UNIX for Dummies Questions & Answers

Hi all,

I have a script which uses sed to replace one string with another. The problem is, the string to be matched, and its replacement are coming in as two command line arguments $1 and $2

$1 and $2 can be absolutely anything, but both should be treated purely as strings. My sed command below doesn't do any escaping which is what I need.

sed "s/$1/$2/g" /tmp/input.txt > /tmp/output.txt

I spent a couple of days making some code which could escape these variables before use in my sed command and it seemed to allow me to enter almost anything but today, when trying to replace one string, with another string that contains an ampersand, some fancy sed backtracking came into play.

function escape {
new=`echo "$1" | sed 's/\\\\/\\\\\\\\/g' | sed 's/\//\\\\\//g' | sed 's/\*/\\\\\*/g' | sed 's/"/\"/g' | sed 's/\"/\\\\\"/g'`
echo $new
}

What I think I really need is a premade escape function for use in sed, or maybe some arguments to sed itself to ignore all special chars and treat them as strings.

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