unable to capture command process id

Question

I am trying to capture the process id of the flume command with in a linux script.

the script is being executed in nohup mode : nohup flume.sh &

flume.sh:

flume-ng agent --conf . -Dflume.root.logger=info,console -Djavax.net.debug=info,console --conf-file FLUME_Surya.conf --name IBMMQ  --classpath $CLASSPATH -Dcom.ibm.mq.cfg.useIBMCipherMappings=false
echo $! > /biph/edl/SG/jobs/Src-104000-IPS_SG/CUL_FLUME_PROCESS_ID.txt

after the script is execute the text file is still empty, please advice

Answer 1

$! contains the process id of the most recent background job. That is, job placed in the background by putting a & at the end of the line. In your script nothing is put into the background, and thus $! is empty. (The echo command line will open the file, creating it if it doesn't exist and truncate it if it does. But it has nothing to write to it.)