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]/ioб /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
Related
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"
I want to monitor all the running processes using strace and when a process ends the output of the strace should be sent to a file.
And how to find every running proc PID. I also want to include process name in the output file.
$ sudo strace -p 1725 -o firefox_trace.txt
$ tail -f firefox_trace.txt
1725 would be the PID of the proccess you want to monitor (you can find the PID with "ps -C firefox-bin", for firefox in the example)
And firefox_trace.txt would be the output file !
The way to got would be to find every running proc PID, and use the command to write them in the output file !
Considering the doc,
-p pid
Attach to the process with the process ID pid and begin tracing. The
trace may be terminated at any time by a keyboard interrupt signal (
CTRL -C). strace will respond by detaching itself from the traced
process(es) leaving it (them) to continue running. Multiple -p options
can be used to attach to up to 32 processes in addition to command
(which is optional if at least one -p option is given).
Use -o to store the output to the file, or 2>&1 to redirect standard error to output, so you can filter it (grep) or redirect it into file (> file).
To monitor process without knowing its PID, but name, you can use pgrep command, e.g.
strace -p $(pgrep command) -o file.out
where command is your name of process (e.g. php, Chrome, etc.).
To learn more about parameters, check man strace.
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)
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.
Is it possible to get the child process id from parent process id in shell script?
I have a file to execute using shell script, which leads to a new process process1 (parent process). This process1 has forked another process process2(child process). Using script, I'm able to get the pid of process1 using the command:
cat /path/of/file/to/be/executed
but i'm unable to fetch the pid of the child process.
Just use :
pgrep -P $your_process1_pid
I am not sure if I understand you correctly, does this help?
ps --ppid <pid of the parent>
I've written a script to get all child process pids of a parent process.
Here is the code. Hope it will help.
function getcpid() {
cpids=`pgrep -P $1|xargs`
# echo "cpids=$cpids"
for cpid in $cpids;
do
echo "$cpid"
getcpid $cpid
done
}
getcpid $1
To get the child process and thread,
pstree -p PID.
It also show the hierarchical tree
The shell process is $$ since it is a special parameter
On Linux, the proc(5) filesystem gives a lot of information about processes. Perhaps
pgrep(1) (which accesses /proc) might help too.
So try cat /proc/$$/status to get the status of the shell process.
Hence, its parent process id could be retrieved with e.g.
parpid=$(awk '/PPid:/{print $2}' /proc/$$/status)
Then use $parpid in your script to refer to the parent process pid (the parent of the shell).
But I don't think you need it!
Read some Bash Guide (or with caution advanced bash scripting guide, which has mistakes) and advanced linux programming.
Notice that some server daemon processes (wich usually need to be unique) are explicitly writing their pid into /var/run, e.g. the sshd server daemon is writing its pid into the textual file /var/run/sshd.pid). You may want to add such a feature into your own server-like programs (coded in C, C++, Ocaml, Go, Rust or some other compiled language).
You can get the pids of all child processes of a given parent process <pid> by reading the /proc/<pid>/task/<tid>/children entry.
This file contain the pids of first level child processes.
Recursively do this for all children pids.
For more information head over to https://lwn.net/Articles/475688/
ps -axf | grep parent_pid
Above command prints respective processes generated from parent_pid, hope it helps.
+++++++++++++++++++++++++++++++++++++++++++
root#root:~/chk_prgrm/lp#
parent...18685
child... 18686
root#root:~/chk_prgrm/lp# ps axf | grep frk
18685 pts/45 R 0:11 | \_ ./frk
18686 pts/45 R 0:11 | | \_ ./frk
18688 pts/45 S+ 0:00 | \_ grep frk
You can print the PID of all child processes invoked by a parent process:
pstree -p <PARENT_PID> | grep -oP '\(\K[^\)]+'
This prints a list of pids for the main process and its children recursively
I used the following to gather the parent process and child processes of a specific process PID:
ps -p $PID --ppid $PID --forest | tail -n +2 | awk '{print$1}'
Note, this will not work to find child processes of child processes.
For the case when the process tree of interest has more than 2 levels (e.g. Chromium spawns 4-level deep process tree), pgrep isn't of much use. As others have mentioned above, procfs files contain all the information about processes and one just needs to read them. I built a CLI tool called Procpath which does exactly this. It reads all /proc/N/stat files, represents the contents as a JSON tree and expose it to JSONPath queries.
To get all descendant process' comma-separated PIDs of a non-root process (for the root it's ..stat.pid) it's:
$ procpath query -d, "..children[?(#.stat.pid == 24243)]..pid"
24243,24259,24284,24289,24260,24262,24333,24337,24439,24570,24592,24606,...
#include<stdio.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
// Create a child process
int pid = fork();
if (pid > 0)
{
int j=getpid();
printf("in parent process %d\n",j);
}
// Note that pid is 0 in child process
// and negative if fork() fails
else if (pid == 0)
{
int i=getppid();
printf("Before sleep %d\n",i);
sleep(5);
int k=getppid();
printf("in child process %d\n",k);
}
return 0;
}