Question

How can i update the particular entry with appropriate values in a given file,

Let say i have a file name hello.conf,

/agent/process="starthelloJava",start="/opt/starthello.sh",start_dir="/opt/hello",start_args=""
/agent/process="stophelloJava",stop="/opt/stophello.sh",stop_dir=/opt/hello",stop_args="",stop_timeout="30"

update the starthelloJava with

start_args="-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/"

output

/agent/process="starthelloJava",start="/opt/starthello.sh",start_dir="/opt/hello",start_args="-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/"

empty the start_args of process starthelloJava

/agent/process="starthelloJava",start="/opt/starthello.sh",start_dir="/opt/hello",start_args=""
/agent/process="stophelloJava",stop="/opt/stophello.sh",stop_dir=/opt/hello",stop_args="",stop_timeout="30"

The way i’m doing is long step’s i’m rewriting the entire file, based on the input.

This is my apprach which is not efficient

cp hello.conf hello.conf_bak
remove entry first
cat /opt/CSCObac/agent/conf/agent.conf_bak | grep -v /opt/starthello.sh  > hello.conf
echo "/agent/process=\"starthelloJava\",start=\"/opt/starthello.sh\",start_dir=\"/opt/hello\",start_args=\"-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/\" >> hello.conf

Answer 1

set -- '-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/'
sed -i -r "s!(.*starthelloJava.*=).*!\1\"$1\"!" hello.conf

or to empty the value

set -- ''
sed -i -r "s!(.*starthelloJava.*=).*!\1\"$1\"!" hello.conf