` - back close or reverse close

shift +tilder

?Command Expansion

cat > lspath.txt

/etc

^C

ls -l  `cat lspath.txt` | grep .conf > etcconf.file

OR

ls -l $(cat lspath.txt)

another example using "du" command:

du -h `cat lspath.txt`

set | grep ETCDIR

ETCDIR=`ls -l /etc`

echo $ETCDIR  ## to reserve the normal format, use echo "$ETCDIR"

netstat -ant | grep 443

### checking https status, if result is 1, it is running; if result is 0, https service is dead###

ssl_status=`netstat -ant | grep 443 | wc -l`

echo $ssl_status

Linux Bash Scripting - Command Substitution