mjhjmtu

I need find and replace in a md file (plain text)

<span class="symbol"></span>

with this:

[]custom-style="symbol"

I tried many times, f.e.

sed -i -e 's/(<span class="symbol">)(</span>)/[/]/custom-style="symbol"/g'myfile.md

or

sed -i -e "s#<span class="symbol"></span>#[]custom-style="symbol"#g" "Dignità umana e bioetica".md

but I get always an error message, like

sed: -e expression #1, char 40: unknown option to `s'

This seems work (no error message):

sed -i -e "s@<span class="symbol"></span>@[]custom-style="symbol"@g" myfile.md

but I get this code

[<span class="symbol"></span>#58771;]custom-style="symbol" 

The new string is added, not replace the old one.

solved

As you said, this command works

sed -i -e 's@<span class="symbol"></span>@[]custom-style="symbol"@g'

This will work:

sed -i -e "s@<span class="symbol"></span>@[]custom-style="symbol"@g" myfile.md

You need to use before &, then it will work fine because & is special in the replacement text: it means “the whole part of the input that was matched by the pattern”.

From man sed:

s/regexp/replacement/

The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes 1 through 9 to refer to the corresponding matching sub-expressions in the regexp.

This seems to work for me

# echo '<span class="symbol"></span>' > test 
# sed -i -e 's@<span class="symbol"></span>@[]custom- 
style="symbol"@g' test
# cat test 
[]custom-style="symbol"

With awk

echo "<span class="symbol"></span>" |awk -F'=|>|<' 'BEGIN OFS=""; print "["$4"]","cumtom-style=""""$3"""""'
[]cumtom-style="symbol"

There are some issues with the code you tried.

First, things are easier if you choose a character that shows up nowhere in your text as the delimiter for the s/// command. Alternatively, you have to escape with a any occurrence of the delimiter in your text.

In your first command,

sed -i -e 's/(<span class="symbol">)(</span>)/[/]/custom-style="symbol"/g'myfile.md

the error you get is due to the / in [/], that is not escaped.

Also, to put a literal & in the output text, you have to escape it with a in your replacement expression. Otherwise & is interpreted as special and replaced with the matched portion of the pattern space.

To keep things simple, here I removed (possibly?) unnecessary escape characters and a couple of (possibly?) unneeded / (from [/]/custom-style="symbol"). I also chose | as the delimiter for the s/// command, since it does not appear in your input text. The command becomes:

sed -e 's|<span class="symbol"></span>|[]custom-style="symbol"|g'

And this is what it does:

$ echo '<span class="symbol"></span>' | sed -e 's|<span class="symbol"></span>|[]custom-style="symbol"|g'
[]custom-style="symbol"

If the string  is not static and you want to replace <span class="symbol"> with [ and </span> with ]custom-style="symbol" around it, whatever its value, you can use a capturing group (()) and a backreference (here, 1):

sed -e 's|<span class="symbol">(.*)</span>|[1]custom-style="symbol"|g'

What this command does:

$ echo '<span class="symbol">whatever is here</span>' | sed -e 's|<span class="symbol">(.*)</span>|[1]custom-style="symbol"|g'
[whatever is here]custom-style="symbol"

Finally, you may generally prefer to use single quotes (') instead of double quotes (") around sed scripts, to protect them from the shell - parameter expansion triggered by $, escaping effects of ...