How do I escape double and single quotes in sed?

Question

From what I can find, when you use single quotes everything inside is considered literal. I want that for my substitution. But I also want to find a string that has single or double quotes.

For example,

sed -i 's/"http://www.fubar.com"/URL_FUBAR/g'

I want to replace "http://www.fubar.com" with URL_FUBAR. How is sed supposed to recognize my // or my double quotes?

Thanks for any help!

EDIT: Could I use s/\"http\:\/\/www\.fubar\.\com\"/URL_FUBAR/g ?

Does \ actually escape chars inside the single quotes?

Answer 1

Regarding the single quote, see the code below used to replace the string let's with let us:

command:

echo "hello, let's go"|sed 's/let'"'"'s/let us/g'

result:

hello, let us go

Answer 2

Escaping a double quote can absolutely be necessary in sed: for instance, if you are using double quotes in the entire sed expression (as you need to do when you want to use a shell variable).

Here's an example that touches on escaping in sed but also captures some other quoting issues in bash:

# cat inventory
PURCHASED="2014-09-01"
SITE="Atlanta"
LOCATION="Room 154"

Let's say you wanted to change the room using a sed script that you can use over and over, so you variablize the input as follows:

# i="Room 101" (these quotes are there so the variable can contains spaces)

This script will add the whole line if it isn't there, or it will simply replace (using sed) the line that is there with the text plus the value of $i.

if grep -q LOCATION inventory; then 
## The sed expression is double quoted to allow for variable expansion; 
## the literal quotes are both escaped with \ 
    sed -i "/^LOCATION/c\LOCATION=\"$i\"" inventory
## Note the three layers of quotes to get echo to expand the variable
## AND insert the literal quotes
else 
    echo LOCATION='"'$i'"' >> inventory
fi

P.S. I wrote out the script above on multiple lines to make the comments parsable but I use it as a one-liner on the command line that looks like this:

i="your location"; if grep -q LOCATION inventory; then sed -i "/^LOCATION/c\LOCATION=\"$i\"" inventory; else echo LOCATION='"'$i'"' >> inventory; fi