![]() ![]() People often get a little confused about the memory information summary in the top part of the screen because the free memory listed seems very low to them. The "r" and "k" keys are used to renice and kill sessions. The sorting of the data can be altered using the following keys: To alter the order of the columns displayed, press the "o" key and use the upper case and lower case letters corresponding to each column to move then left and right of the "Current Fields" string. Toggle fields via field letter, type any other key to return When you are satisfied press the return key and you will see the displayed columns will have changed.Ĭurrent Fields: NAEHIOQTWKMbcdfgjplrsuvyzX for window 1:Def Capital letters mean the column is displayed. If you want to add or remove columns from the display, press the "f" key and toggle the letters in the "Current Fields" string. For the most part you can get away with just running top and looking at the output. The top command is probably the most well know utility for displaying the most resource intensive processes on the system. # omitting the grep line using a regular expression. # omitting the grep line using "grep -v". # Returns only those lines containing the string "ora", # Returns only those lines containing the string "ora". If there are a lot of processes on the system, you will probably want to page through or limit them using one of the filtering options, or the grep command. Ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm Ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm To see every process with a user-defined format: To see every process running as root (real & effective ID) in user Ps -eo euser,ruser,suser,fuser,f,comm,label To see every process on the system using BSD syntax: To see every process on the system using standard syntax: The man page is very comprehensive, including the options to perform some useful common tasks. ![]() The ps command produces a report of the current processes on the system. Remember, the exams are hands-on, so it doesn't matter which method you use to achieve the result, so long as the end product is correct. ![]() This article introduces some of the commands and utilities used to manage processes on Linux, with specific reference to the information needed for the RHCSA EX200 and RHCE EX300 certification exams. If I'm looking for the main shell, I would generally set it to a variable first so its clear that's the one I want.Home » Articles » Linux » Here Linux Process Management (ps, top, renice, kill) Which one is correct? It depends on what you are trying to do. Scripts do this sort of thing all the time, see how the first has 3 lines but the second has only 2? This is because the first we are resolving $$ then running the script and finding out "main" shell, but the second we are doing it the other way which of course has a different PID of the child shell and doesn't match the 3802 of the parent. However, you have to be really careful of $$ in scripts because it means "this shell" but the concept of this depends on when and where it is called.Ĭonsider the two commands: $ sh -c "ps -ax | grep $$"ģ658110 pts/0 S+ 0:00 sh -c ps -ax | grep 3802ģ658142 pts/0 S+ 0:00 sh -c ps -ax | grep $$ The -h option is to remove the header line. ps takes the PIDs of the processes you are interested in as command line options so if you know what you want, specify it directly, rather than hope the grep will work. Something as simple as ps -h $$ > catch will probably do it. then - filter down using grep to a single process, which you had in step 1.plus - all other process that don't have a tty too (x option).plus - all other processes which have a tty (a option). ![]()
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