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I have a script i want to run 2 programs at the same time, One is a c program and the other is cpulimit, I want to start the C program in the background first with "&" and then get the PID of the C program and hand it to cpulimit which will also run in the background with "&".
I tried doing this below and it just starts the first program and never starts cpulimit.
Also i am running this as a startup script as root using systemd in arch linux.
#!/bin/bash
/myprogram &
PID=$!
cpulimit -z -p $PID -l 75 &
exit 0
217
A process is nothing but running instance of a program and each process has a unique PID on a Unix-like system. The easiest way to find out if process is running is run ps aux command and grep process name. If you got output along with process name/pid, your process is running.
As a child process of the main shell, a subshell executes a list of commands in a shell script as a batch (so-called "batch processing"). In some cases, you may want to know the process ID (PID) of the subshell where your shell script is running. This PID information can be used under different circumstances.
$ expands to the process ID of the shell. So, you can see the PID of the current shell with echo $$ . See the Special Paramaters section of man bash for more details.
I think i have this solved now, According to this here: link I need to wrap the commands like this (command) to create a sub shell.
#!/bin/bash
(mygprgram &)
mypid=$!
(cpulimit -z -p $mypid -l 75 &)
exit 0
I just found this while googling and wanted to add something.
While your solution seems to be working (see comments about subshells), in this case you don't need to get the pid at all. Just run the command like this:
cpulimit -z -l 75 myprogram &
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