Sed script in bash script

Question

I am trying to make a script which only gives me code outside braces. I made a bash script to which I can give the braces I like. Then I would like to use sed inside my bash script. My sed script does what it has to do, because when I use sed -f myscript on the command line, the output is right. But I now have problems to replace the braces I give to my bash script in the sed script. Here is my code:

#/bin/bash

if [[ $# != 2 ]]
then
    echo "Gebruik: verwijderhaakjes.sh <openend symbool> <sluitend symbool>"
    exit
fi
if [ "${#1}" != 1 -o "${#2}" != 1 ]
then
    echo "Fout: openend en sluitend symbool moeten uit één enkel karakter bestaan"
    exit
fi
var1=$1
var2=$2
sed "
$!{
    /^[a-zA-Z]/{
        H
        d
    }
    /^${var2}/{
        H
        d
    }
    /^[ ][ ]*/{
        d
    }
}
/^[${var2}a-zA-Z]/{
    H
}
x
s/${var1}\n//g
s/${var2}//g
p
"

As you can see, I already used double quotes and I used the variables in the sed script, so I don't know why I don't get any output.

for example:

testfile:

aaa {
  bbb
  ccc {
    ddd
    eee
  } fff {
    ggg
    hhh
  }
  iii
  jjj
} kkk {
  lll
  mmm
} nnn
ooo
ppp

When I use my sed script like this:

sed -f myscript.sed test.txt

the output is this:

aaa kkk nnn
ooo
ppp

which is right. However when I use my sed script in bash I don't get any ouput. What I want to get is:

cat test | bash bashscript.sh "{" "}"

aaa kkk nnn
ooo
ppp

or

cat test | tr '}' ']' | tr '{' '[' | bash bashscript.sh "[" "]"

aaa kkk nnn
ooo
ppp

Answer 1

Try this instead:

sed '
$!{
    /^[a-zA-Z]/{
        H
        d
    }
    /^'"${var2}"'/{
        H
        d
    }
    /^[ ][ ]*/{
        d
    }
}
/^['"${var2}"'a-zA-Z]/{
    H
}
x
s/'"${var1}"'\n//g
s/'"${var2}"'//g
p
'

If you use double-quotes around the entire sed expression, the shell will expand characters like $ , * etc. So you need to use single quotes around everything except the shell variables.

Another approach would be to escape the characters which are special to the shell.