I'm trying to figure out what's the difference between
ps | wc
and
ps r | wc
In linux the | pipe character issues the output of one command to the input of another. In this case ps output is sent to wc. So the difference in the two commands is really the difference between ps and ps r.
You can issue these commands separately and see the difference in output. You can also view the manpage for the ps command with man ps where you will find:
r Restrict the selection to only running processes.
So, the difference is that one counts the number of processes for the user, while the other counts only the running processes.
By default, ps selects all processes with the same effective user ID (euid=EUID) as the current user and associated with the same terminal as the invoker.
By specifying the 'r', you are restricting it to only running processes.
By piping it through to wc, you get the newline, word, and byte counts respectively.
Related
I'm trying to tweak a bash script to pull back PID's of the individual application accounts when there are multiple applications running as a masterId. This used to run under individual user accounts, but recent changes have forced the applications to all run under a combined "masterId", but still maintain a unique application Id that I can grep against.
Normally
pgrep -u "appId"
would give me a single PID. Now I have to run:
pgrep -u "masterId"
it returns all of the PID's (each one is it's own application).
1234
2345
3456
I'm trying to come up with a command to bring me back just the PID of the appAccount(n) so I can pipe it into other useful commands. I can do a double grep (which is closer to what I want):
ps aux | grep -i "masterId" | grep -i "appAccount(n)"
and that will get me the entire single process information, but I just want the PID to do something like:
ps aux | grep -i "masterId" | grep -i "appAccount(n)" | xargs sudo -u appAccount(n) kill -9
How do I modify the initial above command to get just the PID? Is there a better way to do this?
pgrep --euid "masterId" --list-full | awk '/appAccount(n)/ {print $1}'
Output the full process command line, then select the one with the desired account and print the first field (pid).
I want to use top | grep user to know how many processes are running.
However, after I run top | grep user > temp_file, the command just keeps running.
How can I safely stop it with information being written to the temp_file?
You can use the -n 1 option to top to make it only do one iteration.
Probably the better tool to use would be ps, as in ps aux | grep user.
If count is all you're interested in:
pgrep -cu username
I am doing a bash script and i am essaying to show not logged users processes,which are typically daemon processes, for this,in the exercise, they recommend me:
To process the command line, we will use the cut command, which allows
selecting the different columns of the list through a filter.
I used:
ps -A | grep -v w
ps -A | grep -v who
ps -A | grep -v $USER
but trying all these options all the processes of all users are printed in the output file, and I only want the processes of users who are not logged.
I appreciate your help
Thank you.
grep -v w will remove lines matching the regular expression w (which is simply anything which contains the string w). To run the command w you have to say so; but as hinted in the instructions, you will also need to use cut to post-process the output.
So as not to give the answer away completely, here's rough pseudocode.
w | cut something >tempfile
ps -A | grep -Fvf tempfile
It would be nice if you could pass the post-processed results of w in a pipe, but standard input is already tied to ps -A. If you have a shell which supports process substitution, you can use that.
ps -A | grep -Fvf <(w | cut something)
Unfortunately, the output from w is not properly machine-readable -- you will properly want to cut out the header line(s), too. (On my machine, there are two header lines. Yours might differ.) You'll probably learn a bit of Awk later on in the course, but until then, maybe something like
ps -A | grep -Fvf <(w | tail -n +3 | cut something)
This still doesn't completely handle all possible situations. What if someone's account name is grep?
I'm trying to run a program on a dedicated core in Linux. (I know Jailhouse is a good way to do so, but I have to use off-the-shelf Linux. :-( )
Other processes, such as interrupt handlers, kernel threads, service progresses, may also run on the dedicated core occasionally. I want to disable as many such processes as possible. To do that, I need first pin down the list of processes that may run on the dedicated core.
My question is:
Is there any existing tools that I can use to trace the list of PIDs or processes that run on a specific core over a time interval?
Thank you very much for your time and help in this question!
TL;DR Dirty hacky solution.
