolving Volunteer)