How to use sed to examine the line without specific content?

I'm using CMD on Windows Xp to replace special text with Sed. I'm using this command for replace special characters like $ or * :

sed -i "s/\*/123/g;" 1.txt

But how command must i use to replace this strings with ciao! in my text files? Is possible?

\\
\\\
""
sed.exe -i "s/{\*)(//123/
sed -i "s/\\/123/g;" 1.txt

the previous command does not work because i have \, " and other special strings that sed use to make regex.

Looking for literal strings with a regular expression, when the search-string contains special characters, is sometimes not as simple as looking for patterns, but you can do it with a bit of juggling.

Note: The echo command must cater for CMD-special-characters, so it needs ^^ to escape a single ^ and ^| to escape | ... You don't need CMD's escape-character ^ if you type directly into the file.

Step 1: Create a file, named literal-srch-strings.txt, which containing the exact (unaltered) string to be replaced. There are 2 ways to create this file:

1. As a command issued at CMD's commandline, or as a command in a .cmd/.bat command-script.

   echo sed -i^^/\\*$/$[{" ;"> literal-srch-strings.txt

2. Make literal-srch-strings.txt yourself, in your text editor.
   In this case, you should not use the CMD-escape-character ^, so the line is has just one ^, not ^^ -- This is because you are bypassing the CMD-shell.
   Here is what is needed in the .txt file (just as the filename says :)

   sed -i^/\\*$/$[{" ;"

Step 2: Make a sed script, named str-to-regex.sed , to convert the string(s) into sed regex(s).
Note that the same issue of the CMD-escape-character ^ applies to this step, so again, there are 2 ways you can create the .sed file:

1. As a command:

   echo s/[]\/$*.^^^|[]/\\^&/g; s/.*/s\/^&\/Ciao!\/g/> str-to-regex.sed

2. Using your text editor, make a file named str-to-regex.sed, containing:

   s/[]\/$*.^|[]/\\&/g; s/.*/s\/&\/Ciao!\/g/

Step 3: Run the sed-script which converts the string into a sed regeular expression, and
send its output to another sed-script, replace-text.sed, which will make the actual replacement.

sed -f str-to-regex.sed  literal-srch-strings.txt > replace-text.sed

Step 4: Run replace-text.sed -- For the test we can use literal-srch-strings.txt as the input file, but you can, of course, use any input file.

sed -f replace-text.sed  literal-srch-strings.txt

Here is the output:

Ciao! 

To override the meaning of special characters on the command-line (or lines in a batch file), escape them with the ^ (carat) character. To enter a literal carat character, use two of them in a row.