For example in a bash script you need to delete one or more word from the string , you can use sed to do just that

 sed -e "s/word to delete//g"

sed is searching for “word to delete” and replacing it with nothing ,

you can of course pipe to that command ,

example :

the var $visitor contain the string : ‘current number of users: 234’

But only the number (234) is usefull to you ,

your can do :

echo $visitor | sed -e "s/current number of users: //g"

the result is going to be : 234