I want to know the PID of the last executed command.
I saw this a lot:
$ command &
$ pid=$!
But I'm searching for the same thing without running the command in the background.
You can use the following construction in scripts:
PID=`sh -c "echo $$; exec your_command -with-arguments"`
echo $PID
Related
Let's group two commands (cd and bash ..) together like this:
#!/bin/bash
C="directory"
SH="bash process.sh"
(cd ${C}; ${SH})&
PID=$!
sleep 1
KILL=`kill ${PID}`
process.sh prints out the date (each second and five times):
C=0
while true
do
date
sleep 1
if [ ${C} -eq 4 ]; then
break
fi
C=$((C+1))
done
Now I actually would expect the background subprocess to be killed right after 1 second, but it just continues like nothing happens. INB4: "Why don't you just bash directory/process.sh" No, this cd is just an example.
What am I doing wrong?
Use exec when you want a process to replace itself in-place, rather than creating a new subprocess with its own PID.
That is to say, this code can create two subprocesses, storing the PID of the first one in $! but then using the second one to execute process.sh:
# store the subshell that runs cd in $!; not necessarily the shell that runs process.sh
# ...as the shell that runs cd is allowed to fork off a child and run process.sh there.
(cd "$dir" && bash process.sh) & pid=$!
...whereas this code creates only one subprocess, because it uses exec to make the first process replace itself with the second:
# explicitly replace the shell that runs cd with the one that runs process.sh
# so $! is guaranteed to have the right thing
(cd "$dir" && exec bash process.sh) &
you can check all child processes with "ps --ppid $$"
so,
#!/bin/bash
C="directory"
SH="bash process.sh"
(cd ${C}; ${SH})&
PID=$!
sleep 1
ps -o pid= --ppid $$|xargs kill
How can I implement the following scenario in Ubuntu Linux?
I want to go to my console, then execute ./startdev.sh and then
1) Terminal 1 pops up, starts /home/foobar/bla1.sh
2) Terminal 2 pops up, starts /home/foobar/bla2.sh
3) Terminal 3 pops up, starts /home/foobar/bla3.sh
I already figured that the command "gnome-terminal & disown" starts a new terminal.
However, until now, I don't know how to run a command in that terminal.
I accept any answer that gives me either the entire implementation for startdev.sh or a list of commands that I can use.
Thank you!
Try this content for startdev.sh:
#!/bin/bash
gnome-terminal --command=/home/foobar/bla1.sh & disown
gnome-terminal --command=/home/foobar/bla2.sh & disown
gnome-terminal --command=/home/foobar/bla3.sh & disown
But it is not clear for me why you need to disown the launched processes.
Try this script
If you need to simultaneously pop all terminals
#!/bin/bash
gnome-terminal -e "bash -c '/home/foobar/bla1.sh; sleep 10'" | gnome-terminal -e "bash -c '/home/foobar/bla2.sh; sleep 10'" | gnome-terminal -e "bash -c '/home/foobar/bla3.sh; sleep 10'"
else if you need to run commands one by one terminal then .,
#!/bin/bash
gnome-terminal -e "bash -c '/home/foobar/bla1.sh; sleep 10'"
gnome-terminal -e "bash -c '/home/foobar/bla2.sh; sleep 10'"
gnome-terminal -e "bash -c '/home/foobar/bla3.sh; sleep 10'"
this script will open multiple terminals and execute the command given within the quotes and i have used sleep to hold the terminal from exiting if not added gnome-terminal will execute command and exit immediately.
Inside Jenkins, I have to run 2 separate scripts: start.sh and stop.sh. These scripts are inside my application which is fetched from a SCM . They are inside same directory.
The start.sh script runs a process in the background using nohup, and writes the processId to save_pid.pid. This script works fine. It successfully starts my application.
Then inside stop.sh, I am trying to read the processId from save_pid.pid to delete the process. But,I am unable to delete the process and the application keeps running until I kill the process manually using: sudo kill {processId}.
