Bash - 引用变量扩展与sed混合产生不良替代

Question

I have problem with this sed oneliner

sed -i -n "1h; 1!H; ${g; :a s/\(Name=\"$key\".*<\!\[CDATA\[\"\)$val\(\"\]\]>\)/\1$deval\2/;ta p}"

Obviously I need to expand variable key , val and deval in sed. So I need the " around sed command.

With this command I get

bash: !H: event not found

escaping the ! corrects it

sed -i -n "1h; 1\!H; ${g; :a s/\(Name=\"$key\".*<\!\[CDATA\[\"\)$val(\"\]\]>\)/\1$deval\2/;ta p}"

With this I get

bash: sed -i -n "1h; 1\\!H; ${g; :as/\\(Name=\\"$key\\".*<\\!\\[CDATA\\[\\"\\)$val\\(\\"\\]\\]>\\)/\\1$deval\\2/;ta p}" :bad substitution

So I guess the { is a problem. Trying to fix it like this

sed -i -n "1h; 1\\!H; $\\{g; :as/\\(Name=\\"$key\\".*<\\!\\[CDATA\\[\\"\\)$val(\\"\\]\\]>\\)/\\1$deval\\2/;ta p}"

yields

sed: -e expression 1, char 6: unknown command: "\\"

What is going on here? How can I make this work?

Answer 1

event not found is only a problem in interactive shells because histexpand is enabled by default. If you either run set +H first or put it in a script and run it from there, Bash will leave your ! s alone.

${..} is variable substitution syntax (so a mangled value gives bad substitution ). Let sed treat it as a block of commands to do on the final line by escaping the $ , as in \\${ .. } .

In full:

set +H
key="foo"
val="bar"
deval="puppies"
echo 'Name="foo" <![CDATA["bar"]]>' > file
sed -i -n "1h; 1!H; \${g; :a s/\(Name=\"$key\".*<!\[CDATA\[\"\)$val\(\"\]\]>\)/\1$deval\2/;ta p}" file
cat file

Will print Name="foo" <![CDATA["puppies"]]>

Answer 2

您可以使用单独的单引号字符串：

sed -i -n '1h; 1!H; ${g; :a s/\(Name='"$key"'.*<\!\[CDATA\[\"\)'"$val"'\(\"\]\]>\)/\1'"$deval"'\2/;ta p}'