DISCLAIMER: At some point stops working "column: line too long" :-/
Copy this to: core-pids.sh
#!/bin/bash
TARGET_CPU=0
touch lastPIDs
touch CPU_PIDs
while true; do
ps ax -o cpuid,pid | tail -n +2 | sort | xargs -n 2 | grep -E "^$TARGET_CPU" | awk '{print $2}' > lastPIDs
for i in {1..100}; do printf "#\n" >> lastPIDs; done
cp CPU_PIDs aux
paste lastPIDs aux > CPU_PIDs
column -t CPU_PIDs > CPU_PIDs.humanfriendly.tsv
sleep 1
done
Then
chmod +x core-pids.sh
./core-pids.sh
Then open CPU_PIDs.humanfriendly.tsv with your favorite editor, and ¡inspect!
The key is in the "ps -o cpuid,pid" bit, for more detailed info, please comment. :D
Explanation
Infinite loop with
ps -o cpuid,pid | tail -n +2 | sort | xargs -n 2 | grep -E "^$TARGET_CPU" | awk '{print $2}' > lastPIDs
ps ax -o cpuid,pid
Show pid's associated to CPU
tail -n +2
remove headers
sort
sort by cpuid
xargs -n 2
remove white spaces at begging
grep -E "^$TARGET_CPU"
filter by CPU id
awk '{print $2}'
get pid column
> lastPIDs
output to file those las pid's for the target CPU id
for i in {1..10}; do printf "#\n" >> lastPIDs; done
hack for pretty .tsv print with the "columns -t" command
cp CPU_PIDs aux
CPU_PIDs holds the whole timeline, we copy it to aux file to allow the next command to use it as input and output
paste lastPIDs aux > CPU_PIDs
Append lastPIDs columns to the whole timeline file CPU_PIDs
column -t CPU_PIDs > CPU_PIDs.humanfriendly.tsv
pretty print whole timeline CPU_PIDs file
Attribution
stackoverflow answer to: ps utility in linux (procps), how to check which CPU is used
by Mikel
stackoverflow answer to: Echo newline in Bash prints literal \n
by sth
stackoverflow answer to: shell variable in a grep regex
by David W.
superuser answer to: Aligning columns in output from a UNIX command
Janne Pikkarainen
nixCraft article: HowTo: Unix For Loop 1 to 100 Numbers
The best way to obtain what you want is to operate as follows:
Use the isolcpus= Linux kernel boot parameter to "free" one core from the Linux scheduler
Disable the irqbalance daemon (in case it is executing)
Set the IRQs affinities to the other cores by manually writing the CPU mask on /proc/irq/<irq_number>/smp_affinity
Finally, run your program setting the affinity to the dedicated core through the taskset command.
In this case, such core will only execute your program. For checking, you can type ps -eLF and look at the PSR column (which specifies the CPU number).
Not a direct answer to the question, but I am usually using perf context-switches software event to identify the perturbation of the system or other processes on my benchmarks
Is there way of counting the number of processes being run by a user in the unix/linux/os x terminal?
For instance, top -u taha lists my processes. I want to be able to count these.
This will show all of the users with their counts (I believe this would be close enough for you. :)
ps -u "$(echo $(w -h | cut -d ' ' -f1 | sort -u))" o user= | sort | uniq -c | sort -rn
You can use ps to output it and count the number using wc, as:
ps -u user | sed 1d | wc -l
You can also dump top output and grep it, something like:
top -u user -n1 | grep user | wc -l
I'm somewhat new to *nix, so perhaps I did not fully understand the context of your question, but here is a possible solution:
jobs | wc -l
The output of the above command is a count of all the processes reported by the jobs command. You can manipulate the parameters of the jobs command to change which processes get reported.
EDIT: Just FYI, this would only work if interested in commands originating from a particular shell. If you want more control in looking at system-wide processes you probably want to use ps as others have suggested. However, if you use wc to do your counting, make sure you take into account any extraneous white space jobs, ps or top may have generated as that will affect the output of wc.