Here are the approaches that I have tried so far inside stop.sh but none of these work:
kill $(cat /path/to/save_pid.pid)
kill `cat /path/to/save_pid.pid`
kill -9 $(cat /path/to/save_pid.pid)
kill -9 `cat /path/to/save_pid.pid`
pkill -F /path/to/save_pid.pid
I have also tried all of these steps with sudo as well. But, it just doesn't work. I have kept an echo statement inside stop.sh, which prints and then there is nothing.
What am I doing wrong here ?
UPDATE:
The nohup command that I am using inside start.sh is something like this:
nohup deploy_script > $WORKSPACE/app.log 2>&1 & echo $! > $WORKSPACE/save_pid.pid
Please Note:
In my case, the value written inside save_pid.pid is surprisingly
always less by 1 than the value of actual processId. !!!
I think the reason why this happens is because you are not getting the PID of the process that you are interested in, but the PID of the shell executing your command.
Look:
$ echo "/bin/sleep 10" > /tmp/foo
$ chmod +x /tmp/foo
$ nohup /tmp/foo & echo $!
[1] 26787
26787
nohup: ignoring input and appending output to 'nohup.out'
$ pgrep sleep
26789
So 'nohup' will exec the 'shell', the 'shell' will fork a second 'shell' to exec 'sleep' in, however I can only count two processes here, so I am unable to account for one created PID.
Note that, if you put the nohup and the pgrep on one line, then pgrep will apparently be started faster than the shell that 'exec's 'sleep' and thus pgrep will yield nothing, which somewhat confirms my theory:
$ nohup /tmp/foo & echo $! ; pgrep sleep
[2] 26899
nohup: ignoring input and appending output to 'nohup.out'
$
If you launch your process directly, then nohup will "exec" your process and thus keep the same PID for the process as nohup itself had (see http://sources.debian.net/src/coreutils/8.23-4/src/nohup.c/#L225):
$ nohup /bin/sleep 10 & echo "$!"; pgrep sleep
[1] 27130
27130
nohup: ignoring input and appending output to 'nohup.out'
27130
Also, if you 'exec' 'sleep' inside the script, then there's only one process that's created (as expected):
$ echo "exec /bin/sleep 10" > /tmp/foo
$ nohup /tmp/foo & echo "$!"; pgrep sleep
[1] 27309
27309
nohup: ignoring input and appending output to 'nohup.out'
27309
Thus, according to my theory, if you'd 'exec' your process inside the script, then you'd be getting the correct PID.
I run the this command
$(while true;do echo Something && sleep 0.01; done;) | cat
Now I can not exit by Ctrl+C or background it by Ctrl+Z, and ps aux can't tell me which bash it is.How can I quit that bash ?
EDIT
I narrow donw the pid by find the cwd pgrep bash| (while read -r line; do lsof -p $line|grep cwd|grep EXPECTED_CWD && echo "GOT $line"; done;),finally kill that process.There is easier way to find that, but no /proc on mac.
Closing the terminal can help.
If you are using CLI-only os then you can switch to different terminal using Ctrl + Alt + F1 keys.
There you can use who or ps commands to get process-id and kill it.
ps -ef will list all processes.
you can kill second last bash process, as that will be the last command that you executed.
Note : process id assignment in linux is always greater than old one.
you're able to execute your commands with & symbol in the end of the command to run this command in background
In your case command looks like:
$(while true;do echo Something && sleep 0.01; done;) | cat &
It will show the process ID, and you'll be able to kill it, when you want
I am using the following code to launch a command on another machine:
#!/bin/bash
/usr/bin/rsh -n $Host_Name "cat asdf.txt &"
And I am trying to obtain the PID of the cat command by using the following:
/usr/bin/rsh -n $Host_Name pid="$!"
But when I echo $pid, it is just blank. What am I doing incorrectly? Is there an easier way of obtaining the PID of the last command that was executed on a different machine?
Thanks
You can only get the $! of the backgrounded command in the shell in which you started the command. If your command doesn't output anything to stderr, this could work:
/usr/bin/rsh -n $Host_Name "cat asdf.txt & echo $! >&2" 2> pidfile
The pid of the started command will then be stored locally in 'pidfile'.
Just a side-note: I would never use rsh. It is inherently insecure. I'd use ssh instead ;)