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How can I use a variable in sed?

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# 1  
How can I use a variable in sed?

I'm trying to change a part of a line with sed. Usually I will run
sed 's/mytext/mynewtext/'

Now I have a variable: var=mynewtext

sed 's/mytext/$var/' does not work. I have also tried to protect the $ with different characters but it still does'nt work.

I will be very happy if someone has a solution to this.
# 2  
For starters, you can switch to double quotes:

sed "s/mytext/$var/"

Sometimes that does not work. It would depend on the exact value of mytext. So another solution is to turn the single quoted string into two single quoted strings:

sed 's/mytext/'$var'/'

In this case, the 2nd single quoted string is '/'. Just using a backslash would work to that and it saves a character:

sed 's/mytext/'$var\/

There is actually no reason to quote a slash so this should also work with most shells:

sed 's/mytext/'$var/

And there may be no reason to quote anything at all, but again, the actual vakue of mytext determines this. So this may work:

sed s/mytext/$var/ only wanted a solution, so I'll quit now....Smilie
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