I am trying to see what would happen about system call when I running one command, but it seems those command after | can't be shown? like:
strace -f cat a.txt| cat
It seems strace and -f perimeter can show the whole process. I think the last part is in the child progress created by fork. Why and how to make it?
From the strace manual (emphasis mine).
-f Trace child processes as they are created by
currently traced processes as a result of the fork(2),
vfork(2) and clone(2) system calls.
The traced process in your case is the first cat process. The second cat process is not a child of the first cat process. The fork is done by the shell.
One way to achieve what you want is to trace the shell:
strace -f bash -c "cat a.txt| cat"
Related
I had given a job in a remote server yesterday from my home. The command was
sh run.sh >& out &
The run.sh will excute a program (average.f) more than 1000 times recurssively.
Today, in my office, I found some mistake in my run.sh. So I would like to kill it.
I used top command, but it is not showing the run.sh. It is only showing average.f. So, once, I killed it with kill PID, it is again starting average.f with another PID and producing outputs.
ps -u is not showing either run.sh or average.f.
Can anybody please help me how to kill this job.
find your job id with the process or application name . example is given below - I am killing java process here
ps -aef|grep java
// the above command will give you pid, now fire below command to kill that job
kill -9 pid
// here pid is a number which you get from the first command
ps -ef | grep run.sh | grep -v grep | awk '{print $2}' | xargs kill -9
Use pstree(1) (probably as pstree -p) to list the process tree hierarchy, then kill(1) (first with -TERM, then with -QUIT, and if that does not work, at last with -KILL) your topmost shell process running run.sh (or else the few "higher" processes). Perhaps use killall(1) or pidof(1) (or pgrep(1) or pkill)
You might want to kill the process group, with a negative pid.
You should never at first kill -KILL a process (but only at last resort); some programs (e.g. database servers, sophisticated numerical computations with application checkpointing, ...) have installed a SIGTERM or SIGQUIT signal handler to clean up their mess and e.g. save some state (on the disk) in a sane way. If you kill -KILL them, they could leave the mess uncleaned (since SIGKILL cannot be caught, see signal(7)....)
BTW, you should use ps auxw to list all processes, read ps(1)
If I run top -p $(pgrep -d',' scrapy) I get information on the scrapy process, but this process probably triggers other python related processes. How can I get information on these processes as well in real time as the top command does?
Thanks,
Dani
What you're looking for is a program or script that will gather the CPU usage of all child processes spawned by scrapy.
If you wanted to script this yourself, you could look at the output of ps -p {scrapy pid} -L to get all the threads spawned by the instantiation of scrapy.
Or, you could chain together a couple Linux commands to have a one-liner:
ps -C scrapy -o pcpu= | awk '{cpu_usage+=$1} END {print cpu_usage}'
ps:
-C specifies the command name to output
-o pcou= tells ps to only display cpu usage
awk:
{cpu_usage+=$1} END loops over the response from ps
{print cpu_usage} will send the sum to STDOUT.
I need to track the process status ps axf during executable lifetime.
Let's say I have executable main.exec and want to store into a file all subprocess which are called during main.exec execution.
$ main.exec &
$ echo $! # and redirect every ps change for PID $! in a file.
strace - trace system calls and signals
$ main.exec &
$ strace -f -p $! -o child.txt
-f Trace child processes as they are created by currently traced processes as a result of the fork(2), vfork(2) and clone(2) system calls. Note that -p PID -f will attach all threads of process PID if it is multi-threaded, not only thread with thread_id = PID.
If you can't recompile and instrument main.exec, ps in a loop is a simple option that may work for you:
while true; do ps --ppid=<pid> --pid=<pid> -o pid,ppid,%cpu,... >> mytrace.txt; sleep 0.2; done
Then parse the output accordingly.
top may also work, and can run in batch mode but not sure if you can get it to dynamically monitor child processes like ps. Don't think so.
Currently, I am taking up the long method of doing this by getting a list of processes using the following command
sudo ps -eo pid,command | grep -v grep | awk '{print $1}' > pids.txt
And then iterating through the process ids and executing in background the strace of each process and generating logs for each process with the process id in the log's extension
filename="$1"
while read -r line
do
chmod +x straceProgram.sh
./straceProgram.sh $line &
done < "$filename"
straceProgram.sh
pid="$1"
sudo strace -p $pid -o log.$pid
However, the problem with this approach is that if there is any new process which gets started, it will not be straced since the strace is on the process ids stored in the pids.txt during the first run.
The list of pids.txt can be updated with new process ids, however, I was inquisitive on running a strace at an operating system level which would strace all the activities being performed.
Could there be a better way to do this?
If your resulting filesystem is going to be a kernel filesystem driver, I would recommend using tracefs to gather the information you require. I would recommend against making this a kernel filesystem unless you have a lot of time and a lot of testing resources. It is not trivial.
If you want an easier, safer alternative, write your filesystem using fuse. The downside is that performance is not quite as good and there are a few places where it cannot be used, but it is often acceptable. Note that there is already an implementation of a logging filesystem under fuse.
use the strace -f (fork) option, also I suggest the -s 9999 for more details
I have a bash process which calls another child process (mysqldump) for example. I need to determine the io usage of this child process. I tried cat /proc/self/io but values for io are connected only with the parent process. But I need the data for the child process. I can determine the pid of the child process and try view /proc/[pid of child]/io but when should I do that? If I do mysqldump and then /proc/[pid of child]/ioŠ± /proc/[pid of child] won't exist after the finishing of the child process. Thanks!
You can probably use strace command as below to get that result.
strace -e trace=read,write -o ls.log ls
Here, strace will give the result for ls command. If you want to attach to particular process, use the -p pid option like
strace -e trace=read,write -o ls.log -p <child process PID>
More about Strace Command Here