comment a line using search pattern and insert new line shell script-CodePudding

I am trying to comment a line in a file using search pattern, and then insert new line next to it.

search_variable=Dlog4j2.formatMsgNoLookups
new_variable="wrapper.java.additional.47=-Dlog4j2.formatMsg=false"

cat testfile.txt    
wrapper.java.additional.47=-Dlog4j2.formatMsgNoLookups=true

This one works, but trying to use variable to comment the line and

sed -i '/Dlog4j2.formatMsgNoLookups/s/^/#/g' testfile.txt

output:

#wrapper.java.additional.47=-Dlog4j2.formatMsgNoLookups=true

Desired output

cat testfile.txt
#wrapper.java.additional.47=-Dlog4j2.formatMsgNoLookups=true
wrapper.java.additional.47=-Dlog4j2.formatMsg=false

CodePudding user response：

With GNU sed:

search_variable="Dlog4j2.formatMsgNoLookups"
new_variable="wrapper.java.additional.47=-Dlog4j2.formatMsg=false"

sed -i "s/.*${search_variable}.*/#&\n${new_variable}/" testfile.txt

Output to testfile.txt:

#wrapper.java.additional.47=-Dlog4j2.formatMsgNoLookups=true
wrapper.java.additional.47=-Dlog4j2.formatMsg=false

For the meaning of & see using sed with ampersand (&).

The curly brackets can also be omitted in this case.

This can also be helpful: Difference between single and double quotes in bash