How can I get an output of one command as an argument to other linux command? - linux

I am getting process id for a process using:
ps -ef | awk '$8=="process name" {print $2}'
How can I use the output of above command as an input to the command below:
ps -p <pid> -o %cpu,%mem,cmd
Basically I needed the above two commands executed as a single command.

Pipe it to xargs:
... | xargs -I {} ps -p {} -o %cpu,%mem
The {} is the default argument list marker which can be used to send to your final command.
Alternatively you can also use command substitution
ps -p $(ps -ef | awk ...) -o %cpu,%mem

Related

How to use xargs to get elapsed time for running processes

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?
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.
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)

How to make a command with grep captured fields?

I'm trying to capture a process that runs and make an strace of it in one line:
I managed to capture only the one that i want with this command
ps -ef | grep "[0-9].*[0-9] /usr/bin/python3 /home/pi/readcard.py"
outputs this:
root 676 668 99 11:00 ? 00:34:21 /usr/bin/python3 /home/pi/readcard.py
Now I'm trying to capture the process pid with this regex and use it to make another command:
ps -ef | grep "([0-9]+).*[0-9] /usr/bin/python3 /home/pi/readcard.py"
How I could make to run something like this?
sudo strace -f -p{captured_field} -s9999 -e write
Use awk for only showing the second column:
ps -ef | grep "([0-9]+).*[0-9] /usr/bin/python3 /home/pi/readcard.py" | awk '{print $2}'
This, you can use it as an input for another command, by embedding it into $(...), as follows:
sudo strace -f -p{$(ps -ef | grep "([0-9]+).*[0-9] /usr/bin/python3 /home/pi/readcard.py" | awk '{print $2}')} -s9999 -e write
Good luck

.bashrc saves previous process id and does not update in alias commands

I have made an alias in .bashrc to kill my python service.py & process
alias servicestop="kill $(ps -ef | grep -w service.py | grep -v grep | awk '{print $2}')"
Whenever I run first time servicestop command it will kill the process.
but again whenever I start process python service.py &, and execute command servicestop it gives an error.
After research, I found following things.
when I run first time python service.py & process. its process id was 512.
and, command servicestop kill that process(512).
Now when I run Second time process python service.py &. its process id was 546.(definitely it will be different).
When I run command servicestop. it will give following error:
-bash: kill: (512) - No such process
That means $(ps -ef | grep -w service.py | grep -v grep | awk '{print $2}') will return the previous pid, which is already killed.
Now please suggest the solution if any possible.
so whenever I want to run servicestop command, I have to run source .bashrc command first, then run servicestop command to make it work.
Please remove the servicestop alias from your .bashrc and add :
servicestop(){
kill $(ps -ef | grep -w service.py | grep -v grep | awk '{print $2}');
}
In a way, functions in .bashrc are "aliases 2.0" : simply better
Better : same function; but with the name of script to kill as parameter :
servicestop(){
kill $(ps -ef | grep -w $1 | grep -v servicestop | awk '{print $2}');
}
Use it like that :
servicestop service.py
servicestop otherSuperService.py

Getting pids from ps -ef |grep keyword

I want to use ps -ef | grep "keyword" to determine the pid of a daemon process (there is a unique string in output of ps -ef in it).
I can kill the process with pkill keyword is there any command that returns the pid instead of killing it? (pidof or pgrep doesnt work)
You can use pgrep as long as you include the -f options. That makes pgrep match keywords in the whole command (including arguments) instead of just the process name.
pgrep -f keyword
From the man page:
-f The pattern is normally only matched against the process name. When -f is set, the full command line is used.
If you really want to avoid pgrep, try:
ps -ef | awk '/[k]eyword/{print $2}'
Note the [] around the first letter of the keyword. That's a useful trick to avoid matching the awk command itself.
Try
ps -ef | grep "KEYWORD" | awk '{print $2}'
That command should give you the PID of the processes with KEYWORD in them. In this instance, awk is returning what is in the 2nd column from the output.
ps -ef | grep KEYWORD | grep -v grep | awk '{print $2}'
This is available on linux: pidof keyword
I use
ps -C "keyword" -o pid=
This command should give you a PID number.
To kill a process by a specific keyword you could create an alias in ~/.bashrc (linux) or ~/.bash_profile (mac).
alias killps="kill -9 `ps -ef | grep '[k]eyword' | awk '{print $2}'`"

Finding process count in Linux via command line

I was looking for the best way to find the number of running processes with the same name via the command line in Linux. For example if I wanted to find the number of bash processes running and get "5". Currently I have a script that does a 'pidof ' and then does a count on the tokenized string. This works fine but I was wondering if there was a better way that can be done entirely via the command line. Thanks in advance for your help.
On systems that have pgrep available, the -c option returns a count of the number of processes that match the given name
pgrep -c command_name
Note that this is a grep-style match, not an exact match, so e.g. pgrep sh will also match bash processes. If you want an exact match, also use the -x option.
If pgrep is not available, you can use ps and wc.
ps -C command_name --no-headers | wc -l
The -C option to ps takes command_name as an argument, and the program prints a table of information about processes whose executable name matches the given command name. This is an exact match, not grep-style. The --no-headers option suppresses the headers of the table, which are normally printed as the first line. With --no-headers, you get one line per process matched. Then wc -l counts and prints the number of lines in its input.
result=`ps -Al | grep command-name | wc -l`
echo $result
ps -Al | grep -c bash
You can try :
ps -ef | grep -cw [p]rocess_name
OR
ps aux | grep -cw [p]rocess_name
For e.g.,:
ps -ef | grep -cw [i]nit
Some of the above didn't work for me, but they helped me on my way to this.
ps aux | grep [j]ava -c
For newbies to Linux:
ps aux prints all the currently running processes, grep searches for all processes that match the word java, the [] brackets remove the process you just ran so it wont include that as a running process and finally the -c option stands for count.
List all process names, sort and count
ps --no-headers -A -o comm | sort | uniq -c
You also can list process attached to a tty
ps --no-headers a -o comm | sort | uniq -c
You may filter with:
ps --no-headers -A -o comm | awk '{ list[$1] ++ } END { for (i in list) { if (list[i] > 10) printf ("%20s: %s\n", i, list[i]) } }'
Following bash script can be run as a cron job and you can possibly get email if any process forks itself too much.
for i in `ps -A -o comm= --sort=+comm | uniq`;
do
if (( `ps -C $i --no-headers | wc -l` > 10 )); then
echo `hostname` $i `ps -C $i --no-headers | wc -l` ;
fi
done
Replace 10 with your number of concern.
TODO: "10" could be passed as command line parameter as well. Also, few system processes can be put into exception list.
You can use ps(will show snapshot of processes) with wc(will count number of words, wc -l option will count lines i.e. newline characters).
Which is very easy and simple to remember.
ps -e | grep processName | wc -l
This simple command will print number of processes running on current server.
If you want to find the number of process running on current server for current user then use -U option of ps.
ps -U root | grep processName | wc -l
change root with username.
But as mentioned in lot of other answers you can also use ps -e | grep -c process_name which is more elegant way.
ps aux | wc -l
This command shows number of processes running on the system by all the users.
For a specific user you can use the following command:
ps -u <username> | wc -l
replace with the actual username before running :)
ps -awef | grep CAP | wc -l
Here "CAP" is the word which is in the my Process_Names.
This command output = Number of Processes + 1
This is why When we are running this command , our system read thats "ps -awef | grep CAP | wc -l " is also a process.
So yes our real answer is (Number of Processes) = Command Output - 1
Note : These processes are only those processes who include the name of "CAP"

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