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When I do

node process.js 1>$LOGFOLDER\\$$.log

the created process's PID become the filename. I want to run this process in the background as I want to run many instances of the same process.js. So, I added & at the end,

node process.js 1>$LOGFOLDER\\$$.log &

This made the process to run in the background but the PID(the filename) is always wrong. I did log the process id using $! after the above line. In first case both $!'s output and logfile's name are same. But in second case they are not. Making the process to run in background using & is giving different PID in the $$ placeholder. Why is this happening and how can I make the both work

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That is because the backgrounded process runs in a subshell. To do what you want you could do this:

LOGFOLDER="$LOGFOLDER" bash -c 'node process.js 1>$LOGFOLDER.$$.log' &
| improve this answer | |
  • Oh Thanks. But this one is not executing the process.js. No file is created and no error logs – RaR Mar 25 '17 at 13:11
  • @RaR: It's those single quotes. Look at my edited answer for a resolution. HTH. – user218374 Mar 25 '17 at 13:13
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    Without LOGFOLDER being exported (I see the edit does this in the one-line format) then it's set to nothing in the subshell; if you do an ls -a then you'll see the log file as a hidden .12345.log file in the current directory (if you have write access to it) – Stephen Harris Mar 25 '17 at 13:15

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