How to use xargs to get elapsed time for running processes-CodePudding

I want get the run times of some processes. Here is what I am doing

ps -ef | grep "python3 myTask.py" | awk '{print $2}' | xargs -n1 ps -p {} -o etime

I want to get the pids by

ps -ef | grep "python3 myTask.py" | awk '{print $2}'

then pass these along to the

ps -p {} -o etime

by using xargs, but its not working. I get

error: process ID list syntax error

Usage:
 ps [options]

 Try 'ps --help <simple|list|output|threads|misc|all>'
  or 'ps --help <s|l|o|t|m|a>'
 for additional help text.

For more details see ps(1).
error: process ID list syntax error

Usage:
 ps [options]

 Try 'ps --help <simple|list|output|threads|misc|all>'
  or 'ps --help <s|l|o|t|m|a>'
 for additional help text.

For more details see ps(1).

what am i doing wrong?

CodePudding user response：

You can use the following command:

pgrep -f "python3 myTask.py" | xargs -i{} ps -p {} -o etime

pgrep - Look up or signal processes based on name and other attributes.

-f, --full - The pattern is normally only matched against the process name. When -f is set, the full command line is used.

For further reading, see man pgrep.

The missing part from the xargs segment was -i{}, which invokes the command for each argument, whilst {} will be replaced by it.

-i[replace-str], --replace[=replace-str] - This option is a synonym for -Ireplace-str if replace-str is specified.

For further reading, see man xargs.

CodePudding user response：

You must provide -I{} to xargs to set the placeholder; otherwise it cannot be used.

Nevertheless, your command is too complicated and involves too many intermediate steps (and a race-condition). Simply get your processes including elapsed time and filter the lines you need:

ps -eo etime,cmd | awk '/python3 myTask.py/{print $1}'

(no xargs anymore)